Summary:
We've got a crash with this stack trace:
Program terminated with signal SIGTRAP, Trace/breakpoint trap.
#0 0x00007fc85f2f4009 in raise () from /usr/local/fbcode/gcc-4.9-glibc-2.20-fb/lib/libpthread.so.0
#1 0x00000000005c8f61 in facebook::logdevice::handle_sigsegv(int) () at logdevice/server/sigsegv.cpp:159
#2 0x00007fc85f2f4150 in <signal handler called> () at /usr/local/fbcode/gcc-4.9-glibc-2.20-fb/lib/libpthread.so.0
#3 0x00000000031ed80c in rocksdb::NewReadaheadRandomAccessFile() at util/file_reader_writer.cc:383
#4 0x00000000031ed80c in rocksdb::NewReadaheadRandomAccessFile() at util/file_reader_writer.cc:472
#5 0x00000000031558e7 in rocksdb::TableCache::GetTableReader() at db/table_cache.cc:99
#6 0x0000000003156329 in rocksdb::TableCache::NewIterator() at db/table_cache.cc:198
#7 0x0000000003166568 in rocksdb::VersionSet::MakeInputIterator() at db/version_set.cc:3345
#8 0x000000000324a94f in rocksdb::CompactionJob::ProcessKeyValueCompaction(rocksdb::CompactionJob::SubcompactionState*) () at db/compaction_job.cc:650
#9 0x000000000324c2f6 in rocksdb::CompactionJob::Run() () at db/compaction_job.cc:530
#10 0x00000000030f5ae5 in rocksdb::DBImpl::BackgroundCompaction() at db/db_impl.cc:3269
#11 0x0000000003108d36 in rocksdb::DBImpl::BackgroundCallCompaction(void*) () at db/db_impl.cc:2970
#12 0x00000000029a2a9a in facebook::logdevice::RocksDBEnv::callback(void*) () at logdevice/server/locallogstore/RocksDBEnv.cpp:26
#13 0x00000000029a2a9a in facebook::logdevice::RocksDBEnv::callback(void*) () at logdevice/server/locallogstore/RocksDBEnv.cpp:30
#14 0x00000000031e7521 in rocksdb::ThreadPool::BGThread() at util/threadpool.cc:230
#15 0x00000000031e7663 in rocksdb::BGThreadWrapper(void*) () at util/threadpool.cc:254
#16 0x00007fc85f2ea7f1 in start_thread () at /usr/local/fbcode/gcc-4.9-glibc-2.20-fb/lib/libpthread.so.0
#17 0x00007fc85e8fb46d in clone () at /usr/local/fbcode/gcc-4.9-glibc-2.20-fb/lib/libc.so.6
From looking at the code, probably what happened is this:
- `TableCache::GetTableReader()` called `Env::NewRandomAccessFile()`, which dispatched to a `PosixEnv::NewRandomAccessFile()`, where probably an `open()` call failed, so the `NewRandomAccessFile()` left a nullptr in the resulting file,
- `TableCache::GetTableReader()` called `NewReadaheadRandomAccessFile()` with that `nullptr` file,
- it tried to call file's method and crashed.
This diff is a trivial fix to this crash.
Test Plan: `make -j check`
Reviewers: sdong, andrewkr, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D62451
2be165b291