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2ab1a73efa8ea8ea729e1ab82fab8f0cef680aaa
scylladb/row_cache.cc
Paweł Dziepak 2ab1a73efa memtable: rename partition_entry to memtable_entry 
partition_entry is going to be a more general object used by both
cache and memtable entries.

Signed-off-by: Paweł Dziepak <pdziepak@scylladb.com>
2016-06-20 21:29:51 +01:00

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/*
* Copyright (C) 2015 ScyllaDB
*/
/*
* This file is part of Scylla.
*
* Scylla is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Scylla is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
*/
#include "row_cache.hh"
#include "core/memory.hh"
#include "core/do_with.hh"
#include "core/future-util.hh"
#include <seastar/core/scollectd.hh>
#include <seastar/util/defer.hh>
#include "memtable.hh"
#include <chrono>
#include "utils/move.hh"
using namespace std::chrono_literals;
namespace stdx = std::experimental;
static logging::logger logger("cache");
thread_local seastar::thread_scheduling_group row_cache::_update_thread_scheduling_group(1ms, 0.2);
cache_tracker& global_cache_tracker() {
static thread_local cache_tracker instance;
return instance;
}
cache_tracker::cache_tracker() {
setup_collectd();
_region.make_evictable([this] {
return with_allocator(_region.allocator(), [this] {
// Removing a partition may require reading large keys when we rebalance
// the rbtree, so linearize anything we read
return with_linearized_managed_bytes([&] {
try {
if (_lru.empty()) {
return memory::reclaiming_result::reclaimed_nothing;
}
_lru.pop_back_and_dispose(current_deleter<cache_entry>());
--_partitions;
++_evictions;
++_modification_count;
return memory::reclaiming_result::reclaimed_something;
} catch (std::bad_alloc&) {
// Bad luck, linearization during partition removal caused us to
// fail. Drop the entire cache so we can make forward progress.
clear();
return memory::reclaiming_result::reclaimed_something;
}
});
});
});
}
cache_tracker::~cache_tracker() {
clear();
}
void
cache_tracker::setup_collectd() {
_collectd_registrations = std::make_unique<scollectd::registrations>(scollectd::registrations({
scollectd::add_polled_metric(scollectd::type_instance_id("cache"
, scollectd::per_cpu_plugin_instance
, "bytes", "used")
, scollectd::make_typed(scollectd::data_type::GAUGE, [this] { return _region.occupancy().used_space(); })
),
scollectd::add_polled_metric(scollectd::type_instance_id("cache"
, scollectd::per_cpu_plugin_instance
, "bytes", "total")
, scollectd::make_typed(scollectd::data_type::GAUGE, [this] { return _region.occupancy().total_space(); })
),
scollectd::add_polled_metric(scollectd::type_instance_id("cache"
, scollectd::per_cpu_plugin_instance
, "total_operations", "hits")
, scollectd::make_typed(scollectd::data_type::DERIVE, _hits)
),
scollectd::add_polled_metric(scollectd::type_instance_id("cache"
, scollectd::per_cpu_plugin_instance
, "total_operations", "misses")
, scollectd::make_typed(scollectd::data_type::DERIVE, _misses)
),
scollectd::add_polled_metric(scollectd::type_instance_id("cache"
, scollectd::per_cpu_plugin_instance
, "total_operations", "insertions")
, scollectd::make_typed(scollectd::data_type::DERIVE, _insertions)
),
scollectd::add_polled_metric(scollectd::type_instance_id("cache"
, scollectd::per_cpu_plugin_instance
, "total_operations", "merges")
, scollectd::make_typed(scollectd::data_type::DERIVE, _merges)
),
scollectd::add_polled_metric(scollectd::type_instance_id("cache"
, scollectd::per_cpu_plugin_instance
, "total_operations", "evictions")
, scollectd::make_typed(scollectd::data_type::DERIVE, _evictions)
),
scollectd::add_polled_metric(scollectd::type_instance_id("cache"
, scollectd::per_cpu_plugin_instance
, "total_operations", "removals")
, scollectd::make_typed(scollectd::data_type::DERIVE, _removals)
),
scollectd::add_polled_metric(scollectd::type_instance_id("cache"
, scollectd::per_cpu_plugin_instance
, "objects", "partitions")
, scollectd::make_typed(scollectd::data_type::GAUGE, _partitions)
),
}));
}
void cache_tracker::clear() {
with_allocator(_region.allocator(), [this] {
_lru.clear_and_dispose(current_deleter<cache_entry>());
});
_removals += _partitions;
_partitions = 0;
++_modification_count;
}
void cache_tracker::touch(cache_entry& e) {
_lru.erase(_lru.iterator_to(e));
_lru.push_front(e);
}
void cache_tracker::insert(cache_entry& entry) {
++_insertions;
++_partitions;
++_modification_count;
_lru.push_front(entry);
}
void cache_tracker::on_erase() {
--_partitions;
++_removals;
++_modification_count;
}
void cache_tracker::on_merge() {
++_merges;
}
void cache_tracker::on_hit() {
++_hits;
}
void cache_tracker::on_miss() {
++_misses;
}
allocation_strategy& cache_tracker::allocator() {
return _region.allocator();
}
logalloc::region& cache_tracker::region() {
return _region;
}
const logalloc::region& cache_tracker::region() const {
return _region;
}
// Reader which populates the cache using data from the delegate.
class populating_reader final : public mutation_reader::impl {
schema_ptr _schema;
row_cache& _cache;
mutation_reader _delegate;
public:
populating_reader(schema_ptr s, row_cache& cache, mutation_reader delegate)
: _schema(std::move(s))
, _cache(cache)
, _delegate(std::move(delegate))
{ }
virtual future<streamed_mutation_opt> operator()() override {
return _delegate().then([] (auto sm) {
return mutation_from_streamed_mutation(std::move(sm));
}).then([this, op = _cache._populate_phaser.start()] (mutation_opt&& mo) -> streamed_mutation_opt {
if (mo) {
_cache.populate(*mo);
mo->upgrade(_schema);
return streamed_mutation_from_mutation(std::move(*mo));
}
return { };
});
}
};
void row_cache::on_hit() {
_stats.hits.mark();
_tracker.on_hit();
}
void row_cache::on_miss() {
_stats.misses.mark();
_tracker.on_miss();
}
class just_cache_scanning_reader final : public mutation_reader::impl {
schema_ptr _schema;
row_cache& _cache;
row_cache::partitions_type::iterator _it;
row_cache::partitions_type::iterator _end;
const query::partition_range& _range;
stdx::optional<dht::decorated_key> _last;
uint64_t _last_reclaim_count;
size_t _last_modification_count;
private:
void update_iterators() {
auto cmp = cache_entry::compare(_cache._schema);
auto update_end = [&] {
if (_range.end()) {
if (_range.end()->is_inclusive()) {
_end = _cache._partitions.upper_bound(_range.end()->value(), cmp);
} else {
_end = _cache._partitions.lower_bound(_range.end()->value(), cmp);
}
} else {
_end = _cache._partitions.end();
}
};
auto reclaim_count = _cache.get_cache_tracker().region().reclaim_counter();
auto modification_count = _cache.get_cache_tracker().modification_count();
if (!_last) {
if (_range.start()) {
if (_range.start()->is_inclusive()) {
_it = _cache._partitions.lower_bound(_range.start()->value(), cmp);
} else {
_it = _cache._partitions.upper_bound(_range.start()->value(), cmp);
}
} else {
_it = _cache._partitions.begin();
}
update_end();
} else if (reclaim_count != _last_reclaim_count || modification_count != _last_modification_count) {
_it = _cache._partitions.upper_bound(*_last, cmp);
update_end();
}
_last_reclaim_count = reclaim_count;
_last_modification_count = modification_count;
}
public:
just_cache_scanning_reader(schema_ptr s, row_cache& cache, const query::partition_range& range)
: _schema(std::move(s)), _cache(cache), _range(range)
{ }
virtual future<streamed_mutation_opt> operator()() override {
return _cache._read_section(_cache._tracker.region(), [this] {
return with_linearized_managed_bytes([&] {
update_iterators();
if (_it == _end) {
return make_ready_future<streamed_mutation_opt>();
}
auto& ce = *_it;
++_it;
_last = ce.key();
_cache.upgrade_entry(ce);
return make_ready_future<streamed_mutation_opt>(streamed_mutation_from_mutation(ce.read(_schema)));
});
});
}
};
class scanning_and_populating_reader final : public mutation_reader::impl {
row_cache& _cache;
schema_ptr _schema;
mutation_reader _primary;
bool _secondary_only = false;
streamed_mutation_opt _next_primary;
mutation_source& _underlying;
mutation_reader _secondary;
utils::phased_barrier::phase_type _secondary_phase;
const query::partition_range& _original_range;
query::partition_range _range;
key_source& _underlying_keys;
key_reader _keys;
dht::decorated_key_opt _next_key;
dht::decorated_key_opt _last_secondary_key;
const io_priority_class _pc;
public:
scanning_and_populating_reader(schema_ptr s,
row_cache& cache,
const query::partition_range& range,
const io_priority_class& pc)
: _cache(cache), _schema(s),
_primary(make_mutation_reader<just_cache_scanning_reader>(s, cache, range)),
_underlying(cache._underlying), _original_range(range), _underlying_keys(cache._underlying_keys),
_keys(_underlying_keys(range, pc)),
_pc(pc)
{ }
virtual future<streamed_mutation_opt> operator()() override {
// FIXME: store in cache information whether the immediate successor
// of the current entry is present. As long as it is consulting
// index_reader is not necessary.
if (_secondary_only) {
return next_secondary();
}
return next_key().then([this] (dht::decorated_key_opt dk) mutable {
return _primary().then([this, dk = std::move(dk)] (streamed_mutation_opt&& mo) {
if (!mo && !dk) {
return make_ready_future<streamed_mutation_opt>();
}
if (mo) {
auto cmp = dk ? dk->tri_compare(*_schema, mo->decorated_key()) : 0;
if (cmp >= 0) {
if (cmp) {
_next_key = std::move(dk);
}
_cache.on_hit();
return make_ready_future<streamed_mutation_opt>(std::move(mo));
}
}
_next_primary = std::move(mo);
stdx::optional<query::partition_range::bound> end;
if (_next_primary) {
end = query::partition_range::bound(_next_primary->decorated_key(), false);
} else {
end = _original_range.end();
}
_range = query::partition_range(query::partition_range::bound { std::move(*dk), true }, std::move(end));
_last_secondary_key = {};
_secondary_phase = _cache._populate_phaser.phase();
_secondary = _underlying(_cache._schema, _range, query::no_clustering_key_filtering, _pc);
_secondary_only = true;
return next_secondary();
});
});
}
private:
future<streamed_mutation_opt> next_secondary() {
if (_secondary_phase != _cache._populate_phaser.phase()) {
assert(_last_secondary_key);
auto cmp = dht::ring_position_comparator(*_schema);
_range = _range.split_after(*_last_secondary_key, cmp);
_secondary_phase = _cache._populate_phaser.phase();
_secondary = _underlying(_cache._schema, _range, query::no_clustering_key_filtering, _pc);
}
return _secondary().then([] (auto sm) {
return mutation_from_streamed_mutation(std::move(sm));
}).then([this, op = _cache._populate_phaser.start()] (mutation_opt&& mo) -> streamed_mutation_opt {
if (!mo && _next_primary) {
auto cmp = dht::ring_position_comparator(*_schema);
_range = _original_range.split_after(_next_primary->decorated_key(), cmp);
_keys = _underlying_keys(_range, _pc);
_secondary_only = false;
_cache.on_hit();
return std::move(_next_primary);
}
_cache.on_miss();
if (mo) {
_cache.populate(*mo);
mo->upgrade(_schema);
_last_secondary_key = mo->decorated_key();
return streamed_mutation_from_mutation(std::move(*mo));
}
return { };
});
}
future<dht::decorated_key_opt> next_key() {
if (_next_key) {
return make_ready_future<dht::decorated_key_opt>(move_and_disengage(_next_key));
}
return _keys();
}
};
mutation_reader
row_cache::make_scanning_reader(schema_ptr s,
const query::partition_range& range,
const io_priority_class& pc) {
if (range.is_wrap_around(dht::ring_position_comparator(*s))) {
warn(unimplemented::cause::WRAP_AROUND);
throw std::runtime_error("row_cache doesn't support wrap-around ranges");
}
return make_mutation_reader<scanning_and_populating_reader>(std::move(s), *this, range, pc);
}
class slicing_reader : public mutation_reader::impl {
private:
mutation_reader _underlying;
query::clustering_key_filtering_context _ck_filtering;
future<streamed_mutation_opt> filter(mutation_opt&& mut) {
if (!mut) {
return make_ready_future<streamed_mutation_opt>();
}
const query::clustering_row_ranges& ck_ranges = _ck_filtering.get_ranges(mut->key());
mutation_partition filtered_partition = mutation_partition(mut->partition(), *(mut->schema()), ck_ranges);
if (!filtered_partition.empty()) {
mut->partition() = std::move(filtered_partition);
return make_ready_future<streamed_mutation_opt>(streamed_mutation_from_mutation(std::move(*mut)));
}
return operator()();
}
public:
slicing_reader(mutation_reader&& reader, query::clustering_key_filtering_context ck_filtering)
: _underlying(std::move(reader)), _ck_filtering(std::move(ck_filtering)) {}
virtual future<streamed_mutation_opt> operator()() override {
return _underlying().then([] (auto sm) {
return mutation_from_streamed_mutation(std::move(sm));
}).then([this] (mutation_opt&& mut) { return filter(std::move(mut)); });
}
};
mutation_reader
row_cache::make_reader(schema_ptr s,
const query::partition_range& range,
query::clustering_key_filtering_context ck_filtering,
const io_priority_class& pc) {
if (range.is_singular()) {
const query::ring_position& pos = range.start()->value();
if (!pos.has_key()) {
return make_mutation_reader<slicing_reader>(make_scanning_reader(std::move(s), range, pc), ck_filtering);
}
return _read_section(_tracker.region(), [&] {
return with_linearized_managed_bytes([&] {
const dht::decorated_key& dk = pos.as_decorated_key();
auto i = _partitions.find(dk, cache_entry::compare(_schema));
if (i != _partitions.end()) {
cache_entry& e = *i;
_tracker.touch(e);
on_hit();
upgrade_entry(e);
return make_reader_returning(e.read(s, ck_filtering));
} else {
on_miss();
return make_mutation_reader<slicing_reader>(
make_mutation_reader<populating_reader>(s, *this, _underlying(_schema, range, query::no_clustering_key_filtering, pc)),
ck_filtering);
}
});
});
}
return make_mutation_reader<slicing_reader>(make_scanning_reader(std::move(s), range, pc), ck_filtering);
}
row_cache::~row_cache() {
clear_now();
}
void row_cache::clear_now() noexcept {
with_allocator(_tracker.allocator(), [this] {
_partitions.clear_and_dispose([this, deleter = current_deleter<cache_entry>()] (auto&& p) mutable {
_tracker.on_erase();
deleter(p);
});
});
}
void row_cache::populate(const mutation& m) {
with_allocator(_tracker.allocator(), [this, &m] {
_populate_section(_tracker.region(), [&] {
with_linearized_managed_bytes([&] {
auto i = _partitions.lower_bound(m.decorated_key(), cache_entry::compare(_schema));
if (i == _partitions.end() || !i->key().equal(*_schema, m.decorated_key())) {
cache_entry* entry = current_allocator().construct<cache_entry>(
m.schema(), m.decorated_key(), m.partition());
upgrade_entry(*entry);
_tracker.insert(*entry);
_partitions.insert(i, *entry);
} else {
_tracker.touch(*i);
// We cache whole partitions right now, so if cache already has this partition,
// it must be complete, so do nothing.
}
});
});
});
}
future<> row_cache::clear() {
return invalidate(query::full_partition_range);
}
future<> row_cache::update(memtable& m, partition_presence_checker presence_checker) {
_tracker.region().merge(m._region); // Now all data in memtable belongs to cache
auto attr = seastar::thread_attributes();
attr.scheduling_group = &_update_thread_scheduling_group;
auto t = seastar::thread(attr, [this, &m, presence_checker = std::move(presence_checker)] {
auto cleanup = defer([&] {
with_allocator(_tracker.allocator(), [&m, this] () {
logalloc::reclaim_lock _(_tracker.region());
bool blow_cache = false;
// Note: clear_and_dispose() ought not to look up any keys, so it doesn't require
// with_linearized_managed_bytes(), but invalidate() does.
m.partitions.clear_and_dispose([this, deleter = current_deleter<memtable_entry>(), &blow_cache] (memtable_entry* entry) {
with_linearized_managed_bytes([&] {
try {
invalidate_locked(entry->key());
} catch (...) {
blow_cache = true;
}
deleter(entry);
});
});
if (blow_cache) {
// We failed to invalidate the key, presumably due to with_linearized_managed_bytes()
// running out of memory. Recover using clear_now(), which doesn't throw.
clear_now();
}
});
});
_populate_phaser.advance_and_await().get();
while (!m.partitions.empty()) {
with_allocator(_tracker.allocator(), [this, &m, &presence_checker] () {
unsigned quota = 30;
auto cmp = cache_entry::compare(_schema);
{
_update_section(_tracker.region(), [&] {
auto i = m.partitions.begin();
while (i != m.partitions.end() && quota) {
with_linearized_managed_bytes([&] {
{
memtable_entry& mem_e = *i;
// FIXME: Optimize knowing we lookup in-order.
auto cache_i = _partitions.lower_bound(mem_e.key(), cmp);
// If cache doesn't contain the entry we cannot insert it because the mutation may be incomplete.
// FIXME: keep a bitmap indicating which sstables we do cover, so we don't have to
// search it.
if (cache_i != _partitions.end() && cache_i->key().equal(*_schema, mem_e.key())) {
cache_entry& entry = *cache_i;
upgrade_entry(entry);
entry.partition().apply(*_schema, std::move(mem_e.partition()), *mem_e.schema());
_tracker.touch(entry);
_tracker.on_merge();
} else if (presence_checker(mem_e.key().key()) ==
partition_presence_checker_result::definitely_doesnt_exist) {
cache_entry* entry = current_allocator().construct<cache_entry>(
mem_e.schema(), std::move(mem_e.key()), std::move(mem_e.partition()));
_tracker.insert(*entry);
_partitions.insert(cache_i, *entry);
}
i = m.partitions.erase(i);
current_allocator().destroy(&mem_e);
--quota;
}
});
}
});
if (quota == 0 && seastar::thread::should_yield()) {
return;
}
}
});
seastar::thread::yield();
}
});
return do_with(std::move(t), [] (seastar::thread& t) {
return t.join();
});
}
void row_cache::touch(const dht::decorated_key& dk) {
_read_section(_tracker.region(), [&] {
with_linearized_managed_bytes([&] {
auto i = _partitions.find(dk, cache_entry::compare(_schema));
if (i != _partitions.end()) {
_tracker.touch(*i);
}
});
});
}
void row_cache::invalidate_locked(const dht::decorated_key& dk) {
_partitions.erase_and_dispose(dk, cache_entry::compare(_schema),
[this, deleter = current_deleter<cache_entry>()](auto&& p) mutable {
_tracker.on_erase();
deleter(p);
});
}
future<> row_cache::invalidate(const dht::decorated_key& dk) {
return _populate_phaser.advance_and_await().then([this, &dk] {
_read_section(_tracker.region(), [&] {
with_allocator(_tracker.allocator(), [this, &dk] {
with_linearized_managed_bytes([&] {
invalidate_locked(dk);
});
});
});
});
}
future<> row_cache::invalidate(const query::partition_range& range) {
return _populate_phaser.advance_and_await().then([this, &range] {
with_linearized_managed_bytes([&] {
if (range.is_wrap_around(dht::ring_position_comparator(*_schema))) {
auto unwrapped = range.unwrap();
invalidate_unwrapped(unwrapped.first);
invalidate_unwrapped(unwrapped.second);
} else {
invalidate_unwrapped(range);
}
});
});
}
void row_cache::invalidate_unwrapped(const query::partition_range& range) {
logalloc::reclaim_lock _(_tracker.region());
auto cmp = cache_entry::compare(_schema);
auto begin = _partitions.begin();
if (range.start()) {
if (range.start()->is_inclusive()) {
begin = _partitions.lower_bound(range.start()->value(), cmp);
} else {
begin = _partitions.upper_bound(range.start()->value(), cmp);
}
}
auto end = _partitions.end();
if (range.end()) {
if (range.end()->is_inclusive()) {
end = _partitions.upper_bound(range.end()->value(), cmp);
} else {
end = _partitions.lower_bound(range.end()->value(), cmp);
}
}
with_allocator(_tracker.allocator(), [this, begin, end] {
_partitions.erase_and_dispose(begin, end, [this, deleter = current_deleter<cache_entry>()] (auto&& p) mutable {
_tracker.on_erase();
deleter(p);
});
});
}
row_cache::row_cache(schema_ptr s, mutation_source fallback_factory, key_source underlying_keys,
cache_tracker& tracker)
: _tracker(tracker)
, _schema(std::move(s))
, _partitions(cache_entry::compare(_schema))
, _underlying(std::move(fallback_factory))
, _underlying_keys(std::move(underlying_keys))
{ }
cache_entry::cache_entry(cache_entry&& o) noexcept
: _schema(std::move(o._schema))
, _key(std::move(o._key))
, _p(std::move(o._p))
, _lru_link()
, _cache_link()
{
{
auto prev = o._lru_link.prev_;
o._lru_link.unlink();
cache_tracker::lru_type::node_algorithms::link_after(prev, _lru_link.this_ptr());
}
{
using container_type = row_cache::partitions_type;
container_type::node_algorithms::replace_node(o._cache_link.this_ptr(), _cache_link.this_ptr());
container_type::node_algorithms::init(o._cache_link.this_ptr());
}
}
void row_cache::set_schema(schema_ptr new_schema) noexcept {
_schema = std::move(new_schema);
}
mutation cache_entry::read(const schema_ptr& s) {
auto m = mutation(_schema, _key, _p);
if (_schema != s) {
m.upgrade(s);
}
return m;
}
mutation cache_entry::read(const schema_ptr& s, query::clustering_key_filtering_context ck_filtering) {
const query::clustering_row_ranges& ck_ranges = ck_filtering.get_ranges(_key.key());
mutation_partition filtered_partition = mutation_partition(_p, *_schema, ck_ranges);
auto m = mutation(_schema, _key, std::move(filtered_partition));
if (_schema != s) {
m.upgrade(s);
}
return m;
}
const schema_ptr& row_cache::schema() const {
return _schema;
}
void row_cache::upgrade_entry(cache_entry& e) {
if (e._schema != _schema) {
auto& r = _tracker.region();
assert(!r.reclaiming_enabled());
with_allocator(r.allocator(), [this, &e] {
with_linearized_managed_bytes([&] {
e._p.upgrade(*e._schema, *_schema);
e._schema = _schema;
});
});
}
}
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