Summary:
Pull Request resolved: https://github.com/facebook/rocksdb/pull/15373
Fix worker retirement when changing `WriteBufferManager` from `kFlushLargestAcrossDBs` to `kFlushOldest`. The coordinator could pass its active-policy check, consume the policy-change notification during refresh, and enter a one-second idle wait. This delayed retirement beyond the 300 ms deadline in `WriteBufferManagerTest.FlushPolicyRetiresAndRestartsHandoffWorkers`. Recheck the policy under `sorter_wait_mu` before waiting so the coordinator promptly enters the retirement path. The setter remains non-blocking, and retirement still waits for executor callbacks to finish.
Also fix startup pressure-wait accounting in `BackgroundFlushCycleTest.FastRejectedCandidateDoesNotAddPressureDelay`. Registering the healthy candidate can invalidate the coordinator's initial ranking snapshot and cause a legitimate pressure wait before either handoff runs. The old assertion counted waits from startup and incorrectly attributed that wait to the rejected candidate. Record the counts at rejected and healthy dispatch and require them to match, preserving the check that rejection adds no pressure interval.
Include both fixes in this diff so its `write_buffer_manager_test` target covers both corrected behaviors. Replace worker retirement and restart polling with sync-point synchronization. The rejection test deterministically invalidates the first snapshot during healthy-candidate registration, verifies that a startup wait occurred, and checks that advancing to the healthy candidate adds no further pressure wait. Retain the clang-format 21 line wrapping required by CI.
Reviewed By: pdillinger
Differential Revision: D124377137
fbshipit-source-id: 1420196e47ccba0268d0427c4ed623925aa3ad5b
Summary:
Pull Request resolved: https://github.com/facebook/rocksdb/pull/15343
Problem
The cross-DB WriteBufferManager coordinator dispatches ranked flush candidates asynchronously. A candidate can reject its handoff immediately—for example because its DB mutex is busy, writes are stopped, or equivalent WBM work is already scheduled—and finish before the sorter reaches its pressure wait.
Before this change, completion called RequestRefresh(), but the sorter’s active-pressure branch did not consume that already-recorded notification. Condition-variable notifications are not retained, so if completion won the race, the sorter still slept for the full 10 ms pressure interval before trying the next ranked DB. With many quickly rejected candidates, that delay accumulated once per candidate; 10,000 rejected DBs ahead of a healthy DB could theoretically delay useful relief by roughly 100 seconds while shared memory remained above its limit.
Solution
Snapshot the existing refresh-request generation immediately before ProcessFlushHandoffRequest(). After processing, if the handoff is already idle, the current ranked candidate cycle remains active, and the generation advanced, the sorter knows that asynchronous work completed during the dispatch window. It consumes that persistent notification and immediately continues to the next candidate instead of entering the pressure backoff.
The generation check is deliberately narrower than checking the refresh Boolean alone: it reacts only to notifications that occurred during this handoff attempt and avoids treating an older unrelated refresh as completion of the current candidate. The existing 10 ms backoff remains after a complete no-progress candidate cycle, and queued or executing handoffs retain their existing lease/wait behavior.
Testing
A deterministic SyncPoint test pauses the sorter only after a handoff has actually been submitted, lets a rejecting executor callback finish first, and verifies that the healthy next candidate is reached without entering the pressure-wait point. The synchronization wait is bounded so a broken ordering fails the test rather than hanging CI.
Reviewed By: xingbowang
Differential Revision: D123926506
fbshipit-source-id: b057e5b9a41ee0abd415f72ef2067b0d3f718384
Summary:
Pull Request resolved: https://github.com/facebook/rocksdb/pull/15331
## Motivation
The parent diff already implements cross-DB flushable-memory accounting and a background sorter that ranks DBs outside the write path. This change does not alter how the best candidate is selected.
The remaining liveness problem occurs after the sorter selects a DB and hands it off for execution. Previously, the coordinator tracked one remote handoff as pending and waited for that DB to report completion before advancing. A selected DB could therefore monopolize coordinator progress if its job waited in Env::LOW, blocked on the DB mutex, waited behind an existing write leader or write stall, or otherwise failed to complete promptly. Other ranked DBs could be ready to reclaim memory but would not be attempted while the first handoff remained pending.
## Solution
Make cross-DB flush handoff execution bounded and bypassable.
Cross-DB attempts now run on a small four-worker executor owned by the WriteBufferManager instead of consuming Env::LOW compaction capacity. The executor is created only for kFlushLargestAcrossDBs and its workers are retired when that policy is disabled.
The coordinator distinguishes queued and executing handoffs. A candidate lease begins when an executor worker starts the callback, rather than while the callback is merely waiting in the executor queue. If an executing handoff exceeds its lease, the coordinator releases ownership of that attempt and advances to the next ranked candidate. The original callback is not cancelled and may still complete, so the executor and outstanding-handoff count provide a strict bound on concurrent stuck work.
Each registration has a per-DB outstanding-job reservation, preventing the sorter from dispatching the same DB again while an earlier callback remains alive. The coordinator also records the identity of the active candidate, so late completion from an expired attempt cannot clear or corrupt a newer candidate lease.
DB mutex acquisition, write-thread joining, memtable switching, and flush dispatch continue to happen outside registry and coordinator locks. The executor invokes the existing BackgroundCallWBMFlush path directly; actual immutable-memtable flushing still uses RocksDB normal flush infrastructure.
## Compatibility
This behavior is limited to kFlushLargestAcrossDBs. Existing policies retain their previous local flush behavior, and no WBM executor threads are started for them.
## Validation
Unit coverage exercises lease expiry, advancement to the next candidate, late completion, duplicate suppression, bounded worker capacity, policy changes with blocked callbacks, shutdown, and reranking after progress.
The end-to-end stack was also compared against the original local policy in one matched memory-pressure run with 1,000 DBs and 16 writers. The complete largest-across-DBs policy delivered 61.0% higher throughput, 55.5% fewer WBM flushes, 37.9% lower mean latency, 47.9% lower P99 latency, 5.17x larger average flushes, and 62.8% lower peak RSS. These measurements validate the full policy stack rather than isolating the performance contribution of this liveness follow-up.
Reviewed By: xingbowang
Differential Revision: D123461329
fbshipit-source-id: 4ad86102c2a43beb469f7672d722674dfbda9871
Summary:
Motivation
A WriteBufferManager can be shared by many RocksDB instances and column families. Under the existing policy, the DB whose writer first observes memory pressure flushes its own oldest mutable memtable. That DB might own only a small fraction of the reclaimable memory, so workloads with many DBs or CFs can generate many small flushes while the largest memory consumer remains untouched. Scanning every registered DB while holding process-wide or DB mutexes would improve selection accuracy but would serialize unrelated write paths and is not viable for deployments with thousands of DBs.
Previous behavior
kFlushOldest was the only behavior: the write-group leader that noticed WBM pressure synchronously selected the oldest eligible mutable memtable in its own DB. The WBM had no per-DB view of reclaimable memory and could not direct reclamation to another DB sharing the same budget.
New behavior
This change adds configurable WriteBufferFlushPolicy modes:
- kFlushOldest preserves the existing behavior and remains the default.
- kFlushLargest selects the largest eligible flushable column family in the writing DB.
- kFlushLargestAcrossDBs selects the DB advertising the most reclaimable memory across all DBs sharing the WBM, then flushes its largest eligible CF. Atomic-flush DBs advertise and flush the aggregate eligible memory across their CFs.
High-level implementation
Each writable DB registers a lightweight FlushInitiator with the shared WBM. Per-DB accounting publishes two approximate values using atomics: total mutable memory and the largest flushable CF contribution, including eligible immutable memtables waiting for flush. Allocator reporting is batched, so the allocation hot path avoids registry scans and DB mutexes.
A dedicated WBM coordinator thread maintains an approximate ranked snapshot of registered DBs. Refreshes are driven by accounting changes, threshold crossings, and periodic pressure checks. Ranking and O(number of DBs) work happen on that coordinator thread; writers only update counters and signal the coordinator. Registration lifetime is protected independently so DB close can safely drain an in-flight handoff.
Threading and flush handoff
The coordinator reserves and pins one ranked candidate at a time, without holding a registry lock while invoking the DB. The target DB uses TryLock on its DB mutex and rejects the handoff if it is closing, paused, stopped, stalled, already handling a WBM job, or no longer has flushable memory. Rejected candidates do not block consideration of the next DB.
An accepted handoff queues one LOW-priority WBM job. The LOW worker joins the target DB write thread and revalidates eligibility before switching the memtable. The resulting ordinary flush is then scheduled through RocksDB's existing flush machinery on the HIGH-priority flush pool. Keeping the write-thread join off the requesting writer avoids making one DB's write path wait on another DB's mutex or write queue.
Only one manager-wide remote handoff is active at a time. Completion or cancellation clears the handoff and requests a rerank. If memory reaches the hard limit while remote coordination is delayed, a rate-limited local fallback lets a writer seal a local memtable to preserve forward progress. Write stalls, shutdown, WaitForCompact, policy changes, and DB deregistration explicitly drain or reject outstanding handoffs.
Compatibility
The legacy constructor and kFlushOldest behavior remain unchanged unless a new policy is explicitly selected. There are no on-disk format changes.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/15047
Reviewed By: xingbowang
Differential Revision: D112396106
fbshipit-source-id: 3049adc7034dd4e00d74d7d86e1d19004292d299
Summary:
The definition of the Cache class should not be needed by the vast majority of RocksDB users, so I think it is just distracting to include it in cache.h, which is primarily needed for configuring and creating caches. This change moves the class to a new header advanced_cache.h. It is just cut-and-paste except for modifying the class API comment.
In general, operations on shared_ptr<Cache> should continue to work when only a forward declaration of Cache is available, as long as all the Cache instances provided are already shared_ptr. See https://stackoverflow.com/a/17650101/454544
Also, the most common way to customize a Cache is by wrapping an existing implementation, so it makes sense to provide CacheWrapper in the public API. This was a cut-and-paste job except removing the implementation of Name() so that derived classes must provide it.
Intended follow-up: consolidate Release() into one function to reduce customization bugs / confusion
Pull Request resolved: https://github.com/facebook/rocksdb/pull/11192
Test Plan: `make check`
Reviewed By: anand1976
Differential Revision: D43055487
Pulled By: pdillinger
fbshipit-source-id: 7b05492df35e0f30b581b4c24c579bc275b6d110
Summary:
We haven't been actively mantaining RocksDB LITE recently and the size must have been gone up significantly. We are removing the support.
Most of changes were done through following comments:
unifdef -m -UROCKSDB_LITE `git grep -l ROCKSDB_LITE | egrep '[.](cc|h)'`
by Peter Dillinger. Others changes were manually applied to build scripts, CircleCI manifests, ROCKSDB_LITE is used in an expression and file db_stress_test_base.cc.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/11147
Test Plan: See CI
Reviewed By: pdillinger
Differential Revision: D42796341
fbshipit-source-id: 4920e15fc2060c2cd2221330a6d0e5e65d4b7fe2
Summary:
Instead of existing calls to ps from gnu_parallel, call a new wrapper that does ps, looks for unit test like processes, and uses pstack or gdb to print thread stack traces. Also, using `ps -wwf` instead of `ps -wf` ensures output is not cut off.
For security, CircleCI runs with security restrictions on ptrace (/proc/sys/kernel/yama/ptrace_scope = 1), and this change adds a work-around to `InstallStackTraceHandler()` (only used by testing tools) to allow any process from the same user to debug it. (I've also touched >100 files to ensure all the unit tests call this function.)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10828
Test Plan: local manual + temporary infinite loop in a unit test to observe in CircleCI
Reviewed By: hx235
Differential Revision: D40447634
Pulled By: pdillinger
fbshipit-source-id: 718a4c4a5b54fa0f9af2d01a446162b45e5e84e1
Summary:
Moved linux builds to using docker to avoid CI instability caused by dependency installation site down.
Added the `Dockerfile` which is used to build the image.
The build time is also significantly reduced, because no dependencies installation and with using 2xlarge+ instance for slow build (like tsan test).
Also fixed a few issues detected while building this:
* `DestoryDB()` Status not checked for a few tests
* nullptr might be used in `inlineskiplist.cc`
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10496
Test Plan: CI
Reviewed By: ajkr
Differential Revision: D38554200
Pulled By: jay-zhuang
fbshipit-source-id: 16e8fb2bf07b9c84bb27fb18421c4d54f2f248fd
Summary:
**Context:**
Previous PR https://github.com/facebook/rocksdb/pull/9748, https://github.com/facebook/rocksdb/pull/9073, https://github.com/facebook/rocksdb/pull/8428 added separate flag for each charged memory area. Such API design is not scalable as we charge more and more memory areas. Also, we foresee an opportunity to consolidate this feature with other cache usage related features such as `cache_index_and_filter_blocks` using `CacheEntryRole`.
Therefore we decided to consolidate all these flags with `CacheUsageOptions cache_usage_options` and this PR serves as the first step by consolidating memory-charging related flags.
**Summary:**
- Replaced old API reference with new ones, including making `kCompressionDictionaryBuildingBuffer` opt-out and added a unit test for that
- Added missing db bench/stress test for some memory charging features
- Renamed related test suite to indicate they are under the same theme of memory charging
- Refactored a commonly used mocked cache component in memory charging related tests to reduce code duplication
- Replaced the phrases "memory tracking" / "cache reservation" (other than CacheReservationManager-related ones) with "memory charging" for standard description of this feature.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9926
Test Plan:
- New unit test for opt-out `kCompressionDictionaryBuildingBuffer` `TEST_F(ChargeCompressionDictionaryBuildingBufferTest, Basic)`
- New unit test for option validation/sanitization `TEST_F(CacheUsageOptionsOverridesTest, SanitizeAndValidateOptions)`
- CI
- db bench (in case querying new options introduces regression) **+0.5% micros/op**: `TEST_TMPDIR=/dev/shm/testdb ./db_bench -benchmarks=fillseq -db=$TEST_TMPDIR -charge_compression_dictionary_building_buffer=1(remove this for comparison) -compression_max_dict_bytes=10000 -disable_auto_compactions=1 -write_buffer_size=100000 -num=4000000 | egrep 'fillseq'`
#-run | (pre-PR) avg micros/op | std micros/op | (post-PR) micros/op | std micros/op | change (%)
-- | -- | -- | -- | -- | --
10 | 3.9711 | 0.264408 | 3.9914 | 0.254563 | 0.5111933721
20 | 3.83905 | 0.0664488 | 3.8251 | 0.0695456 | **-0.3633711465**
40 | 3.86625 | 0.136669 | 3.8867 | 0.143765 | **0.5289363078**
- db_stress: `python3 tools/db_crashtest.py blackbox -charge_compression_dictionary_building_buffer=1 -charge_filter_construction=1 -charge_table_reader=1 -cache_size=1` killed as normal
Reviewed By: ajkr
Differential Revision: D36054712
Pulled By: hx235
fbshipit-source-id: d406e90f5e0c5ea4dbcb585a484ad9302d4302af
Summary:
Context:
To help cap various memory usage by a single limit of the block cache capacity, we charge the memory usage through inserting/releasing dummy entries in the block cache. CacheReservationManager is such a class (non thread-safe) responsible for inserting/removing dummy entries to reserve cache space for memory used by the class user.
- Refactored the inner private class CacheRep of WriteBufferManager into public CacheReservationManager class for reusability such as for https://github.com/facebook/rocksdb/pull/8428
- Encapsulated implementation details of cache key generation and dummy entries insertion/release in cache reservation as discussed in https://github.com/facebook/rocksdb/pull/8506#discussion_r666550838
- Consolidated increase/decrease cache reservation into one API - UpdateCacheReservation.
- Adjusted the previous dummy entry release algorithm in decreasing cache reservation to be loop-releasing dummy entries to stay symmetric to dummy entry insertion algorithm
- Made the previous dummy entry release algorithm in delayed decrease mode more aggressive for better decreasing cache reservation when memory used is less likely to increase back.
Previously, the algorithms only release 1 dummy entries when new_mem_used < 3/4 * cache_allocated_size_ and cache_allocated_size_ - kSizeDummyEntry > new_mem_used.
Now, the algorithms loop-releases as many dummy entries as possible when new_mem_used < 3/4 * cache_allocated_size_.
- Updated WriteBufferManager's test cases to adapt to changes on the release algorithm mentioned above and left comment for some test cases for clarity
- Replaced the previous cache key prefix generation (utilizing object address related to the cache client) with one that utilizes Cache->NewID() to prevent cache-key collision among dummy entry clients sharing the same cache.
The specific collision we are preventing happens when the object address is reused for a new cache-key prefix while the old cache-key using that same object address in its prefix still exists in the cache. This could happen due to that, under LRU cache policy, there is a possible delay in releasing a cache entry after the cache client object owning that cache entry get deallocated. In this case, the object address related to the cache client object can get reused for other client object to generate a new cache-key prefix.
This prefix generation can be made obsolete after Peter's unification of all the code generating cache key, mentioned in https://github.com/facebook/rocksdb/pull/8506#discussion_r667265255
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8506
Test Plan:
- Passing the added unit tests cache_reservation_manager_test.cc
- Passing existing and adjusted write_buffer_manager_test.cc
Reviewed By: ajkr
Differential Revision: D29644135
Pulled By: hx235
fbshipit-source-id: 0fc93fbfe4a40bb41be85c314f8f2bafa8b741f7
Summary:
This PR adds SetBufferSize() to the WriteBufferManager object. This enables user code to adjust the global budget for write_buffers based upon other memory conditions such as growth in table reader memory as the dataset grows.
The buffer_size_ member variable is now atomic to match design of other changeable size_t members within WriteBufferManager.
This change is useful as is. However, this change is also essential if someone decides they wanted to enable db_write_buffer_size modifications through the DB::SetOptions() API, i.e. no waste taking this as is.
Any format / spacing changes are due to clang-format as required by check-in automation.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7961
Reviewed By: ajkr
Differential Revision: D26639075
Pulled By: akankshamahajan15
fbshipit-source-id: 0604348caf092d35f44e85715331dc920e5c1033
Summary:
Introduces and uses a SystemClock class to RocksDB. This class contains the time-related functions of an Env and these functions can be redirected from the Env to the SystemClock.
Many of the places that used an Env (Timer, PerfStepTimer, RepeatableThread, RateLimiter, WriteController) for time-related functions have been changed to use SystemClock instead. There are likely more places that can be changed, but this is a start to show what can/should be done. Over time it would be nice to migrate most (if not all) of the uses of the time functions from the Env to the SystemClock.
There are several Env classes that implement these functions. Most of these have not been converted yet to SystemClock implementations; that will come in a subsequent PR. It would be good to unify many of the Mock Timer implementations, so that they behave similarly and be tested similarly (some override Sleep, some use a MockSleep, etc).
Additionally, this change will allow new methods to be introduced to the SystemClock (like https://github.com/facebook/rocksdb/issues/7101 WaitFor) in a consistent manner across a smaller number of classes.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7858
Reviewed By: pdillinger
Differential Revision: D26006406
Pulled By: mrambacher
fbshipit-source-id: ed10a8abbdab7ff2e23d69d85bd25b3e7e899e90
Summary:
Add new API WriteBufferManager::dummy_entries_in_cache_usage() which reports the dummy entries size stored in cache to account for DataBlocks in WriteBufferManager.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7837
Test Plan: Updated test ./write_buffer_manager_test
Reviewed By: ajkr
Differential Revision: D25794312
Pulled By: akankshamahajan15
fbshipit-source-id: 197f5e8701e3dc57a7df72dab1735624f90daf4b
Summary:
https://github.com/facebook/rocksdb/issues/6247 reports that when write buffer manager fails to insert the dummy entry to block cache, null pointer is still stored and used to release the handle and cause corruption. Fix the bug by not releasing it with null handle.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6619
Test Plan: Add a unit test that fails without the fix.
Reviewed By: ajkr
Differential Revision: D20776769
fbshipit-source-id: 4127fbd9f295a0a3e45774746ffcd91f939f6287
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:
For our default block cache, each additional entry has extra memory overhead. It include LRUHandle (72 bytes currently) and the cache key (two varint64, file id and offset). The usage is not negligible. For example for block_size=4k, the overhead accounts for an extra 2% memory usage for the cache. The patch charging the cache for the extra usage, reducing untracked memory usage outside block cache. The feature is enabled by default and can be disabled by passing kDontChargeCacheMetadata to the cache constructor.
This PR builds up on https://github.com/facebook/rocksdb/issues/4258
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5797
Test Plan:
- Existing tests are updated to either disable the feature when the test has too much dependency on the old way of accounting the usage or increasing the cache capacity to account for the additional charge of metadata.
- The Usage tests in cache_test.cc are augmented to test the cache usage under kFullChargeCacheMetadata.
Differential Revision: D17396833
Pulled By: maysamyabandeh
fbshipit-source-id: 7684ccb9f8a40ca595e4f5efcdb03623afea0c6f
Summary:
There are too many types of files under util/. Some test related files don't belong to there or just are just loosely related. Mo
ve them to a new directory test_util/, so that util/ is cleaner.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5377
Differential Revision: D15551366
Pulled By: siying
fbshipit-source-id: 0f5c8653832354ef8caa31749c0143815d719e2c
Summary:
Dummy cache size of 1MB is too large for small block sizes. Our GetDefaultCacheShardBits() use min_shard_size = 512L * 1024L to determine number of shards, so 1MB will excceeds the size of the whole shard and make the cache excceeds the budget.
Change it to 256KB accordingly.
There shouldn't be obvious performance impact, since inserting a cache entry every 256KB of memtable inserts is still infrequently enough.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5175
Differential Revision: D14954289
Pulled By: siying
fbshipit-source-id: 2c275255c1ac3992174e06529e44c55538325c94
Summary:
Even if hard limit hits, flushing more memtable may not help cap the memory usage if already more than half data is scheduled for flush. Not triggering flush instead.
Closes https://github.com/facebook/rocksdb/pull/2469
Differential Revision: D5284249
Pulled By: siying
fbshipit-source-id: 8ab7ba1aba56a634dbe72b318fcab2093063972e
Summary:
Improve write buffer manager in several ways:
1. Size is tracked when arena block is allocated, rather than every allocation, so that it can better track actual memory usage and the tracking overhead is slightly lower.
2. We start to trigger memtable flush when 7/8 of the memory cap hits, instead of 100%, and make 100% much harder to hit.
3. Allow a cache object to be passed into buffer manager and the size allocated by memtable can be costed there. This can help users have one single memory cap across block cache and memtable.
Closes https://github.com/facebook/rocksdb/pull/2350
Differential Revision: D5110648
Pulled By: siying
fbshipit-source-id: b4238113094bf22574001e446b5d88523ba00017
