rocksdb/db/db_impl
Peter (Stig) Edwards c75ef03e58 Do not truncate WAL if in read_only mode (#8313)
Summary:
I noticed ```openat``` system call with ```O_WRONLY``` flag and ```sync_file_range``` and ```truncate``` on WAL file when using ```rocksdb::DB::OpenForReadOnly``` by way of ```db_bench --readonly=true --benchmarks=readseq --use_existing_db=1 --num=1 ...```

Noticed in ```strace``` after seeing the last modification time of the WAL file change after each run (with ```--readonly=true```).

  I think introduced by 7d7f14480e from https://github.com/facebook/rocksdb/pull/8122

I added a test to catch the WAL file being truncated and the modification time on it changing.
I am not sure if a mock filesystem with mock clock could be used to avoid having to sleep 1.1s.
The test could also check the set of files is the same and that the sizes are also unchanged.

Before:

```
[ RUN      ] DBBasicTest.ReadOnlyReopenMtimeUnchanged
db/db_basic_test.cc:182: Failure
Expected equality of these values:
  file_mtime_after_readonly_reopen
    Which is: 1621611136
  file_mtime_before_readonly_reopen
    Which is: 1621611135
  file is: 000010.log
[  FAILED  ] DBBasicTest.ReadOnlyReopenMtimeUnchanged (1108 ms)
```

After:

```
[ RUN      ] DBBasicTest.ReadOnlyReopenMtimeUnchanged
[       OK ] DBBasicTest.ReadOnlyReopenMtimeUnchanged (1108 ms)
```

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8313

Reviewed By: pdillinger

Differential Revision: D28656925

Pulled By: jay-zhuang

fbshipit-source-id: ea9e215cb53e7c830e76bc5fc75c45e21f12a1d6
2021-05-27 10:27:55 -07:00
..
compacted_db_impl.cc Make backups openable as read-only DBs (#8142) 2021-04-06 14:37:53 -07:00
compacted_db_impl.h Move compacted_db_impl.[c|h] to db/db_impl (#8082) 2021-03-23 13:49:26 -07:00
db_impl_compaction_flush.cc Add remote compaction public API (#8300) 2021-05-19 21:41:31 -07:00
db_impl_debug.cc Do not set bg error for compaction in retryable IO Error case (#7899) 2021-01-27 17:58:12 -08:00
db_impl_experimental.cc Replace reinterpret_cast with static_cast_with_check (#7067) 2020-07-02 19:25:41 -07:00
db_impl_files.cc Make types of Immutable/Mutable Options fields match that of the underlying Option (#8176) 2021-04-22 20:43:54 -07:00
db_impl_open.cc Do not truncate WAL if in read_only mode (#8313) 2021-05-27 10:27:55 -07:00
db_impl_readonly.cc Make backups openable as read-only DBs (#8142) 2021-04-06 14:37:53 -07:00
db_impl_readonly.h RocksJava - Add errorIfLogFileExists parameter to RocksDB.openReadOnly (#7046) 2020-09-17 15:41:25 -07:00
db_impl_secondary.cc Add remote compaction public API (#8300) 2021-05-19 21:41:31 -07:00
db_impl_secondary.h Add internal compaction API for Secondary instance (#8171) 2021-04-22 13:02:28 -07:00
db_impl_write.cc Make ImmutableOptions struct that inherits from ImmutableCFOptions and ImmutableDBOptions (#8262) 2021-05-05 14:00:17 -07:00
db_impl.cc Make ImmutableOptions struct that inherits from ImmutableCFOptions and ImmutableDBOptions (#8262) 2021-05-05 14:00:17 -07:00
db_impl.h Add internal compaction API for Secondary instance (#8171) 2021-04-22 13:02:28 -07:00