Summary:
Added an option to BackupableDB implementation that allows users to persist in-memory databases. When the restore happens with keep_log_files = true, it will
*) Not delete existing log files in wal_dir
*) Move log files from archive directory to wal_dir, so that DB can replay them if necessary

Test Plan: Added an unit test

Reviewers: dhruba, ljin

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16941

Summary:
Memtable will now be forced to flush if the one of the following
conditions is met:
1. Already allocated more than write_buffer_size + 60% arena block size.
   (the overflowing condition)
2. Unable to safely allocate one more arena block without hitting the
   overflowing condition AND the unused allocated memory < 25% arena
   block size.

Test Plan: make all check

Reviewers: sdong, haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16893

Summary: We're trying to deprecate prefix iterators, so no need to test them in db_stress

Test Plan: ran it

Reviewers: ljin

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16917

Summary: Prev() now can hang when there is a key with more than max_skipped number of appearance internally but all of them are newer than the sequence ID to seek. Add unit tests to confirm the bug and fix it.

Test Plan: make all check

Reviewers: igor, haobo

Reviewed By: igor

CC: ljin, yhchiang, leveldb

Differential Revision: https://reviews.facebook.net/D16899

Summary:
We need to stop these:
https://github.com/facebook/rocksdb/pull/99
https://github.com/facebook/rocksdb/pull/83

Test Plan: no

Reviewers: dhruba, haobo, sdong, ljin, yhchiang

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16905

Make it compile on Debian/GCC 4.7

Summary:
In the last fix, I forgot to point to the writer when comparing edit,
which is apparently not correct.

Test Plan: still running make whitebox_crash_test

Reviewers: igor, haobo, igor2

Reviewed By: igor2

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16911

Summary:
Here is what it can cause probelm:
There is one memtable flush and one compaction. Both call LogAndApply(). If both edits are applied in the same batch with flush edit first and the compaction edit followed. LogAndApplyHelper() will assign compaction edit current VersionSet's log number(which should be smaller than the log number from flush edit). It cause log_numbers in MANIFEST to be not monotonic increasing, which violates the assume Recover() makes. What is more is after comitting to MANIFEST file, log_number_ in VersionSet is updated to the log_number from the last edit, which is the compaction one. It ends up not updating the log_number.

Test Plan:
make whitebox_crash_test
got another assertion about iter->valid(), not sure if that is related
to this.

Reviewers: igor, haobo

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16875

Fix copyright year

Summary:
Original Summary:
Yesterday, @ljin and I were debugging various db_stress issues. We suspected one of them happens when we concurrently call NewIterator without prefix_seek on HashSkipList. This test demonstrates it.

Update:
Arena is not thread-safe!! When creating a new full iterator, we *have* to create a new arena, otherwise we're doomed.

Test Plan: SIGSEGV and assertion-throwing test now works!

Reviewers: ljin, haobo, sdong

Reviewed By: sdong

CC: leveldb, ljin

Differential Revision: https://reviews.facebook.net/D16857

Summary:
With D16767, there is a case compaction tasks are scheduled infinitely:
(1) no flush thread is configured and more than 1 compaction threads
(2) a flush is going on by one compaction hread
(3) the state of SST files is in the state that versions_->current()->NeedsCompaction() will generate a false positive (return true actually there is no work to be done)
In that case, a infinite loop will be formed.

This patch would fix it.

Test Plan: make all check

Reviewers: haobo, igor, ljin

Reviewed By: igor

CC: dhruba, yhchiang, leveldb

Differential Revision: https://reviews.facebook.net/D16863

This reverts commit 86926d8c.

Summary:
this should fix the hash_skip_list issue, but I still see seqno
assertion failure in the last run. Will continue investigating and
address that in a different diff

Test Plan: make whitebox_crash_test

Reviewers: igor

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16851

Summary:
Hash skip list has issues, causing db_stress to fail badly.

For now, switching back to skip_list by default before we figure out root cause.

Test Plan: db_stress is happy(ier)

Reviewers: ljin

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16845

Summary:
This is is based on https://reviews.facebook.net/D15027. It's not finished but I would like to give a prototype to avoid arena over-allocation while making better use of the already allocated memory blocks.

Instead of check approximate memtable size, we will take a deeper look at the arena, which incorporate essential idea that @sdong suggests: flush when arena has allocated its last and the last is "almost full"

Test Plan: N/A

Reviewers: haobo, sdong

Reviewed By: sdong

CC: leveldb, sdong

Differential Revision: https://reviews.facebook.net/D15051

Summary: Syncing in stress test makes it run much much much slower. It also doesn't add much value IMO.

Test Plan: no

Reviewers: ljin

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16839

Fix outdated copyright year (update to 2014)

The copyright year was out of date. Copyright notices must reflect the current year. This commit updates the listed year to 2014.

see: http://www.copyright.gov/circs/circ01.pdf for more info

This reverts commit 839c8ecf.

Summary:
*) fixed the comment
*) constant 1 was not casted to 64-bit, which (I think) might cause overflow if we shift it too much
*) default prefix size to be 7, like it was before

Test Plan: compiled

Reviewers: ljin

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16827

Summary: A bad Auto-Merge caused log buffer is flushed twice. Remove the unintended one.

Test Plan: Should already be tested (the code looks the same as when I ran unit tests).

Reviewers: haobo, igor

Reviewed By: haobo

CC: ljin, yhchiang, leveldb

Differential Revision: https://reviews.facebook.net/D16821

Summary: as title

Test Plan: running python tools/db_crashtest.py

Reviewers: igor

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16803

Summary:
@igor pointed out that there is a potential data race because of the way we use the newly introduced LogBuffer. After "bg_compaction_scheduled_--" or "bg_flush_scheduled_--", they can both become 0. As soon as the lock is released after that, DBImpl's deconstructor can go ahead and deconstruct all the states inside DB, including the info_log object hold in a shared pointer of the options object it keeps. At that point it is not safe anymore to continue using the info logger to write the delayed logs.

With the patch, lock is released temporarily for log buffer to be flushed before "bg_compaction_scheduled_--" or "bg_flush_scheduled_--". In order to make sure we don't miss any pending flush or compaction, a new flag bg_schedule_needed_ is added, which is set to be true if there is a pending flush or compaction but not scheduled because of the max thread limit. If the flag is set to be true, the scheduling function will be called before compaction or flush thread finishes.

Thanks @igor for this finding!

Test Plan: make all check

Reviewers: haobo, igor

Reviewed By: haobo

CC: dhruba, ljin, yhchiang, igor, leveldb

Differential Revision: https://reviews.facebook.net/D16767

Summary: Fix the db_stress test, let is run with HashSkipList for real

Test Plan:
python tools/db_crashtest.py
python tools/db_crashtest2.py

Reviewers: igor, haobo

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16773

Summary: To temp fix the log buffer flushing. Flush the buffer inside the lock. Clean the trunk before we find an eventual fix.

Test Plan: make all check

Reviewers: haobo, igor

Reviewed By: igor

CC: ljin, leveldb, yhchiang

Differential Revision: https://reviews.facebook.net/D16791

Summary: Having code after SignalAll has already caused 2 bugs. Let's make sure this doesn't happen again.

Test Plan: no test

Reviewers: sdong, dhruba, haobo

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16785

Summary: Add a function to Env so that users can query the waiting queue length of each thread pool

Test Plan: add a test in env_test

Reviewers: haobo

Reviewed By: haobo

CC: dhruba, igor, yhchiang, ljin, nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D16755

Summary: as title

Test Plan: fixed the build failure http://ci-builds.fb.com/job/rocksdb_build/987/console

Reviewers: haobo

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16743

Summary: constructor wasn't properly constructing BackupableDBOptions

Test Plan: no test

Reviewers: benj

Reviewed By: benj

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16749

Summary: DBTest checks  perf_context.seek_internal_seek_time > 0 and perf_context.find_next_user_entry_time > 0, which is not reliable. Remove them.

Test Plan: ./db_test

Reviewers: igor, haobo, ljin

Reviewed By: igor

CC: dhruba, yhchiang, leveldb

Differential Revision: https://reviews.facebook.net/D16737

Summary: as title. also made info log output of file deletion a bit more descriptive.

Test Plan: make check; db_bench and look at LOG output

Reviewers: igor

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16731

Summary:
(1) Fix SanitizeOptions() to also check HashLinkList. The current
dynamic case just happens to work because the 2 classes have the same
layout.
(2) Do not delete SliceTransform object in HashSkipListFactory and
HashLinkListFactory destructor. Reason: SanitizeOptions() enforces
prefix_extractor and SliceTransform to be the same object when
Hash**Factory is used. This makes the behavior strange: when
Hash**Factory is used, prefix_extractor will be released by RocksDB. If
other memtable factory is used, prefix_extractor should be released by
user.

Test Plan: db_bench && make asan_check

Reviewers: haobo, igor, sdong

Reviewed By: igor

CC: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D16587

Summary: KSVObsolete is no longer nullptr and needs to be checked explicitly. Also did some minor code cleanup and added a stat counter to track superversion cleanups incurred in the foreground.

Test Plan: make check

Reviewers: ljin

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16701

Summary:
If the last byte of the timestamp is 0, the output value of the ttl db
can cut off earlier. Change to compare hex format instead.

Test Plan:
this does not happen consistently, but it did not fail after the last
100 runs
for i in {1..100}; do python ./tools/ldb_test.py; done

Reviewers: igor, haobo

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16725