Summary:
In RocksDB, keys are associated with (internal) sequence numbers which denote when the keys are written
to the database. Sequence numbers in different RocksDB instances are unrelated, thus not comparable.
It is nice if we can associate sequence numbers with their corresponding actual timestamps. One thing we can
do is to support user-defined timestamp, which allows the applications to specify the format of custom timestamps
and encode a timestamp with each key. More details can be found at https://github.com/facebook/rocksdb/wiki/User-defined-Timestamp-%28Experimental%29.
This PR provides a different but complementary approach. We can associate rocksdb snapshots (defined in
https://github.com/facebook/rocksdb/blob/7.2.fb/include/rocksdb/snapshot.h#L20) with **user-specified** timestamps.
Since a snapshot is essentially an object representing a sequence number, this PR establishes a bi-directional mapping between sequence numbers and timestamps.
In the past, snapshots are usually taken by readers. The current super-version is grabbed, and a `rocksdb::Snapshot`
object is created with the last published sequence number of the super-version. You can see that the reader actually
has no good idea of what timestamp to assign to this snapshot, because by the time the `GetSnapshot()` is called,
an arbitrarily long period of time may have already elapsed since the last write, which is when the last published
sequence number is written.
This observation motivates the creation of "timestamped" snapshots on the write path. Currently, this functionality is
exposed only to the layer of `TransactionDB`. Application can tell RocksDB to create a snapshot when a transaction
commits, effectively associating the last sequence number with a timestamp. It is also assumed that application will
ensure any two snapshots with timestamps should satisfy the following:
```
snapshot1.seq < snapshot2.seq iff. snapshot1.ts < snapshot2.ts
```
If the application can guarantee that when a reader takes a timestamped snapshot, there is no active writes going on
in the database, then we also allow the user to use a new API `TransactionDB::CreateTimestampedSnapshot()` to create
a snapshot with associated timestamp.
Code example
```cpp
// Create a timestamped snapshot when committing transaction.
txn->SetCommitTimestamp(100);
txn->SetSnapshotOnNextOperation();
txn->Commit();
// A wrapper API for convenience
Status Transaction::CommitAndTryCreateSnapshot(
std::shared_ptr<TransactionNotifier> notifier,
TxnTimestamp ts,
std::shared_ptr<const Snapshot>* ret);
// Create a timestamped snapshot if caller guarantees no concurrent writes
std::pair<Status, std::shared_ptr<const Snapshot>> snapshot = txn_db->CreateTimestampedSnapshot(100);
```
The snapshots created in this way will be managed by RocksDB with ref-counting and potentially shared with
other readers. We provide the following APIs for readers to retrieve a snapshot given a timestamp.
```cpp
// Return the timestamped snapshot correponding to given timestamp. If ts is
// kMaxTxnTimestamp, then we return the latest timestamped snapshot if present.
// Othersise, we return the snapshot whose timestamp is equal to `ts`. If no
// such snapshot exists, then we return null.
std::shared_ptr<const Snapshot> TransactionDB::GetTimestampedSnapshot(TxnTimestamp ts) const;
// Return the latest timestamped snapshot if present.
std::shared_ptr<const Snapshot> TransactionDB::GetLatestTimestampedSnapshot() const;
```
We also provide two additional APIs for stats collection and reporting purposes.
```cpp
Status TransactionDB::GetAllTimestampedSnapshots(
std::vector<std::shared_ptr<const Snapshot>>& snapshots) const;
// Return timestamped snapshots whose timestamps fall in [ts_lb, ts_ub) and store them in `snapshots`.
Status TransactionDB::GetTimestampedSnapshots(
TxnTimestamp ts_lb,
TxnTimestamp ts_ub,
std::vector<std::shared_ptr<const Snapshot>>& snapshots) const;
```
To prevent the number of timestamped snapshots from growing infinitely, we provide the following API to release
timestamped snapshots whose timestamps are older than or equal to a given threshold.
```cpp
void TransactionDB::ReleaseTimestampedSnapshotsOlderThan(TxnTimestamp ts);
```
Before shutdown, RocksDB will release all timestamped snapshots.
Comparison with user-defined timestamp and how they can be combined:
User-defined timestamp persists every key with a timestamp, while timestamped snapshots maintain a volatile
mapping between snapshots (sequence numbers) and timestamps.
Different internal keys with the same user key but different timestamps will be treated as different by compaction,
thus a newer version will not hide older versions (with smaller timestamps) unless they are eligible for garbage collection.
In contrast, taking a timestamped snapshot at a certain sequence number and timestamp prevents all the keys visible in
this snapshot from been dropped by compaction. Here, visible means (seq < snapshot and most recent).
The timestamped snapshot supports the semantics of reading at an exact point in time.
Timestamped snapshots can also be used with user-defined timestamp.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9879
Test Plan:
```
make check
TEST_TMPDIR=/dev/shm make crash_test_with_txn
```
Reviewed By: siying
Differential Revision: D35783919
Pulled By: riversand963
fbshipit-source-id: 586ad905e169189e19d3bfc0cb0177a7239d1bd4
Summary:
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9629
Pessimistic transactions use pessimistic concurrency control, i.e. locking. Keys are
locked upon first operation that writes the key or has the intention of writing. For example,
`PessimisticTransaction::Put()`, `PessimisticTransaction::Delete()`,
`PessimisticTransaction::SingleDelete()` will write to or delete a key, while
`PessimisticTransaction::GetForUpdate()` is used by application to indicate
to RocksDB that the transaction has the intention of performing write operation later
in the same transaction.
Pessimistic transactions support two-phase commit (2PC). A transaction can be
`Prepared()`'ed and then `Commit()`. The prepare phase is similar to a promise: once
`Prepare()` succeeds, the transaction has acquired the necessary resources to commit.
The resources include locks, persistence of WAL, etc.
Write-committed transaction is the default pessimistic transaction implementation. In
RocksDB write-committed transaction, `Prepare()` will write data to the WAL as a prepare
section. `Commit()` will write a commit marker to the WAL and then write data to the
memtables. While writing to the memtables, different keys in the transaction's write batch
will be assigned different sequence numbers in ascending order.
Until commit/rollback, the transaction holds locks on the keys so that no other transaction
can write to the same keys. Furthermore, the keys' sequence numbers represent the order
in which they are committed and should be made visible. This is convenient for us to
implement support for user-defined timestamps.
Since column families with and without timestamps can co-exist in the same database,
a transaction may or may not involve timestamps. Based on this observation, we add two
optional members to each `PessimisticTransaction`, `read_timestamp_` and
`commit_timestamp_`. If no key in the transaction's write batch has timestamp, then
setting these two variables do not have any effect. For the rest of this commit, we discuss
only the cases when these two variables are meaningful.
read_timestamp_ is used mainly for validation, and should be set before first call to
`GetForUpdate()`. Otherwise, the latter will return non-ok status. `GetForUpdate()` calls
`TryLock()` that can verify if another transaction has written the same key since
`read_timestamp_` till this call to `GetForUpdate()`. If another transaction has indeed
written the same key, then validation fails, and RocksDB allows this transaction to
refine `read_timestamp_` by increasing it. Note that a transaction can still use `Get()`
with a different timestamp to read, but the result of the read should not be used to
determine data that will be written later.
commit_timestamp_ must be set after finishing writing and before transaction commit.
This applies to both 2PC and non-2PC cases. In the case of 2PC, it's usually set after
prepare phase succeeds.
We currently require that the commit timestamp be chosen after all keys are locked. This
means we disallow the `TransactionDB`-level APIs if user-defined timestamp is used
by the transaction. Specifically, calling `PessimisticTransactionDB::Put()`,
`PessimisticTransactionDB::Delete()`, `PessimisticTransactionDB::SingleDelete()`,
etc. will return non-ok status because they specify timestamps before locking the keys.
Users are also prompted to use the `Transaction` APIs when they receive the non-ok status.
Reviewed By: ltamasi
Differential Revision: D31822445
fbshipit-source-id: b82abf8e230216dc89cc519564a588224a88fd43
Summary:
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9537
Add `Transaction::SetReadTimestampForValidation()` and
`Transaction::SetCommitTimestamp()` APIs with default implementation
returning `Status::NotSupported()`. Currently, calling these two APIs do not
have any effect.
Also add checks to `PessimisticTransactionDB`
to enforce that column families in the same db either
- disable user-defined timestamp
- enable 64-bit timestamp
Just to clarify, a `PessimisticTransactionDB` can have some column families without
timestamps as well as column families that enable timestamp.
Each `PessimisticTransaction` can have two optional timestamps, `read_timestamp_`
used for additional validation and `commit_timestamp_` which denotes when the transaction commits.
For now, we are going to support `WriteCommittedTxn` (in a series of subsequent PRs)
Once set, we do not allow decreasing `read_timestamp_`. The `commit_timestamp_` must be
greater than `read_timestamp_` for each transaction and must be set before commit, unless
the transaction does not involve any column family that enables user-defined timestamp.
TransactionDB builds on top of RocksDB core `DB` layer. Though `DB` layer assumes
that user-defined timestamps are byte arrays, `TransactionDB` uses uint64_t to store
timestamps. When they are passed down, they are still interpreted as
byte-arrays by `DB`.
Reviewed By: ltamasi
Differential Revision: D31567959
fbshipit-source-id: b0b6b69acab5d8e340cf174f33e8b09f1c3d3502
Summary:
This PR has two commits:
1. Modify the code to allow different Lock Managers (of any kind) to be used. It is implied that a LockManager uses its own custom LockTracker.
2. Add definitions for Range Locking (class Endpoint and GetRangeLock() function.
cheng-chang, is this what you've had in mind (should the PR have both item 1 and item 2?)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7443
Reviewed By: zhichao-cao
Differential Revision: D24123172
Pulled By: cheng-chang
fbshipit-source-id: c6548ad6d4cc3c25f68d13b29147bc6fdf357185
Summary:
In order to be able to introduce more locking protocols, we need to abstract out the locking subsystem in TransactionDB into a set of interfaces.
PR https://github.com/facebook/rocksdb/pull/7013 introduces interface `LockTracker`. This PR is a follow up to take the first step to abstract out a `LockManager` interface.
Further modifications to the interface may be needed when introducing the first implementation of range lock. But the idea here is to put the range lock implementation based on range tree under the `utilities/transactions/lock/range/range_tree`.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7532
Test Plan: point_lock_manager_test
Reviewed By: ajkr
Differential Revision: D24238731
Pulled By: cheng-chang
fbshipit-source-id: 2a9458cd8b3fb008d9529dbc4d3b28c24631f463
Summary:
We're going to support more locking protocols such as range lock in transaction.
However, in current design, `TransactionBase` has a member `tracked_keys` which assumes that point lock (lock a single key) is used, and is used in snapshot checking (isolation protocol). When using range lock, we may use read committed instead of snapshot checking as the isolation protocol.
The most significant usage scenarios of `tracked_keys` are:
1. pessimistic transaction uses it to track the locked keys, and unlock these keys when commit or rollback.
2. optimistic transaction does not lock keys upfront, it only tracks the lock intentions in tracked_keys, and do write conflict checking when commit.
3. each `SavePoint` tracks the keys that are locked since the `SavePoint`, `RollbackToSavePoint` or `PopSavePoint` relies on both the tracked keys in `SavePoint`s and `tracked_keys`.
Based on these scenarios, if we can abstract out a `LockTracker` interface to hold a set of tracked locks (can be keys or key ranges), and have methods that can be composed together to implement the scenarios, then `tracked_keys` can be an internal data structure of one implementation of `LockTracker`. See `utilities/transactions/lock/lock_tracker.h` for the detailed interface design, and `utilities/transactions/lock/point_lock_tracker.cc` for the implementation.
In the future, a `RangeLockTracker` can be implemented to track range locks without affecting other components.
After this PR, a clean interface for lock manager should be possible, and then ideally, we can have pluggable locking protocols.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7013
Test Plan: Run `transaction_test` and `optimistic_transaction_test`.
Reviewed By: ajkr
Differential Revision: D22163706
Pulled By: cheng-chang
fbshipit-source-id: f2860577b5334e31dd2994f5bc6d7c40d502b1b4
Summary:
In current commit protocol of pessimistic transaction, if the transaction is not prepared before commit, the commit protocol implicitly assumes that the user wants to commit without prepare.
This PR adds TransactionOptions::skip_prepare, the default value is `true` because if set to `false`, all existing users who commit without prepare need to update their code to set skip_prepare to true. Although this does not force the user to explicitly express their intention of skip_prepare, it at least lets the user be aware of the assumption of being able to commit without prepare.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6775
Test Plan: added a new unit test TransactionTest::CommitWithoutPrepare
Reviewed By: lth
Differential Revision: D21313270
Pulled By: cheng-chang
fbshipit-source-id: 3d95b7c9b2d6cdddc09bdd66c561bc4fae8c3251
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:
Use delete to disable automatic generated methods instead of private, and put the constructor together for more clear.This modification cause the unused field warning, so add unused attribute to disable this warning.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5009
Differential Revision: D17288733
fbshipit-source-id: 8a767ce096f185f1db01bd28fc88fef1cdd921f3
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
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
Summary:
TransactionOptions::skip_concurrency_control allows pessimistic transactions to skip the overhead of concurrency control. This could be as an optimization if the application knows that the transaction would not have any conflict with concurrent transactions. It is currently used during recovery assuming (i) application guarantees no conflict between prepared transactions in the WAL (ii) application guarantees that recovered transactions will be rolled back/commit before new transactions start.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4346
Differential Revision: D9759149
Pulled By: maysamyabandeh
fbshipit-source-id: f896e84fa58b0b584be904c7fd3883a41ea3215b
Summary:
This adds support for writing unprepared batches based on size defined in `TransactionOptions::max_write_batch_size`. This is done by overriding methods that modify data (Put/Delete/SingleDelete/Merge) and checking first if write batch size has exceeded threshold. If so, the write batch is written to DB as an unprepared batch.
Support for Commit/Rollback for unprepared batch is added as well. This has been done by simply extending the WritePrepared Commit/Rollback logic to take care of all unprep_seq numbers either when updating prepare heap, or adding to commit map. For updating the commit map, this logic exists inside `WriteUnpreparedCommitEntryPreReleaseCallback`.
A test change was also made to have transactions unregister themselves when committing without prepare. This is because with write unprepared, there may be unprepared entries (which act similarly to prepared entries) already when a commit is done without prepare.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4104
Differential Revision: D8785717
Pulled By: lth
fbshipit-source-id: c02006e281ec1ce00f628e2a7beec0ee73096a91
Summary:
This patch takes advantage of memtable being able to detect duplicate <key,seq> and returning TryAgain to handle duplicate keys in WritePrepared Txns. Through WriteBatchWithIndex's index it detects existence of at least a duplicate key in the write batch. If duplicate key was reported, it then pays the cost of counting the number of sub-patches by iterating over the write batch and pass it to DBImpl::Write. DB will make use of the provided batch_count to assign proper sequence numbers before sending them to the WAL. When later inserting the batch to the memtable, it increases the seq each time memtbale reports a duplicate (a sub-patch in our counting) and tries again.
Closes https://github.com/facebook/rocksdb/pull/3455
Differential Revision: D6873699
Pulled By: maysamyabandeh
fbshipit-source-id: db8487526c3a5dc1ddda0ea49f0f979b26ae648d
Summary:
This patch clarifies and refactors the logic around tracked keys in transactions.
Closes https://github.com/facebook/rocksdb/pull/3140
Differential Revision: D6290258
Pulled By: maysamyabandeh
fbshipit-source-id: 03b50646264cbcc550813c060b180fc7451a55c1
Summary:
Implements ValidateSnapshot for WritePrepared txns and also adds a unit test to clarify the contract of this function.
Closes https://github.com/facebook/rocksdb/pull/3101
Differential Revision: D6199405
Pulled By: maysamyabandeh
fbshipit-source-id: ace509934c307ea5d26f4bbac5f836d7c80fd240
Summary:
GetCommitTimeWriteBatch is currently used to store some state as part of commit in 2PC. In MyRocks it is specifically used to store some data that would be needed only during recovery. So it is not need to be stored in memtable right after each commit.
This patch enables an optimization to write the GetCommitTimeWriteBatch only to the WAL. The batch will be written to memtable during recovery when the WAL is replayed. To cover the case when WAL is deleted after memtable flush, the batch is also buffered and written to memtable right before each memtable flush.
Closes https://github.com/facebook/rocksdb/pull/3071
Differential Revision: D6148023
Pulled By: maysamyabandeh
fbshipit-source-id: 2d09bae5565abe2017c0327421010d5c0d55eaa7
Summary:
Implement the rollback of WritePrepared txns. For each modified value, it reads the value before the txn and write it back. This would cancel out the effect of transaction. It also remove the rolled back txn from prepared heap.
Closes https://github.com/facebook/rocksdb/pull/2946
Differential Revision: D5937575
Pulled By: maysamyabandeh
fbshipit-source-id: a6d3c47f44db3729f44b287a80f97d08dc4e888d
Summary:
We had two proposals for lock-free commit maps. This patch implements the latter one that was simpler. We can later experiment with both proposals.
In this impl each entry is an std::atomic of uint64_t, which are accessed via memory_order_acquire/release. In x86_64 arch this is compiled to simple reads and writes from memory.
Closes https://github.com/facebook/rocksdb/pull/2861
Differential Revision: D5800724
Pulled By: maysamyabandeh
fbshipit-source-id: 41abae9a4a5df050a8eb696c43de11c2770afdda
Summary:
TransactionCallback was never used. Remove it to avoid confusion.
Closes https://github.com/facebook/rocksdb/pull/2853
Differential Revision: D5787219
Pulled By: maysamyabandeh
fbshipit-source-id: e2b6a89537e3770a269ad38be71c4b0b160a88ac
Summary:
Implement the main body of WritePrepared pseudo code. This includes PrepareInternal and CommitInternal, as well as AddCommitted which updates the commit map. It also provides a IsInSnapshot method that could be later called form the read path to decide if a version is in the read snapshot or it should other be skipped.
This patch lacks unit tests and does not attempt to offer an efficient implementation. The idea is that to have the API specified so that we can work on related tasks in parallel.
Closes https://github.com/facebook/rocksdb/pull/2713
Differential Revision: D5640021
Pulled By: maysamyabandeh
fbshipit-source-id: bfa7a05e8d8498811fab714ce4b9c21530514e1c
Summary:
This patch splits Commit and Prepare into lock-related logic and db-write-related logic. It moves lock-related logic to PessimisticTransaction to be reused by all children classes and movies the existing impl of db-write-related to PrepareInternal, CommitSingleInternal, and CommitInternal in WriteCommittedTxnImpl.
Closes https://github.com/facebook/rocksdb/pull/2691
Differential Revision: D5569464
Pulled By: maysamyabandeh
fbshipit-source-id: d1b8698e69801a4126c7bc211745d05c636f5325
Summary:
This opens space for the new implementations of TransactionDBImpl such as WritePreparedTxnDBImpl that has a different policy of how to write to DB.
Closes https://github.com/facebook/rocksdb/pull/2689
Differential Revision: D5568918
Pulled By: maysamyabandeh
fbshipit-source-id: f7eac866e175daf3793ae79da108f65cc7dc7b25
Summary:
This patch refactors TransactionImpl by separating the logic for pessimistic concurrency control from the implementation of how to write the data to rocksdb. The existing implementation is named WriteCommittedTxnImpl as it writes committed data to the db. A template named WritePreparedTxnImpl is also added which will be later completed to provide a an alternative implementation.
Closes https://github.com/facebook/rocksdb/pull/2676
Differential Revision: D5549998
Pulled By: maysamyabandeh
fbshipit-source-id: 16298e86b43ca4849324c1f35c731913c6d17bec
Summary:
This reverts the previous commit 1d7048c598, which broke the build.
Did a `git revert 1d7048c`.
Closes https://github.com/facebook/rocksdb/pull/2627
Differential Revision: D5476473
Pulled By: sagar0
fbshipit-source-id: 4756ff5c0dfc88c17eceb00e02c36176de728d06
Summary: This uses `clang-tidy` to comment out unused parameters (in functions, methods and lambdas) in fbcode. Cases that the tool failed to handle are fixed manually.
Reviewed By: igorsugak
Differential Revision: D5454343
fbshipit-source-id: 5dee339b4334e25e963891b519a5aa81fbf627b2
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
Yanqin Jin