91b96f41cf
Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/15179 A remote compaction worker (`DB::OpenAndCompact()`) opens the *live* primary's DB directory read-only, and that open reads `CURRENT`. The primary publishes each MANIFEST rotation by writing a new `CURRENT` under a temp name and renaming it over the old `CURRENT`. POSIX keeps an already-opened `CURRENT` readable after that replacement, but file systems without read-after-unlink semantics (remote or object stores) do not: the replaced object is reported as gone, surfacing in RocksDB as `IO error: No such file or directory` (`Status::PathNotFound`). The secondary open was not retried, so this transient race failed the whole compaction. There is an equivalent, already-recognized race one step later for the MANIFEST file (`ReactiveVersionSet::MaybeSwitchManifest()` converts it into `Status::TryAgain`), which was fatal here for the same reason. `DB::OpenAndCompact()` now retries the secondary open (up to 3 attempts) when it fails with `TryAgain` / `PathNotFound` / `NotFound` -- exactly the statuses a concurrent `CURRENT`/MANIFEST replacement produces. The retry limit is configurable via `OpenAndCompactOptions::max_secondary_open_retries`. Genuine failures are still returned after the bounded retries, and no safety check is weakened or skipped. Found by a `db_stress` crash test failure. Two non-default options in that run make this reachable and fatal: * `remote_compaction_worker_threads=8` with `remote_compaction_failure_fall_back_to_local=0` -- the latter was only recently randomized to 0; before that a remote compaction failure was always silently retried locally. Now `DbStressCompactionService::Wait()` maps the failure to `kFailure`, which becomes a sticky background error on the primary, so every subsequent `Flush()` returns it and `StressTest::ProcessStatus()` aborts with `assert(false)`. * `max_manifest_file_size=8192` -- the primary rotates MANIFEST (and therefore replaces `CURRENT`) constantly, which is what makes the race window hit in practice. Full chain: primary renames a new `CURRENT` over the old one -> the file system reports the replaced object as gone for the reader that already resolved it -> `GetCurrentManifestPath()` inside the worker's secondary open fails with `IO error: No such file or directory` -> `DB::OpenAndCompact()` returns that error with no retry -> `kFailure` (no local fallback) -> primary background error -> `Flush failed: IO error: No such file or directory: ... /CURRENT ...` -> assertion failure in `db_stress`. Reviewed By: joshkang97 Differential Revision: D118480192 fbshipit-source-id: a2618ee24e582e2e713af04464ee1e4038925ccb
RocksDB: A Persistent Key-Value Store for Flash and RAM Storage
RocksDB is developed and maintained by Facebook Database Engineering Team. It is built on earlier work on LevelDB by Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com)
This code is a library that forms the core building block for a fast key-value server, especially suited for storing data on flash drives. It has a Log-Structured-Merge-Database (LSM) design with flexible tradeoffs between Write-Amplification-Factor (WAF), Read-Amplification-Factor (RAF) and Space-Amplification-Factor (SAF). It has multi-threaded compactions, making it especially suitable for storing multiple terabytes of data in a single database.
Start with example usage here: https://github.com/facebook/rocksdb/tree/main/examples
See the github wiki for more explanation.
The public interface is in include/. Callers should not include or
rely on the details of any other header files in this package. Those
internal APIs may be changed without warning.
Questions and discussions are welcome on the RocksDB Developers Public Facebook group and email list on Google Groups.
License
RocksDB is dual-licensed under both the GPLv2 (found in the COPYING file in the root directory) and Apache 2.0 License (found in the LICENSE.Apache file in the root directory). You may select, at your option, one of the above-listed licenses.