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fix potential stale data in cache update

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We currently have a problem in update_cache, that can be trigger by ordering
issues related to memtable flush termination (not initiation) and/or
update_cache() call duration.

That issue is described in #1364, and in short, happens if a call to
update_cache starts before and ongoing call finishes. There is now a new SSTable
that should be consulted by the presence checker that is not.

The partition checker operates in a stale list because we need to make sure the
SSTable we just wrote is excluded from it.  This patch changes the partition
checker so that all SSTables currently in use are consulted, except for the one
we have just flushed. That provides both the guarantee that we won't check our
own SSTable and access to the most up-to-date SSTable list.

Fixes #1364

Signed-off-by: Glauber Costa <glauber@scylladb.com>
Message-Id: <fa1cee672bba8e21725c6847353552791225295f.1466534499.git.glauber@scylladb.com>
This commit is contained in:
Glauber Costa
2016-06-21 14:41:41 -04:00
committed by Tomasz Grabiec
parent bcba45f546
commit e08fa7dafa
2 changed files with 10 additions and 9 deletions
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15
database.cc
View File

@@ -125,10 +125,11 @@ column_family::column_family(schema_ptr schema, config config, db::commitlog* cl
}
partition_presence_checker
column_family::make_partition_presence_checker(lw_shared_ptr<sstable_list> old_sstables) {
return [this, old_sstables = std::move(old_sstables)] (partition_key_view key) {
for (auto&& s : *old_sstables) {
if (s.second->filter_has_key(*_schema, key)) {
column_family::make_partition_presence_checker(sstables::shared_sstable exclude_sstable) {
return [this, exclude_sstable = std::move(exclude_sstable)] (partition_key_view key) {
auto exclude = [e = std::move(exclude_sstable)] (auto s) { return s != e; };
for (auto&& s : boost::make_iterator_range(*_sstables) | boost::adaptors::map_values | boost::adaptors::filtered(exclude)) {
if (s->filter_has_key(*_schema, key)) {
return partition_presence_checker_result::maybe_exists;
}
}
@@ -621,11 +622,11 @@ void column_family::add_sstable(lw_shared_ptr<sstables::sstable> sstable) {
}
future<>
column_family::update_cache(memtable& m, lw_shared_ptr<sstable_list> old_sstables) {
column_family::update_cache(memtable& m, sstables::shared_sstable exclude_sstable) {
if (_config.enable_cache) {
// be careful to use the old sstable list, since the new one will hit every
// mutation in m.
return _cache.update(m, make_partition_presence_checker(std::move(old_sstables)));
return _cache.update(m, make_partition_presence_checker(std::move(exclude_sstable)));
} else {
return make_ready_future<>();
}
@@ -798,7 +799,7 @@ column_family::try_flush_memtable_to_sstable(lw_shared_ptr<memtable> old) {
trigger_compaction();
return update_cache(*old, std::move(old_sstables)).then_wrapped([this, old] (future<> f) {
return update_cache(*old, newtab).then_wrapped([this, old] (future<> f) {
try {
f.get();
} catch(...) {

4
database.hh
View File

@@ -380,7 +380,7 @@ private:
lw_shared_ptr<memtable> new_memtable();
lw_shared_ptr<memtable> new_streaming_memtable();
future<stop_iteration> try_flush_memtable_to_sstable(lw_shared_ptr<memtable> memt);
future<> update_cache(memtable&, lw_shared_ptr<sstable_list> old_sstables);
future<> update_cache(memtable&, sstables::shared_sstable exclude_sstable);
struct merge_comparator;
// update the sstable generation, making sure that new new sstables don't overwrite this one.
@@ -414,7 +414,7 @@ private:
mutation_source sstables_as_mutation_source();
key_source sstables_as_key_source() const;
partition_presence_checker make_partition_presence_checker(lw_shared_ptr<sstable_list> old_sstables);
partition_presence_checker make_partition_presence_checker(sstables::shared_sstable exclude_sstable);
std::chrono::steady_clock::time_point _sstable_writes_disabled_at;
void do_trigger_compaction();
public: