Summary:
After https://github.com/facebook/rocksdb/issues/9984, BackupEngineTest.Concurrency becomes flaky.
During DB::Open(), someone else can rename/remove the LOG file, causing
this thread's `CreateLoggerFromOptions()` to fail. The reason is that the operation sequence
of "FileExists -> Rename" is not atomic. It's possible that a FileExists() returns OK, but the file
gets deleted before Rename(), causing the latter to return IOError with PathNotFound subcode.
Although it's not encouraged to concurrently modify the contents of the directories managed by
the database instance in this case, we can still perform some simple handling to make DB::Open()
more robust. In this case, we can check if a racing thread has deleted the original LOG file, we can
allow this thread to continue creating a new LOG file.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10069
Test Plan: ~/gtest-parallel/gtest-parallel -r 100 ./backup_engine_test --gtest_filter=BackupEngineTest.Concurrency
Reviewed By: jay-zhuang
Differential Revision: D36736913
Pulled By: riversand963
fbshipit-source-id: 3cbe92d77ca175e55e586bdb1a32ac8107217ae6