Summary:
This is an implementation of non-exclusive locks for pessimistic transactions. It is relatively simple and does not prevent starvation (ie. it's possible that request for exclusive access will never be granted if there are always threads holding shared access). It is done by changing `KeyLockInfo` to hold an set a transaction ids, instead of just one, and adding a flag specifying whether this lock is currently held with exclusive access or not.
Some implementation notes:
- Some lock diagnostic functions had to be updated to return a set of transaction ids for a given lock, eg. `GetWaitingTxn` and `GetLockStatusData`.
- Deadlock detection is a bit more complicated since a transaction can now wait on multiple other transactions. A BFS is done in this case, and deadlock detection depth is now just a limit on the number of transactions we visit.
- Expirable transactions do not work efficiently with shared locks at the moment, but that's okay for now.
Closes https://github.com/facebook/rocksdb/pull/1573
Differential Revision: D4239097
Pulled By: lth
fbshipit-source-id: da7c074
Summary:
Currently, deadlock cycles are held in std::unordered_map. The problem with it is that it allocates/deallocates memory on every insertion/deletion. This limits throughput since we're doing this expensive operation while holding a global mutex. Fix this by using a vector which caches memory instead.
Running the deadlock stress test, this change increased throughput from 39k txns/s -> 49k txns/s. The effect is more noticeable in MyRocks.
Closes https://github.com/facebook/rocksdb/pull/1545
Differential Revision: D4205662
Pulled By: lth
fbshipit-source-id: ff990e4
Summary:
Originally sequence ids were calculated, in recovery, based off of the first seqid found if the first log recovered. The working seqid was then incremented from that value based on every insertion that took place. This was faulty because of the potential for missing log files or inserts that skipped the WAL. The current recovery scheme grabs sequence from current recovering batch and increments using memtableinserter to track how many actual inserts take place. This works for 2PC batches as well scenarios where some logs are missing or inserts that skip the WAL.
Closes https://github.com/facebook/rocksdb/pull/1486
Differential Revision: D4156064
Pulled By: reidHoruff
fbshipit-source-id: a6da8d9
Summary:
copied from: 5ebfd2623a
Opening existing RocksDB attempts recovery from log files, which uses
wrong sequence number to create the memtable. This is a regression
introduced in change a400336.
This change includes a test demonstrating the problem, without the fix
the test fails with "Operation failed. Try again.: Transaction could not
check for conflicts for operation at SequenceNumber 1 as the MemTable
only contains changes newer than SequenceNumber 2. Increasing the value
of the max_write_buffer_number_to_maintain option could reduce the
frequency of this error"
This change is a joint effort by Peter 'Stig' Edwards thatsafunnyname
and me.
Closes https://github.com/facebook/rocksdb/pull/1458
Differential Revision: D4143791
Pulled By: reidHoruff
fbshipit-source-id: 5a25033
Summary: Make `IsDeadlockDetect()` virtual member of base class `Transaction` for ease of use in MyRocks
Test Plan: compiles. compiles into MyRocks call-site.
Reviewers: mung
Reviewed By: mung
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D65385
Summary: Implement deadlock detection. This is done by maintaining a TxnID -> TxnID map which represents the edges in the wait for graph (this is named `wait_txn_map_`).
Test Plan: transaction_test
Reviewers: IslamAbdelRahman, sdong
Reviewed By: sdong
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D64491
Summary: Modifies the lock info export test to test multiple column families after I was experiencing a bug while developing the MyRocks front-end for this.
Test Plan: is test.
Reviewers: mung
Reviewed By: mung
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D64725
Summary:
This exposes a transactions state through a public api rather than through a public member variable. I also do some name refactoring.
ExecutionStatus => TransactionState
exec_status_ => trx_state_
Test Plan: It compiles and transaction_test passes.
Reviewers: IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: andrewkr, mung, dhruba, sdong
Differential Revision: https://reviews.facebook.net/D64689
Summary:
When constructing a write batch a client may now call MarkWalTerminationPoint() on that batch. No batch operations after this call will be added written to the WAL but will still be inserted into the Memtable. This facility is used to remove one of the three WriteImpl calls in 2PC transactions. This produces a ~1% perf improvement.
```
RocksDB - unoptimized 2pc, sync_binlog=1, disable_2pc=off
INFO 2016-08-31 14:30:38,814 [main]: REQUEST PHASE COMPLETED. 75000000 requests done in 2619 seconds. Requests/second = 28628
RocksDB - optimized 2pc , sync_binlog=1, disable_2pc=off
INFO 2016-08-31 16:26:59,442 [main]: REQUEST PHASE COMPLETED. 75000000 requests done in 2581 seconds. Requests/second = 29054
```
Test Plan: Two unit tests added.
Reviewers: sdong, yiwu, IslamAbdelRahman
Reviewed By: yiwu
Subscribers: hermanlee4, dhruba, andrewkr
Differential Revision: https://reviews.facebook.net/D64599
Summary:
This diff does 3 things:
Expose TransactionID so that we can identify transactions when we retrieve locking and lock wait information. This is exposed as `Transaction::GetID`.
Expose lock state information by locking all stripes in all column families and copying their contents to a data structure. This is exposed as `TransactionDB::GetLockStatusData`.
Adds support for tracking the transaction and the key being waited on, and exposes this as `Transaction::GetWaitingTxn`.
Test Plan: unit tests
Reviewers: horuff, sdong
Reviewed By: sdong
Subscribers: vasilep, hermanlee4, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D64413
Summary: 1. Range Deletion Tombstone structure 2. Modify Add() in table_builder to make it usable for adding range del tombstones 3. Expose NewTombstoneIterator() API in table_reader
Test Plan: table_test.cc (now BlockBasedTableBuilder::Add() only accepts InternalKey. I make table_test only pass InternalKey to BlockBasedTableBuidler. Also test writing/reading range deletion tombstones in table_test )
Reviewers: sdong, IslamAbdelRahman, lightmark, andrewkr
Reviewed By: andrewkr
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D61473
Summary: make transactionDB working with StackableDB
Test Plan: make all check -j64
Reviewers: andrewkr, yiwu, sdong
Reviewed By: sdong
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D60705
Summary: use of dynamic_cast<TransactionImpl*> is unnecessary and also introduce difficulty for fbrocksdb support of TransactionDB
Test Plan: ./transaction_test
Reviewers: sdong, IslamAbdelRahman, andrewkr
Reviewed By: andrewkr
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D60501
Summary: This tests that a prepared transaction is not lost after several crashes, restarts, and memtable flushes.
Test Plan: TwoPhaseLongPrepareTest
Reviewers: sdong
Subscribers: hermanlee4, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D58185
Summary:
TransactionTest.TwoPhaseMultiThreadTest runs forever under TSAN and our CI builds time out
looks like the reason is that some threads keep running and other threads dont get a chance to increment the counter
Test Plan: run the test under TSAN
Reviewers: sdong, horuff
Reviewed By: horuff
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D58359
Summary:
- Make sure we clean up recovered_transactions_ on DBImpl destructor
- delete leaked txns and env in TransactionTest
Test Plan: Run transaction_test under valgrind
Reviewers: sdong, andrewkr, yhchiang, horuff
Reviewed By: horuff
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D58263
Summary:
1. prepare()
2. crash
3. recover
4. commit()
5. crash
6. data is lost
This is due to the transaction data still only residing in the WAL but because the logs were flushed on the first recovery the data is ignored on the second recovery. We must scan all logs found on recovery and only ignore redundant data at the time of replay. It is not possible to know which logs still contain relevant data at time of recovery. We cannot simply ignore a log because all of the non-2pc data it contains has already been written to L0.
The changes made to MemTableInserter are to ensure that prepared sections are still recovered even if all of the non-2pc data in that log has already been flushed to L0.
Test Plan: Provided test.
Reviewers: sdong
Subscribers: andrewkr, hermanlee4, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D57729
Summary:
Consider the following WAL with 4 batch entries prefixed with their sequence at time of memtable insert.
[1: BEGIN_PREPARE, PUT, PUT, PUT, PUT, END_PREPARE(a)]
[1: BEGIN_PREPARE, PUT, PUT, PUT, PUT, END_PREPARE(b)]
[4: COMMIT(a)]
[7: COMMIT(b)]
The first two batches do not consume any sequence numbers so are both prefixed with seq=1.
For 2pc commit, memtable insertion takes place before COMMIT batch is written to WAL.
We can see that sequence number consumption takes place between WAL entries giving us the seemingly sparse sequence prefix for WAL entries.
This is a valid WAL.
Because with 2PC markers one WriteBatch points to another batch containing its inserts a writebatch can consume more or less sequence numbers than the number of sequence consuming entries that it contains.
We can see that, given the entries in the WAL, 6 sequence ids were consumed. Yet on recovery the maximum sequence consumed would be 7 + 3 (the number of sequence numbers consumed by COMMIT(b))
So, now upon recovery we must track the actual consumption of sequence numbers.
In the provided scenario there will be no sequence gaps, but it is possible to produce a sequence gap. This should not be a problem though. correct?
Test Plan: provided test.
Reviewers: sdong
Subscribers: andrewkr, leveldb, dhruba, hermanlee4
Differential Revision: https://reviews.facebook.net/D57645
Summary: Refactored db_bench transaction stress tests so that they can be called from unit tests as well.
Test Plan: run new unit test as well as db_bench
Reviewers: yhchiang, IslamAbdelRahman, sdong
Reviewed By: IslamAbdelRahman
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D55203
Summary: Previously, reusing a transaction (by passing it as an argument to BeginTransaction) would not clear the transaction's snapshot. This is not a clear, well-definited behavior.
Test Plan: improved test
Reviewers: sdong, IslamAbdelRahman, horuff, jkedgar
Reviewed By: jkedgar
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D55053
Summary: Add function to reinitialize a transaction object so that it can be reused. This is an optimization so users can potentially avoid reallocating transaction objects.
Test Plan: added tests
Reviewers: yhchiang, kradhakrishnan, IslamAbdelRahman, sdong
Reviewed By: sdong
Subscribers: jkedgar, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D53835
Summary: Broke transaction locking in 4.4 in D52197. Will cherry-pick this change into 4.4 (which hasn't yet been fully released). Repro'd using db_bench.
Test Plan: unit tests and db_Bench
Reviewers: sdong, yhchiang, kradhakrishnan, ngbronson
Reviewed By: ngbronson
Subscribers: ngbronson, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D54021
Summary: There is an issue in DBImpl::WriteImpl where if an empty writebatch comes in and sync=true then the logs will be marked as being synced yet the sync never actually happens because there is no data in the writebatch. This causes the next incoming batch to hang while waiting for the logs to complete syncing. This fix syncs logs even if the writebatch is empty.
Test Plan: DoubleEmptyBatch unit test in transaction_test.
Reviewers: yoshinorim, hermanlee4, sdong, ngbronson, anthony
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D54057
Summary:
One test in transaction_test.cc forgets to call SyncPoint::DisableProcessing().
As a result, a program might to access the SyncPoint singleton after it
already goes out of scope.
This patch fix this error by calling SyncPoint::DisableProcessing().
Test Plan: transaction_test
Reviewers: sdong, IslamAbdelRahman, kradhakrishnan, anthony
Reviewed By: anthony
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D54033
Summary: MyRocks wants to be able to un-lock a key that was just locked by GetForUpdate(). To do this safely, I am now keeping track of the number of reads(for update) and writes for each key in a transaction. UndoGetForUpdate() will only unlock a key if it hasn't been written and the read count reaches 0.
Test Plan: more unit tests
Reviewers: igor, rven, yhchiang, spetrunia, sdong
Reviewed By: spetrunia, sdong
Subscribers: spetrunia, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D47043
Summary:
copy from task 8196669:
1) Optimistic transactions do not support batching writes from different threads.
2) Pessimistic transactions do not support batching writes if an expiration time is set.
In these 2 cases, we currently do not do any write batching in DBImpl::WriteImpl() because there is a WriteCallback that could decide at the last minute to abort the write. But we could support batching write operations with callbacks if we make sure to process the callbacks correctly.
To do this, we would first need to modify write_thread.cc to stop preventing writes with callbacks from being batched together. Then we would need to change DBImpl::WriteImpl() to call all WriteCallback's in a batch, only write the batches that succeed, and correctly set the state of each batch's WriteThread::Writer.
Test Plan: Added test WriteWithCallbackTest to write_callback_test.cc which creates multiple client threads and verifies that writes are batched and executed properly.
Reviewers: hermanlee4, anthony, ngbronson
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D52863
Summary:
Doing inline checking of transaction expiration instead of
using a callback.
Test Plan: To be added
Reviewers: anthony
Reviewed By: anthony
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D53673
Summary: Stopped using std::timed_mutex as it has known issues in older versiong of gcc. Ran into these problems when testing MongoRocks.
Test Plan: unit tests. Manual mongo testing on gcc 4.8.
Reviewers: igor, yhchiang, rven, IslamAbdelRahman, kradhakrishnan, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D52197
Summary: Add support to change write options after creating a transaction. This is needed for MongoRocks.
Test Plan: added test
Reviewers: sdong, rven, kradhakrishnan, IslamAbdelRahman, yhchiang
Reviewed By: yhchiang
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D51867
Summary:
Currently, transactions can fail even if there is no actual write conflict. This is due to relying on only the memtables to check for write-conflicts. Users have to tune memtable settings to try to avoid this, but it's hard to figure out exactly how to tune these settings.
With this diff, TransactionDB will use both memtables and SST files to determine if there are any write conflicts. This relies on the fact that BlockBasedTable stores sequence numbers for all writes that happen after any open snapshot. Also, D50295 is needed to prevent SingleDelete from disappearing writes (the TODOs in this test code will be fixed once the other diff is approved and merged).
Note that Optimistic transactions will still rely on tuning memtable settings as we do not want to read from SST while on the write thread. Also, memtable settings can still be used to reduce how often TransactionDB needs to read SST files.
Test Plan: unit tests, db bench
Reviewers: rven, yhchiang, kradhakrishnan, IslamAbdelRahman, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb, yoshinorim
Differential Revision: https://reviews.facebook.net/D50475
Summary:
D51183 was reverted due to breaking the LITE build.
This diff is the same as D51183 but with a fix for the LITE BUILD(D51693)
Test Plan: run all unit tests
Reviewers: sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D51711
Summary:
D50475 enables using SST files for transaction write-conflict checking. In order for this to work, we need to make sure not to compact out SingleDeletes when there is an earlier transaction snapshot(D50295). If there is a long-held snapshot, this could reduce the benefit of the SingleDelete optimization.
This diff allows Transactions to mark snapshots as being used for write-conflict checking. Then, during compaction, we will be able to optimize SingleDeletes better in the future.
This diff adds a flag to SnapshotImpl which is used by Transactions. This diff also passes the earliest write-conflict snapshot's sequence number to CompactionIterator. This diff does not actually change Compaction (after this diff is pushed, D50295 will be able to use this information).
Test Plan: no behavior change, ran existing tests
Reviewers: rven, kradhakrishnan, yhchiang, IslamAbdelRahman, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D51183
Summary: When SetSnapshot() is used the caller immediately knows a snapshot has been created, but when SetSnapshotOnNextOperation() is used the caller needs a way to get notified when that snapshot has been generated. This creates an interface that the client can implement that will be called at the time the snapshot is created.
Test Plan: Added a new SetSnapshotOnNextOperationWithNotification test into the transaction_test.
Reviewers: sdong, anthony
Reviewed By: anthony
Subscribers: yoshinorim, leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D51177
Summary:
Fixes T8781168.
Added a new function EnableAutoCompactions in db.h to be publicly
avialable. This allows compaction to be re-enabled after disabling it via
SetOptions
Refactored code to set the dbptr earlier on in TransactionDB::Open and DB::Open
Temporarily disable auto_compaction in TransactionDB::Open until dbptr is set to
prevent race condition.
Test Plan:
Ran make all check
verified fix on myrocks side:
was able to reproduce the seg fault with
../tools/mysqltest.sh --mem --force rocksdb.drop_table
method was to manually sleep the thread after DB::Open but before TransactionDB ptr was
assigned in transaction_db_impl.cc:
DB::Open(db_options, dbname, column_families_copy, handles, &db);
clock_t goal = (60000 * 10) + clock();
while (goal > clock());
...dbptr(aka rdb) gets assigned below
verified my changes fixed the issue.
Also added unit test 'ToggleAutoCompaction' in transaction_test.cc
Reviewers: hermanlee4, anthony
Reviewed By: anthony
Subscribers: alex, dhruba
Differential Revision: https://reviews.facebook.net/D51147
Summary:
MyRocks needs the ability to clear a snapshot for Read Committed support
Test Plan: transaction_test
Reviewers: anthony
Reviewed By: anthony
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D48861
Summary: Support for Transaction::CreateSnapshotOnNextOperation(). This is to fix a write-conflict race-condition that Yoshinori was running into when testing MyRocks with LinkBench.
Test Plan: New tests
Reviewers: yhchiang, spetrunia, rven, igor, yoshinorim, sdong
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D48099
Daniel Black