release: prepare for 1.6.2

We have:

  auto halves = range.split(midpoint, dht::token_comparator());

We saw a case where midpoint == range.start, as a result, range.split
will assert becasue the range.start is marked non-inclusive, so the
midpoint doesn't appear to be contain()ed in the range - hence the
assertion failure.

Fixes #2148

Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Signed-off-by: Asias He <asias@scylladb.com>
Message-Id: <93af2697637c28fbca261ddfb8375a790824df65.1489023933.git.asias@scylladb.com>
(cherry picked from commit 39d2e59e7e)

.gitmodules

@@ -1,6 +1,6 @@
 [submodule "seastar"]
 	path = seastar
-	url = ../seastar
+	url = ../scylla-seastar
 	ignore = dirty
 [submodule "swagger-ui"]
 	path = swagger-ui

SCYLLA-VERSION-GEN

@@ -1,6 +1,6 @@
 #!/bin/sh
 
-VERSION=666.development
+VERSION=1.6.2
 
 if test -f version
 then

auth/auth.cc

@@ -243,7 +243,8 @@ future<> auth::auth::setup() {
         std::map<sstring, sstring> opts;
         opts["replication_factor"] = "1";
         auto ksm = keyspace_metadata::new_keyspace(AUTH_KS, "org.apache.cassandra.locator.SimpleStrategy", opts, true);
-        f = service::get_local_migration_manager().announce_new_keyspace(ksm, false);
+        // We use min_timestamp so that default keyspace metadata will loose with any manual adjustments. See issue #2129.
+        f = service::get_local_migration_manager().announce_new_keyspace(ksm, api::min_timestamp, false);
     }
 
     return f.then([] {

canonical_mutation.cc

@@ -44,7 +44,7 @@ canonical_mutation::canonical_mutation(const mutation& m)
     mutation_partition_serializer part_ser(*m.schema(), m.partition());
 
     bytes_ostream out;
-    ser::writer_of_canonical_mutation wr(out);
+    ser::writer_of_canonical_mutation<bytes_ostream> wr(out);
     std::move(wr).write_table_id(m.schema()->id())
                  .write_schema_version(m.schema()->version())
                  .write_key(m.key())

cql3/statements/select_statement.cc

@@ -307,7 +307,8 @@ select_statement::execute(distributed<service::storage_proxy>& proxy,
     // doing post-query ordering.
     if (needs_post_query_ordering() && _limit) {
         return do_with(std::forward<std::vector<query::partition_range>>(partition_ranges), [this, &proxy, &state, &options, cmd](auto prs) {
-            query::result_merger merger;
+            assert(cmd->partition_limit == query::max_partitions);
+            query::result_merger merger(cmd->row_limit * prs.size(), query::max_partitions);
             return map_reduce(prs.begin(), prs.end(), [this, &proxy, &state, &options, cmd] (auto pr) {
                 std::vector<query::partition_range> prange { pr };
                 auto command = ::make_lw_shared<query::read_command>(*cmd);
@@ -341,7 +342,8 @@ select_statement::execute_internal(distributed<service::storage_proxy>& proxy,
 
     if (needs_post_query_ordering() && _limit) {
         return do_with(std::move(partition_ranges), [this, &proxy, &state, command] (auto prs) {
-            query::result_merger merger;
+            assert(command->partition_limit == query::max_partitions);
+            query::result_merger merger(command->row_limit * prs.size(), query::max_partitions);
             return map_reduce(prs.begin(), prs.end(), [this, &proxy, &state, command] (auto pr) {
                 std::vector<query::partition_range> prange { pr };
                 auto cmd = ::make_lw_shared<query::read_command>(*command);
@@ -375,8 +377,8 @@ select_statement::process_results(foreign_ptr<lw_shared_ptr<query::result>> resu
         if (_is_reversed) {
             rs->reverse();
         }
+        rs->trim(cmd->row_limit);
     }
-    rs->trim(cmd->row_limit);
     return ::make_shared<transport::messages::result_message::rows>(std::move(rs));
 }
 

database.cc

@@ -816,6 +816,12 @@ void column_family::load_sstable(sstables::shared_sstable& sst, bool reset_level
 // several shards, but we can't start any compaction before all the sstables
 // of this CF were loaded. So call this function to start rewrites, if any.
 void column_family::start_rewrite() {
+    // submit shared sstables in generation order to guarantee that all shards
+    // owning a sstable will agree on its deletion nearly the same time,
+    // therefore, reducing disk space requirements.
+    boost::sort(_sstables_need_rewrite, [] (const sstables::shared_sstable& x, const sstables::shared_sstable& y) {
+        return x->generation() < y->generation();
+    });
     for (auto sst : _sstables_need_rewrite) {
         dblog.info("Splitting {} for shard", sst->get_filename());
         _compaction_manager.submit_sstable_rewrite(this, sst);
@@ -1670,14 +1676,40 @@ database::database(const db::config& cfg)
     dblog.info("Row: max_vector_size: {}, internal_count: {}", size_t(row::max_vector_size), size_t(row::internal_count));
 }
 
+
+void
+dirty_memory_manager::setup_collectd(sstring namestr) {
+    _collectd.push_back(
+        scollectd::add_polled_metric(scollectd::type_instance_id("memory"
+                , scollectd::per_cpu_plugin_instance
+                , "bytes", namestr + "_dirty")
+                , scollectd::make_typed(scollectd::data_type::GAUGE, [this] {
+            return real_dirty_memory();
+    })));
+
+    _collectd.push_back(
+        scollectd::add_polled_metric(scollectd::type_instance_id("memory"
+                , scollectd::per_cpu_plugin_instance
+                , "bytes", namestr +"_virtual_dirty")
+                , scollectd::make_typed(scollectd::data_type::GAUGE, [this] {
+            return virtual_dirty_memory();
+    })));
+}
+
 void
 database::setup_collectd() {
+    _dirty_memory_manager.setup_collectd("regular");
+    _system_dirty_memory_manager.setup_collectd("system");
+    _streaming_dirty_memory_manager.setup_collectd("streaming");
+
     _collectd.push_back(
         scollectd::add_polled_metric(scollectd::type_instance_id("memory"
                 , scollectd::per_cpu_plugin_instance
                 , "bytes", "dirty")
                 , scollectd::make_typed(scollectd::data_type::GAUGE, [this] {
-            return _dirty_memory_manager.real_dirty_memory();
+            return _dirty_memory_manager.real_dirty_memory() +
+                   _system_dirty_memory_manager.real_dirty_memory() +
+                   _streaming_dirty_memory_manager.real_dirty_memory();
     })));
 
     _collectd.push_back(
@@ -1685,7 +1717,9 @@ database::setup_collectd() {
                 , scollectd::per_cpu_plugin_instance
                 , "bytes", "virtual_dirty")
                 , scollectd::make_typed(scollectd::data_type::GAUGE, [this] {
-            return _dirty_memory_manager.virtual_dirty_memory();
+        return _dirty_memory_manager.virtual_dirty_memory() +
+               _system_dirty_memory_manager.virtual_dirty_memory() +
+               _streaming_dirty_memory_manager.virtual_dirty_memory();
     })));
 
     _collectd.push_back(
@@ -1956,13 +1990,12 @@ future<> database::parse_system_tables(distributed<service::storage_proxy>& prox
 
 future<>
 database::init_system_keyspace() {
-    bool durable = _cfg->data_file_directories().size() > 0;
-    db::system_keyspace::make(*this, durable, _cfg->volatile_system_keyspace_for_testing());
-
-    // FIXME support multiple directories
-    return io_check(touch_directory, _cfg->data_file_directories()[0] + "/" + db::system_keyspace::NAME).then([this] {
-        return populate_keyspace(_cfg->data_file_directories()[0], db::system_keyspace::NAME).then([this]() {
-            return init_commitlog();
+    return init_commitlog().then([this] {
+        bool durable = _cfg->data_file_directories().size() > 0;
+        db::system_keyspace::make(*this, durable, _cfg->volatile_system_keyspace_for_testing());
+        // FIXME support multiple directories
+        return io_check(touch_directory, _cfg->data_file_directories()[0] + "/" + db::system_keyspace::NAME).then([this] {
+            return populate_keyspace(_cfg->data_file_directories()[0], db::system_keyspace::NAME);
         });
     }).then([this] {
         auto& ks = find_keyspace(db::system_keyspace::NAME);
@@ -2382,29 +2415,33 @@ struct query_state {
     std::vector<query::partition_range>::const_iterator current_partition_range;
     std::vector<query::partition_range>::const_iterator range_end;
     mutation_reader reader;
+    uint32_t remaining_rows() const {
+        return limit - builder.row_count();
+    }
+    uint32_t remaining_partitions() const {
+        return partition_limit - builder.partition_count();
+    }
     bool done() const {
-        return !limit || !partition_limit || current_partition_range == range_end || builder.is_short_read();
+        return !remaining_rows() || !remaining_partitions() || current_partition_range == range_end || builder.is_short_read();
     }
 };
 
 future<lw_shared_ptr<query::result>>
 column_family::query(schema_ptr s, const query::read_command& cmd, query::result_request request,
                      const std::vector<query::partition_range>& partition_ranges,
-                     tracing::trace_state_ptr trace_state, query::result_memory_limiter& memory_limiter) {
+                     tracing::trace_state_ptr trace_state, query::result_memory_limiter& memory_limiter,
+                     uint64_t max_size) {
     utils::latency_counter lc;
     _stats.reads.set_latency(lc);
     auto f = request == query::result_request::only_digest
-             ? make_ready_future<query::result_memory_accounter>() : memory_limiter.new_read();
+             ? memory_limiter.new_digest_read(max_size) : memory_limiter.new_data_read(max_size);
     return f.then([this, lc, s = std::move(s), &cmd, request, &partition_ranges, trace_state = std::move(trace_state)] (query::result_memory_accounter accounter) mutable {
         auto qs_ptr = std::make_unique<query_state>(std::move(s), cmd, request, partition_ranges, std::move(accounter));
         auto& qs = *qs_ptr;
         return do_until(std::bind(&query_state::done, &qs), [this, &qs, trace_state = std::move(trace_state)] {
             auto&& range = *qs.current_partition_range++;
-            return data_query(qs.schema, as_mutation_source(trace_state), range, qs.cmd.slice, qs.limit, qs.partition_limit,
-                              qs.cmd.timestamp, qs.builder).then([&qs] (auto&& r) {
-                qs.limit -= r.live_rows;
-                qs.partition_limit -= r.partitions;
-            });
+            return data_query(qs.schema, as_mutation_source(trace_state), range, qs.cmd.slice, qs.remaining_rows(),
+                              qs.remaining_partitions(), qs.cmd.timestamp, qs.builder);
         }).then([qs_ptr = std::move(qs_ptr), &qs] {
             return make_ready_future<lw_shared_ptr<query::result>>(
                     make_lw_shared<query::result>(qs.builder.build()));
@@ -2428,9 +2465,10 @@ column_family::as_mutation_source(tracing::trace_state_ptr trace_state) const {
 }
 
 future<lw_shared_ptr<query::result>>
-database::query(schema_ptr s, const query::read_command& cmd, query::result_request request, const std::vector<query::partition_range>& ranges, tracing::trace_state_ptr trace_state) {
+database::query(schema_ptr s, const query::read_command& cmd, query::result_request request, const std::vector<query::partition_range>& ranges, tracing::trace_state_ptr trace_state,
+                uint64_t max_result_size) {
     column_family& cf = find_column_family(cmd.cf_id);
-    return cf.query(std::move(s), cmd, request, ranges, std::move(trace_state), get_result_memory_limiter()).then_wrapped([this, s = _stats] (auto f) {
+    return cf.query(std::move(s), cmd, request, ranges, std::move(trace_state), get_result_memory_limiter(), max_result_size).then_wrapped([this, s = _stats] (auto f) {
         if (f.failed()) {
             ++s->total_reads_failed;
         } else {
@@ -2676,7 +2714,7 @@ future<> dirty_memory_manager::flush_when_needed() {
     });
 }
 
-void dirty_memory_manager::start_reclaiming() {
+void dirty_memory_manager::start_reclaiming() noexcept {
     _should_flush.signal();
 }
 

database.hh

@@ -144,12 +144,16 @@ class dirty_memory_manager: public logalloc::region_group_reclaimer {
     std::unordered_map<const logalloc::region*, flush_permit> _flush_manager;
 
     future<> _waiting_flush;
-    virtual void start_reclaiming() override;
+    virtual void start_reclaiming() noexcept override;
 
     bool has_pressure() const {
         return over_soft_limit();
     }
+
+    std::vector<scollectd::registration> _collectd;
 public:
+    void setup_collectd(sstring namestr);
+
     future<> shutdown();
 
     // Limits and pressure conditions:
@@ -650,7 +654,8 @@ public:
         const query::read_command& cmd, query::result_request request,
         const std::vector<query::partition_range>& ranges,
         tracing::trace_state_ptr trace_state,
-        query::result_memory_limiter& memory_limiter);
+        query::result_memory_limiter& memory_limiter,
+        uint64_t max_result_size);
 
     future<> populate(sstring datadir);
 
@@ -1162,7 +1167,8 @@ public:
     unsigned shard_of(const dht::token& t);
     unsigned shard_of(const mutation& m);
     unsigned shard_of(const frozen_mutation& m);
-    future<lw_shared_ptr<query::result>> query(schema_ptr, const query::read_command& cmd, query::result_request request, const std::vector<query::partition_range>& ranges, tracing::trace_state_ptr trace_state);
+    future<lw_shared_ptr<query::result>> query(schema_ptr, const query::read_command& cmd, query::result_request request, const std::vector<query::partition_range>& ranges,
+                                               tracing::trace_state_ptr trace_state, uint64_t max_result_size);
     future<reconcilable_result> query_mutations(schema_ptr, const query::read_command& cmd, const query::partition_range& range,
                                                 query::result_memory_accounter&& accounter, tracing::trace_state_ptr trace_state);
     // Apply the mutation atomically.

db/config.hh

@@ -736,8 +736,9 @@ public:
     val(lsa_reclamation_step, size_t, 1, Used, "Minimum number of segments to reclaim in a single step") \
     val(prometheus_port, uint16_t, 9180, Used, "Prometheus port, set to zero to disable") \
     val(prometheus_address, sstring, "0.0.0.0", Used, "Prometheus listening address") \
+    val(prometheus_prefix, sstring, "scylla", Used, "Set the prefix of the exported Prometheus metrics. Changing this will break Scylla's dashboard compatibility, do not change unless you know what you are doing.") \
     val(abort_on_lsa_bad_alloc, bool, false, Used, "Abort when allocation in LSA region fails") \
-    val(murmur3_partitioner_ignore_msb_bits, unsigned, 4, Used, "Number of most siginificant token bits to ignore in murmur3 partitioner; increase for very large clusters") \
+    val(murmur3_partitioner_ignore_msb_bits, unsigned, 0, Used, "Number of most siginificant token bits to ignore in murmur3 partitioner; increase for very large clusters") \
     /* done! */
 
 #define _make_value_member(name, type, deflt, status, desc, ...)    \

db/schema_tables.cc

@@ -77,6 +77,15 @@ namespace schema_tables {
 
 logging::logger logger("schema_tables");
 
+struct push_back_and_return {
+    std::vector<mutation> muts;
+
+    std::vector<mutation> operator()(mutation&& m) {
+        muts.emplace_back(std::move(m));
+        return std::move(muts);
+    }
+};
+
 struct qualified_name {
     sstring keyspace_name;
     sstring table_name;
@@ -495,6 +504,14 @@ read_schema_partition_for_table(distributed<service::storage_proxy>& proxy, cons
     return query_partition_mutation(proxy.local(), std::move(schema), std::move(cmd), std::move(keyspace_key));
 }
 
+future<mutation>
+read_keyspace_mutation(distributed<service::storage_proxy>& proxy, const sstring& keyspace_name) {
+    schema_ptr s = keyspaces();
+    auto key = partition_key::from_singular(*s, keyspace_name);
+    auto cmd = make_lw_shared<query::read_command>(s->id(), s->version(), query::full_slice);
+    return query_partition_mutation(proxy.local(), std::move(s), std::move(cmd), std::move(key));
+}
+
 static semaphore the_merge_lock {1};
 
 future<> merge_lock() {
@@ -1115,19 +1132,18 @@ void add_type_to_schema_mutation(user_type type, api::timestamp_type timestamp,
     mutations.emplace_back(std::move(m));
 }
 
-std::vector<mutation> make_create_type_mutations(lw_shared_ptr<keyspace_metadata> keyspace, user_type type, api::timestamp_type timestamp)
+future<std::vector<mutation>> make_create_type_mutations(lw_shared_ptr<keyspace_metadata> keyspace, user_type type, api::timestamp_type timestamp)
 {
-    // Include the serialized keyspace in case the target node missed a CREATE KEYSPACE migration (see CASSANDRA-5631).
-    auto mutations = make_create_keyspace_mutations(keyspace, timestamp, false);
+    std::vector<mutation> mutations;
     add_type_to_schema_mutation(type, timestamp, mutations);
-    return mutations;
+
+    // Include the serialized keyspace in case the target node missed a CREATE KEYSPACE migration (see CASSANDRA-5631).
+    return read_keyspace_mutation(service::get_storage_proxy(), keyspace->name()).then(push_back_and_return{std::move(mutations)});
 }
 
-std::vector<mutation> make_drop_type_mutations(lw_shared_ptr<keyspace_metadata> keyspace, user_type type, api::timestamp_type timestamp)
+future<std::vector<mutation>> make_drop_type_mutations(lw_shared_ptr<keyspace_metadata> keyspace, user_type type, api::timestamp_type timestamp)
 {
-    // Include the serialized keyspace in case the target node missed a CREATE KEYSPACE migration (see CASSANDRA-5631).
-    auto mutations = make_create_keyspace_mutations(keyspace, timestamp, false);
-
+    std::vector<mutation> mutations;
     schema_ptr s = usertypes();
     auto pkey = partition_key::from_singular(*s, type->_keyspace);
     auto ckey = clustering_key::from_singular(*s, type->get_name_as_string());
@@ -1135,19 +1151,21 @@ std::vector<mutation> make_drop_type_mutations(lw_shared_ptr<keyspace_metadata>
     m.partition().apply_delete(*s, ckey, tombstone(timestamp, gc_clock::now()));
     mutations.emplace_back(std::move(m));
 
-    return mutations;
+    // Include the serialized keyspace in case the target node missed a CREATE KEYSPACE migration (see CASSANDRA-5631).
+    return read_keyspace_mutation(service::get_storage_proxy(), keyspace->name()).then(push_back_and_return{std::move(mutations)});
 }
 
 /*
  * Table metadata serialization/deserialization.
  */
 
-std::vector<mutation> make_create_table_mutations(lw_shared_ptr<keyspace_metadata> keyspace, schema_ptr table, api::timestamp_type timestamp)
+future<std::vector<mutation>> make_create_table_mutations(lw_shared_ptr<keyspace_metadata> keyspace, schema_ptr table, api::timestamp_type timestamp)
 {
-    // Include the serialized keyspace in case the target node missed a CREATE KEYSPACE migration (see CASSANDRA-5631).
-    auto mutations = make_create_keyspace_mutations(keyspace, timestamp, false);
+    std::vector<mutation> mutations;
     add_table_to_schema_mutation(table, timestamp, true, mutations);
-    return mutations;
+
+    // Include the serialized keyspace in case the target node missed a CREATE KEYSPACE migration (see CASSANDRA-5631).
+    return read_keyspace_mutation(service::get_storage_proxy(), keyspace->name()).then(push_back_and_return{std::move(mutations)});
 }
 
 schema_mutations make_table_mutations(schema_ptr table, api::timestamp_type timestamp, bool with_columns_and_triggers)
@@ -1250,14 +1268,13 @@ void add_table_to_schema_mutation(schema_ptr table, api::timestamp_type timestam
     make_table_mutations(table, timestamp, with_columns_and_triggers).copy_to(mutations);
 }
 
-std::vector<mutation> make_update_table_mutations(lw_shared_ptr<keyspace_metadata> keyspace,
+future<std::vector<mutation>> make_update_table_mutations(lw_shared_ptr<keyspace_metadata> keyspace,
     schema_ptr old_table,
     schema_ptr new_table,
     api::timestamp_type timestamp,
     bool from_thrift)
 {
-    // Include the serialized keyspace in case the target node missed a CREATE KEYSPACE migration (see CASSANDRA-5631).
-    auto mutations = make_create_keyspace_mutations(keyspace, timestamp, false);
+    std::vector<mutation> mutations;
 
     add_table_to_schema_mutation(new_table, timestamp, false, mutations);
 
@@ -1298,13 +1315,14 @@ std::vector<mutation> make_update_table_mutations(lw_shared_ptr<keyspace_metadat
             addTriggerToSchemaMutation(newTable, trigger, timestamp, mutation);
 
 #endif
-    return mutations;
+
+    // Include the serialized keyspace in case the target node missed a CREATE KEYSPACE migration (see CASSANDRA-5631).
+    return read_keyspace_mutation(service::get_storage_proxy(), keyspace->name()).then(push_back_and_return{std::move(mutations)});
 }
 
-std::vector<mutation> make_drop_table_mutations(lw_shared_ptr<keyspace_metadata> keyspace, schema_ptr table, api::timestamp_type timestamp)
+future<std::vector<mutation>> make_drop_table_mutations(lw_shared_ptr<keyspace_metadata> keyspace, schema_ptr table, api::timestamp_type timestamp)
 {
-    // Include the serialized keyspace in case the target node missed a CREATE KEYSPACE migration (see CASSANDRA-5631).
-    auto mutations = make_create_keyspace_mutations(keyspace, timestamp, false);
+    std::vector<mutation> mutations;
     schema_ptr s = columnfamilies();
     auto pkey = partition_key::from_singular(*s, table->ks_name());
     auto ckey = clustering_key::from_singular(*s, table->cf_name());
@@ -1324,7 +1342,9 @@ std::vector<mutation> make_drop_table_mutations(lw_shared_ptr<keyspace_metadata>
     for (String indexName : Keyspace.open(keyspace.name).getColumnFamilyStore(table.cfName).getBuiltIndexes())
         indexCells.addTombstone(indexCells.getComparator().makeCellName(indexName), ldt, timestamp);
 #endif
-    return mutations;
+
+    // Include the serialized keyspace in case the target node missed a CREATE KEYSPACE migration (see CASSANDRA-5631).
+    return read_keyspace_mutation(service::get_storage_proxy(), keyspace->name()).then(push_back_and_return{std::move(mutations)});
 }
 
 static future<schema_mutations> read_table_mutations(distributed<service::storage_proxy>& proxy, const qualified_name& table)

db/schema_tables.hh

@@ -79,6 +79,7 @@ future<std::vector<frozen_mutation>> convert_schema_to_mutations(distributed<ser
 
 future<schema_result_value_type>
 read_schema_partition_for_keyspace(distributed<service::storage_proxy>& proxy, const sstring& schema_table_name, const sstring& keyspace_name);
+future<mutation> read_keyspace_mutation(distributed<service::storage_proxy>&, const sstring& keyspace_name);
 
 future<> merge_schema(distributed<service::storage_proxy>& proxy, std::vector<mutation> mutations);
 
@@ -94,17 +95,17 @@ std::vector<mutation> make_drop_keyspace_mutations(lw_shared_ptr<keyspace_metada
 
 lw_shared_ptr<keyspace_metadata> create_keyspace_from_schema_partition(const schema_result_value_type& partition);
 
-std::vector<mutation> make_create_type_mutations(lw_shared_ptr<keyspace_metadata> keyspace, user_type type, api::timestamp_type timestamp);
+future<std::vector<mutation>> make_create_type_mutations(lw_shared_ptr<keyspace_metadata> keyspace, user_type type, api::timestamp_type timestamp);
 
 std::vector<user_type> create_types_from_schema_partition(const schema_result_value_type& result);
 
-std::vector<mutation> make_drop_type_mutations(lw_shared_ptr<keyspace_metadata> keyspace, user_type type, api::timestamp_type timestamp);
+future<std::vector<mutation>> make_drop_type_mutations(lw_shared_ptr<keyspace_metadata> keyspace, user_type type, api::timestamp_type timestamp);
 
 void add_type_to_schema_mutation(user_type type, api::timestamp_type timestamp, std::vector<mutation>& mutations);
 
-std::vector<mutation> make_create_table_mutations(lw_shared_ptr<keyspace_metadata> keyspace, schema_ptr table, api::timestamp_type timestamp);
+future<std::vector<mutation>> make_create_table_mutations(lw_shared_ptr<keyspace_metadata> keyspace, schema_ptr table, api::timestamp_type timestamp);
 
-std::vector<mutation> make_update_table_mutations(
+future<std::vector<mutation>> make_update_table_mutations(
     lw_shared_ptr<keyspace_metadata> keyspace,
     schema_ptr old_table,
     schema_ptr new_table,
@@ -117,7 +118,7 @@ future<std::map<sstring, schema_ptr>> create_tables_from_tables_partition(distri
 
 void add_table_to_schema_mutation(schema_ptr table, api::timestamp_type timestamp, bool with_columns_and_triggers, std::vector<mutation>& mutations);
 
-std::vector<mutation> make_drop_table_mutations(lw_shared_ptr<keyspace_metadata> keyspace, schema_ptr table, api::timestamp_type timestamp);
+future<std::vector<mutation>> make_drop_table_mutations(lw_shared_ptr<keyspace_metadata> keyspace, schema_ptr table, api::timestamp_type timestamp);
 
 future<schema_ptr> create_table_from_name(distributed<service::storage_proxy>& proxy, const sstring& keyspace, const sstring& table);
 

dht/i_partitioner.cc

@@ -276,15 +276,19 @@ ring_position_range_vector_sharder::ring_position_range_vector_sharder(std::vect
     next_range();
 }
 
-stdx::optional<ring_position_range_and_shard>
+stdx::optional<ring_position_range_and_shard_and_element>
 ring_position_range_vector_sharder::next(const schema& s) {
     if (!_current_sharder) {
         return stdx::nullopt;
     }
-    auto ret = _current_sharder->next(s);
-    while (!ret && _current_range != _ranges.end()) {
+    auto range_and_shard = _current_sharder->next(s);
+    while (!range_and_shard && _current_range != _ranges.end()) {
         next_range();
-        ret = _current_sharder->next(s);
+        range_and_shard = _current_sharder->next(s);
+    }
+    auto ret = stdx::optional<ring_position_range_and_shard_and_element>();
+    if (range_and_shard) {
+        ret.emplace(std::move(*range_and_shard), _current_range - _ranges.begin() - 1);
     }
     return ret;
 }

dht/i_partitioner.hh

@@ -445,13 +445,20 @@ class ring_position_range_sharder {
     nonwrapping_range<ring_position> _range;
     bool _done = false;
 public:
-    explicit ring_position_range_sharder(range<ring_position> rrp)
+    explicit ring_position_range_sharder(nonwrapping_range<ring_position> rrp)
             : ring_position_range_sharder(global_partitioner(), std::move(rrp)) {}
-    ring_position_range_sharder(const i_partitioner& partitioner, range<ring_position> rrp)
+    ring_position_range_sharder(const i_partitioner& partitioner, nonwrapping_range<ring_position> rrp)
             : _partitioner(partitioner), _range(std::move(rrp)) {}
     stdx::optional<ring_position_range_and_shard> next(const schema& s);
 };
 
+struct ring_position_range_and_shard_and_element : ring_position_range_and_shard {
+    ring_position_range_and_shard_and_element(ring_position_range_and_shard&& rpras, unsigned element)
+            : ring_position_range_and_shard(std::move(rpras)), element(element) {
+    }
+    unsigned element;
+};
+
 class ring_position_range_vector_sharder {
     using vec_type = std::vector<nonwrapping_range<ring_position>>;
     vec_type _ranges;
@@ -465,7 +472,8 @@ private:
     }
 public:
     explicit ring_position_range_vector_sharder(std::vector<nonwrapping_range<ring_position>> ranges);
-    stdx::optional<ring_position_range_and_shard> next(const schema& s);
+    // results are returned sorted by index within the vector first, then within each vector item
+    stdx::optional<ring_position_range_and_shard_and_element> next(const schema& s);
 };
 
 nonwrapping_range<ring_position> to_partition_range(nonwrapping_range<dht::token>);

dist/common/scripts/scylla_setup

@@ -79,8 +79,16 @@ verify_package() {
     fi
 }
 
+list_block_devices() {
+    if lsblk --help | grep -q -e -p; then
+        lsblk -pnr | awk '{ print $1 }'
+    else
+        ls -1 /dev/sd* /dev/hd* /dev/xvd* /dev/nvme* /dev/mapper/*  2>/dev/null|grep -v control
+    fi
+}
+
 get_unused_disks() {
-    blkid -c /dev/null|cut -f 1 -d ' '|sed s/://g|grep -v loop|while read dev
+    list_block_devices|grep -v loop|while read dev
     do
         count_raw=$(grep $dev /proc/mounts|wc -l)
         count_pvs=0
@@ -266,14 +274,9 @@ if [ $ENABLE_SERVICE -eq 1 ]; then
     fi
 fi
 
-if [ ! -f /etc/scylla.d/housekeeping.uuid ]; then
-   uuidgen > /etc/scylla.d/housekeeping.uuid
-fi
-
-UUID=`cat /etc/scylla.d/housekeeping.uuid` || true
 CUR_VERSION=`scylla --version` || true
 if [ "$CUR_VERSION" != "" ] && [ "$UUID" != "" ]; then
-    NEW_VERSION=`/usr/lib/scylla/scylla-housekeeping --uuid $UUID version --version $CUR_VERSION --mode i` || true
+    NEW_VERSION=`sudo -u scylla /usr/lib/scylla/scylla-housekeeping --uuid-file /var/lib/scylla-housekeeping/housekeeping.uuid version --version $CUR_VERSION --mode i` || true
     if [ "$NEW_VERSION" != "" ]; then
        echo $NEW_VERSION
     fi
@@ -316,7 +319,7 @@ if [ $INTERACTIVE -eq 1 ]; then
             echo
             RAID_SETUP=0
         else
-            echo "Please select disks from the following list: $DEVS"
+            echo "Please select unmounted disks from the following list: $DEVS"
         fi
         while [ "$DEVS" != "" ]; do
             echo "type 'done' to finish selection. selected: $DISKS"

dist/common/systemd/scylla-housekeeping.service

@@ -6,7 +6,7 @@ After=network.target
 Type=simple
 User=scylla
 Group=scylla
-ExecStart=/usr/lib/scylla/scylla-housekeeping --uuid-file /etc/scylla.d/housekeeping.uuid -q -c /etc/scylla.d/housekeeping.cfg version --mode d
+ExecStart=/usr/lib/scylla/scylla-housekeeping --uuid-file /var/lib/scylla-housekeeping/housekeeping.uuid -q -c /etc/scylla.d/housekeeping.cfg version --mode d
 
 [Install]
 WantedBy=multi-user.target

dist/docker/redhat/Dockerfile

@@ -7,7 +7,7 @@ ENV container docker
 VOLUME [ "/sys/fs/cgroup" ]
 
 #install scylla
-RUN curl http://downloads.scylladb.com/rpm/unstable/centos/master/latest/scylla.repo -o /etc/yum.repos.d/scylla.repo
+RUN curl http://downloads.scylladb.com/rpm/centos/scylla-1.6.repo -o /etc/yum.repos.d/scylla.repo
 RUN yum -y install epel-release
 RUN yum -y clean expire-cache
 RUN yum -y update

dist/redhat/centos_dep/build_dependency.sh

@@ -28,10 +28,6 @@ if [ ! -f boost-1.58.0-11.fc23.src.rpm ]; then
     wget -nv https://kojipkgs.fedoraproject.org//packages/boost/1.58.0/11.fc23/src/boost-1.58.0-11.fc23.src.rpm
 fi
 
-if [ ! -f ninja-build-1.6.0-2.fc23.src.rpm ]; then
-    wget -nv https://kojipkgs.fedoraproject.org//packages/ninja-build/1.6.0/2.fc23/src/ninja-build-1.6.0-2.fc23.src.rpm
-fi
-
 if [ ! -f ragel-6.8-5.fc23.src.rpm ]; then
    wget -nv https://kojipkgs.fedoraproject.org//packages/ragel/6.8/5.fc23/src/ragel-6.8-5.fc23.src.rpm
 fi
@@ -94,13 +90,6 @@ if [ ! -f $RPMBUILD/RPMS/x86_64/scylla-boost-1.58.0-11.el7*.x86_64.rpm ]; then
 fi
 do_install scylla-boost*
 
-if [ ! -f $RPMBUILD/RPMS/x86_64/scylla-ninja-build-1.6.0-2.el7*.x86_64.rpm ]; then
-   rpm --define "_topdir $RPMBUILD" -ivh build/srpms/ninja-build-1.6.0-2.fc23.src.rpm
-   patch $RPMBUILD/SPECS/ninja-build.spec < dist/redhat/centos_dep/ninja-build.diff
-   rpmbuild --define "_topdir $RPMBUILD" -ba $RPMBUILD/SPECS/ninja-build.spec
-fi
-do_install scylla-ninja-build-1.6.0-2.el7*.x86_64.rpm
-
 if [ ! -f $RPMBUILD/RPMS/x86_64/scylla-ragel-6.8-5.el7*.x86_64.rpm ]; then
     rpm --define "_topdir $RPMBUILD" -ivh build/srpms/ragel-6.8-5.fc23.src.rpm
     patch $RPMBUILD/SPECS/ragel.spec < dist/redhat/centos_dep/ragel.diff

dist/redhat/centos_dep/ninja-build.diff

@@ -1,56 +0,0 @@
---- ninja-build.spec.orig	2016-01-20 14:41:16.892802134 +0000
-+++ ninja-build.spec	2016-01-20 14:44:42.453227192 +0000
-@@ -1,19 +1,18 @@
--Name:           ninja-build
-+Name:           scylla-ninja-build
- Version:        1.6.0
- Release:        2%{?dist}
- Summary:        A small build system with a focus on speed
- License:        ASL 2.0
- URL:            http://martine.github.com/ninja/
- Source0:        https://github.com/martine/ninja/archive/v%{version}.tar.gz#/ninja-%{version}.tar.gz
--Source1:        ninja.vim
- # Rename mentions of the executable name to be ninja-build.
- Patch1000:      ninja-1.6.0-binary-rename.patch
-+Requires:	scylla-env
- BuildRequires:  asciidoc
- BuildRequires:  gtest-devel
- BuildRequires:  python2-devel
--BuildRequires:  re2c >= 0.11.3
--Requires:       emacs-filesystem
--Requires:       vim-filesystem
-+#BuildRequires:  scylla-re2c >= 0.11.3
-+%define _prefix /opt/scylladb
- 
- %description
- Ninja is a small build system with a focus on speed. It differs from other
-@@ -32,15 +31,8 @@
- ./ninja -v ninja_test
- 
- %install
--# TODO: Install ninja_syntax.py?
--mkdir -p %{buildroot}/{%{_bindir},%{_datadir}/bash-completion/completions,%{_datadir}/emacs/site-lisp,%{_datadir}/vim/vimfiles/syntax,%{_datadir}/vim/vimfiles/ftdetect,%{_datadir}/zsh/site-functions}
--
-+mkdir -p %{buildroot}/opt/scylladb/bin
- install -pm755 ninja %{buildroot}%{_bindir}/ninja-build
--install -pm644 misc/bash-completion %{buildroot}%{_datadir}/bash-completion/completions/ninja-bash-completion
--install -pm644 misc/ninja-mode.el %{buildroot}%{_datadir}/emacs/site-lisp/ninja-mode.el
--install -pm644 misc/ninja.vim %{buildroot}%{_datadir}/vim/vimfiles/syntax/ninja.vim
--install -pm644 %{SOURCE1} %{buildroot}%{_datadir}/vim/vimfiles/ftdetect/ninja.vim
--install -pm644 misc/zsh-completion %{buildroot}%{_datadir}/zsh/site-functions/_ninja
- 
- %check
- # workaround possible too low default limits
-@@ -50,12 +42,6 @@
- %files
- %doc COPYING HACKING.md README doc/manual.html
- %{_bindir}/ninja-build
--%{_datadir}/bash-completion/completions/ninja-bash-completion
--%{_datadir}/emacs/site-lisp/ninja-mode.el
--%{_datadir}/vim/vimfiles/syntax/ninja.vim
--%{_datadir}/vim/vimfiles/ftdetect/ninja.vim
--# zsh does not have a -filesystem package
--%{_datadir}/zsh/
- 
- %changelog
- * Mon Nov 16 2015 Ben Boeckel <mathstuf@gmail.com> - 1.6.0-2

dist/redhat/scylla.spec.in

@@ -27,10 +27,10 @@ Group:          Applications/Databases
 Summary:        The Scylla database server
 License:        AGPLv3
 URL:            http://www.scylladb.com/
-BuildRequires:  libaio-devel libstdc++-devel cryptopp-devel hwloc-devel numactl-devel libpciaccess-devel libxml2-devel zlib-devel thrift-devel yaml-cpp-devel lz4-devel snappy-devel jsoncpp-devel systemd-devel xz-devel pcre-devel elfutils-libelf-devel bzip2-devel keyutils-libs-devel xfsprogs-devel make gnutls-devel systemd-devel lksctp-tools-devel protobuf-devel protobuf-compiler libunwind-devel systemtap-sdt-devel
-%{?fedora:BuildRequires: boost-devel ninja-build ragel antlr3-tool antlr3-C++-devel python3 gcc-c++ libasan libubsan python3-pyparsing dnf-yum}
-%{?rhel:BuildRequires: scylla-libstdc++-static scylla-boost-devel scylla-boost-static scylla-ninja-build scylla-ragel scylla-antlr3-tool scylla-antlr3-C++-devel python34 scylla-gcc-c++ >= 5.1.1, python34-pyparsing}
-Requires:       scylla-conf systemd-libs hwloc collectd PyYAML python-urwid pciutils pyparsing python-requests curl util-linux
+BuildRequires:  libaio-devel libstdc++-devel cryptopp-devel hwloc-devel numactl-devel libpciaccess-devel libxml2-devel zlib-devel thrift-devel yaml-cpp-devel lz4-devel snappy-devel jsoncpp-devel systemd-devel xz-devel pcre-devel elfutils-libelf-devel bzip2-devel keyutils-libs-devel xfsprogs-devel make gnutls-devel systemd-devel lksctp-tools-devel protobuf-devel protobuf-compiler libunwind-devel systemtap-sdt-devel ninja-build
+%{?fedora:BuildRequires: boost-devel ragel antlr3-tool antlr3-C++-devel python3 gcc-c++ libasan libubsan python3-pyparsing dnf-yum}
+%{?rhel:BuildRequires: scylla-libstdc++-static scylla-boost-devel scylla-boost-static scylla-ragel scylla-antlr3-tool scylla-antlr3-C++-devel python34 scylla-gcc-c++ >= 5.1.1, python34-pyparsing}
+Requires:       scylla-conf systemd-libs hwloc collectd PyYAML python-urwid pciutils pyparsing python-requests curl util-linux python-setuptools pciutils
 %{?rhel:Requires: python34 python34-PyYAML}
 Conflicts:      abrt
 
@@ -88,7 +88,7 @@ install -m755 dist/common/bin/scyllatop $RPM_BUILD_ROOT%{_bindir}
 install -m755 scylla-blocktune $RPM_BUILD_ROOT%{_prefix}/lib/scylla/
 install -m755 scylla-housekeeping $RPM_BUILD_ROOT%{_prefix}/lib/scylla/
 if @@HOUSEKEEPING_CONF@@; then
-    install -m644 conf/housekeeping.cfg $RPM_BUILD_ROOT%{_sysconfdir}/scylla/
+    install -m644 conf/housekeeping.cfg $RPM_BUILD_ROOT%{_sysconfdir}/scylla.d/
 fi
 install -d -m755 $RPM_BUILD_ROOT%{_docdir}/scylla
 install -m644 README.md $RPM_BUILD_ROOT%{_docdir}/scylla/
@@ -101,6 +101,7 @@ install -d -m755 $RPM_BUILD_ROOT%{_sharedstatedir}/scylla/
 install -d -m755 $RPM_BUILD_ROOT%{_sharedstatedir}/scylla/data
 install -d -m755 $RPM_BUILD_ROOT%{_sharedstatedir}/scylla/commitlog
 install -d -m755 $RPM_BUILD_ROOT%{_sharedstatedir}/scylla/coredump
+install -d -m755 $RPM_BUILD_ROOT%{_sharedstatedir}/scylla-housekeeping
 install -d -m755 $RPM_BUILD_ROOT%{_prefix}/lib/scylla/swagger-ui
 cp -r swagger-ui/dist $RPM_BUILD_ROOT%{_prefix}/lib/scylla/swagger-ui
 install -d -m755 $RPM_BUILD_ROOT%{_prefix}/lib/scylla/api
@@ -110,8 +111,8 @@ cp -r scylla-housekeeping $RPM_BUILD_ROOT%{_prefix}/lib/scylla/scylla-housekeepi
 cp -P dist/common/sbin/*  $RPM_BUILD_ROOT%{_sbindir}/
 
 %pre server
-/usr/sbin/groupadd scylla 2> /dev/null || :
-/usr/sbin/useradd -g scylla -s /sbin/nologin -r -d %{_sharedstatedir}/scylla scylla 2> /dev/null || :
+getent group scylla || /usr/sbin/groupadd scylla 2> /dev/null || :
+getent passwd scylla || /usr/sbin/useradd -g scylla -s /sbin/nologin -r -d %{_sharedstatedir}/scylla scylla 2> /dev/null || :
 
 %post server
 # Upgrade coredump settings
@@ -193,6 +194,7 @@ rm -rf $RPM_BUILD_ROOT
 %attr(0755,scylla,scylla) %dir %{_sharedstatedir}/scylla/data
 %attr(0755,scylla,scylla) %dir %{_sharedstatedir}/scylla/commitlog
 %attr(0755,scylla,scylla) %dir %{_sharedstatedir}/scylla/coredump
+%attr(0755,scylla,scylla) %dir %{_sharedstatedir}/scylla-housekeeping
 
 %package conf
 Group:          Applications/Databases
@@ -216,7 +218,7 @@ mv /tmp/scylla.yaml /etc/scylla/scylla.yaml
 %config(noreplace) %{_sysconfdir}/scylla/scylla.yaml
 %config(noreplace) %{_sysconfdir}/scylla/cassandra-rackdc.properties
 %if %is_housekeeping_conf
-%config(noreplace) %{_sysconfdir}/scylla/housekeeping.cfg
+%config(noreplace) %{_sysconfdir}/scylla.d/housekeeping.cfg
 %endif
 
 

dist/ubuntu/build_deb.sh

@@ -51,6 +51,9 @@ fi
 if [ ! -f /usr/bin/wget ]; then
     sudo apt-get -y install wget
 fi
+if [ ! -f /usr/bin/lsb_release ]; then
+    sudo apt-get -y install lsb-release
+fi
 
 DISTRIBUTION=`lsb_release -i|awk '{print $3}'`
 CODENAME=`lsb_release -c|awk '{print $2}'`

dist/ubuntu/control.in

@@ -16,7 +16,7 @@ Conflicts: scylla-server (<< 1.1)
 
 Package: scylla-server
 Architecture: amd64
-Depends: ${shlibs:Depends}, ${misc:Depends}, adduser, hwloc-nox, collectd, scylla-conf, python-yaml, python-urwid, python-requests, curl, util-linux, realpath, python3-yaml, python3, uuid-runtime, @@DEPENDS@@
+Depends: ${shlibs:Depends}, ${misc:Depends}, adduser, hwloc-nox, collectd, scylla-conf, python-yaml, python-urwid, python-requests, curl, util-linux, realpath, python3-yaml, python3, uuid-runtime, pciutils, @@DEPENDS@@
 Description: Scylla database server binaries 
  Scylla is a highly scalable, eventually consistent, distributed,
  partitioned row DB.

dist/ubuntu/debian/scylla-server.dirs

@@ -4,3 +4,4 @@ var/lib/scylla
 var/lib/scylla/data
 var/lib/scylla/commitlog
 var/lib/scylla/coredump
+var/lib/scylla-housekeeping

dist/ubuntu/debian/scylla-server.postinst

@@ -10,6 +10,7 @@ if [ "$1" = configure ]; then
             --disabled-password \
             --group scylla
     chown -R scylla:scylla /var/lib/scylla
+    chown -R scylla:scylla /var/lib/scylla-housekeeping
 fi
 
 ln -sfT /etc/scylla /var/lib/scylla/conf

dist/ubuntu/debian/scylla-server.scylla-housekeeping.upstart

@@ -23,13 +23,16 @@ description "A timer job file for running scylla-housekeeping"
 start on started scylla-server
 stop on stopping scylla-server
 
+setuid scylla
+setgid scylla
+
 script
  # make sure scylla is up before checking for the version
   sleep 5
-  /usr/lib/scylla/scylla-housekeeping --uuid-file /etc/scylla.d/housekeeping.uuid -c /etc/scylla.d/housekeeping.cfg  -q version --mode r || true
+  /usr/lib/scylla/scylla-housekeeping --uuid-file /var/lib/scylla-housekeeping/housekeeping.uuid -c /etc/scylla.d/housekeeping.cfg  -q version --mode r || true
   while [ 1 ]
   do
     sleep 1d
-    /usr/lib/scylla/scylla-housekeeping --uuid-file /etc/scylla.d/housekeeping.uuid -c /etc/scylla.d/housekeeping.cfg  -q version --mode d || true
+    /usr/lib/scylla/scylla-housekeeping --uuid-file /var/lib/scylla-housekeeping/housekeeping.uuid -c /etc/scylla.d/housekeeping.cfg  -q version --mode d || true
   done
 end script

dist/ubuntu/dep/build_dependency.sh

@@ -77,10 +77,11 @@ fi
 
 if [ "$DISTRIBUTION" = "Debian" ] && [ "$VERSION_ID" = "8" ]; then
     if [ ! -f build/gcc-5_*.deb ]; then
-        sudo cp dist/ubuntu/dep/debian-stretch-source.list /etc/apt/sources.list.d/
-        sudo apt-get update
         cd build
-        apt-get source gcc-5/stretch=5.4.1-2
+        wget https://launchpad.net/debian/+archive/primary/+files/gcc-5_5.4.1-5.dsc
+        wget https://launchpad.net/debian/+archive/primary/+files/gcc-5_5.4.1.orig.tar.gz
+        wget https://launchpad.net/debian/+archive/primary/+files/gcc-5_5.4.1-5.diff.gz
+        dpkg-source -x gcc-5_5.4.1-5.dsc
         cd gcc-5-5.4.1
         # resolve build time dependencies manually, since mk-build-deps doesn't works for gcc package
         sudo apt-get install -y g++-multilib libc6-dev-i386 lib32gcc1 libc6-dev-x32 libx32gcc1 libc6-dbg m4 libtool autoconf2.64 autogen gawk zlib1g-dev systemtap-sdt-dev gperf bison flex gdb texinfo locales sharutils libantlr-java libffi-dev gnat-4.9 libisl-dev libmpc-dev libmpfr-dev libgmp-dev dejagnu realpath chrpath quilt doxygen graphviz ghostscript texlive-latex-base xsltproc libxml2-utils docbook-xsl-ns

dist/ubuntu/dep/debian-gcc-5-jessie.diff

@@ -1,6 +1,5 @@
-diff -Nur debian/rules.conf /home/syuu/gcc-5-5.4.1/debian/rules.conf
---- debian/rules.conf	2016-10-14 04:54:21.000000000 +0000
-+++ /home/syuu/gcc-5-5.4.1/debian/rules.conf	2016-10-12 17:28:54.138711378 +0000
+--- debian/rules.conf	2017-02-24 19:02:52.000000000 +0000
++++ /home/syuu/gcc-5.5/gcc-5-5.4.1/debian/rules.conf	2017-02-24 18:13:59.000000000 +0000
 @@ -206,7 +206,7 @@
    ifneq (,$(filter $(distrelease),vivid))
      BINUTILSBDV = 2.25-3~
@@ -10,14 +9,16 @@ diff -Nur debian/rules.conf /home/syuu/gcc-5-5.4.1/debian/rules.conf
    else ifneq (,$(filter $(distrelease),sid stretch xenial))
      BINUTILSBDV = 2.26.1
    endif
-@@ -387,9 +387,9 @@
+@@ -386,10 +386,10 @@
+   MPFR_BUILD_DEP = libmpfr-dev (>= 3.0.0-9~),
  endif
  
- ISL_BUILD_DEP = libisl-dev,
--ifneq (,$(filter $(distrelease),jessie sid experimental))
+-ISL_BUILD_DEP = libisl-dev,
+-ifneq (,$(filter $(distrelease),jessie stretch sid experimental))
 -  ISL_BUILD_DEP = libisl-dev (>= 0.14),
 -endif
-+#ifneq (,$(filter $(distrelease),jessie sid experimental))
++#ISL_BUILD_DEP = libisl-dev,
++#ifneq (,$(filter $(distrelease),jessie stretch sid experimental))
 +#  ISL_BUILD_DEP = libisl-dev (>= 0.14),
 +#endif
  
@@ -37,9 +38,8 @@ diff -Nur debian/rules.conf /home/syuu/gcc-5-5.4.1/debian/rules.conf
  ifneq ($(DEB_CROSS),yes)
  # all archs for which to create b-d's
  any_archs = alpha amd64 armel armhf arm64 i386 mips mipsel mips64 mips64el powerpc ppc64 ppc64el m68k sh4 sparc64 s390x x32
-diff -Nur debian/rules.defs /home/syuu/gcc-5-5.4.1/debian/rules.defs
---- debian/rules.defs	2016-10-14 04:54:21.000000000 +0000
-+++ /home/syuu/gcc-5-5.4.1/debian/rules.defs	2016-10-13 10:18:51.647631508 +0000
+--- debian/rules.defs	2017-02-24 19:02:52.000000000 +0000
++++ /home/syuu/gcc-5.5/gcc-5-5.4.1/debian/rules.defs	2017-02-24 18:13:59.000000000 +0000
 @@ -412,7 +412,7 @@
  # gcc versions (fixincludes, libgcj-common) ...
  #with_common_pkgs := yes

dist/ubuntu/dep/debian-stretch-source.list

@@ -1,2 +0,0 @@
-deb-src http://httpredir.debian.org/debian stretch main
-deb-src http://httpredir.debian.org/debian stretch-updates main

frozen_mutation.cc

@@ -94,7 +94,7 @@ frozen_mutation::frozen_mutation(const mutation& m)
 {
     mutation_partition_serializer part_ser(*m.schema(), m.partition());
 
-    ser::writer_of_mutation wom(_bytes);
+    ser::writer_of_mutation<bytes_ostream> wom(_bytes);
     std::move(wom).write_table_id(m.schema()->id())
                   .write_schema_version(m.schema()->version())
                   .write_key(m.key())
@@ -157,7 +157,7 @@ stop_iteration streamed_mutation_freezer::consume(range_tombstone&& rt) {
 
 frozen_mutation streamed_mutation_freezer::consume_end_of_stream() {
     bytes_ostream out;
-    ser::writer_of_mutation wom(out);
+    ser::writer_of_mutation<bytes_ostream> wom(out);
     std::move(wom).write_table_id(_schema.id())
                   .write_schema_version(_schema.version())
                   .write_key(_key)
@@ -192,7 +192,7 @@ class fragmenting_mutation_freezer {
 private:
     future<> flush() {
         bytes_ostream out;
-        ser::writer_of_mutation wom(out);
+        ser::writer_of_mutation<bytes_ostream> wom(out);
         std::move(wom).write_table_id(_schema.id())
                       .write_schema_version(_schema.version())
                       .write_key(_key)

frozen_schema.cc

@@ -34,7 +34,7 @@ frozen_schema::frozen_schema(const schema_ptr& s)
     : _data([&s] {
         schema_mutations sm = db::schema_tables::make_table_mutations(s, api::new_timestamp());
         bytes_ostream out;
-        ser::writer_of_schema wr(out);
+        ser::writer_of_schema<bytes_ostream> wr(out);
         std::move(wr).write_version(s->version())
                      .write_mutations(sm)
                      .end_schema();

gc_clock.hh

@@ -50,6 +50,12 @@ public:
     // for real time waits.
 };
 
+// Returns a time point which is earlier from t by d, or minimum time point if it cannot be represented.
+template<typename Clock, typename Duration, typename Rep, typename Period>
+inline
+auto saturating_subtract(std::chrono::time_point<Clock, Duration> t, std::chrono::duration<Rep, Period> d) -> decltype(t) {
+    return std::max(t, decltype(t)::min() + d) - d;
+}
 
 using expiry_opt = std::experimental::optional<gc_clock::time_point>;
 using ttl_opt = std::experimental::optional<gc_clock::duration>;

idl-compiler.py

@@ -303,10 +303,11 @@ def handle_visitors_state(info, hout, clases = []):
     name = "__".join(clases) if clases else cls["name"]
     frame = "empty_frame" if "final" in cls else "frame"
     fprintln(hout, Template("""
+template<typename Output>
 struct state_of_$name {
-    $frame f;""").substitute({'name': name, 'frame': frame }))
+    $frame<Output> f;""").substitute({'name': name, 'frame': frame }))
     if clases:
-        local_state = "state_of_" + "__".join(clases[:-1])
+        local_state = "state_of_" + "__".join(clases[:-1]) + '<Output>'
         fprintln(hout, Template("    $name _parent;").substitute({'name':  local_state}))
         if "final" in cls:
             fprintln(hout, Template("    state_of_$name($state parent) : _parent(parent) {}").substitute({'name':  name, 'state' : local_state}))
@@ -327,18 +328,19 @@ def add_vector_node(hout, cls, members, base_state, current_node, ind):
     current = members[ind]
     typ = current["type"][1]
     fprintln(hout, Template("""
+template<typename Output>
 struct $node_name {
-    bytes_ostream& _out;
-    state_of_$base_state _state;
-    place_holder _size;
+    Outout& _out;
+    state_of_$base_state<Output> _state;
+    place_holder<Output> _size;
     size_type _count = 0;
-    $node_name(bytes_ostream& out, state_of_$base_state state)
+    $node_name(Output& out, state_of_$base_state<Output> state)
         : _out(out)
         , _state(state)
         , _size(start_place_holder(out))
     {
     }
-    $next_state end_$name() {
+    $next_state<Output> end_$name() {
         _size.set(_out, _count);
     }""").substitute({'node_name': '', 'name': current["name"] }))
 
@@ -363,7 +365,7 @@ def optional_add_methods(typ):
     }""")).substitute({'type' : added_type})
     if is_local_type(typ):
         res = res + Template(reindent(4, """
-    writer_of_$type write() {
+    writer_of_$type<Output> write() {
         serialize(_out, true);
         return {_out};
     }""")).substitute({'type' : param_type(typ)})
@@ -381,7 +383,7 @@ def vector_add_method(current, base_state):
   }""").substitute({'type': param_type(typ[1][0]), 'name': current["name"]})
     else:
         res = res + Template("""
-  writer_of_$type add() {
+  writer_of_$type<Output> add() {
         _count++;
         return {_out};
   }""").substitute({'type': flat_type(typ[1][0]), 'name': current["name"]})
@@ -391,7 +393,7 @@ def vector_add_method(current, base_state):
         _count++;
   }""").substitute({'type': param_view_type(typ[1][0])})
     return res + Template("""
-  after_${basestate}__$name end_$name() && {
+  after_${basestate}__$name<Output> end_$name() && {
         _size.set(_out, _count);
         return { _out, std::move(_state) };
   }
@@ -418,7 +420,7 @@ def add_param_writer_basic_type(name, base_state, typ, var_type = "", var_index
         typ = 'const ' + typ + '&'
 
     return Template(reindent(4, """
-        after_${base_state}__$name write_$name$var_type($typ t) && {
+        after_${base_state}__$name<Output> write_$name$var_type($typ t) && {
             $set_varient_index
             serialize(_out, t);
             $set_command
@@ -431,7 +433,7 @@ def add_param_writer_object(name, base_state, typ, var_type = "", var_index = No
         var_index = "uint32_t(" + str(var_index) +")"
     set_varient_index = "serialize(_out, " + var_index +");\n" if var_index is not None else ""
     ret = Template(reindent(4,"""
-        ${base_state}__${name}$var_type1 start_${name}$var_type() && {
+        ${base_state}__${name}$var_type1<Output> start_${name}$var_type() && {
             $set_varient_index
             return { _out, std::move(_state) };
         }
@@ -443,9 +445,9 @@ def add_param_writer_object(name, base_state, typ, var_type = "", var_index = No
         return_command = "{ _out, std::move(_state._parent) }" if var_type is not "" and not root_node else "{ _out, std::move(_state) }"
         ret += Template(reindent(4, """
             template<typename Serializer>
-            after_${base_state}__${name} ${name}$var_type(Serializer&& f) && {
+            after_${base_state}__${name}<Output> ${name}$var_type(Serializer&& f) && {
                 $set_varient_index
-                f(writer_of_$typ(_out));
+                f(writer_of_$typ<Output>(_out));
                 $set_command
                 return $return_command;
             }""")).substitute(locals())
@@ -458,7 +460,7 @@ def add_param_write(current, base_state, vector = False, root_node = False):
         res = res + add_param_writer_basic_type(current["name"], base_state, typ)
     elif is_optional(typ):
             res = res +  Template(reindent(4, """
-    after_${basestate}__$name skip_$name() && {
+    after_${basestate}__$name<Output> skip_$name() && {
         serialize(_out, false);
         return { _out, std::move(_state) };
     }""")).substitute({'type': param_type(typ), 'name': current["name"], 'basestate' : base_state})
@@ -472,11 +474,11 @@ def add_param_write(current, base_state, vector = False, root_node = False):
         set_size = "_size.set(_out, 0);" if vector else "serialize(_out, size_type(0));"
 
         res = res +  Template("""
-    ${basestate}__$name start_$name() && {
+    ${basestate}__$name<Output> start_$name() && {
         return { _out, std::move(_state) };
     }
 
-    after_${basestate}__$name skip_$name() && {
+    after_${basestate}__$name<Output> skip_$name() && {
         $set
         return { _out, std::move(_state) };
     }
@@ -506,7 +508,7 @@ def get_return_struct(variant_node, clases):
 
 def add_variant_end_method(base_state, name, clases):
 
-    return_struct = "after_" + base_state
+    return_struct = "after_" + base_state + '<Output>'
     return Template("""
     $return_struct  end_$name() && {
         _state.f.end(_out);
@@ -520,7 +522,7 @@ def add_end_method(parents, name, variant_node = False, return_value = True):
         return add_variant_end_method(parents, name, return_value)
     base_state = parents + "__" + name
     if return_value:
-        return_struct =  "after_" + base_state
+        return_struct =  "after_" + base_state + '<Output>'
         return Template("""
     $return_struct  end_$name() && {
         _state.f.end(_out);
@@ -534,7 +536,7 @@ def add_end_method(parents, name, variant_node = False, return_value = True):
 """).substitute({'name': name, 'basestate':base_state})
 
 def add_vector_placeholder():
-    return """    place_holder _size;
+    return """    place_holder<Output> _size;
     size_type _count = 0;"""
 
 def add_node(hout, name, member, base_state, prefix, parents, fun, is_type_vector = False, is_type_final = False):
@@ -554,21 +556,22 @@ def add_node(hout, name, member, base_state, prefix, parents, fun, is_type_vecto
         else:
             state_init = ""
     if prefix == "writer_of_":
-        constructor = Template("""$name(bytes_ostream& out)
+        constructor = Template("""$name(Output& out)
             : _out(out)
             , _state{start_frame(out)}${vector_init}
             {}""").substitute({'name': struct_name, 'vector_init' : vector_init})
     elif state_init != "":
-        constructor = Template("""$name(bytes_ostream& out, state_of_$state state)
+        constructor = Template("""$name(Output& out, state_of_$state<Output> state)
             : _out(out)
             , $state_init${vector_init}
             {}""").substitute({'name': struct_name, 'vector_init' : vector_init, 'state' : parents, 'state_init' : state_init})
     else:
         constructor = ""
     fprintln(hout, Template("""
+template<typename Output>
 struct $name {
-    bytes_ostream& _out;
-    state_of_$state _state;
+    Output& _out;
+    state_of_$state<Output> _state;
     ${vector_placeholder}
     ${constructor}
     $fun
@@ -588,8 +591,9 @@ def add_optional_node(hout, typ):
         return
     optional_nodes.add(full_type)
     fprintln(hout, Template(reindent(0,"""
+template<typename Output>
 struct writer_of_$type {
-    bytes_ostream& _out;
+    Output& _out;
     $add_method
 };""")).substitute({'type': full_type, 'add_method': optional_add_methods(typ[1][0])}))
 
@@ -604,7 +608,7 @@ def add_variant_nodes(hout, member, param, base_state, parents, classes):
             new_member = {"type": typ, "name" : "variant"}
             return_struct = "after_" + par
             end_method = Template("""
-    $return_struct  end_variant() && {
+    $return_struct<Output>  end_variant() && {
         _state.f.end(_out);
         return { _out, std::move(_state._parent) };
     }

idl/reconcilable_result.idl.hh

@@ -27,5 +27,5 @@ class partition {
 class reconcilable_result {
     uint32_t row_count();
     std::vector<partition> partitions();
-    query::short_read is_short_read() [[version 1.7]] = query::short_read::no;
+    query::short_read is_short_read() [[version 1.6]] = query::short_read::no;
 };

idl/result.idl.hh

@@ -29,7 +29,7 @@ class result {
     bytes buf();
     std::experimental::optional<query::result_digest> digest();
     api::timestamp_type last_modified() [ [version 1.2] ] = api::missing_timestamp;
-    query::short_read is_short_read() [[version 1.7]] = query::short_read::no;
+    query::short_read is_short_read() [[version 1.6]] = query::short_read::no;
 };
 
 }

main.cc

@@ -426,6 +426,8 @@ int main(int ac, char** av) {
             if (opts.count("developer-mode")) {
                 smp::invoke_on_all([] { engine().set_strict_dma(false); }).get();
             }
+            supervisor_notify("creating tracing");
+            tracing::tracing::create_tracing("trace_keyspace_helper").get();
             supervisor_notify("creating snitch");
             i_endpoint_snitch::create_snitch(cfg->endpoint_snitch()).get();
             // #293 - do not stop anything
@@ -580,7 +582,12 @@ int main(int ac, char** av) {
             // we will have races between the compaction and loading processes
             // We also want to trigger regular compaction on boot.
             db.invoke_on_all([&proxy] (database& db) {
-                for (auto& x : db.get_column_families()) {
+                // avoid excessive disk usage by making sure all shards reshard
+                // shared sstables in the same order. That's done by choosing
+                // column families in UUID order, and each individual column
+                // family will reshard shared sstables in generation order.
+                auto cfs = boost::copy_range<std::map<utils::UUID, lw_shared_ptr<column_family>>>(db.get_column_families());
+                for (auto& x : cfs) {
                     column_family& cf = *(x.second);
                     // We start the rewrite, but do not wait for it.
                     cf.start_rewrite();
@@ -632,7 +639,7 @@ int main(int ac, char** av) {
             gms::get_local_gossiper().wait_for_gossip_to_settle().get();
             api::set_server_gossip_settle(ctx).get();
             supervisor_notify("starting tracing");
-            tracing::tracing::create_tracing("trace_keyspace_helper").get();
+            tracing::tracing::start_tracing().get();
             supervisor_notify("starting native transport");
             service::get_local_storage_service().start_native_transport().get();
             if (start_thrift) {
@@ -659,6 +666,7 @@ int main(int ac, char** av) {
             uint16_t pport = cfg->prometheus_port();
             if (pport) {
                 pctx.metric_help = "Scylla server statistics";
+                pctx.prefix = cfg->prometheus_prefix();
                 prometheus_server.start().get();
                 prometheus::start(prometheus_server, pctx);
                 prometheus_server.listen(ipv4_addr{prom_addr.addresses[0].in.s_addr, pport}).get();

memtable.cc

@@ -65,17 +65,15 @@ future<> memtable::clear_gently() noexcept {
         auto t = std::make_unique<seastar::thread>(attr, [this] {
             auto& alloc = allocator();
 
-            // entries can no longer be moved after unlink_leftmost_without_rebalance()
-            // so need to disable compaction.
-            logalloc::reclaim_lock rl(*this);
-
             auto p = std::move(partitions);
             while (!p.empty()) {
                 auto batch_size = std::min<size_t>(p.size(), 32);
                 auto dirty_before = dirty_size();
                 with_allocator(alloc, [&] () noexcept {
                     while (batch_size--) {
-                        alloc.destroy(p.unlink_leftmost_without_rebalance());
+                        p.erase_and_dispose(p.begin(), [&] (auto e) {
+                            alloc.destroy(e);
+                        });
                     }
                 });
                 remove_flushed_memory(dirty_before - dirty_size());
@@ -205,19 +203,23 @@ protected:
         , _range(&range)
     { }
 
-    memtable_entry* fetch_next_entry() {
+    memtable_entry* fetch_entry() {
         update_iterators();
         if (_i == _end) {
             return nullptr;
         } else {
             memtable_entry& e = *_i;
-            ++_i;
-            _last = e.key();
             _memtable->upgrade_entry(e);
             return &e;
         }
     }
 
+    void advance() {
+        memtable_entry& e = *_i;
+        _last = e.key();
+        ++_i;
+    }
+
     logalloc::allocating_section& read_section() {
         return _memtable->_read_section;
     }
@@ -287,14 +289,18 @@ public:
             return _delegate();
         }
 
-        logalloc::reclaim_lock _(region());
-        managed_bytes::linearization_context_guard lcg;
-        memtable_entry* e = fetch_next_entry();
-        if (!e) {
-             return make_ready_future<streamed_mutation_opt>(stdx::nullopt);
-        } else {
-            return make_ready_future<streamed_mutation_opt>(e->read(mtbl(), schema(), _slice));
-        }
+        return read_section()(region(), [&] {
+            return with_linearized_managed_bytes([&] {
+                memtable_entry* e = fetch_entry();
+                if (!e) {
+                    return make_ready_future<streamed_mutation_opt>(stdx::nullopt);
+                } else {
+                    auto ret =  make_ready_future<streamed_mutation_opt>(e->read(mtbl(), schema(), _slice));
+                    advance();
+                    return ret;
+                }
+            });
+        });
     }
 };
 
@@ -391,19 +397,24 @@ public:
     flush_reader& operator=(const flush_reader&) = delete;
 
     virtual future<streamed_mutation_opt> operator()() override {
-        logalloc::reclaim_lock _(region());
-        managed_bytes::linearization_context_guard lcg;
-        memtable_entry* e = fetch_next_entry();
-        if (!e) {
-            return make_ready_future<streamed_mutation_opt>(stdx::nullopt);
-        } else {
-            auto cr = query::clustering_key_filter_ranges::get_ranges(*schema(), query::full_slice, e->key().key());
-            auto snp = e->partition().read(schema());
-            auto mpsr = make_partition_snapshot_reader<partition_snapshot_accounter>(schema(), e->key(), std::move(cr), snp, region(), read_section(), mtbl(), _flushed_memory);
-            _flushed_memory.account_component(*e);
-            _flushed_memory.account_component(*snp);
-            return make_ready_future<streamed_mutation_opt>(std::move(mpsr));
-        }
+        return read_section()(region(), [&] {
+            return with_linearized_managed_bytes([&] {
+                memtable_entry* e = fetch_entry();
+                if (!e) {
+                    return make_ready_future<streamed_mutation_opt>(stdx::nullopt);
+                } else {
+                    auto cr = query::clustering_key_filter_ranges::get_ranges(*schema(), query::full_slice, e->key().key());
+                    auto snp = e->partition().read(schema());
+                    auto mpsr = make_partition_snapshot_reader<partition_snapshot_accounter>(schema(), e->key(), std::move(cr),
+                            snp, region(), read_section(), mtbl(), _flushed_memory);
+                    _flushed_memory.account_component(*e);
+                    _flushed_memory.account_component(*snp);
+                    auto ret = make_ready_future<streamed_mutation_opt>(std::move(mpsr));
+                    advance();
+                    return ret;
+                }
+            });
+        });
     }
 };
 

message/messaging_service.cc

@@ -296,9 +296,10 @@ messaging_service::messaging_service(gms::inet_address ip
     _rpc->set_logger([] (const sstring& log) {
             rpc_logger.info("{}", log);
     });
-    register_handler(this, messaging_verb::CLIENT_ID, [] (rpc::client_info& ci, gms::inet_address broadcast_address, uint32_t src_cpu_id) {
+    register_handler(this, messaging_verb::CLIENT_ID, [] (rpc::client_info& ci, gms::inet_address broadcast_address, uint32_t src_cpu_id, rpc::optional<uint64_t> max_result_size) {
         ci.attach_auxiliary("baddr", broadcast_address);
         ci.attach_auxiliary("src_cpu_id", src_cpu_id);
+        ci.attach_auxiliary("max_result_size", max_result_size.value_or(query::result_memory_limiter::maximum_result_size));
         return rpc::no_wait;
     });
 
@@ -385,6 +386,8 @@ static unsigned get_rpc_client_idx(messaging_verb verb) {
                verb == messaging_verb::STREAM_MUTATION_DONE ||
                verb == messaging_verb::COMPLETE_MESSAGE) {
         idx = 2;
+    } else if (verb == messaging_verb::MUTATION_DONE) {
+        idx = 3;
     }
     return idx;
 }
@@ -499,7 +502,8 @@ shared_ptr<messaging_service::rpc_protocol_client_wrapper> messaging_service::ge
 
     it = _clients[idx].emplace(id, shard_info(std::move(client))).first;
     uint32_t src_cpu_id = engine().cpu_id();
-    _rpc->make_client<rpc::no_wait_type(gms::inet_address, uint32_t)>(messaging_verb::CLIENT_ID)(*it->second.rpc_client, utils::fb_utilities::get_broadcast_address(), src_cpu_id);
+    _rpc->make_client<rpc::no_wait_type(gms::inet_address, uint32_t, uint64_t)>(messaging_verb::CLIENT_ID)(*it->second.rpc_client, utils::fb_utilities::get_broadcast_address(), src_cpu_id,
+                                                                                                           query::result_memory_limiter::maximum_result_size);
     return it->second.rpc_client;
 }
 

message/messaging_service.hh

@@ -196,7 +196,7 @@ private:
     std::array<std::unique_ptr<rpc_protocol_server_wrapper>, 2> _server;
     ::shared_ptr<seastar::tls::server_credentials> _credentials;
     std::array<std::unique_ptr<rpc_protocol_server_wrapper>, 2> _server_tls;
-    std::array<clients_map, 3> _clients;
+    std::array<clients_map, 4> _clients;
     uint64_t _dropped_messages[static_cast<int32_t>(messaging_verb::LAST)] = {};
     bool _stopping = false;
 public:

mutation_compactor.hh

@@ -123,7 +123,7 @@ public:
               uint32_t partition_limit, CompactedMutationsConsumer consumer)
         : _schema(s)
         , _query_time(query_time)
-        , _gc_before(query_time - s.gc_grace_seconds())
+        , _gc_before(saturating_subtract(query_time, s.gc_grace_seconds()))
         , _can_gc(always_gc)
         , _slice(slice)
         , _row_limit(limit)
@@ -139,7 +139,7 @@ public:
                      std::function<api::timestamp_type(const dht::decorated_key&)> get_max_purgeable)
         : _schema(s)
         , _query_time(compaction_time)
-        , _gc_before(_query_time - s.gc_grace_seconds())
+        , _gc_before(saturating_subtract(_query_time, s.gc_grace_seconds()))
         , _get_max_purgeable(std::move(get_max_purgeable))
         , _can_gc([this] (tombstone t) { return can_gc(t); })
         , _slice(query::full_slice)

mutation_partition.cc

@@ -256,9 +256,7 @@ mutation_partition::mutation_partition(const mutation_partition& x, const schema
     try {
         for(auto&& r : ck_ranges) {
             for (const rows_entry& e : x.range(schema, r)) {
-                std::unique_ptr<rows_entry> copy(current_allocator().construct<rows_entry>(e));
-                _rows.insert(_rows.end(), *copy);
-                copy.release();
+                _rows.push_back(*current_allocator().construct<rows_entry>(e));
             }
         }
     } catch (...) {
@@ -578,7 +576,7 @@ void mutation_partition::for_each_row(const schema& schema, const query::cluster
 template<typename RowWriter>
 void write_cell(RowWriter& w, const query::partition_slice& slice, ::atomic_cell_view c) {
     assert(c.is_live());
-    ser::writer_of_qr_cell wr = w.add().write();
+    auto wr = w.add().write();
     auto after_timestamp = [&, wr = std::move(wr)] () mutable {
         if (slice.options.contains<query::partition_slice::option::send_timestamp>()) {
             return std::move(wr).write_timestamp(c.timestamp());
@@ -769,13 +767,14 @@ mutation_partition::query_compacted(query::result::partition_writer& pw, const s
     // If ck:s exist, and we do a restriction on them, we either have maching
     // rows, or return nothing, since cql does not allow "is null".
     if (row_count == 0
-			&& (has_ck_selector(pw.ranges())
-					|| !has_any_live_data(s, column_kind::static_column, static_row()))) {
-		pw.retract();
-	} else {
-	    pw.row_count() += row_count ? : 1;
+            && (has_ck_selector(pw.ranges())
+                    || !has_any_live_data(s, column_kind::static_column, static_row()))) {
+        pw.retract();
+    } else {
+        pw.row_count() += row_count ? : 1;
+        pw.partition_count() += 1;
         std::move(rows_wr).end_rows().end_qr_partition();
-	}
+    }
 }
 
 std::ostream&
@@ -1177,7 +1176,7 @@ uint32_t mutation_partition::do_compact(const schema& s,
 {
     assert(row_limit > 0);
 
-    auto gc_before = query_time - s.gc_grace_seconds();
+    auto gc_before = saturating_subtract(query_time, s.gc_grace_seconds());
 
     auto should_purge_tombstone = [&] (const tombstone& t) {
         return t.deletion_time < gc_before && can_gc(t);
@@ -1670,10 +1669,11 @@ class mutation_querier {
     const schema& _schema;
     query::result_memory_accounter& _memory_accounter;
     query::result::partition_writer& _pw;
-    ser::qr_partition__static_row__cells _static_cells_wr;
+    ser::qr_partition__static_row__cells<bytes_ostream> _static_cells_wr;
     bool _live_data_in_static_row{};
     uint32_t _live_clustering_rows = 0;
-    stdx::optional<ser::qr_partition__rows> _rows_wr;
+    stdx::optional<ser::qr_partition__rows<bytes_ostream>> _rows_wr;
+    bool _short_reads_allowed;
 private:
     void query_static_row(const row& r, tombstone current_tombstone);
     void prepare_writers();
@@ -1695,6 +1695,7 @@ mutation_querier::mutation_querier(const schema& s, query::result::partition_wri
     , _memory_accounter(memory_accounter)
     , _pw(pw)
     , _static_cells_wr(pw.start().start_static_row().start_cells())
+    , _short_reads_allowed(pw.slice().options.contains<query::partition_slice::option::allow_short_read>())
 {
 }
 
@@ -1706,7 +1707,13 @@ void mutation_querier::query_static_row(const row& r, tombstone current_tombston
             auto start = _static_cells_wr._out.size();
             get_compacted_row_slice(_schema, slice, column_kind::static_column,
                                     r, slice.static_columns, _static_cells_wr);
-            _memory_accounter.update_and_check(_static_cells_wr._out.size() - start);
+            _memory_accounter.update(_static_cells_wr._out.size() - start);
+        } else if (_short_reads_allowed) {
+            seastar::measuring_output_stream stream;
+            ser::qr_partition__static_row__cells<seastar::measuring_output_stream> out(stream, { });
+            get_compacted_row_slice(_schema, slice, column_kind::static_column,
+                                    r, slice.static_columns, _static_cells_wr);
+            _memory_accounter.update(stream.size());
         }
         if (_pw.requested_digest()) {
             ::feed_hash(_pw.digest(), current_tombstone);
@@ -1744,23 +1751,32 @@ stop_iteration mutation_querier::consume(clustering_row&& cr, tombstone current_
         _pw.last_modified() = std::max({_pw.last_modified(), current_tombstone.timestamp, t});
     }
 
-    auto stop = stop_iteration::no;
-    if (_pw.requested_result()) {
-        auto start = _rows_wr->_out.size();
+    auto write_row = [&] (auto& rows_writer) {
         auto cells_wr = [&] {
             if (slice.options.contains(query::partition_slice::option::send_clustering_key)) {
-                return _rows_wr->add().write_key(cr.key()).start_cells().start_cells();
+                return rows_writer.add().write_key(cr.key()).start_cells().start_cells();
             } else {
-                return _rows_wr->add().skip_key().start_cells().start_cells();
+                return rows_writer.add().skip_key().start_cells().start_cells();
             }
         }();
         get_compacted_row_slice(_schema, slice, column_kind::regular_column, cr.cells(), slice.regular_columns, cells_wr);
         std::move(cells_wr).end_cells().end_cells().end_qr_clustered_row();
+    };
+
+    auto stop = stop_iteration::no;
+    if (_pw.requested_result()) {
+        auto start = _rows_wr->_out.size();
+        write_row(*_rows_wr);
         stop = _memory_accounter.update_and_check(_rows_wr->_out.size() - start);
+    } else if (_short_reads_allowed) {
+        seastar::measuring_output_stream stream;
+        ser::qr_partition__rows<seastar::measuring_output_stream> out(stream, { });
+        write_row(out);
+        stop = _memory_accounter.update_and_check(stream.size());
     }
 
     _live_clustering_rows++;
-    return stop;
+    return stop && stop_iteration(_short_reads_allowed);
 }
 
 uint32_t mutation_querier::consume_end_of_stream() {
@@ -1776,15 +1792,16 @@ uint32_t mutation_querier::consume_end_of_stream() {
         _pw.retract();
         return 0;
     } else {
+        auto live_rows = std::max(_live_clustering_rows, uint32_t(1));
+        _pw.row_count() += live_rows;
+        _pw.partition_count() += 1;
         std::move(*_rows_wr).end_rows().end_qr_partition();
-        return std::max(_live_clustering_rows, uint32_t(1));
+        return live_rows;
     }
 }
 
 class query_result_builder {
     const schema& _schema;
-    uint32_t _live_rows = 0;
-    uint32_t _partitions = 0;
     query::result::builder& _rb;
     stdx::optional<query::result::partition_writer> _pw;
     stdx::optional<mutation_querier> _mutation_consumer;
@@ -1819,9 +1836,7 @@ public:
 
     stop_iteration consume_end_of_partition() {
         auto live_rows_in_partition = _mutation_consumer->consume_end_of_stream();
-        _live_rows += live_rows_in_partition;
-        _partitions += live_rows_in_partition > 0;
-        if (live_rows_in_partition && !_stop) {
+        if (_short_read_allowed && live_rows_in_partition > 0 && !_stop) {
             _stop = _rb.memory_accounter().check();
         }
         if (_stop) {
@@ -1830,17 +1845,17 @@ public:
         return _stop;
     }
 
-    data_query_result consume_end_of_stream() {
-        return {_live_rows, _partitions};
+    void consume_end_of_stream() {
     }
 };
 
-future<data_query_result> data_query(schema_ptr s, const mutation_source& source, const query::partition_range& range,
-                            const query::partition_slice& slice, uint32_t row_limit, uint32_t partition_limit,
-                            gc_clock::time_point query_time, query::result::builder& builder)
+future<> data_query(
+        schema_ptr s, const mutation_source& source, const query::partition_range& range,
+        const query::partition_slice& slice, uint32_t row_limit, uint32_t partition_limit,
+        gc_clock::time_point query_time, query::result::builder& builder)
 {
     if (row_limit == 0 || slice.partition_row_limit() == 0 || partition_limit == 0) {
-        return make_ready_future<data_query_result>();
+        return make_ready_future<>();
     }
 
     auto is_reversed = slice.options.contains(query::partition_slice::option::reversed);
@@ -1918,7 +1933,7 @@ public:
             // well. Next page fetch will ask for the next partition and if we
             // don't do that we could end up with an unbounded number of
             // partitions with only a static row.
-            _stop = _stop || _memory_accounter.check();
+            _stop = _stop || (_memory_accounter.check() && stop_iteration(_short_read_allowed));
         }
         _total_live_rows += _live_rows;
         _result.emplace_back(partition { _live_rows, _mutation_consumer->consume_end_of_stream() });

mutation_partition_serializer.cc

@@ -189,17 +189,17 @@ mutation_partition_serializer::mutation_partition_serializer(const schema& schem
 
 void
 mutation_partition_serializer::write(bytes_ostream& out) const {
-    write(ser::writer_of_mutation_partition(out));
+    write(ser::writer_of_mutation_partition<bytes_ostream>(out));
 }
 
-void mutation_partition_serializer::write(ser::writer_of_mutation_partition&& wr) const
+void mutation_partition_serializer::write(ser::writer_of_mutation_partition<bytes_ostream>&& wr) const
 {
     write_serialized(std::move(wr), _schema, _p);
 }
 
 void serialize_mutation_fragments(const schema& s, tombstone partition_tombstone,
     stdx::optional<static_row> sr,  range_tombstone_list rts,
-    std::deque<clustering_row> crs, ser::writer_of_mutation_partition&& wr)
+    std::deque<clustering_row> crs, ser::writer_of_mutation_partition<bytes_ostream>&& wr)
 {
     auto srow_writer = std::move(wr).write_tomb(partition_tombstone).start_static_row();
     auto row_tombstones = [&] {

mutation_partition_serializer.hh

@@ -29,6 +29,7 @@
 #include "streamed_mutation.hh"
 
 namespace ser {
+template<typename Output>
 class writer_of_mutation_partition;
 }
 
@@ -47,9 +48,9 @@ public:
     mutation_partition_serializer(const schema&, const mutation_partition&);
 public:
     void write(bytes_ostream&) const;
-    void write(ser::writer_of_mutation_partition&&) const;
+    void write(ser::writer_of_mutation_partition<bytes_ostream>&&) const;
 };
 
 void serialize_mutation_fragments(const schema& s, tombstone partition_tombstone,
     stdx::optional<static_row> sr, range_tombstone_list range_tombstones,
-    std::deque<clustering_row> clustering_rows, ser::writer_of_mutation_partition&&);
+    std::deque<clustering_row> clustering_rows, ser::writer_of_mutation_partition<bytes_ostream>&&);

mutation_query.cc

@@ -57,13 +57,14 @@ bool reconcilable_result::operator!=(const reconcilable_result& other) const {
 }
 
 query::result
-to_data_query_result(const reconcilable_result& r, schema_ptr s, const query::partition_slice& slice, uint32_t max_partitions) {
+to_data_query_result(const reconcilable_result& r, schema_ptr s, const query::partition_slice& slice, uint32_t max_rows, uint32_t max_partitions) {
     query::result::builder builder(slice, query::result_request::only_result, { });
     for (const partition& p : r.partitions()) {
-        if (!max_partitions--) {
+        if (builder.row_count() >= max_rows || builder.partition_count() >= max_partitions) {
             break;
         }
-        p.mut().unfreeze(s).query(builder, slice, gc_clock::time_point::min(), query::max_rows);
+        // Also enforces the per-partition limit.
+        p.mut().unfreeze(s).query(builder, slice, gc_clock::time_point::min(), max_rows - builder.row_count());
     }
     if (r.is_short_read()) {
         builder.mark_as_short_read();

mutation_query.hh

@@ -105,7 +105,7 @@ public:
     printer pretty_printer(schema_ptr) const;
 };
 
-query::result to_data_query_result(const reconcilable_result&, schema_ptr, const query::partition_slice&, uint32_t partition_limit = query::max_partitions);
+query::result to_data_query_result(const reconcilable_result&, schema_ptr, const query::partition_slice&, uint32_t row_limit, uint32_t partition_limit);
 
 // Performs a query on given data source returning data in reconcilable form.
 //
@@ -128,11 +128,7 @@ future<reconcilable_result> mutation_query(
     gc_clock::time_point query_time,
     query::result_memory_accounter&& accounter = { });
 
-struct data_query_result {
-    uint32_t live_rows{0};
-    uint32_t partitions{0};
-};
-
-future<data_query_result> data_query(schema_ptr s, const mutation_source& source, const query::partition_range& range,
-                            const query::partition_slice& slice, uint32_t row_limit, uint32_t partition_limit,
-                            gc_clock::time_point query_time, query::result::builder& builder);
+future<> data_query(
+    schema_ptr s, const mutation_source& source, const query::partition_range& range,
+    const query::partition_slice& slice, uint32_t row_limit, uint32_t partition_limit,
+    gc_clock::time_point query_time, query::result::builder& builder);

query-result-writer.hh

@@ -40,29 +40,31 @@ namespace query {
 
 class result::partition_writer {
     result_request _request;
-    ser::after_qr_partition__key _w;
+    ser::after_qr_partition__key<bytes_ostream> _w;
     const partition_slice& _slice;
     // We are tasked with keeping track of the range
     // as well, since we are the primary "context"
     // when iterating "inside" a partition
     const clustering_row_ranges& _ranges;
-    ser::query_result__partitions& _pw;
+    ser::query_result__partitions<bytes_ostream>& _pw;
     ser::vector_position _pos;
     bool _static_row_added = false;
     md5_hasher& _digest;
     md5_hasher _digest_pos;
     uint32_t& _row_count;
+    uint32_t& _partition_count;
     api::timestamp_type& _last_modified;
 public:
     partition_writer(
         result_request request,
         const partition_slice& slice,
         const clustering_row_ranges& ranges,
-        ser::query_result__partitions& pw,
+        ser::query_result__partitions<bytes_ostream>& pw,
         ser::vector_position pos,
-        ser::after_qr_partition__key w,
+        ser::after_qr_partition__key<bytes_ostream> w,
         md5_hasher& digest,
         uint32_t& row_count,
+        uint32_t& partition_count,
         api::timestamp_type& last_modified)
         : _request(request)
         , _w(std::move(w))
@@ -73,6 +75,7 @@ public:
         , _digest(digest)
         , _digest_pos(digest)
         , _row_count(row_count)
+        , _partition_count(partition_count)
         , _last_modified(last_modified)
     { }
 
@@ -84,7 +87,7 @@ public:
         return _request != result_request::only_digest;
     }
 
-    ser::after_qr_partition__key start() {
+    ser::after_qr_partition__key<bytes_ostream> start() {
         return std::move(_w);
     }
 
@@ -108,6 +111,9 @@ public:
     uint32_t& row_count() {
         return _row_count;
     }
+    uint32_t& partition_count() {
+        return _partition_count;
+    }
     api::timestamp_type& last_modified() {
         return _last_modified;
     }
@@ -118,16 +124,17 @@ class result::builder {
     bytes_ostream _out;
     md5_hasher _digest;
     const partition_slice& _slice;
-    ser::query_result__partitions _w;
+    ser::query_result__partitions<bytes_ostream> _w;
     result_request _request;
     uint32_t _row_count = 0;
+    uint32_t _partition_count = 0;
     api::timestamp_type _last_modified = api::missing_timestamp;
     short_read _short_read;
     result_memory_accounter _memory_accounter;
 public:
     builder(const partition_slice& slice, result_request request, result_memory_accounter memory_accounter)
         : _slice(slice)
-        , _w(ser::writer_of_query_result(_out).start_partitions())
+        , _w(ser::writer_of_query_result<bytes_ostream>(_out).start_partitions())
         , _request(request)
         , _memory_accounter(std::move(memory_accounter))
     { }
@@ -140,6 +147,14 @@ public:
 
     const partition_slice& slice() const { return _slice; }
 
+    uint32_t row_count() const {
+        return _row_count;
+    }
+
+    uint32_t partition_count() const {
+        return _partition_count;
+    }
+
     // Starts new partition and returns a builder for its contents.
     // Invalidates all previously obtained builders
     partition_writer add_partition(const schema& s, const partition_key& key) {
@@ -156,22 +171,23 @@ public:
         if (_request != result_request::only_result) {
             key.feed_hash(_digest, s);
         }
-        return partition_writer(_request, _slice, ranges, _w, std::move(pos), std::move(after_key), _digest, _row_count, _last_modified);
+        return partition_writer(_request, _slice, ranges, _w, std::move(pos), std::move(after_key), _digest, _row_count,
+                                _partition_count, _last_modified);
     }
 
     result build() {
         std::move(_w).end_partitions().end_query_result();
         switch (_request) {
         case result_request::only_result:
-            return result(std::move(_out), _short_read, _row_count, std::move(_memory_accounter).done());
+            return result(std::move(_out), _short_read, _row_count, _partition_count, std::move(_memory_accounter).done());
         case result_request::only_digest: {
             bytes_ostream buf;
-            ser::writer_of_query_result(buf).start_partitions().end_partitions().end_query_result();
+            ser::writer_of_query_result<bytes_ostream>(buf).start_partitions().end_partitions().end_query_result();
             return result(std::move(buf), result_digest(_digest.finalize_array()), _last_modified, _short_read);
         }
         case result_request::result_and_digest:
             return result(std::move(_out), result_digest(_digest.finalize_array()),
-                          _last_modified, _short_read, _row_count, std::move(_memory_accounter).done());
+                          _last_modified, _short_read, _row_count, _partition_count, std::move(_memory_accounter).done());
         }
         abort();
     }

query-result.hh

@@ -67,8 +67,21 @@ public:
         return _maximum_total_result_memory - _memory_limiter.available_units();
     }
 
-    // Reserves minimum_result_size and creates new memory accounter.
-    future<result_memory_accounter> new_read();
+    // Reserves minimum_result_size and creates new memory accounter for
+    // mutation query. Uses the specified maximum result size and may be
+    // stopped before reaching it due to memory pressure on shard.
+    future<result_memory_accounter> new_mutation_read(size_t max_result_size);
+
+    // Reserves minimum_result_size and creates new memory accounter for
+    // data query. Uses the specified maximum result size, result will *not*
+    // be stopped due to on shard memory pressure in order to avoid digest
+    // mismatches.
+    future<result_memory_accounter> new_data_read(size_t max_result_size);
+
+    // Creates a memory accounter for digest reads. Such accounter doesn't
+    // contribute to the shard memory usage, but still stops producing the
+    // result after individual limit has been reached.
+    future<result_memory_accounter> new_digest_read(size_t max_result_size);
 
     // Checks whether the result can grow any more, takes into account only
     // the per shard limit.
@@ -108,12 +121,50 @@ class result_memory_accounter {
     size_t _blocked_bytes = 0;
     size_t _used_memory = 0;
     size_t _total_used_memory = 0;
+    size_t _maximum_result_size = 0;
+    stop_iteration _stop_on_global_limit;
 private:
-    explicit result_memory_accounter(result_memory_limiter& limiter) noexcept
+    // Mutation query accounter. Uses provided individual result size limit and
+    // will stop when shard memory pressure grows too high.
+    struct mutation_query_tag { };
+    explicit result_memory_accounter(mutation_query_tag, result_memory_limiter& limiter, size_t max_size) noexcept
         : _limiter(&limiter)
         , _blocked_bytes(result_memory_limiter::minimum_result_size)
+        , _maximum_result_size(max_size)
+        , _stop_on_global_limit(true)
     { }
+
+    // Data query accounter. Uses provided individual result size limit and
+    // will *not* stop even though shard memory pressure grows too high.
+    struct data_query_tag { };
+    explicit result_memory_accounter(data_query_tag, result_memory_limiter& limiter, size_t max_size) noexcept
+        : _limiter(&limiter)
+        , _blocked_bytes(result_memory_limiter::minimum_result_size)
+        , _maximum_result_size(max_size)
+    { }
+
+    // Digest query accounter. Uses provided individual result size limit and
+    // will *not* stop even though shard memory pressure grows too high. This
+    // accounter does not contribute to the shard memory limits.
+    struct digest_query_tag { };
+    explicit result_memory_accounter(digest_query_tag, result_memory_limiter&, size_t max_size) noexcept
+        : _blocked_bytes(0)
+        , _maximum_result_size(max_size)
+    { }
+
     friend class result_memory_limiter;
+public:
+    // State of a accounter on another shard. Used to pass information about
+    // the size of the result so far in range queries.
+    class foreign_state {
+        size_t _used_memory;
+        size_t _max_result_size;
+    public:
+        foreign_state(size_t used_mem, size_t max_result_size)
+                : _used_memory(used_mem), _max_result_size(max_result_size) { }
+        size_t used_memory() const { return _used_memory; }
+        size_t max_result_size() const { return _max_result_size; }
+    };
 public:
     result_memory_accounter() = default;
 
@@ -123,9 +174,10 @@ public:
     // accouter will learn how big the total result alread is and limit the
     // part produced on this shard so that after merging the final result
     // does not exceed the individual limit.
-    result_memory_accounter(result_memory_limiter& limiter, const result_memory_accounter& foreign_accounter) noexcept
+    result_memory_accounter(result_memory_limiter& limiter, foreign_state fstate) noexcept
         : _limiter(&limiter)
-        , _total_used_memory(foreign_accounter.used_memory())
+        , _total_used_memory(fstate.used_memory())
+        , _maximum_result_size(fstate.max_result_size())
     { }
 
     result_memory_accounter(result_memory_accounter&& other) noexcept
@@ -133,6 +185,8 @@ public:
         , _blocked_bytes(other._blocked_bytes)
         , _used_memory(other._used_memory)
         , _total_used_memory(other._total_used_memory)
+        , _maximum_result_size(other._maximum_result_size)
+        , _stop_on_global_limit(other._stop_on_global_limit)
     { }
 
     result_memory_accounter& operator=(result_memory_accounter&& other) noexcept {
@@ -151,17 +205,21 @@ public:
 
     size_t used_memory() const { return _used_memory; }
 
+    foreign_state state_for_another_shard() {
+        return foreign_state(_used_memory, _maximum_result_size);
+    }
+
     // Consume n more bytes for the result. Returns stop_iteration::yes if
     // the result cannot grow any more (taking into account both individual
     // and per-shard limits).
     stop_iteration update_and_check(size_t n) {
         _used_memory += n;
         _total_used_memory += n;
-        auto stop = stop_iteration(_total_used_memory > result_memory_limiter::maximum_result_size);
+        auto stop = stop_iteration(_total_used_memory > _maximum_result_size);
         if (_limiter && _used_memory > _blocked_bytes) {
             auto to_block = std::min(_used_memory - _blocked_bytes, n);
             _blocked_bytes += to_block;
-            stop = _limiter->update_and_check(to_block) || stop;
+            stop = (_limiter->update_and_check(to_block) && _stop_on_global_limit) || stop;
         }
         return stop;
     }
@@ -170,7 +228,7 @@ public:
     stop_iteration check() const {
         stop_iteration stop { _total_used_memory > result_memory_limiter::maximum_result_size };
         if (!stop && _used_memory >= _blocked_bytes && _limiter) {
-            return _limiter->check();
+            return _limiter->check() && _stop_on_global_limit;
         }
         return stop;
     }
@@ -189,12 +247,22 @@ public:
     }
 };
 
-inline future<result_memory_accounter> result_memory_limiter::new_read() {
-    return _memory_limiter.wait(minimum_result_size).then([this] {
-        return result_memory_accounter(*this);
+inline future<result_memory_accounter> result_memory_limiter::new_mutation_read(size_t max_size) {
+    return _memory_limiter.wait(minimum_result_size).then([this, max_size] {
+        return result_memory_accounter(result_memory_accounter::mutation_query_tag(), *this, max_size);
     });
 }
 
+inline future<result_memory_accounter> result_memory_limiter::new_data_read(size_t max_size) {
+    return _memory_limiter.wait(minimum_result_size).then([this, max_size] {
+        return result_memory_accounter(result_memory_accounter::data_query_tag(), *this, max_size);
+    });
+}
+
+inline future<result_memory_accounter> result_memory_limiter::new_digest_read(size_t max_size) {
+    return make_ready_future<result_memory_accounter>(result_memory_accounter(result_memory_accounter::digest_query_tag(), *this, max_size));
+}
+
 enum class result_request {
     only_result,
     only_digest,
@@ -265,29 +333,32 @@ class result {
     api::timestamp_type _last_modified = api::missing_timestamp;
     short_read _short_read;
     query::result_memory_tracker _memory_tracker;
+    stdx::optional<uint32_t> _partition_count;
 public:
     class builder;
     class partition_writer;
     friend class result_merger;
 
     result();
-    result(bytes_ostream&& w, short_read sr, stdx::optional<uint32_t> c = { },
+    result(bytes_ostream&& w, short_read sr, stdx::optional<uint32_t> c = { }, stdx::optional<uint32_t> pc = { },
            result_memory_tracker memory_tracker = { })
         : _w(std::move(w))
         , _row_count(c)
         , _short_read(sr)
-        , _memory_tracker(std::move(_memory_tracker))
+        , _memory_tracker(std::move(memory_tracker))
+        , _partition_count(pc)
     {
         w.reduce_chunk_count();
     }
     result(bytes_ostream&& w, stdx::optional<result_digest> d, api::timestamp_type last_modified,
-           short_read sr, stdx::optional<uint32_t> c = { }, result_memory_tracker memory_tracker = { })
+           short_read sr, stdx::optional<uint32_t> c = { }, stdx::optional<uint32_t> pc = { }, result_memory_tracker memory_tracker = { })
         : _w(std::move(w))
         , _digest(d)
         , _row_count(c)
         , _last_modified(last_modified)
         , _short_read(sr)
         , _memory_tracker(std::move(memory_tracker))
+        , _partition_count(pc)
     {
         w.reduce_chunk_count();
     }
@@ -316,7 +387,11 @@ public:
         return _short_read;
     }
 
-    uint32_t calculate_row_count(const query::partition_slice&);
+    const stdx::optional<uint32_t>& partition_count() const {
+        return _partition_count;
+    }
+
+    void calculate_counts(const query::partition_slice&);
 
     struct printer {
         schema_ptr s;

query.cc

@@ -32,6 +32,9 @@
 
 namespace query {
 
+constexpr size_t result_memory_limiter::minimum_result_size;
+constexpr size_t result_memory_limiter::maximum_result_size;
+
 thread_local semaphore result_memory_tracker::_dummy { 0 };
 
 const partition_range full_partition_range = partition_range::make_open_ended_both_sides();
@@ -161,16 +164,18 @@ std::ostream& operator<<(std::ostream& os, const query::result::printer& p) {
     return os;
 }
 
-uint32_t result::calculate_row_count(const query::partition_slice& slice) {
+void result::calculate_counts(const query::partition_slice& slice) {
     struct {
         uint32_t total_count = 0;
         uint32_t current_partition_count = 0;
+        uint32_t live_partitions = 0;
         void accept_new_partition(const partition_key& key, uint32_t row_count) {
             accept_new_partition(row_count);
         }
         void accept_new_partition(uint32_t row_count) {
             total_count += row_count;
             current_partition_count = row_count;
+            live_partitions += 1;
         }
         void accept_new_row(const clustering_key& key, const result_row_view& static_row, const result_row_view& row) {}
         void accept_new_row(const result_row_view& static_row, const result_row_view& row) {}
@@ -182,44 +187,78 @@ uint32_t result::calculate_row_count(const query::partition_slice& slice) {
     } counter;
 
     result_view::consume(*this, slice, counter);
-    return counter.total_count;
+    _row_count = counter.total_count;
+    _partition_count = counter.live_partitions;
 }
 
 result::result()
     : result([] {
         bytes_ostream out;
-        ser::writer_of_query_result(out).skip_partitions().end_query_result();
+        ser::writer_of_query_result<bytes_ostream>(out).skip_partitions().end_query_result();
         return out;
-    }(), short_read::no)
+    }(), short_read::no, 0, 0)
 { }
 
+static void write_partial_partition(ser::writer_of_qr_partition<bytes_ostream>&& pw, const ser::qr_partition_view& pv, uint32_t rows_to_include) {
+    auto key = pv.key();
+    auto static_cells_wr = (key ? std::move(pw).write_key(*key) : std::move(pw).skip_key())
+            .start_static_row()
+            .start_cells();
+    for (auto&& cell : pv.static_row().cells()) {
+        static_cells_wr.add(cell);
+    }
+    auto rows_wr = std::move(static_cells_wr)
+            .end_cells()
+            .end_static_row()
+            .start_rows();
+    auto rows = pv.rows();
+    // rows.size() can be 0 is there's a single static row
+    auto it = rows.begin();
+    for (uint32_t i = 0; i < std::min(rows.size(), uint64_t{rows_to_include}); ++i) {
+        rows_wr.add(*it++);
+    }
+    std::move(rows_wr).end_rows().end_qr_partition();
+}
+
 foreign_ptr<lw_shared_ptr<query::result>> result_merger::get() {
     if (_partial.size() == 1) {
         return std::move(_partial[0]);
     }
 
     bytes_ostream w;
-    auto partitions = ser::writer_of_query_result(w).start_partitions();
-    std::experimental::optional<uint32_t> row_count = 0;
+    auto partitions = ser::writer_of_query_result<bytes_ostream>(w).start_partitions();
+    uint32_t row_count = 0;
     short_read is_short_read;
+    uint32_t partition_count = 0;
 
     for (auto&& r : _partial) {
-        if (row_count) {
-            if (r->row_count()) {
-                row_count = row_count.value() + r->row_count().value();
-            } else {
-                row_count = std::experimental::nullopt;
-            }
-        }
         result_view::do_with(*r, [&] (result_view rv) {
             for (auto&& pv : rv._v.partitions()) {
-                partitions.add(pv);
+                auto rows = pv.rows();
+                // If rows.empty(), then there's a static row, or there wouldn't be a partition
+                const uint32_t rows_in_partition = rows.size() ? : 1;
+                const uint32_t rows_to_include = std::min(_max_rows - row_count, rows_in_partition);
+                row_count += rows_to_include;
+                if (rows_to_include >= rows_in_partition) {
+                    partitions.add(pv);
+                    if (++partition_count >= _max_partitions) {
+                        return;
+                    }
+                } else if (rows_to_include > 0) {
+                    write_partial_partition(partitions.add(), pv, rows_to_include);
+                    return;
+                } else {
+                    return;
+                }
             }
         });
         if (r->is_short_read()) {
             is_short_read = short_read::yes;
             break;
         }
+        if (row_count >= _max_rows || partition_count >= _max_partitions) {
+            break;
+        }
     }
 
     std::move(partitions).end_partitions().end_query_result();

query_result_merger.hh

@@ -30,7 +30,14 @@ namespace query {
 // Implements @Reducer concept from distributed.hh
 class result_merger {
     std::vector<foreign_ptr<lw_shared_ptr<query::result>>> _partial;
+    const uint32_t _max_rows;
+    const uint32_t _max_partitions;
 public:
+    explicit result_merger(uint32_t max_rows, uint32_t max_partitions)
+            : _max_rows(max_rows)
+            , _max_partitions(max_partitions)
+    { }
+
     void reserve(size_t size) {
         _partial.reserve(size);
     }

repair/repair.cc

@@ -490,6 +490,13 @@ static void split_and_add(std::vector<::nonwrapping_range<dht::token>>& ranges,
     auto midpoint = dht::global_partitioner().midpoint(
             range.start() ? range.start()->value() : dht::minimum_token(),
             range.end() ? range.end()->value() : dht::minimum_token());
+    // This shouldn't happen, but if the range included just one token, we
+    // can't split further (split() may actually fail with assertion failure)
+    if ((range.start() && midpoint == range.start()->value()) ||
+        (range.end() && midpoint == range.end()->value())) {
+        ranges.push_back(range);
+        return;
+    }
     auto halves = range.split(midpoint, dht::token_comparator());
     ranges.push_back(halves.first);
     ranges.push_back(halves.second);

scylla-housekeeping

@@ -30,6 +30,7 @@ import ConfigParser
 import os
 import sys
 import subprocess
+import uuid
 from pkg_resources import parse_version
 
 VERSION = "1.0"
@@ -64,6 +65,10 @@ def get_api(path):
 def version_compare(a, b):
     return parse_version(a) < parse_version(b)
 
+def create_uuid_file(fl):
+    with open(args.uuid_file, 'w') as myfile:
+        myfile.write(str(uuid.uuid1()) + "\n")
+
 def check_version(ar):
     if config and (not config.has_option("housekeeping", "check-version") or not config.getboolean("housekeeping", "check-version")):
         return
@@ -80,8 +85,8 @@ def check_version(ar):
             # mode would accept any string.
             # use i for install, c (default) for running from the command line
             params = params + "&sts=" + ar.mode
-        if uuid:
-            params = params + "&uu=" + uuid
+        if uid:
+            params = params + "&uu=" + uid
         latest_version = get_json_from_url(version_url + params)["version"]
     except:
         traceln("Unable to retrieve version information")
@@ -112,10 +117,12 @@ if args.config != "":
         sys.exit(0)
     config = ConfigParser.SafeConfigParser()
     config.read(args.config)
-uuid = None
+uid = None
 if args.uuid != "":
-    uuid = args.uuid
-if args.uuid_file != "" and os.path.exists(args.uuid_file):
+    uid = args.uuid
+if args.uuid_file != "":
+    if not os.path.exists(args.uuid_file):
+        create_uuid_file(args.uuid_file)
     with open(args.uuid_file, 'r') as myfile:
-        uuid = myfile.read().replace('\n', '')
+        uid = myfile.read().replace('\n', '')
 args.func(args)

serialization_visitors.hh

@@ -27,8 +27,14 @@ namespace ser {
 
 // frame represents a place holder for object size which will be known later
 
+template<typename Output>
+struct place_holder { };
 
-struct place_holder {
+template<typename Output>
+struct frame { };
+
+template<>
+struct place_holder<bytes_ostream> {
     bytes_ostream::place_holder<size_type> ph;
 
     place_holder(bytes_ostream::place_holder<size_type> ph) : ph(ph) { }
@@ -39,7 +45,8 @@ struct place_holder {
     }
 };
 
-struct frame : public place_holder {
+template<>
+struct frame<bytes_ostream> : public place_holder<bytes_ostream> {
     bytes_ostream::size_type offset;
 
     frame(bytes_ostream::place_holder<size_type> ph, bytes_ostream::size_type offset)
@@ -56,25 +63,26 @@ struct vector_position {
 };
 
 //empty frame, behave like a place holder, but is used when no place holder is needed
+template<typename Output>
 struct empty_frame {
-    void end(bytes_ostream&) {}
+    void end(Output&) {}
     empty_frame() = default;
-    empty_frame(const frame&){}
+    empty_frame(const frame<Output>&){}
 };
 
-inline place_holder start_place_holder(bytes_ostream& out) {
+inline place_holder<bytes_ostream> start_place_holder(bytes_ostream& out) {
     auto size_ph = out.write_place_holder<size_type>();
     return { size_ph};
 }
 
-inline frame start_frame(bytes_ostream& out) {
+inline frame<bytes_ostream> start_frame(bytes_ostream& out) {
     auto offset = out.size();
     auto size_ph = out.write_place_holder<size_type>();
     {
         auto out = size_ph.get_stream();
         serialize(out, (size_type)0);
     }
-    return frame { size_ph, offset };
+    return frame<bytes_ostream> { size_ph, offset };
 }
 
 template<typename Input>
@@ -86,4 +94,25 @@ size_type read_frame_size(Input& in) {
     return sz - sizeof(size_type);
 }
 
+
+template<>
+struct place_holder<seastar::measuring_output_stream> {
+    void set(seastar::measuring_output_stream&, size_type) { }
+};
+
+template<>
+struct frame<seastar::measuring_output_stream> : public place_holder<seastar::measuring_output_stream> {
+    void end(seastar::measuring_output_stream& out) { }
+};
+
+inline place_holder<seastar::measuring_output_stream> start_place_holder(seastar::measuring_output_stream& out) {
+    serialize(out, size_type());
+    return { };
+}
+
+inline frame<seastar::measuring_output_stream> start_frame(seastar::measuring_output_stream& out) {
+    serialize(out, size_type());
+    return { };
+}
+
 }

service/migration_manager.cc

@@ -439,8 +439,10 @@ future<> migration_manager::announce_new_column_family(schema_ptr cfm, bool anno
             throw exceptions::already_exists_exception(cfm->ks_name(), cfm->cf_name());
         }
         logger.info("Create new ColumnFamily: {}", cfm);
-        auto mutations = db::schema_tables::make_create_table_mutations(keyspace.metadata(), cfm, api::new_timestamp());
-        return announce(std::move(mutations), announce_locally);
+        return db::schema_tables::make_create_table_mutations(keyspace.metadata(), cfm, api::new_timestamp())
+            .then([announce_locally, this] (auto&& mutations) {
+                return announce(std::move(mutations), announce_locally);
+            });
     } catch (const no_such_keyspace& e) {
         throw exceptions::configuration_exception(sprint("Cannot add table '%s' to non existing keyspace '%s'.", cfm->cf_name(), cfm->ks_name()));
     }
@@ -459,8 +461,10 @@ future<> migration_manager::announce_column_family_update(schema_ptr cfm, bool f
 #endif
         logger.info("Update table '{}.{}' From {} To {}", cfm->ks_name(), cfm->cf_name(), *old_schema, *cfm);
         auto&& keyspace = db.find_keyspace(cfm->ks_name());
-        auto mutations = db::schema_tables::make_update_table_mutations(keyspace.metadata(), old_schema, cfm, api::new_timestamp(), from_thrift);
-        return announce(std::move(mutations), announce_locally);
+        return db::schema_tables::make_update_table_mutations(keyspace.metadata(), old_schema, cfm, api::new_timestamp(), from_thrift)
+            .then([announce_locally] (auto&& mutations) {
+                return announce(std::move(mutations), announce_locally);
+            });
     } catch (const no_such_column_family& e) {
         throw exceptions::configuration_exception(sprint("Cannot update non existing table '%s' in keyspace '%s'.",
                                                          cfm->cf_name(), cfm->ks_name()));
@@ -470,8 +474,10 @@ future<> migration_manager::announce_column_family_update(schema_ptr cfm, bool f
 static future<> do_announce_new_type(user_type new_type, bool announce_locally) {
     auto& db = get_local_storage_proxy().get_db().local();
     auto&& keyspace = db.find_keyspace(new_type->_keyspace);
-    auto mutations = db::schema_tables::make_create_type_mutations(keyspace.metadata(), new_type, api::new_timestamp());
-    return migration_manager::announce(std::move(mutations), announce_locally);
+    return db::schema_tables::make_create_type_mutations(keyspace.metadata(), new_type, api::new_timestamp())
+        .then([announce_locally] (auto&& mutations) {
+            return migration_manager::announce(std::move(mutations), announce_locally);
+        });
 }
 
 future<> migration_manager::announce_new_type(user_type new_type, bool announce_locally) {
@@ -558,8 +564,10 @@ future<> migration_manager::announce_column_family_drop(const sstring& ks_name,
         auto&& old_cfm = db.find_schema(ks_name, cf_name);
         auto&& keyspace = db.find_keyspace(ks_name);
         logger.info("Drop table '{}.{}'", old_cfm->ks_name(), old_cfm->cf_name());
-        auto mutations = db::schema_tables::make_drop_table_mutations(keyspace.metadata(), old_cfm, api::new_timestamp());
-        return announce(std::move(mutations), announce_locally);
+        return db::schema_tables::make_drop_table_mutations(keyspace.metadata(), old_cfm, api::new_timestamp())
+            .then([announce_locally] (auto&& mutations) {
+                return announce(std::move(mutations), announce_locally);
+            });
     } catch (const no_such_column_family& e) {
         throw exceptions::configuration_exception(sprint("Cannot drop non existing table '%s' in keyspace '%s'.", cf_name, ks_name));
     }
@@ -570,8 +578,10 @@ future<> migration_manager::announce_type_drop(user_type dropped_type, bool anno
     auto& db = get_local_storage_proxy().get_db().local();
     auto&& keyspace = db.find_keyspace(dropped_type->_keyspace);
     logger.info("Drop User Type: {}", dropped_type->get_name_as_string());
-    auto mutations = db::schema_tables::make_drop_type_mutations(keyspace.metadata(), dropped_type, api::new_timestamp());
-    return announce(std::move(mutations), announce_locally);
+    return db::schema_tables::make_drop_type_mutations(keyspace.metadata(), dropped_type, api::new_timestamp())
+        .then([announce_locally] (auto&& mutations) {
+            return announce(std::move(mutations), announce_locally);
+        });
 }
 
 #if 0

service/pager/query_pagers.cc

@@ -64,7 +64,7 @@ public:
                     , _ranges(std::move(ranges))
     {}
 
-private:   
+private:
     static bool has_clustering_keys(const schema& s, const query::read_command& cmd) {
         return s.clustering_key_size() > 0
                && !cmd.slice.options.contains<query::partition_slice::option::distinct>();
@@ -229,94 +229,42 @@ private:
 
         class myvisitor : public cql3::selection::result_set_builder::visitor {
         public:
-            impl& _impl;
-            uint32_t page_size;
-            uint32_t part_rows = 0;
-
-            uint32_t included_rows = 0;
             uint32_t total_rows = 0;
             std::experimental::optional<partition_key> last_pkey;
             std::experimental::optional<clustering_key> last_ckey;
 
-            // just for verbosity
-            uint32_t part_ignored = 0;
-
-            clustering_key::less_compare _less;
-
-            bool include_row() {
-                ++total_rows;
-                ++part_rows;
-                if (included_rows >= page_size) {
-                    ++part_ignored;
-                    return false;
-                }
-                ++included_rows;
-                return true;
-            }
-
-            bool include_row(const clustering_key& key) {
-                if (!include_row()) {
-                    return false;
-                }
-                last_ckey = key;
-                return true;
-            }
-            myvisitor(impl& i, uint32_t ps,
-                    cql3::selection::result_set_builder& builder,
+            myvisitor(cql3::selection::result_set_builder& builder,
                     const schema& s,
                     const cql3::selection::selection& selection)
-                    : visitor(builder, s, selection), _impl(i), page_size(ps), _less(*_impl._schema) {
+                    : visitor(builder, s, selection) {
             }
 
             void accept_new_partition(uint32_t) {
                 throw std::logic_error("Should not reach!");
             }
             void accept_new_partition(const partition_key& key, uint32_t row_count) {
-                logger.trace("Begin partition: {} ({})", key, row_count);
-                part_rows = 0;
-                part_ignored = 0;
-                if (included_rows < page_size) {
-                    last_pkey = key;
-                    last_ckey = { };
-                }
+                logger.trace("Accepting partition: {} ({})", key, row_count);
+                total_rows += row_count;
+                last_pkey = key;
+                last_ckey = { };
                 visitor::accept_new_partition(key, row_count);
             }
             void accept_new_row(const clustering_key& key,
                     const query::result_row_view& static_row,
                     const query::result_row_view& row) {
-                // TODO: should we use exception/long jump or introduce
-                // a "stop" condition to the calling result_view and
-                // avoid processing unneeded rows?
-                auto ok = include_row(key);
-                if (ok) {
-                    visitor::accept_new_row(key, static_row, row);
-                }
+                last_ckey = key;
+                visitor::accept_new_row(key, static_row, row);
             }
             void accept_new_row(const query::result_row_view& static_row,
                     const query::result_row_view& row) {
-                auto ok = include_row();
-                if (ok) {
-                    visitor::accept_new_row(static_row, row);
-                }
+                visitor::accept_new_row(static_row, row);
             }
             void accept_partition_end(const query::result_row_view& static_row) {
-                // accept_partition_end with row_count == 0
-                // means we had an empty partition but live
-                // static columns, and since the fix,
-                // no CK restrictions.
-                // I.e. _row_count == 0 -> add a partially empty row
-                // So, treat this case as an accept_row variant
-                if (_row_count > 0 || include_row()) {
-                    visitor::accept_partition_end(static_row);
-                }
-                logger.trace(
-                        "End partition, included={}, ignored={}",
-                        part_rows - part_ignored,
-                        part_ignored);
+                visitor::accept_partition_end(static_row);
             }
         };
 
-        myvisitor v(*this, std::min(page_size, _max), builder, *_schema, *_selection);
+        myvisitor v(builder, *_schema, *_selection);
         query::result_view::consume(*results, _cmd->slice, v);
 
         if (_last_pkey) {
@@ -328,13 +276,12 @@ private:
             _cmd->slice.clear_range(*_schema, *_last_pkey);
         }
 
-        _max = _max - v.included_rows;
-        _exhausted = (v.included_rows < page_size && !results->is_short_read()) || _max == 0;
+        _max = _max - v.total_rows;
+        _exhausted = (v.total_rows < page_size && !results->is_short_read()) || _max == 0;
         _last_pkey = v.last_pkey;
         _last_ckey = v.last_ckey;
 
-        logger.debug("Fetched {}/{} rows, max_remain={} {}", v.included_rows, v.total_rows,
-                _max, _exhausted ? "(exh)" : "");
+        logger.debug("Fetched {} rows, max_remain={} {}", v.total_rows, _max, _exhausted ? "(exh)" : "");
 
         if (_last_pkey) {
             logger.debug("Last partition key: {}", *_last_pkey);
@@ -363,7 +310,6 @@ private:
     // remember if we use clustering. if not, each partition == one row
     const bool _has_clustering_keys;
     bool _exhausted = false;
-    uint32_t _rem = 0;
     uint32_t _max;
 
     std::experimental::optional<partition_key> _last_pkey;

service/storage_proxy.cc

@@ -2074,7 +2074,7 @@ public:
         versions.reserve(_data_results.front().result->partitions().size());
 
         for (auto& r : _data_results) {
-            _is_short_read = r.result->is_short_read();
+            _is_short_read = _is_short_read || r.result->is_short_read();
             r.reached_end = !r.result->is_short_read() && r.result->row_count() < cmd.row_limit
                             && (cmd.partition_limit == query::max_partitions
                                 || boost::range::count_if(r.result->partitions(), [] (const partition& p) {
@@ -2346,7 +2346,8 @@ protected:
                 if (rr_opt && (can_send_short_read || data_resolver->all_reached_end() || rr_opt->row_count() >= original_row_limit()
                                || data_resolver->live_partition_count() >= original_partition_limit())
                         && !data_resolver->any_partition_short_read()) {
-                    auto result = ::make_foreign(::make_lw_shared(to_data_query_result(std::move(*rr_opt), _schema, _cmd->slice)));
+                    auto result = ::make_foreign(::make_lw_shared(
+                            to_data_query_result(std::move(*rr_opt), _schema, _cmd->slice, _cmd->row_limit, cmd->partition_limit)));
                     // wait for write to complete before returning result to prevent multiple concurrent read requests to
                     // trigger repair multiple times and to prevent quorum read to return an old value, even after a quorum
                     // another read had returned a newer value (but the newer value had not yet been sent to the other replicas)
@@ -2387,6 +2388,13 @@ protected:
                             _retry_cmd->row_limit = x(cmd->row_limit, data_resolver->total_live_count());
                         }
                     }
+
+                    // We may be unable to send a single live row because of replicas bailing out too early.
+                    // If that is the case disallow short reads so that we can make progress.
+                    if (!data_resolver->total_live_count()) {
+                        _retry_cmd->slice.options.remove<query::partition_slice::option::allow_short_read>();
+                    }
+
                     logger.trace("Retrying query with command {} (previous is {})", *_retry_cmd, *cmd);
                     reconcile(cl, timeout, _retry_cmd);
                 }
@@ -2626,17 +2634,17 @@ db::read_repair_decision storage_proxy::new_read_repair_decision(const schema& s
 }
 
 future<query::result_digest, api::timestamp_type>
-storage_proxy::query_singular_local_digest(schema_ptr s, lw_shared_ptr<query::read_command> cmd, const query::partition_range& pr, tracing::trace_state_ptr trace_state) {
-    return query_singular_local(std::move(s), std::move(cmd), pr, query::result_request::only_digest, std::move(trace_state)).then([] (foreign_ptr<lw_shared_ptr<query::result>> result) {
+storage_proxy::query_singular_local_digest(schema_ptr s, lw_shared_ptr<query::read_command> cmd, const query::partition_range& pr, tracing::trace_state_ptr trace_state, uint64_t max_size) {
+    return query_singular_local(std::move(s), std::move(cmd), pr, query::result_request::only_digest, std::move(trace_state), max_size).then([] (foreign_ptr<lw_shared_ptr<query::result>> result) {
         return make_ready_future<query::result_digest, api::timestamp_type>(*result->digest(), result->last_modified());
     });
 }
 
 future<foreign_ptr<lw_shared_ptr<query::result>>>
-storage_proxy::query_singular_local(schema_ptr s, lw_shared_ptr<query::read_command> cmd, const query::partition_range& pr, query::result_request request, tracing::trace_state_ptr trace_state) {
+storage_proxy::query_singular_local(schema_ptr s, lw_shared_ptr<query::read_command> cmd, const query::partition_range& pr, query::result_request request, tracing::trace_state_ptr trace_state, uint64_t max_size) {
     unsigned shard = _db.local().shard_of(pr.start()->value().token());
-    return _db.invoke_on(shard, [gs = global_schema_ptr(s), prv = std::vector<query::partition_range>({pr}) /* FIXME: pr is copied */, cmd, request, gt = tracing::global_trace_state_ptr(std::move(trace_state))] (database& db) mutable {
-        return db.query(gs, *cmd, request, prv, gt).then([](auto&& f) {
+    return _db.invoke_on(shard, [max_size, gs = global_schema_ptr(s), prv = std::vector<query::partition_range>({pr}) /* FIXME: pr is copied */, cmd, request, gt = tracing::global_trace_state_ptr(std::move(trace_state))] (database& db) mutable {
+        return db.query(gs, *cmd, request, prv, gt, max_size).then([](auto&& f) {
             return make_foreign(std::move(f));
         });
     });
@@ -2670,7 +2678,7 @@ storage_proxy::query_singular(lw_shared_ptr<query::read_command> cmd, std::vecto
         exec.push_back(get_read_executor(cmd, std::move(pr), cl, trace_state));
     }
 
-    query::result_merger merger;
+    query::result_merger merger(cmd->row_limit, cmd->partition_limit);
     merger.reserve(exec.size());
 
     auto f = ::map_reduce(exec.begin(), exec.end(), [timeout] (::shared_ptr<abstract_read_executor>& rex) {
@@ -2687,7 +2695,8 @@ storage_proxy::query_singular(lw_shared_ptr<query::read_command> cmd, std::vecto
 future<std::vector<foreign_ptr<lw_shared_ptr<query::result>>>>
 storage_proxy::query_partition_key_range_concurrent(std::chrono::steady_clock::time_point timeout, std::vector<foreign_ptr<lw_shared_ptr<query::result>>>&& results,
         lw_shared_ptr<query::read_command> cmd, db::consistency_level cl, std::vector<query::partition_range>::iterator&& i,
-        std::vector<query::partition_range>&& ranges, int concurrency_factor, tracing::trace_state_ptr trace_state, uint32_t total_row_count) {
+        std::vector<query::partition_range>&& ranges, int concurrency_factor, tracing::trace_state_ptr trace_state,
+        uint32_t remaining_row_count, uint32_t remaining_partition_count) {
     schema_ptr schema = local_schema_registry().get(cmd->schema_version);
     keyspace& ks = _db.local().find_keyspace(schema->ks_name());
     std::vector<::shared_ptr<abstract_read_executor>> exec;
@@ -2752,22 +2761,30 @@ storage_proxy::query_partition_key_range_concurrent(std::chrono::steady_clock::t
         exec.push_back(::make_shared<range_slice_read_executor>(schema, p, cmd, std::move(range), cl, std::move(filtered_endpoints), trace_state));
     }
 
-    query::result_merger merger;
+    query::result_merger merger(cmd->row_limit, cmd->partition_limit);
     merger.reserve(exec.size());
 
     auto f = ::map_reduce(exec.begin(), exec.end(), [timeout] (::shared_ptr<abstract_read_executor>& rex) {
         return rex->execute(timeout);
     }, std::move(merger));
 
-    return f.then([p, exec = std::move(exec), results = std::move(results), i = std::move(i), ranges = std::move(ranges), cl, cmd, concurrency_factor, timeout, total_row_count, trace_state = std::move(trace_state)]
+    return f.then([p, exec = std::move(exec), results = std::move(results), i = std::move(i), ranges = std::move(ranges),
+                   cl, cmd, concurrency_factor, timeout, remaining_row_count, remaining_partition_count, trace_state = std::move(trace_state)]
                    (foreign_ptr<lw_shared_ptr<query::result>>&& result) mutable {
-        total_row_count += result->row_count() ? result->row_count().value() :
-                (logger.error("no row count in query result, should not happen here"), result->calculate_row_count(cmd->slice));
+        if (!result->row_count() || !result->partition_count()) {
+            logger.error("no row count in query result, should not happen here");
+            result->calculate_counts(cmd->slice);
+        }
+        remaining_row_count -= result->row_count().value();
+        remaining_partition_count -= result->partition_count().value();
         results.emplace_back(std::move(result));
-        if (i == ranges.end() || total_row_count >= cmd->row_limit) {
+        if (i == ranges.end() || !remaining_row_count || !remaining_partition_count) {
             return make_ready_future<std::vector<foreign_ptr<lw_shared_ptr<query::result>>>>(std::move(results));
         } else {
-            return p->query_partition_key_range_concurrent(timeout, std::move(results), cmd, cl, std::move(i), std::move(ranges), concurrency_factor, std::move(trace_state), total_row_count);
+            cmd->row_limit = remaining_row_count;
+            cmd->partition_limit = remaining_partition_count;
+            return p->query_partition_key_range_concurrent(timeout, std::move(results), cmd, cl, std::move(i),
+                    std::move(ranges), concurrency_factor, std::move(trace_state), remaining_row_count, remaining_partition_count);
         }
     }).handle_exception([p] (std::exception_ptr eptr) {
         p->handle_read_error(eptr, true);
@@ -2812,9 +2829,10 @@ storage_proxy::query_partition_key_range(lw_shared_ptr<query::read_command> cmd,
     logger.debug("Estimated result rows per range: {}; requested rows: {}, ranges.size(): {}; concurrent range requests: {}",
             result_rows_per_range, cmd->row_limit, ranges.size(), concurrency_factor);
 
-    return query_partition_key_range_concurrent(timeout, std::move(results), cmd, cl, ranges.begin(), std::move(ranges), concurrency_factor, std::move(trace_state))
-            .then([](std::vector<foreign_ptr<lw_shared_ptr<query::result>>> results) {
-        query::result_merger merger;
+    return query_partition_key_range_concurrent(timeout, std::move(results), cmd, cl, ranges.begin(), std::move(ranges), concurrency_factor,
+                                                std::move(trace_state), cmd->row_limit, cmd->partition_limit)
+            .then([row_limit = cmd->row_limit, partition_limit = cmd->partition_limit](std::vector<foreign_ptr<lw_shared_ptr<query::result>>> results) {
+        query::result_merger merger(row_limit, partition_limit);
         merger.reserve(results.size());
 
         for (auto&& r: results) {
@@ -2838,7 +2856,8 @@ storage_proxy::query(schema_ptr s,
         logger.trace("query {}.{} cmd={}, ranges={}, id={}", s->ks_name(), s->cf_name(), *cmd, partition_ranges, query_id);
         return do_query(s, cmd, std::move(partition_ranges), cl, std::move(trace_state)).then([query_id, cmd, s] (foreign_ptr<lw_shared_ptr<query::result>>&& res) {
             if (res->buf().is_linearized()) {
-                logger.trace("query_result id={}, size={}, rows={}", query_id, res->buf().size(), res->calculate_row_count(cmd->slice));
+                res->calculate_counts(cmd->slice);
+                logger.trace("query_result id={}, size={}, rows={}, partitions={}", query_id, res->buf().size(), *res->row_count(), *res->partition_count());
             } else {
                 logger.trace("query_result id={}, size={}", query_id, res->buf().size());
             }
@@ -3447,9 +3466,10 @@ void storage_proxy::init_messaging_service() {
             tracing::trace(trace_state_ptr, "read_data: message received from /{}", src_addr.addr);
         }
         auto da = oda.value_or(query::digest_algorithm::MD5);
-        return do_with(std::move(pr), get_local_shared_storage_proxy(), std::move(trace_state_ptr), [&cinfo, cmd = make_lw_shared<query::read_command>(std::move(cmd)), src_addr = std::move(src_addr), da] (compat::wrapping_partition_range& pr, shared_ptr<storage_proxy>& p, tracing::trace_state_ptr& trace_state_ptr) mutable {
+        auto max_size = cinfo.retrieve_auxiliary<uint64_t>("max_result_size");
+        return do_with(std::move(pr), get_local_shared_storage_proxy(), std::move(trace_state_ptr), [&cinfo, cmd = make_lw_shared<query::read_command>(std::move(cmd)), src_addr = std::move(src_addr), da, max_size] (compat::wrapping_partition_range& pr, shared_ptr<storage_proxy>& p, tracing::trace_state_ptr& trace_state_ptr) mutable {
             auto src_ip = src_addr.addr;
-            return get_schema_for_read(cmd->schema_version, std::move(src_addr)).then([cmd, da, &pr, &p, &trace_state_ptr] (schema_ptr s) {
+            return get_schema_for_read(cmd->schema_version, std::move(src_addr)).then([cmd, da, &pr, &p, &trace_state_ptr, max_size] (schema_ptr s) {
                 auto pr2 = compat::unwrap(std::move(pr), *s);
                 if (pr2.second) {
                     // this function assumes singular queries but doesn't validate
@@ -3464,7 +3484,7 @@ void storage_proxy::init_messaging_service() {
                     qrr = query::result_request::result_and_digest;
                     break;
                 }
-                return p->query_singular_local(std::move(s), cmd, std::move(pr2.first), qrr, trace_state_ptr);
+                return p->query_singular_local(std::move(s), cmd, std::move(pr2.first), qrr, trace_state_ptr, max_size);
             }).finally([&trace_state_ptr, src_ip] () mutable {
                 tracing::trace(trace_state_ptr, "read_data handling is done, sending a response to /{}", src_ip);
             });
@@ -3478,10 +3498,20 @@ void storage_proxy::init_messaging_service() {
             tracing::begin(trace_state_ptr);
             tracing::trace(trace_state_ptr, "read_mutation_data: message received from /{}", src_addr.addr);
         }
-        return do_with(std::move(pr), get_local_shared_storage_proxy(), std::move(trace_state_ptr), [&cinfo, cmd = make_lw_shared<query::read_command>(std::move(cmd)), src_addr = std::move(src_addr)] (compat::wrapping_partition_range& pr, shared_ptr<storage_proxy>& p, tracing::trace_state_ptr& trace_state_ptr) mutable {
+        auto max_size = cinfo.retrieve_auxiliary<uint64_t>("max_result_size");
+        return do_with(std::move(pr),
+                       get_local_shared_storage_proxy(),
+                       std::move(trace_state_ptr),
+                       compat::one_or_two_partition_ranges({}),
+                       [&cinfo, cmd = make_lw_shared<query::read_command>(std::move(cmd)), src_addr = std::move(src_addr), max_size] (
+                               compat::wrapping_partition_range& pr,
+                               shared_ptr<storage_proxy>& p,
+                               tracing::trace_state_ptr& trace_state_ptr,
+                               compat::one_or_two_partition_ranges& unwrapped) mutable {
             auto src_ip = src_addr.addr;
-            return get_schema_for_read(cmd->schema_version, std::move(src_addr)).then([cmd, &pr, &p, &trace_state_ptr] (schema_ptr s) mutable {
-                return p->query_mutations_locally(std::move(s), cmd, compat::unwrap(std::move(pr), *s), trace_state_ptr);
+            return get_schema_for_read(cmd->schema_version, std::move(src_addr)).then([cmd, &pr, &p, &trace_state_ptr, max_size, &unwrapped] (schema_ptr s) mutable {
+                unwrapped = compat::unwrap(std::move(pr), *s);
+                return p->query_mutations_locally(std::move(s), std::move(cmd), unwrapped, trace_state_ptr, max_size);
             }).finally([&trace_state_ptr, src_ip] () mutable {
                 tracing::trace(trace_state_ptr, "read_mutation_data handling is done, sending a response to /{}", src_ip);
             });
@@ -3495,15 +3525,16 @@ void storage_proxy::init_messaging_service() {
             tracing::begin(trace_state_ptr);
             tracing::trace(trace_state_ptr, "read_digest: message received from /{}", src_addr.addr);
         }
-        return do_with(std::move(pr), get_local_shared_storage_proxy(), std::move(trace_state_ptr), [&cinfo, cmd = make_lw_shared<query::read_command>(std::move(cmd)), src_addr = std::move(src_addr)] (compat::wrapping_partition_range& pr, shared_ptr<storage_proxy>& p, tracing::trace_state_ptr& trace_state_ptr) mutable {
+        auto max_size = cinfo.retrieve_auxiliary<uint64_t>("max_result_size");
+        return do_with(std::move(pr), get_local_shared_storage_proxy(), std::move(trace_state_ptr), [&cinfo, cmd = make_lw_shared<query::read_command>(std::move(cmd)), src_addr = std::move(src_addr), max_size] (compat::wrapping_partition_range& pr, shared_ptr<storage_proxy>& p, tracing::trace_state_ptr& trace_state_ptr) mutable {
             auto src_ip = src_addr.addr;
-            return get_schema_for_read(cmd->schema_version, std::move(src_addr)).then([cmd, &pr, &p, &trace_state_ptr] (schema_ptr s) {
+            return get_schema_for_read(cmd->schema_version, std::move(src_addr)).then([cmd, &pr, &p, &trace_state_ptr, max_size] (schema_ptr s) {
                 auto pr2 = compat::unwrap(std::move(pr), *s);
                 if (pr2.second) {
                     // this function assumes singular queries but doesn't validate
                     throw std::runtime_error("READ_DIGEST called with wrapping range");
                 }
-                return p->query_singular_local_digest(std::move(s), cmd, std::move(pr2.first), trace_state_ptr);
+                return p->query_singular_local_digest(std::move(s), cmd, std::move(pr2.first), trace_state_ptr, max_size);
             }).finally([&trace_state_ptr, src_ip] () mutable {
                 tracing::trace(trace_state_ptr, "read_digest handling is done, sending a response to /{}", src_ip);
             });
@@ -3539,41 +3570,166 @@ void storage_proxy::uninit_messaging_service() {
 // Merges reconcilable_result:s from different shards into one
 // Drops partitions which exceed the limit.
 class mutation_result_merger {
+    schema_ptr _schema;
+    lw_shared_ptr<const query::read_command> _cmd;
     unsigned _row_count = 0;
     unsigned _partition_count = 0;
     bool _short_read_allowed;
-    query::short_read _short_read;
-    std::vector<partition> _partitions;
+    // we get a batch of partitions each time, each with a key
+    // partition batches should be maintained in key order
+    // batches that share a key should be merged and sorted in decorated_key
+    // order
+    struct partitions_batch {
+        std::vector<partition> partitions;
+        query::short_read short_read;
+    };
+    std::multimap<unsigned, partitions_batch> _partitions;
     query::result_memory_accounter _memory_accounter;
+    stdx::optional<unsigned> _stop_after_key;
 public:
-    explicit mutation_result_merger(const query::read_command& cmd)
-        : _short_read_allowed(cmd.slice.options.contains(query::partition_slice::option::allow_short_read))
-    { }
-
+    explicit mutation_result_merger(schema_ptr schema, lw_shared_ptr<const query::read_command> cmd)
+            : _schema(std::move(schema))
+            , _cmd(std::move(cmd))
+            , _short_read_allowed(_cmd->slice.options.contains(query::partition_slice::option::allow_short_read)) {
+    }
     query::result_memory_accounter& memory() {
         return _memory_accounter;
     }
     const query::result_memory_accounter& memory() const {
         return _memory_accounter;
     }
-    void add_result(foreign_ptr<lw_shared_ptr<reconcilable_result>> partial_result) {
+    void add_result(unsigned key, foreign_ptr<lw_shared_ptr<reconcilable_result>> partial_result) {
+        if (_stop_after_key && key > *_stop_after_key) {
+            // A short result was added that goes before this one.
+            return;
+        }
+        std::vector<partition> partitions;
+        partitions.reserve(partial_result->partitions().size());
         // Following three lines to simplify patch; can remove later
         for (const partition& p : partial_result->partitions()) {
-            _partitions.push_back(p);
+            partitions.push_back(p);
             _row_count += p._row_count;
             _partition_count += p._row_count > 0;
         }
-        _short_read = partial_result->is_short_read();
-        if (_memory_accounter.update_and_check(partial_result->memory_usage()) && _short_read_allowed) {
-            _short_read = query::short_read::yes;
+        _memory_accounter.update(partial_result->memory_usage());
+        if (partial_result->is_short_read()) {
+            _stop_after_key = key;
         }
+        _partitions.emplace(key, partitions_batch { std::move(partitions), partial_result->is_short_read() });
     }
     reconcilable_result get() && {
-        return reconcilable_result(_row_count, std::move(_partitions), _short_read,
-                                   std::move(_memory_accounter).done());
+        auto unsorted = std::unordered_set<unsigned>();
+        struct partitions_and_last_key {
+            std::vector<partition> partitions;
+            stdx::optional<dht::decorated_key> last; // set if we had a short read
+        };
+        auto merged = std::map<unsigned, partitions_and_last_key>();
+        auto short_read = query::short_read(this->short_read());
+        // merge batches with equal keys, and note if we need to sort afterwards
+        for (auto&& key_value : _partitions) {
+            auto&& key = key_value.first;
+            if (_stop_after_key && key > *_stop_after_key) {
+                break;
+            }
+            auto&& batch = key_value.second;
+            auto&& dest = merged[key];
+            if (dest.partitions.empty()) {
+                dest.partitions = std::move(batch.partitions);
+            } else {
+                unsorted.insert(key);
+                std::move(batch.partitions.begin(), batch.partitions.end(), std::back_inserter(dest.partitions));
+            }
+            // In case of a short read we need to remove all partitions from the
+            // batch that come after the last partition of the short read
+            // result.
+            if (batch.short_read) {
+                // Nobody sends a short read with no data.
+                const auto& last = dest.partitions.back().mut().decorated_key(*_schema);
+                if (!dest.last || last.less_compare(*_schema, *dest.last)) {
+                    dest.last = last;
+                }
+                short_read = query::short_read::yes;
+            }
+        }
+
+        // Sort batches that arrived with the same keys
+        for (auto key : unsorted) {
+            struct comparator {
+                const schema& s;
+                dht::decorated_key::less_comparator dkcmp;
+
+                bool operator()(const partition& a, const partition& b) const {
+                    return dkcmp(a.mut().decorated_key(s), b.mut().decorated_key(s));
+                }
+                bool operator()(const dht::decorated_key& a, const partition& b) const {
+                    return dkcmp(a, b.mut().decorated_key(s));
+                }
+                bool operator()(const partition& a, const dht::decorated_key& b) const {
+                    return dkcmp(a.mut().decorated_key(s), b);
+                }
+            };
+            auto cmp = comparator { *_schema, dht::decorated_key::less_comparator(_schema) };
+
+            auto&& batch = merged[key];
+            boost::sort(batch.partitions, cmp);
+            if (batch.last) {
+                // This batch was built from a result that was a short read.
+                // We need to remove all partitions that are after that short
+                // read.
+                auto it = boost::range::upper_bound(batch.partitions, std::move(*batch.last), cmp);
+                batch.partitions.erase(it, batch.partitions.end());
+            }
+        }
+
+        auto final = std::vector<partition>();
+        final.reserve(_partition_count);
+        for (auto&& batch : merged | boost::adaptors::map_values) {
+            std::move(batch.partitions.begin(), batch.partitions.end(), std::back_inserter(final));
+        }
+
+        if (short_read) {
+            // Short read row and partition counts may be incorrect, recalculate.
+            _row_count = 0;
+            _partition_count = 0;
+            for (const auto& p : final) {
+                _row_count += p.row_count();
+                _partition_count += p.row_count() > 0;
+            }
+
+            if (_row_count >= _cmd->row_limit || _partition_count > _cmd->partition_limit) {
+                // Even though there was a short read contributing to the final
+                // result we got limited by total row limit or partition limit.
+                // Note that we cannot with trivial check make unset short read flag
+                // in case _partition_count == _cmd->partition_limit since the short
+                // read may have caused the last partition to contain less rows
+                // than asked for.
+                short_read = query::short_read::no;
+            }
+        }
+
+        // Trim back partition count and row count in case we overshot.
+        // Should be rare for dense tables.
+        while ((_partition_count > _cmd->partition_limit)
+                || (_partition_count && (_row_count - final.back().row_count() >= _cmd->row_limit))) {
+            _row_count -= final.back().row_count();
+            _partition_count -= final.back().row_count() > 0;
+            final.pop_back();
+        }
+        if (_row_count > _cmd->row_limit) {
+            auto mut = final.back().mut().unfreeze(_schema);
+            static const auto all = std::vector<query::clustering_range>({query::clustering_range::make_open_ended_both_sides()});
+            auto is_reversed = _cmd->slice.options.contains(query::partition_slice::option::reversed);
+            auto final_rows = _cmd->row_limit - (_row_count - final.back().row_count());
+            _row_count -= final.back().row_count();
+            auto rc = mut.partition().compact_for_query(*_schema, _cmd->timestamp, all, is_reversed, final_rows);
+            final.back() = partition(rc, freeze(mut));
+            _row_count += rc;
+        }
+
+        return reconcilable_result(_row_count, std::move(final), short_read, std::move(_memory_accounter).done());
     }
     bool short_read() const {
-        return bool(_short_read);
+        return bool(_stop_after_key) || (_short_read_allowed && _row_count > 0 && _memory_accounter.check());
     }
     unsigned partition_count() const {
         return _partition_count;
@@ -3584,65 +3740,159 @@ public:
 };
 
 future<foreign_ptr<lw_shared_ptr<reconcilable_result>>>
-storage_proxy::query_mutations_locally(schema_ptr s, lw_shared_ptr<query::read_command> cmd, const query::partition_range& pr, tracing::trace_state_ptr trace_state) {
+storage_proxy::query_mutations_locally(schema_ptr s, lw_shared_ptr<query::read_command> cmd, const query::partition_range& pr,
+                                       tracing::trace_state_ptr trace_state, uint64_t max_size) {
     if (pr.is_singular()) {
         unsigned shard = _db.local().shard_of(pr.start()->value().token());
-        return _db.invoke_on(shard, [cmd, &pr, gs=global_schema_ptr(s), gt = tracing::global_trace_state_ptr(std::move(trace_state))] (database& db) mutable {
-          return db.get_result_memory_limiter().new_read().then([&] (query::result_memory_accounter ma) {
+        return _db.invoke_on(shard, [max_size, cmd, &pr, gs=global_schema_ptr(s), gt = tracing::global_trace_state_ptr(std::move(trace_state))] (database& db) mutable {
+          return db.get_result_memory_limiter().new_mutation_read(max_size).then([&] (query::result_memory_accounter ma) {
             return db.query_mutations(gs, *cmd, pr, std::move(ma), gt).then([] (reconcilable_result&& result) {
                 return make_foreign(make_lw_shared(std::move(result)));
             });
           });
         });
     } else {
-        return query_nonsingular_mutations_locally(std::move(s), std::move(cmd), {pr}, std::move(trace_state));
+        return query_nonsingular_mutations_locally(std::move(s), std::move(cmd), {pr}, std::move(trace_state), max_size);
     }
 }
 
 future<foreign_ptr<lw_shared_ptr<reconcilable_result>>>
-storage_proxy::query_mutations_locally(schema_ptr s, lw_shared_ptr<query::read_command> cmd, const compat::one_or_two_partition_ranges& pr, tracing::trace_state_ptr trace_state) {
+storage_proxy::query_mutations_locally(schema_ptr s, lw_shared_ptr<query::read_command> cmd, const compat::one_or_two_partition_ranges& pr,
+                                       tracing::trace_state_ptr trace_state, uint64_t max_size) {
     if (!pr.second) {
-        return query_mutations_locally(std::move(s), std::move(cmd), pr.first, std::move(trace_state));
+        return query_mutations_locally(std::move(s), std::move(cmd), pr.first, std::move(trace_state), max_size);
     } else {
-        return query_nonsingular_mutations_locally(std::move(s), std::move(cmd), pr, std::move(trace_state));
+        return query_nonsingular_mutations_locally(std::move(s), std::move(cmd), pr, std::move(trace_state), max_size);
     }
 }
 
+}
+
+namespace {
+
+struct element_and_shard {
+    unsigned element;   // element in a partition range vector
+    unsigned shard;
+};
+
+bool operator==(element_and_shard a, element_and_shard b) {
+    return a.element == b.element && a.shard == b.shard;
+}
+
+}
+
+namespace std {
+
+template <>
+struct hash<element_and_shard> {
+    size_t operator()(element_and_shard es) const {
+        return es.element * 31 + es.shard;
+    }
+};
+
+}
+
+namespace service {
+
+struct partition_range_and_sort_key {
+    query::partition_range pr;
+    unsigned sort_key_shard_order;   // for the same source partition range, we sort in shard order
+};
 
 future<foreign_ptr<lw_shared_ptr<reconcilable_result>>>
-storage_proxy::query_nonsingular_mutations_locally(schema_ptr s, lw_shared_ptr<query::read_command> cmd, const std::vector<query::partition_range>& prs, tracing::trace_state_ptr trace_state) {
+storage_proxy::query_nonsingular_mutations_locally(schema_ptr s, lw_shared_ptr<query::read_command> cmd, const std::vector<query::partition_range>& prs,
+                                                   tracing::trace_state_ptr trace_state, uint64_t max_size) {
     // no one permitted us to modify *cmd, so make a copy
     auto shard_cmd = make_lw_shared<query::read_command>(*cmd);
     return do_with(cmd,
             shard_cmd,
-            mutation_result_merger{*cmd},
+            1u,
+            0u,
+            false,
+            static_cast<unsigned>(prs.size()),
+            std::unordered_map<element_and_shard, partition_range_and_sort_key>{},
+            mutation_result_merger{s, cmd},
             dht::ring_position_range_vector_sharder{prs},
             global_schema_ptr(s),
             tracing::global_trace_state_ptr(std::move(trace_state)),
-            [this, s] (lw_shared_ptr<query::read_command>& cmd,
+            [this, s, max_size] (lw_shared_ptr<query::read_command>& cmd,
                     lw_shared_ptr<query::read_command>& shard_cmd,
+                    unsigned& shards_in_parallel,
+                    unsigned& mutation_result_merger_key,
+                    bool& no_more_ranges,
+                    unsigned& partition_range_count,
+                    std::unordered_map<element_and_shard, partition_range_and_sort_key>& shards_for_this_iteration,
                     mutation_result_merger& mrm,
                     dht::ring_position_range_vector_sharder& rprs,
                     global_schema_ptr& gs,
                     tracing::global_trace_state_ptr& gt) {
-      return _db.local().get_result_memory_limiter().new_read().then([&, s] (query::result_memory_accounter ma) {
+      return _db.local().get_result_memory_limiter().new_mutation_read(max_size).then([&, s] (query::result_memory_accounter ma) {
         mrm.memory() = std::move(ma);
         return repeat_until_value([&, s] () -> future<stdx::optional<reconcilable_result>> {
-            auto now = rprs.next(*s);
-            if (!now) {
-                return make_ready_future<stdx::optional<reconcilable_result>>(std::move(mrm).get());
+            // We don't want to query a sparsely populated table sequentially, because the latency
+            // will go through the roof.  We don't want to query a densely populated table in parallel,
+            // because we'll throw away most of the results.  So we'll exponentially increase
+            // concurrency starting at 1, so we won't waste on dense tables and at most
+            // `log(nr_shards) + ignore_msb_bits` latency multiplier for near-empty tables.
+            shards_for_this_iteration.clear();
+            // If we're reading from less than smp::count shards, then we can just append
+            // each shard in order without sorting.  If we're reading from more, then
+            // we'll read from some shards at least twice, so the partitions within will be
+            // out-of-order wrt. other shards
+            auto retain_shard_order = true;
+            for (auto i = 0u; i < shards_in_parallel; ++i) {
+                auto now = rprs.next(*s);
+                if (!now) {
+                    no_more_ranges = true;
+                    break;
+                }
+                // Let's see if this is a new shard, or if we can expand an existing range
+                auto&& rng_ok = shards_for_this_iteration.emplace(element_and_shard{now->element, now->shard}, partition_range_and_sort_key{now->ring_range, i});
+                if (!rng_ok.second) {
+                    // We saw this shard already, enlarge the range (we know now->ring_range came from the same partition range;
+                    // otherwise it would have had a unique now->element).
+                    auto& rng = rng_ok.first->second.pr;
+                    rng = nonwrapping_range<dht::ring_position>(std::move(rng.start()), std::move(now->ring_range.end()));
+                    // This range is no longer ordered with respect to the others, so:
+                    retain_shard_order = false;
+                }
             }
+            auto key_base = mutation_result_merger_key;
+
+            // prepare for next iteration
+            // Each iteration uses a merger key that is either i in the loop above (so in the range [0, shards_in_parallel),
+            // or, the element index in prs (so in the range [0, partition_range_count).  Make room for sufficient keys.
+            mutation_result_merger_key += std::max(shards_in_parallel, partition_range_count);
+            shards_in_parallel *= 2;
+
             shard_cmd->partition_limit = cmd->partition_limit - mrm.partition_count();
             shard_cmd->row_limit = cmd->row_limit - mrm.row_count();
-            return _db.invoke_on(now->shard, [&, now = std::move(*now), gt] (database& db) {
-                query::result_memory_accounter accounter(db.get_result_memory_limiter(), mrm.memory());
-                return db.query_mutations(gs, *shard_cmd, now.ring_range, std::move(accounter), std::move(gt)).then([] (reconcilable_result&& rr) {
-                    return make_foreign(make_lw_shared(std::move(rr)));
+
+            return parallel_for_each(shards_for_this_iteration, [&, key_base, retain_shard_order] (const std::pair<const element_and_shard, partition_range_and_sort_key>& elem_shard_range) {
+                auto&& elem = elem_shard_range.first.element;
+                auto&& shard = elem_shard_range.first.shard;
+                auto&& range = elem_shard_range.second.pr;
+                auto sort_key_shard_order = elem_shard_range.second.sort_key_shard_order;
+                return _db.invoke_on(shard, [&, range, gt, fstate = mrm.memory().state_for_another_shard()] (database& db) {
+                    query::result_memory_accounter accounter(db.get_result_memory_limiter(), std::move(fstate));
+                    return db.query_mutations(gs, *shard_cmd, range, std::move(accounter), std::move(gt)).then([] (reconcilable_result&& rr) {
+                        return make_foreign(make_lw_shared(std::move(rr)));
+                    });
+                }).then([&, key_base, retain_shard_order, elem, sort_key_shard_order] (foreign_ptr<lw_shared_ptr<reconcilable_result>> partial_result) {
+                    // Each outer (sequential) iteration is in result order, so we pick increasing keys.
+                    // Within the inner (parallel) iteration, the results can be in order (if retain_shard_order), or not (if !retain_shard_order).
+                    // If the results are unordered, we still have to order them according to which element of prs they originated from.
+                    auto key = key_base; // for outer loop
+                    if (retain_shard_order) {
+                        key += sort_key_shard_order;  // inner loop is ordered
+                    } else {
+                        key += elem;  // inner loop ordered only by position within prs
+                    }
+                    mrm.add_result(key, std::move(partial_result));
                 });
-            }).then([&] (foreign_ptr<lw_shared_ptr<reconcilable_result>> rr) -> stdx::optional<reconcilable_result> {
-                mrm.add_result(std::move(rr));
-                if (mrm.short_read() || mrm.partition_count() >= cmd->partition_limit || mrm.row_count() >= cmd->row_limit) {
-                    return std::move(mrm).get();
+            }).then([&] () -> stdx::optional<reconcilable_result> {
+                if (mrm.short_read() || mrm.partition_count() >= cmd->partition_limit || mrm.row_count() >= cmd->row_limit || no_more_ranges) {
+                    return stdx::make_optional(std::move(mrm).get());
                 }
                 return stdx::nullopt;
             });

service/storage_proxy.hh

@@ -235,15 +235,18 @@ private:
     ::shared_ptr<abstract_read_executor> get_read_executor(lw_shared_ptr<query::read_command> cmd, query::partition_range pr, db::consistency_level cl, tracing::trace_state_ptr trace_state);
     future<foreign_ptr<lw_shared_ptr<query::result>>> query_singular_local(schema_ptr, lw_shared_ptr<query::read_command> cmd, const query::partition_range& pr,
                                                                            query::result_request request,
-                                                                           tracing::trace_state_ptr trace_state);
-    future<query::result_digest, api::timestamp_type> query_singular_local_digest(schema_ptr, lw_shared_ptr<query::read_command> cmd, const query::partition_range& pr, tracing::trace_state_ptr trace_state);
-    future<foreign_ptr<lw_shared_ptr<query::result>>> query_partition_key_range(lw_shared_ptr<query::read_command> cmd, std::vector<query::partition_range> partition_ranges, db::consistency_level cl, tracing::trace_state_ptr trace_state);
+                                                                           tracing::trace_state_ptr trace_state,
+                                                                           uint64_t max_size = query::result_memory_limiter::maximum_result_size);
+    future<query::result_digest, api::timestamp_type> query_singular_local_digest(schema_ptr, lw_shared_ptr<query::read_command> cmd, const query::partition_range& pr, tracing::trace_state_ptr trace_state,
+                                                                                  uint64_t max_size  = query::result_memory_limiter::maximum_result_size);
+    future<foreign_ptr<lw_shared_ptr<query::result>>> query_partition_key_range(lw_shared_ptr<query::read_command> cmd, const std::vector<query::partition_range> partition_ranges, db::consistency_level cl, tracing::trace_state_ptr trace_state);
     std::vector<query::partition_range> get_restricted_ranges(keyspace& ks, const schema& s, query::partition_range range);
     float estimate_result_rows_per_range(lw_shared_ptr<query::read_command> cmd, keyspace& ks);
     static std::vector<gms::inet_address> intersection(const std::vector<gms::inet_address>& l1, const std::vector<gms::inet_address>& l2);
     future<std::vector<foreign_ptr<lw_shared_ptr<query::result>>>> query_partition_key_range_concurrent(std::chrono::steady_clock::time_point timeout,
             std::vector<foreign_ptr<lw_shared_ptr<query::result>>>&& results, lw_shared_ptr<query::read_command> cmd, db::consistency_level cl, std::vector<query::partition_range>::iterator&& i,
-            std::vector<query::partition_range>&& ranges, int concurrency_factor, tracing::trace_state_ptr trace_state, uint32_t total_row_count = 0);
+            std::vector<query::partition_range>&& ranges, int concurrency_factor, tracing::trace_state_ptr trace_state,
+            uint32_t remaining_row_count, uint32_t remaining_partition_count);
 
     future<foreign_ptr<lw_shared_ptr<query::result>>> do_query(schema_ptr,
         lw_shared_ptr<query::read_command> cmd,
@@ -262,7 +265,7 @@ private:
     template<typename Range>
     future<> mutate_internal(Range mutations, db::consistency_level cl, tracing::trace_state_ptr tr_state);
     future<foreign_ptr<lw_shared_ptr<reconcilable_result>>> query_nonsingular_mutations_locally(
-            schema_ptr s, lw_shared_ptr<query::read_command> cmd, const std::vector<query::partition_range>& pr, tracing::trace_state_ptr trace_state);
+            schema_ptr s, lw_shared_ptr<query::read_command> cmd, const std::vector<query::partition_range>& pr, tracing::trace_state_ptr trace_state, uint64_t max_size);
 
 public:
     storage_proxy(distributed<database>& db);
@@ -337,16 +340,19 @@ public:
 
     future<foreign_ptr<lw_shared_ptr<reconcilable_result>>> query_mutations_locally(
         schema_ptr, lw_shared_ptr<query::read_command> cmd, const query::partition_range&,
-        tracing::trace_state_ptr trace_state = nullptr);
+        tracing::trace_state_ptr trace_state = nullptr,
+        uint64_t max_size = query::result_memory_limiter::maximum_result_size);
 
 
     future<foreign_ptr<lw_shared_ptr<reconcilable_result>>> query_mutations_locally(
         schema_ptr, lw_shared_ptr<query::read_command> cmd, const compat::one_or_two_partition_ranges&,
-        tracing::trace_state_ptr trace_state = nullptr);
+        tracing::trace_state_ptr trace_state = nullptr,
+        uint64_t max_size = query::result_memory_limiter::maximum_result_size);
 
     future<foreign_ptr<lw_shared_ptr<reconcilable_result>>> query_mutations_locally(
             schema_ptr s, lw_shared_ptr<query::read_command> cmd, const std::vector<query::partition_range>& pr,
-            tracing::trace_state_ptr trace_state = nullptr);
+            tracing::trace_state_ptr trace_state = nullptr,
+            uint64_t max_size = query::result_memory_limiter::maximum_result_size);
 
 
     future<> stop();

sstables/compress.cc

@@ -71,6 +71,12 @@ void compression::set_compressor(compressor c) {
      }
 }
 
+// locate() takes a byte position in the uncompressed stream, and finds the
+// the location of the compressed chunk on disk which contains it, and the
+// offset in this chunk.
+// locate() may only be used for offsets of actual bytes, and in particular
+// the end-of-file position (one past the last byte) MUST not be used. If the
+// caller wants to read from the end of file, it should simply read nothing.
 compression::chunk_and_offset
 compression::locate(uint64_t position) const {
     auto ucl = uncompressed_chunk_length();
@@ -310,6 +316,9 @@ public:
     virtual future<temporary_buffer<char>> skip(uint64_t n) override {
         _pos += n;
         assert(_pos <= _end_pos);
+        if (_pos == _end_pos) {
+            return make_ready_future<temporary_buffer<char>>();
+        }
         auto addr = _compression_metadata->locate(_pos);
         auto underlying_n = addr.chunk_start - _underlying_pos;
         _underlying_pos = addr.chunk_start;

sstables/sstables.cc

@@ -1703,7 +1703,7 @@ file_writer components_writer::index_file_writer(sstable& sst, const io_priority
     options.buffer_size = sst.sstable_buffer_size;
     options.io_priority_class = pc;
     options.write_behind = 10;
-    return file_writer(sst._index_file, std::move(options));
+    return file_writer(std::move(sst._index_file), std::move(options));
 }
 
 // Get the currently loaded configuration, or the default configuration in
@@ -1855,7 +1855,6 @@ void components_writer::consume_end_of_stream() {
     seal_summary(_sst._summary, std::move(_first_key), std::move(_last_key)); // what if there is only one partition? what if it is empty?
 
     _index.close().get();
-    _sst._index_file = file(); // index->close() closed _index_file
 
     if (_sst.has_component(sstable::component_type::CompressionInfo)) {
         _sst._collector.add_compression_ratio(_sst._compression.compressed_file_length(), _sst._compression.uncompressed_file_length());
@@ -1905,20 +1904,20 @@ void sstable_writer::prepare_file_writer()
     options.write_behind = 10;
 
     if (!_compression_enabled) {
-        _writer = make_shared<checksummed_file_writer>(_sst._data_file, std::move(options), true);
+        _writer = std::make_unique<checksummed_file_writer>(std::move(_sst._data_file), std::move(options), true);
     } else {
         prepare_compression(_sst._compression, _schema);
-        _writer = make_shared<file_writer>(make_compressed_file_output_stream(_sst._data_file, std::move(options), &_sst._compression));
+        _writer = std::make_unique<file_writer>(make_compressed_file_output_stream(std::move(_sst._data_file), std::move(options), &_sst._compression));
     }
 }
 
 void sstable_writer::finish_file_writer()
 {
-    _writer->close().get();
-    _sst._data_file = file(); // w->close() closed _data_file
+    auto writer = std::move(_writer);
+    writer->close().get();
 
     if (!_compression_enabled) {
-        auto chksum_wr = static_pointer_cast<checksummed_file_writer>(_writer);
+        auto chksum_wr = static_cast<checksummed_file_writer*>(writer.get());
         write_digest(_sst._write_error_handler, _sst.filename(sstable::component_type::Digest), chksum_wr->full_checksum());
         write_crc(_sst._write_error_handler, _sst.filename(sstable::component_type::CRC), chksum_wr->finalize_checksum());
     } else {
@@ -1926,6 +1925,16 @@ void sstable_writer::finish_file_writer()
     }
 }
 
+sstable_writer::~sstable_writer() {
+    if (_writer) {
+        try {
+            _writer->close().get();
+        } catch (...) {
+            sstlog.error("sstable_writer failed to close file: {}", std::current_exception());
+        }
+    }
+}
+
 sstable_writer::sstable_writer(sstable& sst, const schema& s, uint64_t estimated_partitions,
                                uint64_t max_sstable_size, bool backup, bool leave_unsealed, const io_priority_class& pc)
     : _sst(sst)

sstables/sstables.hh

@@ -781,7 +781,7 @@ class sstable_writer {
     bool _backup;
     bool _leave_unsealed;
     bool _compression_enabled;
-    shared_ptr<file_writer> _writer;
+    std::unique_ptr<file_writer> _writer;
     stdx::optional<components_writer> _components_writer;
 private:
     void prepare_file_writer();
@@ -789,6 +789,10 @@ private:
 public:
     sstable_writer(sstable& sst, const schema& s, uint64_t estimated_partitions,
                    uint64_t max_sstable_size, bool backup, bool leave_unsealed, const io_priority_class& pc);
+    ~sstable_writer();
+    sstable_writer(sstable_writer&& o) : _sst(o._sst), _schema(o._schema), _pc(o._pc), _backup(o._backup),
+            _leave_unsealed(o._leave_unsealed), _compression_enabled(o._compression_enabled), _writer(std::move(o._writer)),
+            _components_writer(std::move(o._components_writer)) {}
     void consume_new_partition(const dht::decorated_key& dk) { return _components_writer->consume_new_partition(dk); }
     void consume(tombstone t) { _components_writer->consume(t); }
     stop_iteration consume(static_row&& sr) { return _components_writer->consume(std::move(sr)); }

sstables/types.hh

@@ -153,7 +153,12 @@ struct summary_ka {
      * Similar to origin off heap size
      */
     uint64_t memory_footprint() const {
-        return sizeof(summary_entry) * entries.size() + sizeof(uint32_t) * positions.size() + sizeof(*this);
+        auto sz = sizeof(summary_entry) * entries.size() + sizeof(uint32_t) * positions.size() + sizeof(*this);
+        sz += first_key.value.size() + last_key.value.size();
+        for (auto& e : entries) {
+            sz += e.key.size();
+        }
+        return sz;
     }
 
     explicit operator bool() const {

tests/database_test.cc

@@ -56,23 +56,24 @@ SEASTAR_TEST_CASE(test_querying_with_limits) {
                 pranges.emplace_back(query::partition_range::make_singular(dht::global_partitioner().decorate_key(*s, std::move(pkey))));
             }
 
+            auto max_size = std::numeric_limits<size_t>::max();
             {
                 auto cmd = query::read_command(s->id(), s->version(), partition_slice_builder(*s).build(), 3);
-                auto result = db.query(s, cmd, query::result_request::only_result, pranges, nullptr).get0();
+                auto result = db.query(s, cmd, query::result_request::only_result, pranges, nullptr, max_size).get0();
                 assert_that(query::result_set::from_raw_result(s, cmd.slice, *result)).has_size(3);
             }
 
             {
                 auto cmd = query::read_command(s->id(), s->version(), partition_slice_builder(*s).build(),
                         query::max_rows, gc_clock::now(), std::experimental::nullopt, 5);
-                auto result = db.query(s, cmd, query::result_request::only_result, pranges, nullptr).get0();
+                auto result = db.query(s, cmd, query::result_request::only_result, pranges, nullptr, max_size).get0();
                 assert_that(query::result_set::from_raw_result(s, cmd.slice, *result)).has_size(5);
             }
 
             {
                 auto cmd = query::read_command(s->id(), s->version(), partition_slice_builder(*s).build(),
                         query::max_rows, gc_clock::now(), std::experimental::nullopt, 3);
-                auto result = db.query(s, cmd, query::result_request::only_result, pranges, nullptr).get0();
+                auto result = db.query(s, cmd, query::result_request::only_result, pranges, nullptr, max_size).get0();
                 assert_that(query::result_set::from_raw_result(s, cmd.slice, *result)).has_size(3);
             }
         });

tests/idl_test.cc

@@ -131,7 +131,7 @@ BOOST_AUTO_TEST_CASE(test_simple_compound)
     BOOST_REQUIRE_EQUAL(buf1.size(), 12);
 
     bytes_ostream buf2;
-    ser::writer_of_writable_simple_compound wowsc(buf2);
+    ser::writer_of_writable_simple_compound<bytes_ostream> wowsc(buf2);
     std::move(wowsc).write_foo(sc.foo).write_bar(sc.bar).end_writable_simple_compound();
     BOOST_REQUIRE_EQUAL(buf1.linearize(), buf2.linearize());
 
@@ -170,7 +170,7 @@ BOOST_AUTO_TEST_CASE(test_vector)
     BOOST_REQUIRE_EQUAL(buf1.size(), 136);
 
     bytes_ostream buf2;
-    ser::writer_of_writable_vectors_of_compounds wowvoc(buf2);
+    ser::writer_of_writable_vectors_of_compounds<bytes_ostream> wowvoc(buf2);
     auto first_writer = std::move(wowvoc).start_first();
     for (auto& c : vec1) {
         first_writer.add().write_foo(c.foo).write_bar(c.bar).end_writable_simple_compound();
@@ -221,7 +221,7 @@ BOOST_AUTO_TEST_CASE(test_variant)
     simple_compound sc2 = { 0x12344321, 0x56788765 };
 
     bytes_ostream buf;
-    ser::writer_of_writable_variants wowv(buf);
+    ser::writer_of_writable_variants<bytes_ostream> wowv(buf);
     auto second_writer = std::move(wowv).write_id(17).write_first_simple_compound(sc).start_second_writable_vector().start_vector();
     for (auto&& v : vec) {
         second_writer.add_vector(v);

tests/logalloc_test.cc

@@ -29,7 +29,9 @@
 #include <seastar/core/timer.hh>
 #include <seastar/core/sleep.hh>
 #include <seastar/tests/test-utils.hh>
+#include <seastar/util/defer.hh>
 #include <deque>
+#include "utils/phased_barrier.hh"
 
 #include "utils/logalloc.hh"
 #include "utils/managed_ref.hh"
@@ -529,11 +531,7 @@ inline void quiesce(FutureType&& fut) {
     // a request may be broken into many continuations. While we could just yield many times, the
     // exact amount needed to guarantee execution would be dependent on the internals of the
     // implementation, we want to avoid that.
-    timer<> tmr;
-    tmr.set_callback([] { BOOST_FAIL("The future we were waiting for took too long to get ready"); });
-    tmr.arm(2s);
-    fut.get();
-    tmr.cancel();
+    with_timeout(lowres_clock::now() + 2s, std::move(fut)).get();
 }
 
 // Simple RAII structure that wraps around a region_group
@@ -859,15 +857,22 @@ class test_reclaimer: public region_group_reclaimer {
     region_group _rg;
     std::vector<size_t> _reclaim_sizes;
     bool _shutdown = false;
+    shared_promise<> _unleash_reclaimer;
+    seastar::gate _reclaimers_done;
 public:
-    virtual void start_reclaiming() override {
-        while (this->under_pressure()) {
-            size_t reclaimed = test_async_reclaim_region::from_region(_rg.get_largest_region()).evict();
-            _result_accumulator->_reclaim_sizes.push_back(reclaimed);
-        }
+    virtual void start_reclaiming() noexcept override {
+        with_gate(_reclaimers_done, [this] {
+            return _unleash_reclaimer.get_shared_future().then([this] {
+                while (this->under_pressure()) {
+                    size_t reclaimed = test_async_reclaim_region::from_region(_rg.get_largest_region()).evict();
+                    _result_accumulator->_reclaim_sizes.push_back(reclaimed);
+                }
+            });
+        });
     }
 
     ~test_reclaimer() {
+        _reclaimers_done.close().get();
         _rg.shutdown().get();
     }
 
@@ -881,6 +886,10 @@ public:
 
     test_reclaimer(size_t threshold) : region_group_reclaimer(threshold), _result_accumulator(this), _rg(*this) {}
     test_reclaimer(test_reclaimer& parent, size_t threshold) : region_group_reclaimer(threshold), _result_accumulator(&parent), _rg(&parent._rg, *this) {}
+
+    void unleash() {
+        _unleash_reclaimer.set_value();
+    }
 };
 
 SEASTAR_TEST_CASE(test_region_groups_basic_throttling_simple_active_reclaim) {
@@ -888,6 +897,7 @@ SEASTAR_TEST_CASE(test_region_groups_basic_throttling_simple_active_reclaim) {
         // allocate a single region to exhaustion, and make sure active reclaim is activated.
         test_reclaimer simple(logalloc::segment_size);
         test_async_reclaim_region simple_region(simple.rg(), logalloc::segment_size);
+        simple.unleash();
 
         // Can't run this function until we have reclaimed something
         auto fut = simple.rg().run_when_memory_available([] {});
@@ -912,6 +922,7 @@ SEASTAR_TEST_CASE(test_region_groups_basic_throttling_active_reclaim_worst_offen
         test_async_reclaim_region small_region(simple.rg(), logalloc::segment_size);
         test_async_reclaim_region medium_region(simple.rg(), 2 * logalloc::segment_size);
         test_async_reclaim_region big_region(simple.rg(), 3 * logalloc::segment_size);
+        simple.unleash();
 
         // Can't run this function until we have reclaimed
         auto fut = simple.rg().run_when_memory_available([&simple] {
@@ -941,6 +952,9 @@ SEASTAR_TEST_CASE(test_region_groups_basic_throttling_active_reclaim_leaf_offend
         test_async_reclaim_region small_region(small_leaf.rg(), logalloc::segment_size);
         test_async_reclaim_region medium_region(root.rg(), 2 * logalloc::segment_size);
         test_async_reclaim_region big_region(large_leaf.rg(), 3 * logalloc::segment_size);
+        root.unleash();
+        large_leaf.unleash();
+        small_leaf.unleash();
 
         // Can't run this function until we have reclaimed. Try at the root, and we'll make sure
         // that the leaves are forced correctly.
@@ -967,6 +981,8 @@ SEASTAR_TEST_CASE(test_region_groups_basic_throttling_active_reclaim_ancestor_bl
         test_reclaimer leaf(root, logalloc::segment_size);
 
         test_async_reclaim_region root_region(root.rg(), logalloc::segment_size);
+        root.unleash();
+        leaf.unleash();
 
         // Can't run this function until we have reclaimed. Try at the leaf, and we'll make sure
         // that the root reclaims
@@ -992,6 +1008,8 @@ SEASTAR_TEST_CASE(test_region_groups_basic_throttling_active_reclaim_big_region_
         test_async_reclaim_region root_region(root.rg(), 4 * logalloc::segment_size);
         test_async_reclaim_region big_leaf_region(leaf.rg(), 3 * logalloc::segment_size);
         test_async_reclaim_region small_leaf_region(leaf.rg(), 2 * logalloc::segment_size);
+        root.unleash();
+        leaf.unleash();
 
         auto fut = root.rg().run_when_memory_available([&root] {
             BOOST_REQUIRE_EQUAL(root.reclaim_sizes().size(), 3);
@@ -1018,6 +1036,8 @@ SEASTAR_TEST_CASE(test_region_groups_basic_throttling_active_reclaim_no_double_r
         test_reclaimer leaf(root, logalloc::segment_size);
 
         test_async_reclaim_region leaf_region(leaf.rg(), logalloc::segment_size);
+        root.unleash();
+        leaf.unleash();
 
         auto fut_root = root.rg().run_when_memory_available([&root] {
             BOOST_REQUIRE_EQUAL(root.reclaim_sizes().size(), 1);
@@ -1037,3 +1057,117 @@ SEASTAR_TEST_CASE(test_region_groups_basic_throttling_active_reclaim_no_double_r
         BOOST_REQUIRE_EQUAL(root.reclaim_sizes()[0], logalloc::segment_size);
     });
 }
+
+// Reproduces issue #2021
+SEASTAR_TEST_CASE(test_no_crash_when_a_lot_of_requests_released_which_change_region_group_size) {
+    return seastar::async([] {
+#ifndef DEFAULT_ALLOCATOR // Because we need memory::stats().free_memory();
+        logging::logger_registry().set_logger_level("lsa", seastar::log_level::debug);
+
+        auto free_space = memory::stats().free_memory();
+        size_t threshold = size_t(0.75 * free_space);
+        region_group_reclaimer recl(threshold, threshold);
+        region_group gr(recl);
+        auto close_gr = defer([&gr] { gr.shutdown().get(); });
+        region r(gr);
+
+        with_allocator(r.allocator(), [&] {
+            std::vector<managed_bytes> objs;
+
+            r.make_evictable([&] {
+                if (objs.empty()) {
+                    return memory::reclaiming_result::reclaimed_nothing;
+                }
+                with_allocator(r.allocator(), [&] {
+                    objs.pop_back();
+                });
+                return memory::reclaiming_result::reclaimed_something;
+            });
+
+            auto fill_to_pressure = [&] {
+                while (!recl.under_pressure()) {
+                    objs.emplace_back(managed_bytes(managed_bytes::initialized_later(), 1024));
+                }
+            };
+
+            utils::phased_barrier request_barrier;
+            auto wait_for_requests = defer([&] { request_barrier.advance_and_await().get(); });
+
+            for (int i = 0; i < 1000000; ++i) {
+                fill_to_pressure();
+                future<> f = gr.run_when_memory_available([&, op = request_barrier.start()] {
+                    // Trigger group size change (Refs issue #2021)
+                    gr.update(-10);
+                    gr.update(+10);
+                });
+                BOOST_REQUIRE(!f.available());
+            }
+
+            // Release
+            while (recl.under_pressure()) {
+                objs.pop_back();
+            }
+        });
+#endif
+    });
+}
+
+SEASTAR_TEST_CASE(test_reclaiming_runs_as_long_as_there_is_soft_pressure) {
+    return seastar::async([] {
+        size_t hard_threshold = logalloc::segment_size * 8;
+        size_t soft_threshold = hard_threshold / 2;
+
+        class reclaimer : public region_group_reclaimer {
+            bool _reclaim = false;
+        protected:
+            void start_reclaiming() noexcept override {
+                _reclaim = true;
+            }
+
+            void stop_reclaiming() noexcept override {
+                _reclaim = false;
+            }
+        public:
+            reclaimer(size_t hard_threshold, size_t soft_threshold)
+                : region_group_reclaimer(hard_threshold, soft_threshold)
+            { }
+            bool reclaiming() const { return _reclaim; };
+        };
+
+        reclaimer recl(hard_threshold, soft_threshold);
+        region_group gr(recl);
+        auto close_gr = defer([&gr] { gr.shutdown().get(); });
+        region r(gr);
+
+        with_allocator(r.allocator(), [&] {
+            std::vector<managed_bytes> objs;
+
+            BOOST_REQUIRE(!recl.reclaiming());
+
+            while (!recl.over_soft_limit()) {
+                objs.emplace_back(managed_bytes(managed_bytes::initialized_later(), logalloc::segment_size));
+            }
+
+            BOOST_REQUIRE(recl.reclaiming());
+
+            while (!recl.under_pressure()) {
+                objs.emplace_back(managed_bytes(managed_bytes::initialized_later(), logalloc::segment_size));
+            }
+
+            BOOST_REQUIRE(recl.reclaiming());
+
+            while (recl.under_pressure()) {
+                objs.pop_back();
+            }
+
+            BOOST_REQUIRE(recl.over_soft_limit());
+            BOOST_REQUIRE(recl.reclaiming());
+
+            while (recl.over_soft_limit()) {
+                objs.pop_back();
+            }
+
+            BOOST_REQUIRE(!recl.reclaiming());
+        });
+    });
+}

tests/mutation_query_test.cc

@@ -76,8 +76,10 @@ static query::partition_slice make_full_slice(const schema& s) {
     return partition_slice_builder(s).build();
 }
 
+static auto inf32 = std::numeric_limits<unsigned>::max();
+
 query::result_set to_result_set(const reconcilable_result& r, schema_ptr s, const query::partition_slice& slice) {
-    return query::result_set::from_raw_result(s, slice, to_data_query_result(r, s, slice));
+    return query::result_set::from_raw_result(s, slice, to_data_query_result(r, s, slice, inf32, inf32));
 }
 
 SEASTAR_TEST_CASE(test_reading_from_single_partition) {
@@ -460,25 +462,24 @@ SEASTAR_TEST_CASE(test_result_row_count) {
 
             auto src = make_source({m1});
 
-
-            auto r = to_data_query_result(mutation_query(s, make_source({m1}), query::full_partition_range, slice, 10000, query::max_partitions, now).get0(), s, slice);
+            auto r = to_data_query_result(mutation_query(s, make_source({m1}), query::full_partition_range, slice, 10000, query::max_partitions, now).get0(), s, slice, inf32, inf32);
             BOOST_REQUIRE_EQUAL(r.row_count().value(), 0);
 
             m1.set_static_cell("s1", data_value(bytes("S_v1")), 1);
-            r = to_data_query_result(mutation_query(s, make_source({m1}), query::full_partition_range, slice, 10000, query::max_partitions, now).get0(), s, slice);
+            r = to_data_query_result(mutation_query(s, make_source({m1}), query::full_partition_range, slice, 10000, query::max_partitions, now).get0(), s, slice, inf32, inf32);
             BOOST_REQUIRE_EQUAL(r.row_count().value(), 1);
 
             m1.set_clustered_cell(clustering_key::from_single_value(*s, bytes("A")), "v1", data_value(bytes("A_v1")), 1);
-            r = to_data_query_result(mutation_query(s, make_source({m1}), query::full_partition_range, slice, 10000, query::max_partitions, now).get0(), s, slice);
+            r = to_data_query_result(mutation_query(s, make_source({m1}), query::full_partition_range, slice, 10000, query::max_partitions, now).get0(), s, slice, inf32, inf32);
             BOOST_REQUIRE_EQUAL(r.row_count().value(), 1);
 
             m1.set_clustered_cell(clustering_key::from_single_value(*s, bytes("B")), "v1", data_value(bytes("B_v1")), 1);
-            r = to_data_query_result(mutation_query(s, make_source({m1}), query::full_partition_range, slice, 10000, query::max_partitions, now).get0(), s, slice);
+            r = to_data_query_result(mutation_query(s, make_source({m1}), query::full_partition_range, slice, 10000, query::max_partitions, now).get0(), s, slice, inf32, inf32);
             BOOST_REQUIRE_EQUAL(r.row_count().value(), 2);
 
             mutation m2(partition_key::from_single_value(*s, "key2"), s);
             m2.set_static_cell("s1", data_value(bytes("S_v1")), 1);
-            r = to_data_query_result(mutation_query(s, make_source({m1, m2}), query::full_partition_range, slice, 10000, query::max_partitions, now).get0(), s, slice);
+            r = to_data_query_result(mutation_query(s, make_source({m1, m2}), query::full_partition_range, slice, 10000, query::max_partitions, now).get0(), s, slice, inf32, inf32);
             BOOST_REQUIRE_EQUAL(r.row_count().value(), 3);
     });
 }

tracing/trace_keyspace_helper.cc

@@ -118,11 +118,27 @@ future<> trace_keyspace_helper::setup_table(const sstring& name, const sstring&
         return make_ready_future<>();
     }
 
+    ::shared_ptr<cql3::statements::raw::cf_statement> parsed = static_pointer_cast<
+                    cql3::statements::raw::cf_statement>(cql3::query_processor::parse_statement(cql));
+    parsed->prepare_keyspace(KEYSPACE_NAME);
+    ::shared_ptr<cql3::statements::create_table_statement> statement =
+                    static_pointer_cast<cql3::statements::create_table_statement>(
+                                    parsed->prepare(db, qp.get_cql_stats())->statement);
+    auto schema = statement->get_cf_meta_data();
+
+    // Generate the CF UUID based on its KF names. This is needed to ensure that
+    // all Nodes that create it would create it with the same UUID and we don't
+    // hit the #420 issue.
+    auto uuid = generate_legacy_id(schema->ks_name(), schema->cf_name());
+
+    schema_builder b(schema);
+    b.set_uuid(uuid);
+
     // We don't care it it fails really - this may happen due to concurrent
     // "CREATE TABLE" invocation on different Nodes.
     // The important thing is that it will converge eventually (some traces may
     // be lost in a process but that's ok).
-    return qp.process(cql, db::consistency_level::ONE).discard_result().handle_exception([this] (auto ep) {});
+    return service::get_local_migration_manager().announce_new_column_family(b.build(), false).discard_result().handle_exception([this] (auto ep) {});;
 }
 
 bool trace_keyspace_helper::cache_sessions_table_handles(const schema_ptr& schema) {
@@ -218,7 +234,8 @@ future<> trace_keyspace_helper::start() {
                 std::map<sstring, sstring> opts;
                 opts["replication_factor"] = "2";
                 auto ksm = keyspace_metadata::new_keyspace(KEYSPACE_NAME, "org.apache.cassandra.locator.SimpleStrategy", std::move(opts), true);
-                service::get_local_migration_manager().announce_new_keyspace(ksm, false).get();
+                // We use min_timestamp so that default keyspace metadata will loose with any manual adjustments. See issue #2129.
+                service::get_local_migration_manager().announce_new_keyspace(ksm, api::min_timestamp, false).get();
             }
 
             // Create tables

tracing/tracing.cc

@@ -55,9 +55,10 @@ std::vector<sstring> trace_type_names = {
     "REPAIR"
 };
 
-tracing::tracing(const sstring& tracing_backend_helper_class_name)
+tracing::tracing(sstring tracing_backend_helper_class_name)
         : _write_timer([this] { write_timer_callback(); })
         , _thread_name(seastar::format("shard {:d}", engine().cpu_id()))
+        , _tracing_backend_helper_class_name(std::move(tracing_backend_helper_class_name))
         , _registrations{
             scollectd::add_polled_metric(scollectd::type_instance_id("tracing"
                     , scollectd::per_cpu_plugin_instance
@@ -93,27 +94,23 @@ tracing::tracing(const sstring& tracing_backend_helper_class_name)
                     , scollectd::make_typed(scollectd::data_type::GAUGE, _flushing_records))}
         , _gen(std::random_device()())
         , _slow_query_duration_threshold(default_slow_query_duraion_threshold)
-        , _slow_query_record_ttl(default_slow_query_record_ttl) {
-    try {
-        _tracing_backend_helper_ptr = create_object<i_tracing_backend_helper>(tracing_backend_helper_class_name, *this);
-    } catch (no_such_class& e) {
-        tracing_logger.error("Can't create tracing backend helper {}: not supported", tracing_backend_helper_class_name);
-        throw;
-    } catch (...) {
-        throw;
-    }
+        , _slow_query_record_ttl(default_slow_query_record_ttl) {}
+
+future<> tracing::create_tracing(sstring tracing_backend_class_name) {
+    return tracing_instance().start(std::move(tracing_backend_class_name));
 }
 
-future<> tracing::create_tracing(const sstring& tracing_backend_class_name) {
-    return tracing_instance().start(tracing_backend_class_name).then([] {
-        return tracing_instance().invoke_on_all([] (tracing& local_tracing) {
-            return local_tracing.start();
-        });
+future<> tracing::start_tracing() {
+    return tracing_instance().invoke_on_all([] (tracing& local_tracing) {
+        return local_tracing.start();
     });
 }
 
 trace_state_ptr tracing::create_session(trace_type type, trace_state_props_set props) {
-    trace_state_ptr tstate;
+    if (!started()) {
+        return trace_state_ptr();
+    }
+
     try {
         // Don't create a session if its records are likely to be dropped
         if (!may_create_new_session()) {
@@ -129,6 +126,10 @@ trace_state_ptr tracing::create_session(trace_type type, trace_state_props_set p
 }
 
 trace_state_ptr tracing::create_session(const trace_info& secondary_session_info) {
+    if (!started()) {
+        return trace_state_ptr();
+    }
+
     try {
         // Don't create a session if its records are likely to be dropped
         if (!may_create_new_session(secondary_session_info.session_id)) {
@@ -144,7 +145,17 @@ trace_state_ptr tracing::create_session(const trace_info& secondary_session_info
 }
 
 future<> tracing::start() {
+    try {
+        _tracing_backend_helper_ptr = create_object<i_tracing_backend_helper>(_tracing_backend_helper_class_name, *this);
+    } catch (no_such_class& e) {
+        tracing_logger.error("Can't create tracing backend helper {}: not supported", _tracing_backend_helper_class_name);
+        throw;
+    } catch (...) {
+        throw;
+    }
+
     return _tracing_backend_helper_ptr->start().then([this] {
+        _down = false;
         _write_timer.arm(write_period);
     });
 }

tracing/tracing.hh

@@ -43,6 +43,7 @@
 #include <vector>
 #include <atomic>
 #include <random>
+#include <seastar/core/scollectd.hh>
 #include <seastar/core/sharded.hh>
 #include <seastar/core/sstring.hh>
 #include "gc_clock.hh"
@@ -345,10 +346,15 @@ private:
 
     records_bulk _pending_for_write_records_bulk;
     timer<lowres_clock> _write_timer;
-    bool _down = false;
+    // _down becomes FALSE after the local service is fully initialized and
+    // tracing records are allowed to be created and collected. It becomes TRUE
+    // after the shutdown() call and prevents further write attempts to I/O
+    // backend.
+    bool _down = true;
     bool _slow_query_logging_enabled = false;
     std::unique_ptr<i_tracing_backend_helper> _tracing_backend_helper_ptr;
     sstring _thread_name;
+    sstring _tracing_backend_helper_class_name;
     scollectd::registrations _registrations;
     double _trace_probability = 0.0; // keep this one for querying purposes
     uint64_t _normalized_trace_probability = 0;
@@ -376,8 +382,13 @@ public:
         return tracing_instance().local();
     }
 
-    static future<> create_tracing(const sstring& tracing_backend_helper_class_name);
-    tracing(const sstring& tracing_backend_helper_class_name);
+    bool started() const {
+        return !_down;
+    }
+
+    static future<> create_tracing(sstring tracing_backend_helper_class_name);
+    static future<> start_tracing();
+    tracing(sstring tracing_backend_helper_class_name);
 
     // Initialize a tracing backend (e.g. tracing_keyspace or logstash)
     future<> start();

utils/logalloc.cc

@@ -2076,56 +2076,6 @@ uint64_t region_group::top_region_evictable_space() const {
     return _regions.empty() ? 0 : _regions.top()->evictable_occupancy().total_space();
 }
 
-void region_group::release_requests() noexcept {
-    // The later() statement is here  to avoid executing the function in update() context. But
-    // also guarantees that we won't dominate the CPU if we have many requests to release.
-    //
-    // However, both with_gate() and later() can ultimately call to schedule() and consequently
-    // allocate memory, which (if that allocation triggers a compaction - that frees memory) would
-    // defeat the very purpose of not executing this on update() context. Allocations should be rare
-    // on those but can happen, so we need to at least make sure they will not reclaim.
-    //
-    // Whatever comes after later() is already in a safe context, so we don't need to keep the lock
-    // alive until we are done with the whole execution - only until later is successfully executed.
-    tracker_reclaimer_lock rl;
-
-    _reclaimer.notify_relief();
-    if (_descendant_blocked_requests) {
-        _descendant_blocked_requests->set_value();
-    }
-    _descendant_blocked_requests = {};
-
-    if (_blocked_requests.empty()) {
-        return;
-    }
-
-    with_gate(_asynchronous_gate, [this, rl = std::move(rl)] () mutable {
-        return later().then([this] {
-            // Check again, we may have executed release_requests() in this mean time from another entry
-            // point (for instance, a descendant notification)
-            if (_blocked_requests.empty()) {
-                return;
-            }
-
-            auto blocked_at = do_for_each_parent(this, [] (auto rg) {
-                return rg->execution_permitted() ? stop_iteration::no : stop_iteration::yes;
-            });
-
-            if (!blocked_at) {
-                auto req = std::move(_blocked_requests.front());
-                _blocked_requests.pop_front();
-                req->allocate();
-                release_requests();
-            } else {
-                // If someone blocked us in the mean time then we can't execute. We need to make
-                // sure that we are listening to notifications, though. It could be that we used to
-                // be blocked on ourselves and now we are blocking on an ancestor
-                subscribe_for_ancestor_available_memory_notification(blocked_at);
-            }
-        });
-    });
-}
-
 region* region_group::get_largest_region() {
     if (!_maximal_rg || _maximal_rg->_regions.empty()) {
         return nullptr;
@@ -2159,6 +2109,88 @@ region_group::del(region_impl* child) {
     update(-child->occupancy().total_space());
 }
 
+bool
+region_group::execution_permitted() noexcept {
+    return do_for_each_parent(this, [] (auto rg) {
+        return rg->under_pressure() ? stop_iteration::yes : stop_iteration::no;
+    }) == nullptr;
+}
+
+future<>
+region_group::start_releaser() {
+    return later().then([this] {
+        return repeat([this] () noexcept {
+            if (_shutdown_requested) {
+                return make_ready_future<stop_iteration>(stop_iteration::yes);
+            }
+
+            if (!_blocked_requests.empty() && execution_permitted()) {
+                auto req = std::move(_blocked_requests.front());
+                _blocked_requests.pop_front();
+                req->allocate();
+                return make_ready_future<stop_iteration>(stop_iteration::no);
+            } else {
+                // Block reclaiming to prevent signal() from being called by reclaimer inside wait()
+                // FIXME: handle allocation failures (not very likely) like allocating_section does
+                tracker_reclaimer_lock rl;
+                return _relief.wait().then([] {
+                    return stop_iteration::no;
+                });
+            }
+        });
+    });
+}
+
+region_group::region_group(region_group *parent, region_group_reclaimer& reclaimer)
+    : _parent(parent)
+    , _reclaimer(reclaimer)
+    , _releaser(reclaimer_can_block() ? start_releaser() : make_ready_future<>())
+{
+    if (_parent) {
+        _parent->add(this);
+    }
+}
+
+bool region_group::reclaimer_can_block() const {
+    return _reclaimer.throttle_threshold() != std::numeric_limits<size_t>::max();
+}
+
+void region_group::notify_relief() {
+    _relief.signal();
+    for (region_group* child : _subgroups) {
+        child->notify_relief();
+    }
+}
+
+void region_group::update(ssize_t delta) {
+    // Most-enclosing group which was relieved.
+    region_group* top_relief = nullptr;
+
+    do_for_each_parent(this, [&top_relief, delta] (region_group* rg) mutable {
+        rg->update_maximal_rg();
+        rg->_total_memory += delta;
+
+        if (rg->_total_memory >= rg->_reclaimer.soft_limit_threshold()) {
+            rg->_reclaimer.notify_soft_pressure();
+        } else {
+            rg->_reclaimer.notify_soft_relief();
+        }
+
+        if (rg->_total_memory > rg->_reclaimer.throttle_threshold()) {
+            rg->_reclaimer.notify_pressure();
+        } else if (rg->_reclaimer.under_pressure()) {
+            rg->_reclaimer.notify_relief();
+            top_relief = rg;
+        }
+
+        return stop_iteration::no;
+    });
+
+    if (top_relief) {
+        top_relief->notify_relief();
+    }
+}
+
 allocating_section::guard::guard()
     : _prev(shard_segment_pool.emergency_reserve_max())
 { }

utils/logalloc.hh

@@ -65,8 +65,20 @@ protected:
     size_t _soft_limit;
     bool _under_pressure = false;
     bool _under_soft_pressure = false;
-    virtual void start_reclaiming() {}
-    virtual void stop_reclaiming() {}
+    // The following restrictions apply to implementations of start_reclaiming() and stop_reclaiming():
+    //
+    //  - must not use any region or region_group objects, because they're invoked synchronously
+    //    with operations on those.
+    //
+    //  - must be noexcept, because they're called on the free path.
+    //
+    //  - the implementation may be called synchronously with any operation
+    //    which allocates memory, because these are called by memory reclaimer.
+    //    In particular, the implementation should not depend on memory allocation
+    //    because that may fail when in reclaiming context.
+    //
+    virtual void start_reclaiming() noexcept {}
+    virtual void stop_reclaiming() noexcept {}
 public:
     bool under_pressure() const {
         return _under_pressure;
@@ -76,32 +88,26 @@ public:
         return _under_soft_pressure;
     }
 
-    void notify_soft_pressure() {
+    void notify_soft_pressure() noexcept {
         if (!_under_soft_pressure) {
             _under_soft_pressure = true;
             start_reclaiming();
         }
     }
 
-    void notify_soft_relief() {
+    void notify_soft_relief() noexcept {
         if (_under_soft_pressure) {
             _under_soft_pressure = false;
             stop_reclaiming();
         }
     }
 
-    void notify_pressure() {
-        if (!_under_pressure) {
-            _under_pressure = true;
-            start_reclaiming();
-        }
+    void notify_pressure() noexcept {
+        _under_pressure = true;
     }
 
-    void notify_relief() {
-        if (_under_pressure) {
-            _under_pressure = false;
-            stop_reclaiming();
-        }
+    void notify_relief() noexcept {
+        _under_pressure = false;
     }
 
     region_group_reclaimer()
@@ -109,7 +115,9 @@ public:
     region_group_reclaimer(size_t threshold)
         : _threshold(threshold), _soft_limit(threshold) {}
     region_group_reclaimer(size_t threshold, size_t soft)
-        : _threshold(threshold), _soft_limit(soft) {}
+        : _threshold(threshold), _soft_limit(soft) {
+        assert(_soft_limit <= _threshold);
+    }
 
     virtual ~region_group_reclaimer() {}
 
@@ -230,9 +238,13 @@ class region_group {
     // a different ancestor)
     std::experimental::optional<shared_promise<>> _descendant_blocked_requests = {};
 
-    region_group* _waiting_on_ancestor = nullptr;
-    seastar::gate _asynchronous_gate;
+    condition_variable _relief;
+    future<> _releaser;
     bool _shutdown_requested = false;
+
+    bool reclaimer_can_block() const;
+    future<> start_releaser();
+    void notify_relief();
 public:
     // When creating a region_group, one can specify an optional throttle_threshold parameter. This
     // parameter won't affect normal allocations, but an API is provided, through the region_group's
@@ -240,17 +252,13 @@ public:
     // the total memory for the region group (and all of its parents) is lower or equal to the
     // region_group's throttle_treshold (and respectively for its parents).
     region_group(region_group_reclaimer& reclaimer = no_reclaimer) : region_group(nullptr, reclaimer) {}
-    region_group(region_group* parent, region_group_reclaimer& reclaimer = no_reclaimer) : _parent(parent), _reclaimer(reclaimer) {
-        if (_parent) {
-            _parent->add(this);
-        }
-    }
+    region_group(region_group* parent, region_group_reclaimer& reclaimer = no_reclaimer);
     region_group(region_group&& o) = delete;
     region_group(const region_group&) = delete;
     ~region_group() {
         // If we set a throttle threshold, we'd be postponing many operations. So shutdown must be
         // called.
-        if (_reclaimer.throttle_threshold() != std::numeric_limits<size_t>::max()) {
+        if (reclaimer_can_block()) {
             assert(_shutdown_requested);
         }
         if (_parent) {
@@ -262,24 +270,7 @@ public:
     size_t memory_used() const {
         return _total_memory;
     }
-    void update(ssize_t delta) {
-        do_for_each_parent(this, [delta] (auto rg) mutable {
-            rg->update_maximal_rg();
-            rg->_total_memory += delta;
-            // It is okay to call release_requests for a region_group that can't allow execution.
-            // But that can generate various spurious messages to groups waiting on us that will be
-            // then woken up just so they can go to wait again. So let's filter that.
-            if (rg->execution_permitted()) {
-                rg->release_requests();
-            }
-            if (rg->_total_memory >= rg->_reclaimer.soft_limit_threshold()) {
-                rg->_reclaimer.notify_soft_pressure();
-            } else if (rg->_total_memory < rg->_reclaimer.soft_limit_threshold()) {
-                rg->_reclaimer.notify_soft_relief();
-            }
-            return stop_iteration::no;
-        });
-    }
+    void update(ssize_t delta);
 
     // It would be easier to call update, but it is unfortunately broken in boost versions up to at
     // least 1.59.
@@ -325,36 +316,18 @@ public:
         using futurator = futurize<std::result_of_t<Func()>>;
 
         auto blocked_at = do_for_each_parent(this, [] (auto rg) {
-            return (rg->_blocked_requests.empty() && rg->execution_permitted()) ? stop_iteration::no : stop_iteration::yes;
+            return (rg->_blocked_requests.empty() && !rg->under_pressure()) ? stop_iteration::no : stop_iteration::yes;
         });
 
         if (!blocked_at) {
             return futurator::apply(func);
         }
-        subscribe_for_ancestor_available_memory_notification(blocked_at);
 
         auto fn = std::make_unique<concrete_allocating_function<Func>>(std::forward<Func>(func));
         auto fut = fn->get_future();
         _blocked_requests.push_back(std::move(fn), timeout);
         ++_blocked_requests_counter;
 
-        // This is called here, and not at update(), for two reasons: the first, is that things that
-        // are done during the free() path should be done carefuly, in the sense that they can
-        // trigger another update call and put us in a loop. Not to mention we would like to keep
-        // those from having exceptions. We solve that for release_requests by using later(), but in
-        // here we can do away with that need altogether.
-        //
-        // Second and most important, until we actually block a request, the pressure condition may
-        // very well be transient. There are opportunities for compactions, the condition can go
-        // away on its own, etc.
-        //
-        // The reason we check execution permitted(), is that we'll still block requests if we have
-        // free memory but existing requests in the queue. That is so we can keep our FIFO ordering
-        // guarantee. So we need to distinguish here the case in which we're blocking merely to
-        // serialize requests, so that the caller does not evict more than it should.
-        if (!blocked_at->execution_permitted()) {
-            blocked_at->_reclaimer.notify_pressure();
-        }
         return fut;
     }
 
@@ -364,9 +337,11 @@ public:
     region* get_largest_region();
 
     // Shutdown is mandatory for every user who has set a threshold
+    // Can be called at most once.
     future<> shutdown() {
         _shutdown_requested = true;
-        return _asynchronous_gate.close();
+        _relief.signal();
+        return std::move(_releaser);
     }
 
     size_t blocked_requests() {
@@ -377,43 +352,9 @@ public:
         return _blocked_requests_counter;
     }
 private:
-    // Make sure we get a notification and can call release_requests when one of our ancestors that
-    // used to block us is no longer under memory pressure.
-    void subscribe_for_ancestor_available_memory_notification(region_group *ancestor) {
-        if ((this == ancestor) || (_waiting_on_ancestor)) {
-            return; // already subscribed, or no need to
-        }
-
-        _waiting_on_ancestor = ancestor;
-
-        with_gate(_asynchronous_gate, [this] {
-            // We reevaluate _waiting_on_ancestor here so we make sure there is no deferring point
-            // between determining the ancestor and registering with it for a notification. We start
-            // with _waiting_on_ancestor set to the initial value, and after we are notified, we
-            // will set _waiting_on_ancestor to nullptr to force this lambda to reevaluate it.
-            auto evaluate_ancestor_and_stop = [this] {
-                if (!_waiting_on_ancestor) {
-                    auto new_blocking_point = do_for_each_parent(this, [] (auto rg) {
-                        return (rg->execution_permitted()) ? stop_iteration::no : stop_iteration::yes;
-                    });
-                    if (!new_blocking_point) {
-                        release_requests();
-                    }
-                    _waiting_on_ancestor = (new_blocking_point == this) ? nullptr : new_blocking_point;
-                }
-                return _waiting_on_ancestor == nullptr;
-            };
-
-            return do_until(evaluate_ancestor_and_stop, [this] {
-                if (!_waiting_on_ancestor->_descendant_blocked_requests) {
-                    _waiting_on_ancestor->_descendant_blocked_requests = shared_promise<>();
-                }
-                return _waiting_on_ancestor->_descendant_blocked_requests->get_shared_future().then([this] {
-                    _waiting_on_ancestor = nullptr;
-                });
-            });
-        });
-    }
+    // Returns true if and only if constraints of this group are not violated.
+    // That's taking into account any constraints imposed by enclosing (parent) groups.
+    bool execution_permitted() noexcept;
 
     // Executes the function func for each region_group upwards in the hierarchy, starting with the
     // parameter node. The function func may return stop_iteration::no, in which case it proceeds to
@@ -433,11 +374,10 @@ private:
         }
         return nullptr;
     }
-    inline bool execution_permitted() const {
-        return _total_memory <= _reclaimer.throttle_threshold();
-    }
 
-    void release_requests() noexcept;
+    inline bool under_pressure() const {
+        return _reclaimer.under_pressure();
+    }
 
     uint64_t top_region_evictable_space() const;