Andrew Kryczka a4fb1f8c04 Add crash-recovery correctness check to db_stress ... Summary: Previously, our `db_stress` tool held the expected state of the DB in-memory, so after crash-recovery, there was no way to verify data correctness. This PR adds an option, `--expected_values_file`, which specifies a file holding the expected values. In black-box testing, the `db_stress` process can be killed arbitrarily, so updates to the `--expected_values_file` must be atomic. We achieve this by `mmap`ing the file and relying on `std::atomic<uint32_t>` for atomicity. Actually this doesn't provide a total guarantee on what we want as `std::atomic<uint32_t>` could, in theory, be translated into multiple stores surrounded by a mutex. We can verify our assumption by looking at `std::atomic::is_always_lock_free`. For the `mmap`'d file, we didn't have an existing way to expose its contents as a raw memory buffer. This PR adds it in the `Env::NewMemoryMappedFileBuffer` function, and `MemoryMappedFileBuffer` class. `db_crashtest.py` is updated to use an expected values file for black-box testing. On the first iteration (when the DB is created), an empty file is provided as `db_stress` will populate it when it runs. On subsequent iterations, that same filename is provided so `db_stress` can check the data is as expected on startup. Closes https://github.com/facebook/rocksdb/pull/3629 Differential Revision: D7463144 Pulled By: ajkr fbshipit-source-id: c8f3e82c93e045a90055e2468316be155633bd8b		2018-04-24 15:58:22 -07:00
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rocksdb	Add crash-recovery correctness check to db_stress	2018-04-24 15:58:22 -07:00