Summary:
The following sequence of events can cause silent data loss for write-committed
transactions.
```
Time thread 1 bg flush
| db->Put("a")
| txn = NewTxn()
| txn->Put("b", "v")
| txn->Prepare() // writes only to 5.log
| db->SwitchMemtable() // memtable 1 has "a"
| // close 5.log,
| // creates 8.log
| trigger flush
| pick memtable 1
| unlock db mutex
| write new sst
| txn->ctwb->Put("gtid", "1") // writes 8.log
| txn->Commit() // writes to 8.log
| // writes to memtable 2
| compute min_log_number_to_keep_2pc, this
| will be 8 (incorrect).
|
| Purge obsolete wals, including 5.log
|
V
```
At this point, writes of txn exists only in memtable. Close db without flush because db thinks the data in
memtable are backed by log. Then reopen, the writes are lost except key-value pair {"gtid"->"1"},
only the commit marker of txn is in 8.log
The reason lies in `PrecomputeMinLogNumberToKeep2PC()` which calls `FindMinPrepLogReferencedByMemTable()`.
In the above example, when bg flush thread tries to find obsolete wals, it uses the information
computed by `PrecomputeMinLogNumberToKeep2PC()`. The return value of `PrecomputeMinLogNumberToKeep2PC()`
depends on three components
- `PrecomputeMinLogNumberToKeepNon2PC()`. This represents the WAL that has unflushed data. As the name of this method suggests, it does not account for 2PC. Although the keys reside in the prepare section of a previous WAL, the column family references the current WAL when they are actually inserted into the memtable during txn commit.
- `prep_tracker->FindMinLogContainingOutstandingPrep()`. This represents the WAL with a prepare section but the txn hasn't committed.
- `FindMinPrepLogReferencedByMemTable()`. This represents the WAL on which some memtables (mutable and immutable) depend for their unflushed data.
The bug lies in `FindMinPrepLogReferencedByMemTable()`. Originally, this function skips checking the column families
that are being flushed, but the unit test added in this PR shows that they should not be. In this unit test, there is
only the default column family, and one of its memtables has unflushed data backed by a prepare section in 5.log.
We should return this information via `FindMinPrepLogReferencedByMemTable()`.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9571
Test Plan:
```
./transaction_test --gtest_filter=*/TransactionTest.SwitchMemtableDuringPrepareAndCommit_WC/*
make check
```
Reviewed By: siying
Differential Revision: D34235236
Pulled By: riversand963
fbshipit-source-id: 120eb21a666728a38dda77b96276c6af72b008b1
Summary:
Wasn't able to easily reproduce error, but easy to see a race
condition between TestFlushListener::OnFlushCompleted and
DBTestBase::Close(), which frees CF handles before closing DB.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9400
Test Plan: CI etc.
Reviewed By: riversand963
Differential Revision: D33645134
Pulled By: pdillinger
fbshipit-source-id: d0ec914cc43c9e14f53da633876b95b61995138d
Summary:
The failure looked like this:
```
utilities/backupable/backupable_db_test.cc:3161: Failure
Value of: db_chroot_env_->FileExists(prev_manifest_path).IsNotFound()
Actual: false
Expected: true
```
The failure could be coerced consistently with the following patch:
```
diff --git a/db/db_impl/db_impl_compaction_flush.cc b/db/db_impl/db_impl_compaction_flush.cc
index 80410f671..637636791 100644
--- a/db/db_impl/db_impl_compaction_flush.cc
+++ b/db/db_impl/db_impl_compaction_flush.cc
@@ -2772,6 +2772,8 @@ void DBImpl::BackgroundCallFlush(Env::Priority thread_pri) {
if (job_context.HaveSomethingToClean() ||
job_context.HaveSomethingToDelete() || !log_buffer.IsEmpty()) {
mutex_.Unlock();
+ bg_cv_.SignalAll();
+ sleep(1);
TEST_SYNC_POINT("DBImpl::BackgroundCallFlush:FilesFound");
// Have to flush the info logs before bg_flush_scheduled_--
// because if bg_flush_scheduled_ becomes 0 and the lock is
```
The cause was a familiar problem, which is manual flush/compaction may
return before files they obsoleted are removed. The solution is just to
wait for "scheduled" work to complete, which includes all phases
including cleanup.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9327
Test Plan:
after this PR, even the above patch to coerce the bug cannot
cause the test to fail.
Reviewed By: riversand963
Differential Revision: D33252208
Pulled By: ajkr
fbshipit-source-id: 720a7eaca58c7247d221911fffe3d5e1dbf581e9
Summary:
Directory fsync might be expensive on btrfs and it may not be needed.
Here are 4 directory fsync cases:
1. creating a new file: dir-fsync is not needed on btrfs, as long as the
new file itself is synced.
2. renaming a file: dir-fsync is not needed if the renamed file is
synced. So an API `FsyncAfterFileRename(filename, ...)` is provided
to sync the file on btrfs. By default, it just calls dir-fsync.
3. deleting files: dir-fsync is forced by set
`IOOptions.force_dir_fsync = true`
4. renaming multiple files (like backup and checkpoint): dir-fsync is
forced, the same as above.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8903
Test Plan: run tests on btrfs and non btrfs
Reviewed By: ajkr
Differential Revision: D30885059
Pulled By: jay-zhuang
fbshipit-source-id: dd2730b31580b0bcaedffc318a762d7dbf25de4a
Summary:
Added BlobMetaData to ColumnFamilyMetaData and LiveBlobMetaData and DB API GetLiveBlobMetaData to retrieve it.
First pass at struct. More tests and maybe fields to come...
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8273
Reviewed By: ltamasi
Differential Revision: D29102400
Pulled By: mrambacher
fbshipit-source-id: 8a2383a4446328be6b91dced9841fdd3dfc80b73
Summary:
When retryable IO error occurs during compaction, it is mapped to soft error and set the BG error. However, auto resume is not called to clean the soft error since compaction will reschedule by itself. In this change, When retryable IO error occurs during compaction, BG error is not set. User will be informed the error via EventHelper.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7899
Test Plan: tested with error_handler_fs_test
Reviewed By: anand1976
Differential Revision: D26094097
Pulled By: zhichao-cao
fbshipit-source-id: c53424f11d237405592cd762f43cbbdf8da8234f
Summary:
This change eliminates the need for a lot of the PermitUncheckedError calls on return from ErrorHandler methods. The calls are no longer needed as the status is returned as a reference rather than a copy. Additionally, this means that the originating status (recovery_error_, bg_error_) is not cleared implicitly as a result of calling one of these methods.
For this class, I do not know if the proper behavior should be to call PermitUncheckedError in the destructor or if the checked state should be cleared when the status is cleared. I did tests both ways. Without the code in the destructor, the status will need to be cleared in at least some of the places where it is set to OK. When running tests, I found no instances where this class was destructed with a non-OK, non-checked Status.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7539
Reviewed By: anand1976
Differential Revision: D25340565
Pulled By: pdillinger
fbshipit-source-id: 1730c035c81a475875ea745226112030ec25136c
Summary:
This PR schedules a background thread (shared across all DB instances)
to flush info log every ten seconds. This improves debuggability in case
of RocksDB hanging since it ensures the log messages leading up to the hang
will eventually become visible in the log.
The bulk of this PR is moving monitoring/stats_dump_scheduler* to db/periodic_work_scheduler*
and making the corresponding name changes since now the scheduler handles info
log flushing, not just stats dumping.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7488
Reviewed By: riversand963
Differential Revision: D24065165
Pulled By: ajkr
fbshipit-source-id: 339c47a0ff43b79fdbd055fbd9fefbb6f9d8d3b5
Summary:
Have a global StatsDumpScheduler for all DB instance stats dumping, including `DumpStats()` and `PersistStats()`. Before this, there're 2 dedicate threads for every DB instance, one for DumpStats() one for PersistStats(), which could create lots of threads if there're hundreds DB instances.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7223
Reviewed By: riversand963
Differential Revision: D23056737
Pulled By: jay-zhuang
fbshipit-source-id: 0faa2311142a73433ebb3317361db7cbf43faeba
Summary:
When dynamically linking two binaries together, different builds of RocksDB from two sources might cause errors. To provide a tool for user to solve the problem, the RocksDB namespace is changed to a flag which can be overridden in build time.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6433
Test Plan: Build release, all and jtest. Try to build with ROCKSDB_NAMESPACE with another flag.
Differential Revision: D19977691
fbshipit-source-id: aa7f2d0972e1c31d75339ac48478f34f6cfcfb3e
Summary:
We were removing the file from `log_recycle_files_` before renaming it
with `ReuseWritableFile()`. Since `ReuseWritableFile()` occurs outside
the DB mutex, it was possible for a concurrent full purge to sneak in
and delete the file before it could be renamed. Consequently, `SwitchMemtable()`
would fail and the DB would enter read-only mode.
The fix is to hold the old file number in `log_recycle_files_` until
after the file has been renamed. Full purge uses that list to decide
which files to keep, so it can no longer delete a file pending recycling.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5900
Test Plan: new unit test
Differential Revision: D19771719
Pulled By: ajkr
fbshipit-source-id: 094346349ca3fb499712e62de03905acc30b5ce8
Summary:
When two_write_queue enable, IngestExternalFile performs EnterUnbatched on both write queues. SwitchMemtable also EnterUnbatched on 2nd write queue when this option is enabled. When the call stack includes IngestExternalFile -> FlushMemTable -> SwitchMemtable, this results into a deadlock.
The implemented solution is to pass on the existing writes_stopped argument in FlushMemTable to skip EnterUnbatched in SwitchMemtable.
Fixes https://github.com/facebook/rocksdb/issues/5974
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5976
Differential Revision: D18535943
Pulled By: maysamyabandeh
fbshipit-source-id: a4f9d4964c10d4a7ca06b1e0102ca2ec395512bc
Summary:
Add a command in ldb so that users can print out tombstones in SST files.
In order to test the code, change the interface of LDBCommandRunner::RunCommand() so that it doesn't return from the program, but return the status code.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5615
Test Plan: Add a new unit test
Differential Revision: D16550326
fbshipit-source-id: 88ddfe6984bdcbb3a528abdd115089df09eba52e
Summary:
This is to prevent bg flush thread from unrefing and deleting the cfd that has been dropped by a concurrent thread.
Before RocksDB calls `DBImpl::WaitForFlushMemTables`, we should increase the refcount of each `ColumnFamilyData` so that its ref count will not drop to 0 even if the column family is dropped by another thread. Otherwise the bg flush thread can deref the cfd and deletes it, causing a segfault in `WaitForFlushMemtables` upon accessing `cfd`.
Test plan (on devserver):
```
$make clean && COMPILE_WITH_ASAN=1 make -j32
$make check
```
All unit tests must pass.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5513
Differential Revision: D16062898
Pulled By: riversand963
fbshipit-source-id: 37dc511f1dc99f036d0201bbd7f0a8f5677c763d
Summary:
This PR continues the work in https://github.com/facebook/rocksdb/pull/4748 and https://github.com/facebook/rocksdb/pull/4535 by adding a new DBOption `persist_stats_to_disk` which instructs RocksDB to persist stats history to RocksDB itself. When statistics is enabled, and both options `stats_persist_period_sec` and `persist_stats_to_disk` are set, RocksDB will periodically write stats to a built-in column family in the following form: key -> (timestamp in microseconds)#(stats name), value -> stats value. The existing API `GetStatsHistory` will detect the current value of `persist_stats_to_disk` and either read from in-memory data structure or from the hidden column family on disk.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5046
Differential Revision: D15863138
Pulled By: miasantreble
fbshipit-source-id: bb82abdb3f2ca581aa42531734ac799f113e931b
