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: 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:
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: 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: 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: 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
Summary: Transaction::RollbackToSavePoint() will now release any locks that were taken since the previous SavePoint. To do this cleanly, I moved tracked_keys_ management into TransactionBase.
Test Plan: New Transaction test.
Reviewers: igor, rven, sdong
Reviewed By: sdong
Subscribers: dhruba, spetrunia, leveldb
Differential Revision: https://reviews.facebook.net/D46761
Summary: Added funtions to fetch the number of locked keys in a transaction, the number of pending puts/merge/deletes, and the elapsed time
Test Plan: unit tests
Reviewers: yoshinorim, jkedgar, rven, sdong, yhchiang, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D45417
Summary:
Prototype of API to allow MyRocks to override default Mutex/CondVar used by transactions with their own implementations. They would simply need to pass their own implementations of Mutex/CondVar to the templated TransactionDB::Open().
Default implementation of TransactionDBMutex/TransactionDBCondVar provided (but the code is not currently changed to use this).
Let me know if this API makes sense or if it should be changed
Test Plan: n/a
Reviewers: yhchiang, rven, igor, sdong, spetrunia
Reviewed By: spetrunia
Subscribers: maykov, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D43761
Summary: MyRocks wants to be able to change the lock timeout of a transaction that has already started. Expose existing SetLockTimeout function to users.
Test Plan: unit test
Reviewers: spetrunia, rven, sdong, yhchiang, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D45987
Summary:
As I keep adding new features to transactions, I keep creating more duplicate code. This diff cleans this up by creating a base implementation class for Transaction and OptimisticTransaction to inherit from.
The code in TransactionBase.h/.cc is all just copied from elsewhere. The only entertaining part of this class worth looking at is the virtual TryLock method which allows OptimisticTransactions and Transactions to share the same common code for Put/Get/etc.
The rest of this diff is mostly red and easy on the eyes.
Test Plan: No functionality change. existing tests pass.
Reviewers: sdong, jkedgar, rven, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D45135
Summary:
Clean up transactions to use the new RollbackToSavePoint api in WriteBatchWithIndex.
Note, this diff depends on Pessimistic Transactions diff and ManagedSnapshot diff (D40869 and D43293).
Test Plan: unit tests
Reviewers: rven, yhchiang, kradhakrishnan, spetrunia, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D43371
Summary:
Initial implementation of Pessimistic Transactions. This diff contains the api changes discussed in D38913. This diff is pretty large, so let me know if people would prefer to meet up to discuss it.
MyRocks folks: please take a look at the API in include/rocksdb/utilities/transaction[_db].h and let me know if you have any issues.
Also, you'll notice a couple of TODOs in the implementation of RollbackToSavePoint(). After chatting with Siying, I'm going to send out a separate diff for an alternate implementation of this feature that implements the rollback inside of WriteBatch/WriteBatchWithIndex. We can then decide which route is preferable.
Next, I'm planning on doing some perf testing and then integrating this diff into MongoRocks for further testing.
Test Plan: Unit tests, db_bench parallel testing.
Reviewers: igor, rven, sdong, yhchiang, yoshinorim
Reviewed By: sdong
Subscribers: hermanlee4, maykov, spetrunia, leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D40869
Manuel Ung