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Summary: ## Summary Pull Request resolved: https://github.com/facebook/rocksdb/pull/15073 The callback-based async read APIs make coroutine-native implementations and StackableDB composition awkward because wrappers must bridge callbacks back into tasks. This change introduces `CoroDB` as a side capability exposing lazy `GetCoroutine` and `MultiGetCoroutine` tasks. `DBImpl` and `CompactedDBImpl` implement this capability directly, while `DB::GetAsync` and `DB::MultiGetAsync` remain available as compatibility entry points with synchronous fallback. The native interface should also be more efficient because callers directly await the DB coroutine. It avoids the callback/Baton adapter, callback context handoff, and explicit rescheduling required for each request. Native tasks must run on the DB filesystem read executor's EventBase; debug builds verify this affinity. Public API documentation, a release note, and native-coroutine support in `db_bench` and `db_stress` are included. ## Dispatch DB::GetAsync -> GetCoroDB() on the concrete DB -> virtual CoroDB::GetCoroutine(...) -> DBImpl::GetCoroutine or CompactedDBImpl::GetCoroutine -> AsyncCallback::OnComplete(...) Virtual dispatch selects the coroutine implementation belonging to the concrete DB while preserving the existing callback API. ## Statistics Coroutine reads preserve RocksDB's TLS statistics behavior while keeping concurrent requests isolated. Each top-level task copies only the caller's statistics configuration—`PerfLevel`, per-level perf context enablement, and IO statistics enablement—into fresh request-local `PerfContext` and `IOStatsContext` objects. Existing counters are not inherited. If both perf and IO statistics are disabled, no request statistics context is installed. Folly `RequestContext` preserves these contexts across suspension and resumption on the read executor's EventBase. At completion, RocksDB publishes the request's collected values to TLS, allowing the awaiting caller to use `get_perf_context()` and `get_iostats_context()` as after a synchronous read. Callers must consume or copy them before leaving that EventBase. Statistics scopes are installed only by top-level coroutine reads and cannot be nested. ## Benchmarks Compared the previous `GetAsync` callback bridge with native `GetCoroutine`. Both variants used optimized builds, the same compacted DB, a fixed seed, eight executor threads, ten jobs per thread, and 2.56M reads per invocation. Results are the mean of three independent invocations using the default RocksDB block cache. A sequential read warmed the OS page cache before the non-direct-read measurements. | Workload | `GetAsync` bridge | Native `GetCoroutine` | Change | | Direct I/O | 237,710 ops/s | 243,588 ops/s | +2.47% | | Warm OS page cache | 783,859 ops/s | 891,531 ops/s | +13.74% | The direct-I/O difference is within observed run-to-run variation. When reads are served from the OS page cache and API overhead is a larger portion of latency, the native interface improves throughput by 13.74%. Every invocation completed all requested reads. ```bash db_bench \ --benchmarks=readrandomcoroutine \ --db=$CORO_BENCH_DB \ --use_existing_db=true \ --num=2000000 \ --value_size=1024 \ --compression_type=none \ --threads=8 \ --coro_jobs_per_thread=10 \ --reads=320000 \ --use_direct_reads=<true|false> \ --perf_level=1 \ --statistics=true \ --seed=20260807 ``` Reviewed By: xingbowang Differential Revision: D115232511 fbshipit-source-id: 30b48da2a798094d9080178f5430aae26e6c5954
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.