Commit Graph

256 Commits

Author SHA1 Message Date
Maysam Yabandeh
5c0e304170 WritePrepared: Clarify the need for two_write_queues in unordered_write (#5313)
Summary:
WritePrepared transactions when configured with two_write_queues=true offers higher throughput with unordered_write feature without however compromising the rocksdb guarantees. This is because it performs ordering among writes in a 2nd step that is not tied to memtable write speed. The 2nd step is naturally provided by 2PC when the commit phase does the ordering as well. Without 2PC, the 2nd step would only be provided when we use two_write_queues=true, where WritePrepared after performing the writes, in a 2nd step uses the 2nd queue to assign order to the writes.
The patch clarifies the need for two_write_queues=true in the HISTORY and inline comments of unordered_writes. Moreover it extends the stress tests of WritePrepared to unordred_write.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5313

Differential Revision: D15379977

Pulled By: maysamyabandeh

fbshipit-source-id: 5b6f05b9b59285dcbf3b0532215ba9fe7d926e00
2019-05-20 07:49:20 -07:00
Maysam Yabandeh
c71f5bb9aa Disable WriteUnPrepared stress tests (#5315)
Summary:
They are kind of flaky at the moment. Will re-enable it when flakiness is fixed.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5315

Differential Revision: D15382744

Pulled By: maysamyabandeh

fbshipit-source-id: 8b2f9d81a4bb34bfd51481727a682d5cd063c5e3
2019-05-16 15:39:33 -07:00
Maysam Yabandeh
f0e8216197 WritePrepared: Fix deadlock in WriteRecoverableState (#5306)
Summary:
The recent improvement in https://github.com/facebook/rocksdb/pull/3661 could cause a deadlock: When writing recoverable state, we also commit its sequence number to commit table, which could result into evicting existing commit entry, which could result into advancing max_evicted_seq_, which would need to get snapshots from database, which requires obtaining db mutex. The patch releases db_mutex before calling the callback in WriteRecoverableState to avoid the potential deadlock. It also improves the stress tests to let the issue be manifested in the tests.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5306

Differential Revision: D15341458

Pulled By: maysamyabandeh

fbshipit-source-id: 05dcbed7e21b789fd1e5fd5ee8eea08077162323
2019-05-15 13:53:54 -07:00
Thomas Fersch
a42757607d Use pre-increment instead of post-increment for iterators (#5296)
Summary:
Google C++ style guide indicates pre-increment should be used for iterators: https://google.github.io/styleguide/cppguide.html#Preincrement_and_Predecrement. Replaced all instances of ' it++' by ' ++it' (where type is iterator). So this covers the cases where iterators are named 'it'.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5296

Differential Revision: D15301256

Pulled By: tfersch

fbshipit-source-id: 2803483c1392504ad3b281d21db615429c71114b
2019-05-15 13:19:15 -07:00
Maysam Yabandeh
f383641a1d Unordered Writes (#5218)
Summary:
Performing unordered writes in rocksdb when unordered_write option is set to true. When enabled the writes to memtable are done without joining any write thread. This offers much higher write throughput since the upcoming writes would not have to wait for the slowest memtable write to finish. The tradeoff is that the writes visible to a snapshot might change over time. If the application cannot tolerate that, it should implement its own mechanisms to work around that. Using TransactionDB with WRITE_PREPARED write policy is one way to achieve that. Doing so increases the max throughput by 2.2x without however compromising the snapshot guarantees.
The patch is prepared based on an original by siying
Existing unit tests are extended to include unordered_write option.

Benchmark Results:
```
TEST_TMPDIR=/dev/shm/ ./db_bench_unordered --benchmarks=fillrandom --threads=32 --num=10000000 -max_write_buffer_number=16 --max_background_jobs=64 --batch_size=8 --writes=3000000 -level0_file_num_compaction_trigger=99999 --level0_slowdown_writes_trigger=99999 --level0_stop_writes_trigger=99999 -enable_pipelined_write=false -disable_auto_compactions  --unordered_write=1
```
With WAL
- Vanilla RocksDB: 78.6 MB/s
- WRITER_PREPARED with unordered_write: 177.8 MB/s (2.2x)
- unordered_write: 368.9 MB/s (4.7x with relaxed snapshot guarantees)

Without WAL
- Vanilla RocksDB: 111.3 MB/s
- WRITER_PREPARED with unordered_write: 259.3 MB/s MB/s (2.3x)
- unordered_write: 645.6 MB/s (5.8x with relaxed snapshot guarantees)

- WRITER_PREPARED with unordered_write disable concurrency control: 185.3 MB/s MB/s (2.35x)

Limitations:
- The feature is not yet extended to `max_successive_merges` > 0. The feature is also incompatible with `enable_pipelined_write` = true as well as with `allow_concurrent_memtable_write` = false.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5218

Differential Revision: D15219029

Pulled By: maysamyabandeh

fbshipit-source-id: 38f2abc4af8780148c6128acdba2b3227bc81759
2019-05-13 17:47:21 -07:00
anand76
1c8cbf315f Extend MultiGet batching to Transactions (#5210)
Summary:
MultiGet batching was implemented in #5011 in order to reduce CPU utilization when looking up multiple keys at once. This PR implements corresponding ```MultiGet``` and ```MultiGetSingleCFForUpdate``` in ```rocksdb::Transaction``` that call the underlying batching implementation.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5210

Differential Revision: D15048164

Pulled By: anand1976

fbshipit-source-id: c52f6043102ab0cbc723f4cba2a7b7d1767f6f52
2019-04-23 14:11:26 -07:00
jsteemann
de76909464 refactor SavePoints (#5192)
Summary:
Savepoints are assumed to be used in a stack-wise fashion (only
the top element should be used), so they were stored by `WriteBatch`
in a member variable `save_points` using an std::stack.

Conceptually this is fine, but the implementation had a few issues:
- the `save_points_` instance variable was a plain pointer to a heap-
  allocated `SavePoints` struct. The destructor of `WriteBatch` simply
  deletes this pointer. However, the copy constructor of WriteBatch
  just copied that pointer, meaning that copying a WriteBatch with
  active savepoints will very likely have crashed before. Now a proper
  copy of the savepoints is made in the copy constructor, and not just
  a copy of the pointer
- `save_points_` was an std::stack, which defaults to `std::deque` for
  the underlying container. A deque is a bit over the top here, as we
  only need access to the most recent savepoint (i.e. stack.top()) but
  never any elements at the front. std::deque is rather expensive to
  initialize in common environments. For example, the STL implementation
  shipped with GNU g++ will perform a heap allocation of more than 500
  bytes to create an empty deque object. Although the `save_points_`
  container is created lazily by RocksDB, moving from a deque to a plain
  `std::vector` is much more memory-efficient. So `save_points_` is now
  a vector.
- `save_points_` was changed from a plain pointer to an `std::unique_ptr`,
  making ownership more explicit.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5192

Differential Revision: D15024074

Pulled By: maysamyabandeh

fbshipit-source-id: 5b128786d3789cde94e46465c9e91badd07a25d7
2019-04-19 20:33:04 -07:00
jsteemann
8295d364e2 Improve transaction lock details (#5193)
Summary:
This branch contains two small improvements:
* Create `LockMap` entries using `std::make_shared`. This saves one heap allocation per LockMap entry but also locates the control block and the LockMap object closely together in memory, which can help with caching
* Reorder the members of `TrackedTrxInfo`, so that the resulting struct uses less memory (at least on 64bit systems)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5193

Differential Revision: D14934536

Pulled By: maysamyabandeh

fbshipit-source-id: f7b49812bb4b6029eef9d131e7cd56260df5b28e
2019-04-15 10:44:03 -07:00
Manuel Ung
d655a3aab7 Remove extraneous call to TrackKey (#5173)
Summary:
In `PessimisticTransaction::TryLock`, we were calling `TrackKey` even when assume_tracked=true, which defeats the purpose of assume_tracked. Remove this.

For keys that are already tracked, TrackKey will actually bump some counters (num_reads/num_writes) which are consumed in `TransactionBaseImpl::GetTrackedKeysSinceSavePoint`, and this is used to determine which keys were tracked since the last savepoint. I believe this functionality should still work, since I think the user should not call GetForUpdate/Put(assume_tracked=true) across savepoints, and if they do, they should not expect the Put(assume_tracked=true) to show up as a tracked key in the second savepoint.

This is another 2-3% cpu improvement.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5173

Differential Revision: D14883809

Pulled By: lth

fbshipit-source-id: 7d09f0772da422384af0519773e310c22b0cbca3
2019-04-12 16:37:12 -07:00
Maysam Yabandeh
fe642cbee6 WritePrepared: fix race condition in reading batch with duplicate keys (#5147)
Summary:
When ReadOption doesn't specify a snapshot, WritePrepared::Get used kMaxSequenceNumber to avoid the cost of creating a new snapshot object (that requires sync over db_mutex). This creates a race condition if it is reading from the writes of a transaction that had duplicate keys: each instance of duplicate key is inserted with a different sequence number and depending on the ordering the ::Get might skip the newer one and read the older one that is obsolete.
The patch fixes that by using last published seq as the snapshot sequence number. It also adds a check after the read is done to ensure that the max_evicted_seq has not advanced the aforementioned seq, which is a very unlikely event. If it did, then the read is not valid since the seq is not backed by an actually snapshot to let IsInSnapshot handle that properly when an overlapping commit is evicted from commit cache.
A unit  test is added to reproduce the race condition with duplicate keys.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5147

Differential Revision: D14758815

Pulled By: maysamyabandeh

fbshipit-source-id: a56915657132cf6ba5e3f5ea1b5d78c803407719
2019-04-12 14:40:41 -07:00
Manuel Ung
ef0fc1b461 Reduce copies of LockInfo (#5172)
Summary:
The LockInfo struct is not easy to copy because it contains std::vector. Reduce copies by using move constructor and `unordered_map::emplace`.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5172

Differential Revision: D14882053

Pulled By: lth

fbshipit-source-id: 93999ec6ab1a5841fb5115abb764b6c1831a6de1
2019-04-10 15:58:58 -07:00
Siying Dong
0bb555630f Consolidate hash function used for non-persistent data in a new function (#5155)
Summary:
Create new function NPHash64() and GetSliceNPHash64(), which are currently
implemented using murmurhash.
Replace the current direct call of murmurhash() to use the new functions
if the hash results are not used in on-disk format.
This will make it easier to try out or switch to alternative functions
in the uses where data format compatibility doesn't need to be considered.
This part shouldn't have any performance impact.

Also, the sharded cache hash function is changed to the new format, because
it falls into this categoery. It doesn't show visible performance impact
in db_bench results. CPU showed by perf is increased from about 0.2% to 0.4%
in an extreme benchmark setting (4KB blocks, no-compression, everything
cached in block cache). We've known that the current hash function used,
our own Hash() has serious hash quality problem. It can generate a lots of
conflicts with similar input. In this use case, it means extra lock contention
for reads from the same file. This slight CPU regression is worthy to me
to counter the potential bad performance with hot keys. And hopefully this
will get further improved in the future with a better hash function.

cache_test's condition is relaxed a little bit to. The new hash is slightly
more skewed in this use case, but I manually checked the data and see
the hash results are still in a reasonable range.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5155

Differential Revision: D14834821

Pulled By: siying

fbshipit-source-id: ec9a2c0a2f8ae4b54d08b13a5c2e9cc97aa80cb5
2019-04-08 13:32:06 -07:00
Maysam Yabandeh
7441a0ecba WriteUnPrepared: fix ubsan complaint (#5148)
Summary:
Ubsna complains that in initialization of WriteUnpreparedTxnReadCallback the method of the child class is used before the parent class is constructed. The patch fixes that by making the aforementioned method static.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5148

Differential Revision: D14760098

Pulled By: maysamyabandeh

fbshipit-source-id: cf19b7c1fdb5de0a54e62c1deebe09a0fa048ded
2019-04-03 15:51:30 -07:00
Maysam Yabandeh
5234fc1b70 Mark logs with prepare in PreReleaseCallback (#5121)
Summary:
In prepare phase of 2PC, the db promises to remember the prepared data, for possible future commits. To fulfill the promise the prepared data must be persisted in the WAL so that they could be recovered after a crash. The log that contains a prepare batch that is not committed yet, is marked so that it is not garbage collected before the transaction commits/rollbacks. The bug was that the write to the log file and the mark of the file was not atomic, and WAL gc could have happened before the WAL log is actually marked. This patch moves the marking logic to PreReleaseCallback so that the WAL gc logic that joins both write threads would see the WAL write and WAL mark atomically.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5121

Differential Revision: D14665210

Pulled By: maysamyabandeh

fbshipit-source-id: 1d66aeb1c66a296cb4899a5a20c4d40c59e4b534
2019-04-02 15:17:47 -07:00
Maysam Yabandeh
14b3f683a1 WriteUnPrepared: less virtual in iterator callback (#5049)
Summary:
WriteUnPrepared adds a virtual function, MaxUnpreparedSequenceNumber, to ReadCallback, which returns 0 unless WriteUnPrepared is enabled and the transaction has uncommitted data written to the DB. Together with snapshot sequence number, this determines the last sequence that is visible to reads.
The patch clarifies the guarantees of the GetIterator API in WriteUnPrepared transactions and make use of that to statically initialize the read callback and thus avoid the virtual call.
Furthermore it increases the minimum value for min_uncommitted from 0 to 1 as seq 0 is used only for last level keys that are committed in all snapshots.

The following benchmark shows +0.26% higher throughput in seekrandom benchmark.

Benchmark:
./db_bench --benchmarks=fillrandom --use_existing_db=0 --num=1000000 --db=/dev/shm/dbbench

./db_bench --benchmarks=seekrandom[X10] --use_existing_db=1 --db=/dev/shm/dbbench --num=1000000 --duration=60 --seek_nexts=100
seekrandom [AVG    10 runs] : 20355 ops/sec;  225.2 MB/sec
seekrandom [MEDIAN 10 runs] : 20425 ops/sec;  225.9 MB/sec

./db_bench_lessvirtual3 --benchmarks=seekrandom[X10] --use_existing_db=1 --db=/dev/shm/dbbench --num=1000000 --duration=60 --seek_nexts=100
seekrandom [AVG    10 runs] : 20409 ops/sec;  225.8 MB/sec
seekrandom [MEDIAN 10 runs] : 20487 ops/sec;  226.6 MB/sec
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5049

Differential Revision: D14366459

Pulled By: maysamyabandeh

fbshipit-source-id: ebaff8908332a5ae9af7defeadabcb624be660ef
2019-04-02 14:47:16 -07:00
Maysam Yabandeh
a703f16da9 WriteUnPrepared: Enable auto-compaction after max_evicted_seq_ init (#5128)
Summary:
Compaction would depend on max_evicted_seq_ value. The ::Initialize method should do that after max_evicted_seq_ is properly initialized. The patch also back ports #4853 from WritePrepared txn to WriteUnPrepared.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5128

Differential Revision: D14686562

Pulled By: maysamyabandeh

fbshipit-source-id: b2355025712a72676ac3b20a95258adcf4774490
2019-03-29 13:18:57 -07:00
Maysam Yabandeh
04d3ac4e63 Fix tsan compliant on AddPreparedBeforeMax (#5052)
Summary:
Add a mutex to the test to synchronize before accessing the shared txn object.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5052

Differential Revision: D14386861

Pulled By: maysamyabandeh

fbshipit-source-id: 5b32e209840b210c35af53848dc77f489a76c95a
2019-03-08 09:39:00 -08:00
Maysam Yabandeh
04a2631dbe WritePrepared: handle adding prepare before max_evicted_seq_ (#5025)
Summary:
The patch fixes an improbable race condition between AddPrepared from one write queue and AdvanceMaxEvictedSeq from another queue. In this scenario AddPrepared finds prepare_seq lower than max and adding to PrepareHeap as usual while AdvanceMaxEvictedSeq has finished checking PrepareHeap against the future max. Thus when AdvanceMaxEvictedSeq finishes off by updating the max_evicted_seq_, PrepareHeap ends up with a prepared_seq lower than it which breaks the PrepareHeap contract. The fix is that in AddPrepared we check against the future_max_evicted_seq_ instead, which is update before AdvanceMaxEvictedSeq acquire prepare_mutex_ and looks into PrepareHeap.
A unit test added to test for the failure scenario. The code is also refactored a bit to remove the duplicate code between AdvanceMaxEvictedSeq and AddPrepared.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5025

Differential Revision: D14249028

Pulled By: maysamyabandeh

fbshipit-source-id: 072ea56663f40359662c05fafa6ac524417b0622
2019-03-07 07:41:15 -08:00
Maysam Yabandeh
703f1375c2 WritePrepared: Add rollback batch to PreparedHeap (#5026)
Summary:
The patch adds the sequence number of the rollback patch to the PrepareHeap when two_write_queues is enabled. Although the current behavior is still correct, the change simplifies reasoning about the code, by having all uncommitted batches registered with the PreparedHeap.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5026

Differential Revision: D14249401

Pulled By: maysamyabandeh

fbshipit-source-id: 1e3424edee5cd14e56ee35931ad3c93ed997cd5a
2019-03-07 07:33:31 -08:00
Maysam Yabandeh
68a2f94d5d WritePrepared: commit only from the 2nd queue (#5014)
Summary:
When two_write_queues is enabled we call ::AddPrepared only from the main queue, which writes to both WAL and memtable, and call ::AddCommitted from the 2nd queue, which writes only to WAL. This simplifies the logic by avoiding concurrency between AddPrepared and also between AddCommitted. The patch fixes one case that did not conform with the rule above. This would allow future refactoring. For example AdvaneMaxEvictedSeq, which is invoked by AddCommitted, can be simplified by assuming lack of concurrent calls to it.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5014

Differential Revision: D14210493

Pulled By: maysamyabandeh

fbshipit-source-id: 6db5ba372a294a568a14caa010576460917a4eab
2019-02-28 15:23:34 -08:00
Maysam Yabandeh
a661c0d208 WritePrepared: optimize read path by avoiding virtual (#5018)
Summary:
The read path includes a callback function, ReadCallback, which would eventually calls IsInSnapshot to figure if a particular seq is in the reading snapshot or not. This callback is virtual, which adds the cost of multiple virtual function call to each read. The first few checks in IsInSnapshot, however, are quite trivial and take care of majority of the cases. The patch moves those to a non-virtual function in the the parent class, ReadCallback, to lower the virtual callback cost.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5018

Differential Revision: D14226562

Pulled By: maysamyabandeh

fbshipit-source-id: 6feed5b34f3b082e52092c5ef143e29b49c46b44
2019-02-26 16:56:19 -08:00
Maysam Yabandeh
cf98df34c1 Change random seed for txn stress tests on each run (#5004)
Summary:
Currently the transaction stress tests use thread id as the seed. Since the thread ids are likely to be the same across multiple runs, the seed is thus going to be the same. The patch includes time in calculating the seed to help covering a very different part of state space in each run of the stress tests. To be able to reproduce the bug in case the stress tests failed, it also prints out the time that was used to calculate the seed value.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5004

Differential Revision: D14144356

Pulled By: maysamyabandeh

fbshipit-source-id: 728ed522f550fc8b4f5f9f373259c05fe9a54556
2019-02-19 19:58:55 -08:00
Maysam Yabandeh
0f4244fe00 WritePrepared: Improve stress tests with slow threads (#4974)
Summary:
The transaction stress tests, stress a high concurrency scenario. In WritePrepared/WriteUnPrepared we need to also stress the scenarios where an inserting/reading transaction is very slow. This would stress the corner cases that the caching is not sufficient and other slower data structures are engaged. To emulate such cases we make use of slow inserter/verifier threads and also reduce the size of cache data structures.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4974

Differential Revision: D14143070

Pulled By: maysamyabandeh

fbshipit-source-id: 81eb674678faf9fae0f654cd60ebcc74e26aeee7
2019-02-19 16:56:49 -08:00
Maysam Yabandeh
bcdc8c8b19 WritePrepared: max_evicted_seq_ update during commit cache lookup (#4955)
Summary:
max_evicted_seq_ could be updated in the middle of the read in ::IsInSnapshot. The code to be correct in presence of this update would be complicated. The patch simplifies it by checking the value of max_evicted_seq_ before and after looking into commit_cache_ and retries in the unlucky case that it was changed.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4955

Differential Revision: D13999556

Pulled By: maysamyabandeh

fbshipit-source-id: 7a1bdfa95ea8b5d8d73ddff3263ed31d7297b39c
2019-02-19 16:14:08 -08:00
Michael Liu
ca89ac2ba9 Apply modernize-use-override (2nd iteration)
Summary:
Use C++11’s override and remove virtual where applicable.
Change are automatically generated.

Reviewed By: Orvid

Differential Revision: D14090024

fbshipit-source-id: 1e9432e87d2657e1ff0028e15370a85d1739ba2a
2019-02-14 14:41:36 -08:00
Maysam Yabandeh
d6b9b3b884 Enhance transaction_test_util with delays (#4970)
Summary:
Enhance ::Insert and ::Verify test functions to add artificial delay between prepare and commit, and take snapshot and reads respectively.  A future PR will make use of these to improve stress tests to test against long-running transactions as well as long-running backup jobs. Also randomly sets set_snapshot to false for inserters to skip setting the snapshot in the initialization phase and let the snapshot be taken later explicitly.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4970

Differential Revision: D14031342

Pulled By: maysamyabandeh

fbshipit-source-id: b52b453751f0b25b81b23c48892bc1d152464cab
2019-02-11 16:02:37 -08:00
Maysam Yabandeh
9144d1f186 WritePrepared: add private options to TransactionDBOptions (#4966)
Summary:
WritePreparedTransactionDB operates with more options which should not be configurable to avoid complicating it for the users. For testing purposes however we need to change the default value of this parameters. This patch makes these parameters private fields in TransactionDBOptions so that the existing ::Open API could use them seamlessly without however exposing them to the users.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4966

Differential Revision: D14015986

Pulled By: maysamyabandeh

fbshipit-source-id: 13037efa7dfdd6f73ec7a19414b66571e044c633
2019-02-11 14:44:02 -08:00
Maysam Yabandeh
10d14693ac WritePrepared: fix ValidateSnapshot with long-running txn (#4961)
Summary:
ValidateSnapshot checks if another txn has committed a value to about-to-be-locked key since a particular snapshot. It applies an optimization of looking into only the memtable if snapshot seq is larger than the earliest seq in the memtables. With a long-running txn in WritePrepared, the prepared value might be flushed out to the disk and yet it commits after the snapshot, which breaks this optimization. The patch fixes that by disabling this optimization when the min_uncomitted seq at the time the snapshot was taken is lower than earliest seq in the memtables.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4961

Differential Revision: D14009947

Pulled By: maysamyabandeh

fbshipit-source-id: 1d11679950326f7c4094b433e6b821b729f08850
2019-02-08 18:01:25 -08:00
Maysam Yabandeh
199fabc197 WritePrepared: non-atomic commit of delayed prepared (#4947)
Summary:
Commit of delayed prepared has two non-atomic steps: add to commit cache, remove from delayed_prepared_. Similarly in ::IsInSnapshot we read from commit cache first and then look into delayed_prepared_. Due to non-atomicity thus the reader might not find the
prep_seq that is just committed neither in commit cache nor in delayed_prepared_. To fix that i)
we check if there was any delayed prepared BEFORE looking into commit
cache, ii) if there was, we complete the search steps to be these: i)
commit cache, ii) delayed prepared, commit cache again. In this way if
the first query to commit cache missed the commit, the 2nd will catch it. The cost of the redundant read from commit cache is paid only if delayed_prepared_ is nonempty which should be a very rare scenario.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4947

Differential Revision: D13952754

Pulled By: maysamyabandeh

fbshipit-source-id: 8f47826b13f8ce154398d842028342423f4ca2b2
2019-02-06 08:48:06 -08:00
Maysam Yabandeh
dcb73e7735 WritePrepared: release snapshot equal to max (#4944)
Summary:
WritePrepared maintains a list of snapshots that are <= max_evicted_seq_. Based on this list, old_commit_map_ is updated if an evicted commit entry overlaps with such snapshot. Such lists are garbage collected when the release of snapshot is reported to WritePreparedTxnDB, which is the next time max_evicted_seq_ is updated and yet the snapshot is not found is the list returned from DB. This logic was broken since ReleaseSnapshotInternal was using "< max_evicted_seq_" to cleanup old_commit_map_, which would leave a snapshot uncleaned if it "= max_evicted_seq_". The patch fixes that and adds a unit test to check for the bug.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4944

Differential Revision: D13945000

Pulled By: maysamyabandeh

fbshipit-source-id: 0c904294f735911f52348a148bf1f945282fc17c
2019-02-04 12:57:23 -08:00
Alexander Zinoviev
32a6dd9a41 Add a new CPU time counter to compaction report (#4889)
Summary:
Measure CPU time consumed for a compaction and report it in the stats report
Enable NowCPUNanos() to work for MacOS
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4889

Differential Revision: D13701276

Pulled By: zinoale

fbshipit-source-id: 5024e5bbccd4dd10fd90d947870237f436445055
2019-01-29 17:24:00 -08:00
Yi Wu
b1ad6ebba8 WritePrepared: fix two versions in compaction see different status for released snapshots (#4890)
Summary:
Fix how CompactionIterator::findEarliestVisibleSnapshots handles released snapshot. It fixing the two scenarios:

Scenario 1:
key1 has two values v1 and v2. There're two snapshots s1 and s2 taken after v1 and v2 are committed. Right after compaction output v2, s1 is released. Now findEarliestVisibleSnapshot may see s1 being released, and return the next snapshot, which is s2. That's larger than v2's earliest visible snapshot, which was s1.
The fix: the only place we check against last snapshot and current key snapshot is when we decide whether to compact out a value if it is hidden by a later value. In the check if we see current snapshot is even larger than last snapshot, we know last snapshot is released, and we are safe to compact out current key.

Scenario 2:
key1 has two values v1 and v2. there are two snapshots s1 and s2 taken after v1 and v2 are committed. During compaction before we process the key, s1 is released. When compaction process v2, snapshot checker may return kSnapshotReleased, and the earliest visible snapshot for v2 become s2. When compaction process v1, snapshot checker may return kIsInSnapshot (for WritePrepared transaction, it could be because v1 is still in commit cache). The result will become inconsistent here.
The fix: remember the set of released snapshots ever reported by snapshot checker, and ignore them when finding result for findEarliestVisibleSnapshot.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4890

Differential Revision: D13705538

Pulled By: maysamyabandeh

fbshipit-source-id: e577f0d9ee1ff5a6035f26859e56902ecc85a5a4
2019-01-18 17:24:06 -08:00
Maysam Yabandeh
7fd9813b9f WritePrepared: commit of delayed prepared entries (#4894)
Summary:
Here is the order of ops in a commit: 1) update commit cache 2) publish seq, 3) RemovePrepared. In case of a delayed prepared, there will be a gap between when the commit is visible to snapshots until delayed_prepared_ is cleaned up. To tell apart this case from a delayed uncommitted txn from, the commit entry of a delayed prepared is also stored in delayed_prepared_commits_, which is updated before publishing the commit.
Also logic in GetSnapshotInternal that ensures that each new snapshot is always larger than max_evicted_seq_ is updated to check against the upcoming value of max_evicted_seq_ rather than its current one. This is because AdvanceMaxEvictedSeq gets the list of snapshots lower than the new max, before updating max_evicted_seq_.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4894

Differential Revision: D13726988

Pulled By: maysamyabandeh

fbshipit-source-id: 1e70d78061b50c944c9816bf4b6dac405ab4ccd3
2019-01-18 11:36:36 -08:00
tom wang
73ff15c07b WritePrepared: fix typo in comments
Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/4891

Differential Revision: D13718016

Pulled By: miasantreble

fbshipit-source-id: 90bd372cff453a1c2d104c1cf49731d5dd770c14
2019-01-17 12:36:36 -08:00
Yanqin Jin
dd9eca1c58 Remove unused variable to fix clang compilation err (#4893)
Summary:
as title.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4893

Differential Revision: D13716733

Pulled By: riversand963

fbshipit-source-id: 6811d6a99fe2094d5344f854e8939f01238b2adb
2019-01-17 11:57:31 -08:00
Yi Wu
128f532858 WritePrepared: fix issue with snapshot released during compaction (#4858)
Summary:
Compaction iterator keep a copy of list of live snapshots at the beginning of compaction, and then query snapshot checker to verify if values of a sequence number is visible to these snapshots. However when the snapshot is released in the middle of compaction, the snapshot checker implementation (i.e. WritePreparedSnapshotChecker) may remove info with the snapshot and may report incorrect result, which lead to values being compacted out when it shouldn't. This patch conservatively keep the values if snapshot checker determines that the snapshots is released.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4858

Differential Revision: D13617146

Pulled By: maysamyabandeh

fbshipit-source-id: cf18a94f6f61a94bcff73c280f117b224af5fbc3
2019-01-16 09:55:32 -08:00
Yi Wu
5d4fddfa52 WritePrepared: Fix visible key compacted out by compaction (#4883)
Summary:
With WritePrepared transaction, flush/compaction can contain uncommitted keys, and those keys can get committed during compaction. If a snapshot is taken before the key is committed, it should not see the key. On the other hand, compaction grab the list of snapshots at its beginning, and only consider those snapshots to dedup keys. Consider the case:
```
seq = 1: put "foo" = "bar"
seq = 2: transaction T: delete "foo", prepare
seq = 3: compaction start
seq = 4: take snapshot S
seq = 5: transaction T: commit.
...
seq = N: compaction iterator reached key "foo".
```
When compaction start, the list of snapshot is empty. Compaction doesn't take snapshot S into account. When it reached "foo", transaction T is committed. Compaction may think the value "foo=bar" is not visible by any snapshot (which is wrong), and compact the value out.

The fix is to explicitly take a snapshot before compaction grabbing the list of snapshots. Compaction will then has to keep keys visible to this snapshot.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4883

Differential Revision: D13668775

Pulled By: maysamyabandeh

fbshipit-source-id: 1cab9615f94b7d3e8522cc3d44c3a14c7d4720e4
2019-01-15 21:34:38 -08:00
Maysam Yabandeh
cad99a6031 WritePrepared: snapshot should be larger than max_evicted_seq_ (#4886)
Summary:
The AdvanceMaxEvictedSeq algorithm assumes that new snapshots always have sequence number larger than the last max_evicted_seq_. To enforce this assumption we make two changes:
i) max is not advanced beyond the last published seq, with the exception that the evicted commit entry itself is not published yet, which is quite rare.
ii) When obtaining the snapshot if the max_evicted_seq_ is not published yet, commit a dummy entry so that it waits for it to be published and also increased the latest published seq by one above the max.
To test these non-realistic corner cases we create a commit cache with size 1 so that every single commit results into eviction.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4886

Differential Revision: D13685270

Pulled By: maysamyabandeh

fbshipit-source-id: 5461bc09c2a9b75798bfcb9853a256c81cdac0b0
2019-01-15 18:11:52 -08:00
Yi Wu
d50c10ed37 WritePrepared: Fix SmallestUnCommittedSeq() doesn't check delayed_prepared (#4867)
Summary:
When prepared_txns_ heap is empty, SmallestUnCommittedSeq() should check delayed_prepared_ set as well.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4867

Differential Revision: D13632134

Pulled By: maysamyabandeh

fbshipit-source-id: b0423bb0a58dc95f1e636d5ed3f6e619df801fb7
2019-01-15 09:17:53 -08:00
Maysam Yabandeh
856ac24484 WritePrepared: fix race condition on GetSnapshotListFromDB (#4872)
Summary:
Fixes a typo that made mutex_ to remain unlocked when GetSnapshotListFromDB called from WritePreparedTxnDB.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4872

Differential Revision: D13640381

Pulled By: maysamyabandeh

fbshipit-source-id: 50f6600568f9092b4b43115f6ebd96e6c7388ad7
2019-01-11 13:46:23 -08:00
Zhongyi Xie
6a4ec41fed add assert to silence clang warning (#4871)
Summary:
currently clang analyze fails with the following warning:
> utilities/transactions/write_prepared_transaction_test.cc:1451:5: warning: Forming reference to null pointer
    ASSERT_GT(wp_db->max_evicted_seq_, 0);  // max after recovery
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4871

Differential Revision: D13638053

Pulled By: miasantreble

fbshipit-source-id: b192b0c13c411c58defc9e280b34cdfcab3fa8e3
2019-01-11 12:17:34 -08:00
Maysam Yabandeh
f3a99e8a4d WritePrepared: Report released snapshots in IsInSnapshot (#4856)
Summary:
Previously IsInSnapshot assumed that the snapshot is valid at the time that the function is called. However there are cases where that might not be valid. Example is background compactions where the compaction algorithm operates with a list of snapshots some of which might be released by the time they are being passed to IsInSnapshot. The patch make two changes to enable the caller to tell difference: i) any live snapshot below max is added to max_committed_seq_, which allows IsInSnapshot to confidently tell whether the passed snapshot is invalid if it below max, ii) extends IsInSnapshot API with a "released" variable that is set true when IsInSnapshot find no such snapshot below max and also find no other way to give a certain return value. In such cases the return value is true but the caller should also check the "released" boolean after the call.
In short here is the changes in the API:
i) If the snapshot is valid, no change is required.
ii) If the snapshot might be invalid, a reference to "released" boolean must be passed to IsInSnapshot.
ii-a) If snapshot is above max, IsInSnapshot can figure the return valid using the commit cache.
ii-b) otherwise if snapshot is in old_commit_map_, IsInSnapshot can use that to tell if value was visible to the snapshot.
ii-c) otherwise it sets "released" to true and returns true as well.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4856

Differential Revision: D13599847

Pulled By: maysamyabandeh

fbshipit-source-id: 1752be28667f886a1efec8cae5714b9b7a8f1e0f
2019-01-08 14:47:29 -08:00
Maysam Yabandeh
cd227d74ba WritePrepared: improve IsInSnapshotEmptyMapTest (#4853)
Summary:
IsInSnapshotEmptyMapTest tests that IsInSnapshot returns correct value for existing data after a recovery, where max is not zero and yet commit cache is empty. The existing test was preliminary which is improved in this patch. It also increases the db sequence after recovery so that there the snapshot immediately taken after recovery would have a sequence number different than that of max_evicted_seq. This simplifies the logic in IsInSnapshot by not having to consider the special case that an old snapshot might be equal to max_evicted_seq and yet not present in old_commit_map.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4853

Differential Revision: D13595223

Pulled By: maysamyabandeh

fbshipit-source-id: 77c12ca8a3f61a47479a93bef2038ff502dc3322
2019-01-08 11:27:11 -08:00
Maysam Yabandeh
0ed98bf89e WritePrepared: fix snapshot sequence in rollback (#4851)
Summary:
The rollback algorithm in WritePrepared transactions requires reading the values before the transaction start. Currently it uses the prepare_seq -1 as the snapshot sequence number for the read. This is not correct since the passed sequence number must be for a valid snapshot. The patch fixes it by passing kMaxSequenceNumber instead. This is fine since all the writes done by the aborted transaction will be skipped during the read anyway.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4851

Differential Revision: D13592773

Pulled By: maysamyabandeh

fbshipit-source-id: ff1bf92ea9909d4cccb173bdff49febc0e9eb7a2
2019-01-07 14:57:03 -08:00
Faustin Lammler
7d65bd5ce4 Fix spelling errors (#4827)
Summary:
Hi, Lintian, the Debian package checker complains about spelling error (spelling-error-in-binary).

See https://salsa.debian.org/mariadb-team/mariadb-10.3/-/jobs/98380
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4827

Differential Revision: D13566362

Pulled By: riversand963

fbshipit-source-id: cd4e9212133c73b0591030de6cdedaa47575968d
2019-01-02 11:17:57 -08:00
DorianZheng
2670fe8c73 Get CompactionJobInfo from CompactFiles
Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/4716

Differential Revision: D13207677

Pulled By: ajkr

fbshipit-source-id: d0ccf5a66df6cbb07288b0c5ebad81fd9df3926b
2018-12-13 14:21:24 -08:00
Maysam Yabandeh
b878f93c70 Extend Transaction::GetForUpdate with do_validate (#4680)
Summary:
Transaction::GetForUpdate is extended with a do_validate parameter with default value of true. If false it skips validating the snapshot (if there is any) before doing the read. After the read it also returns the latest value (expects the ReadOptions::snapshot to be nullptr). This allows RocksDB applications to use GetForUpdate similarly to how InnoDB does. Similarly ::Merge, ::Put, ::Delete, and ::SingleDelete are extended with assume_exclusive_tracked with default value of false. It true it indicates that call is assumed to be after a ::GetForUpdate(do_validate=false).
The Java APIs are accordingly updated.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4680

Differential Revision: D13068508

Pulled By: maysamyabandeh

fbshipit-source-id: f0b59db28f7f6a078b60844d902057140765e67d
2018-12-06 17:49:00 -08:00
Zhongyi Xie
2f1ca4e838 Revert "BaseDeltaIterator: always check valid() before accessing key(… (#4744)
Summary:
…) (#4702)"

This reverts commit 3a18bb3e15.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4744

Differential Revision: D13311869

Pulled By: miasantreble

fbshipit-source-id: 6300b12cc34828d8b9274e907a3aef1506d5d553
2018-12-03 23:38:27 -08:00
Zhongyi Xie
3a18bb3e15 BaseDeltaIterator: always check valid() before accessing key() (#4702)
Summary:
Current implementation of `current_over_upper_bound_` fails to take into consideration that keys might be invalid in either base iterator or delta iterator. Calling key() in such scenario will lead to assertion failure and runtime errors.
This PR addresses the bug by adding check for valid keys before calling `IsOverUpperBound()`, also added test coverage for iterate_upper_bound usage in BaseDeltaIterator
Also recommit https://github.com/facebook/rocksdb/pull/4656 (It was reverted earlier due to bugs)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4702

Differential Revision: D13146643

Pulled By: miasantreble

fbshipit-source-id: 6d136929da12d0f2e2a5cea474a8038ec5cdf1d0
2018-11-30 15:35:13 -08:00
Maysam Yabandeh
f1b0841f06 WritePrepared: followup fix for snapshot double release issue (#4734)
Summary:
The fix in #4727 for double snapshot release was incomplete since it does not properly remove the duplicate entires in the snapshot list after finding that a snapshot is still valid. The patch does that and also improves the unit test to show the issue.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4734

Differential Revision: D13266260

Pulled By: maysamyabandeh

fbshipit-source-id: 351e2c40cca45a87b757774c11af74182314911e
2018-11-29 21:01:57 -08:00