mirror of https://github.com/facebook/rocksdb.git
ec11c23caa
Summary: BackupEngine previously had unclear but strict concurrency requirements that the API user must follow for safe use. Now we make that clear, by separating operations into "Read," "Append," and "Write" operations, and specifying which combinations are safe across threads on the same BackupEngine object (previously none; now all, using a read-write lock), and which are safe across different BackupEngine instances open on the same backup_dir. The changes to backupable_db.h should be backward compatible. It is mostly about eliminating copies of what should be the same function and (unsurprisingly) useful documentation comments were often placed on only one of the two copies. With the re-organization, we are also grouping different categories of operations. In the future we might add BackupEngineReadAppendOnly, but that didn't seem necessary. To mark API Read operations 'const', I had to mark some implementation functions 'const' and some fields mutable. Functional changes: * Added RWMutex locking around public API functions to implement thread safety on a single object. To avoid future bugs, this is another internal class layered on top (removing many "override" in BackupEngineImpl). It would be possible to allow more concurrency between operations, rather than mutual exclusion, but IMHO not worth the work. * Fixed a race between Open() (Initialize()) and CreateNewBackup() for different objects on the same backup_dir, where Initialize() could delete the temporary meta file created during CreateNewBackup(). (This was found by the new test.) Also cleaned up a couple of "status checked" TODOs, and improved a checksum mismatch error message to include involved files. Potential follow-up work: * CreateNewBackup has an API wart because it doesn't tell you the BackupID it just created, which makes it of limited use in a multithreaded setting. * We could also consider a Refresh() function to catch up to changes made from another BackupEngine object to the same dir. * Use a lock file to prevent multiple writer BackupEngines, but this won't work on remote filesystems not supporting lock files. Pull Request resolved: https://github.com/facebook/rocksdb/pull/8115 Test Plan: new mini-stress test in backup unit tests, run with gcc, clang, ASC, TSAN, and UBSAN, 100 iterations each. Reviewed By: ajkr Differential Revision: D27347589 Pulled By: pdillinger fbshipit-source-id: 28d82ed2ac672e44085a739ddb19d297dad14b15 |
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| .. | ||
| backupable | ||
| blob_db | ||
| cassandra | ||
| checkpoint | ||
| compaction_filters | ||
| convenience | ||
| leveldb_options | ||
| memory | ||
| merge_operators | ||
| option_change_migration | ||
| options | ||
| persistent_cache | ||
| simulator_cache | ||
| table_properties_collectors | ||
| trace | ||
| transactions | ||
| ttl | ||
| write_batch_with_index | ||
| debug.cc | ||
| env_librados.cc | ||
| env_librados.md | ||
| env_librados_test.cc | ||
| env_mirror.cc | ||
| env_mirror_test.cc | ||
| env_timed.cc | ||
| env_timed_test.cc | ||
| fault_injection_env.cc | ||
| fault_injection_env.h | ||
| fault_injection_fs.cc | ||
| fault_injection_fs.h | ||
| merge_operators.h | ||
| object_registry.cc | ||
| object_registry_test.cc | ||
| util_merge_operators_test.cc | ||