fc61e98ae6
Summary:
**Context:**
`DBLogicalBlockSizeCacheTest.CreateColumnFamilies` is flaky on a rare occurrence of assertion failure below
```
db/db_logical_block_size_cache_test.cc:210
Expected equality of these values:
1
cache_->GetRefCount(cf_path_0_)
Which is: 2
```
Root-cause: `ASSERT_OK(db->DestroyColumnFamilyHandle(cfs[0]));` in the test may not successfully decrease the ref count of `cf_path_0_` since the decreasing only happens in the clean-up of `ColumnFamilyData` when `ColumnFamilyData` has no referencing to it, which may not be true when `db->DestroyColumnFamilyHandle(cfs[0])` is called since background work such as `DumpStats()` can hold reference to that `ColumnFamilyData` (suggested and repro-d by ajkr ). Similar case `ASSERT_OK(db->DestroyColumnFamilyHandle(cfs[1]));`.
See following for a deterministic repro:
```
diff --git a/db/db_impl/db_impl.cc b/db/db_impl/db_impl.cc
index 196b428a3..4e7a834c4 100644
--- a/db/db_impl/db_impl.cc
+++ b/db/db_impl/db_impl.cc
@@ -956,10 +956,16 @@ void DBImpl::DumpStats() {
// near-atomically.
// Get a ref before unlocking
cfd->Ref();
+ if (cfd->GetName() == "cf1" || cfd->GetName() == "cf2") {
+ TEST_SYNC_POINT("DBImpl::DumpStats:PostCFDRef");
+ }
{
InstrumentedMutexUnlock u(&mutex_);
cfd->internal_stats()->CollectCacheEntryStats(/*foreground=*/false);
}
+ if (cfd->GetName() == "cf1" || cfd->GetName() == "cf2") {
+ TEST_SYNC_POINT("DBImpl::DumpStats::PreCFDUnrefAndTryDelete");
+ }
cfd->UnrefAndTryDelete();
}
}
diff --git a/db/db_logical_block_size_cache_test.cc b/db/db_logical_block_size_cache_test.cc
index 1057871c9..c3872c036 100644
--- a/db/db_logical_block_size_cache_test.cc
+++ b/db/db_logical_block_size_cache_test.cc
@@ -9,6 +9,7 @@
#include "env/io_posix.h"
#include "rocksdb/db.h"
#include "rocksdb/env.h"
+#include "test_util/sync_point.h"
namespace ROCKSDB_NAMESPACE {
class EnvWithCustomLogicalBlockSizeCache : public EnvWrapper {
@@ -183,6 +184,15 @@ TEST_F(DBLogicalBlockSizeCacheTest, CreateColumnFamilies) {
ASSERT_EQ(1, cache_->GetRefCount(dbname_));
std::vector<ColumnFamilyHandle*> cfs;
+ ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->EnableProcessing();
+ ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->LoadDependency(
+ {{"DBLogicalBlockSizeCacheTest::CreateColumnFamilies::PostSetupTwoCFH",
+ "DBImpl::DumpStats:StartRunning"},
+ {"DBImpl::DumpStats:PostCFDRef",
+ "DBLogicalBlockSizeCacheTest::CreateColumnFamilies::PreDeleteTwoCFH"},
+ {"DBLogicalBlockSizeCacheTest::CreateColumnFamilies::"
+ "PostFinishCheckingRef",
+ "DBImpl::DumpStats::PreCFDUnrefAndTryDelete"}});
ASSERT_OK(db->CreateColumnFamilies(cf_options, {"cf1", "cf2"}, &cfs));
ASSERT_EQ(2, cache_->Size());
ASSERT_TRUE(cache_->Contains(dbname_));
@@ -190,7 +200,7 @@ TEST_F(DBLogicalBlockSizeCacheTest, CreateColumnFamilies) {
ASSERT_TRUE(cache_->Contains(cf_path_0_));
ASSERT_EQ(2, cache_->GetRefCount(cf_path_0_));
}
// Delete one handle will not drop cache because another handle is still
// referencing cf_path_0_.
+ TEST_SYNC_POINT(
+ "DBLogicalBlockSizeCacheTest::CreateColumnFamilies::PostSetupTwoCFH");
+ TEST_SYNC_POINT(
+ "DBLogicalBlockSizeCacheTest::CreateColumnFamilies::PreDeleteTwoCFH");
ASSERT_OK(db->DestroyColumnFamilyHandle(cfs[0]));
ASSERT_EQ(2, cache_->Size());
ASSERT_TRUE(cache_->Contains(dbname_));
@@ -209,16 +221,20 @@ TEST_F(DBLogicalBlockSizeCacheTest, CreateColumnFamilies) {
ASSERT_TRUE(cache_->Contains(cf_path_0_));
// Will fail
ASSERT_EQ(1, cache_->GetRefCount(cf_path_0_));
// Delete the last handle will drop cache.
ASSERT_OK(db->DestroyColumnFamilyHandle(cfs[1]));
ASSERT_EQ(1, cache_->Size());
ASSERT_TRUE(cache_->Contains(dbname_));
// Will fail
ASSERT_EQ(1, cache_->GetRefCount(dbname_));
+ TEST_SYNC_POINT(
+ "DBLogicalBlockSizeCacheTest::CreateColumnFamilies::"
+ "PostFinishCheckingRef");
delete db;
ASSERT_EQ(0, cache_->Size());
ASSERT_OK(DestroyDB(dbname_, options,
{{"cf1", cf_options}, {"cf2", cf_options}}));
+ ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->DisableProcessing();
}
```
**Summary**
- Removed the flaky assertion
- Clarified the comments for the test
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9516
Test Plan:
- CI
- Monitor for future flakiness
Reviewed By: ajkr
Differential Revision: D34055232
Pulled By: hx235
fbshipit-source-id: 9bf83ae5fa88bf6fc829876494d4692082e4c357
RocksDB: A Persistent Key-Value Store for Flash and RAM Storage
RocksDB is developed and maintained by Facebook Database Engineering Team. It is built on earlier work on LevelDB by Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com)
This code is a library that forms the core building block for a fast key-value server, especially suited for storing data on flash drives. It has a Log-Structured-Merge-Database (LSM) design with flexible tradeoffs between Write-Amplification-Factor (WAF), Read-Amplification-Factor (RAF) and Space-Amplification-Factor (SAF). It has multi-threaded compactions, making it especially suitable for storing multiple terabytes of data in a single database.
Start with example usage here: https://github.com/facebook/rocksdb/tree/main/examples
See the github wiki for more explanation.
The public interface is in include/. Callers should not include or
rely on the details of any other header files in this package. Those
internal APIs may be changed without warning.
Questions and discussions are welcome on the RocksDB Developers Public Facebook group and email list on Google Groups.
License
RocksDB is dual-licensed under both the GPLv2 (found in the COPYING file in the root directory) and Apache 2.0 License (found in the LICENSE.Apache file in the root directory). You may select, at your option, one of the above-listed licenses.