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Summary: `db_stress` is a user of `FaultInjectionTestFS`. After injecting a write error, `db_stress` probabilistically determins data drop (https://github.com/facebook/rocksdb/blob/6.27.fb/db_stress_tool/db_stress_test_base.cc#L2615:L2619). In some of our recent runs of `db_stress`, we found duplicate trailing entries corresponding to file trivial move in the MANIFEST, causing the recovery to fail, because the file move operation is not idempotent: you cannot delete a file from a given level twice. Investigation suggests that data buffering in both `WritableFileWriter` and `FaultInjectionTestFS` may be the root cause. WritableFileWriter buffers data to write in a memory buffer, `WritableFileWriter::buf_`. After each `WriteBuffered()`/`WriteBufferedWithChecksum()` succeeds, the `buf_` is cleared. If the underlying file `WritableFileWriter::writable_file_` is opened in buffered IO mode, then `FaultInjectionTestFS` buffers data written for each file until next file sync. After an injected error, user of `FaultInjectionFS` can choose to drop some or none of previously buffered data. If `db_stress` does not drop any unsynced data, then such data will still exist in the `FaultInjectionTestFS`'s buffer. Existing implementation of `WritableileWriter::WriteBuffered()` does not clear `buf_` if there is an error. This may lead to the data being buffered two copies: one in `WritableFileWriter`, and another in `FaultInjectionTestFS`. We also know that the `WritableFileWriter` of MANIFEST file will close upon an error. During `Close()`, it will flush the content in `buf_`. If no write error is injected to `FaultInjectionTestFS` this time, then we end up with two copies of the data appended to the file. To fix, we clear the `WritableFileWriter::buf_` upon failure as well. We focus this PR on files opened in non-direct mode. This PR includes a unit test to reproduce a case when write error injection to `WritableFile` can cause duplicate trailing entries. Pull Request resolved: https://github.com/facebook/rocksdb/pull/9236 Test Plan: make check Reviewed By: zhichao-cao Differential Revision: D33033984 Pulled By: riversand963 fbshipit-source-id: ebfa5a0db8cbf1ed73100528b34fcba543c5db31 |
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| .. | ||
| delete_scheduler.cc | ||
| delete_scheduler.h | ||
| delete_scheduler_test.cc | ||
| file_prefetch_buffer.cc | ||
| file_prefetch_buffer.h | ||
| file_util.cc | ||
| file_util.h | ||
| filename.cc | ||
| filename.h | ||
| line_file_reader.cc | ||
| line_file_reader.h | ||
| prefetch_test.cc | ||
| random_access_file_reader.cc | ||
| random_access_file_reader.h | ||
| random_access_file_reader_test.cc | ||
| read_write_util.cc | ||
| read_write_util.h | ||
| readahead_file_info.h | ||
| readahead_raf.cc | ||
| readahead_raf.h | ||
| sequence_file_reader.cc | ||
| sequence_file_reader.h | ||
| sst_file_manager_impl.cc | ||
| sst_file_manager_impl.h | ||
| writable_file_writer.cc | ||
| writable_file_writer.h | ||