6134ce6444
Summary: Currently, the following interleaving of events can lead to SuperVersion containing both immutable memtables as well as the resulting L0. This can cause Get to return incorrect result if there are merge operands. This may also affect other operations such as single deletes. ``` time main_thr bg_flush_thr bg_compact_thr compact_thr set_opts_thr 0 | WriteManifest:0 1 | issue compact 2 | wait 3 | Merge(counter) 4 | issue flush 5 | wait 6 | WriteManifest:1 7 | wake up 8 | write manifest 9 | wake up 10 | Get(counter) 11 | remove imm V ``` The reason behind is that: one bg flush thread's installing new `Version` can be batched and performed by another thread that is the "leader" MANIFEST writer. This bg thread removes the memtables from current super version only after `LogAndApply` returns. After the leader MANIFEST writer signals (releasing mutex) this bg flush thread, it is possible that another thread sees this cf with both memtables (whose data have been flushed to the newest L0) and the L0 before this bg flush thread removes the memtables. To address this issue, each bg flush thread can pass a callback function to `LogAndApply`. The callback is responsible for removing the memtables. Therefore, the leader MANIFEST writer can call this callback and remove the memtables before releasing the mutex. Test plan (devserver) ``` $make merge_test $./merge_test --gtest_filter=MergeTest.MergeWithCompactionAndFlush $make check ``` Pull Request resolved: https://github.com/facebook/rocksdb/pull/6069 Reviewed By: cheng-chang Differential Revision: D18790894 Pulled By: riversand963 fbshipit-source-id: e41bd600c0448b4f4b2deb3f7677f95e3076b4ed |
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| cmake | ||
| coverage | ||
| db | ||
| db_stress_tool | ||
| docs | ||
| env | ||
| examples | ||
| file | ||
| hdfs | ||
| include/rocksdb | ||
| java | ||
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| memory | ||
| memtable | ||
| monitoring | ||
| options | ||
| port | ||
| table | ||
| test_util | ||
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| AUTHORS | ||
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| CODE_OF_CONDUCT.md | ||
| CONTRIBUTING.md | ||
| COPYING | ||
| DEFAULT_OPTIONS_HISTORY.md | ||
| defs.bzl | ||
| DUMP_FORMAT.md | ||
| HISTORY.md | ||
| INSTALL.md | ||
| issue_template.md | ||
| LANGUAGE-BINDINGS.md | ||
| LICENSE.Apache | ||
| LICENSE.leveldb | ||
| Makefile | ||
| README.md | ||
| ROCKSDB_LITE.md | ||
| src.mk | ||
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| USERS.md | ||
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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/master/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.
Design discussions are conducted in https://www.facebook.com/groups/rocksdb.dev/ and https://rocksdb.slack.com/
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.