Summary:
Currently, when rocksdb tries to run manual compaction to refit data into a level,
there's a ReFitLevel() process that requires no bg work is currently running.
When RocksDB plans to ReFitLevel(), it will do the following:

 1. pause scheduling new bg work.
 2. wait until all bg work finished
 3. do the ReFitLevel()
 4. unpause scheduling new bg work.

However, as it pause scheduling new bg work at step one and waiting for all bg work
finished in step 2, RocksDB will stop flushing until all bg work is done (which
could take a long time.)

This patch fix this issue by changing the way ReFitLevel() pause the background work:

1. pause scheduling compaction.
2. wait until all bg work finished.
3. pause scheduling flush
4. do ReFitLevel()
5. unpause both flush and compaction.

The major difference is that.  We only pause scheduling compaction in step 1 and wait
for all bg work finished in step 2.  This prevent flush being blocked for a long time.
Although there's a very rare case that ReFitLevel() might be in starvation in step 2,
but it's less likely the case as flush typically finish very fast.

Test Plan: existing test.

Reviewers: anthony, IslamAbdelRahman, kradhakrishnan, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D55029

Summary:
The call to

```
CaptureCurrentFileNumberInPendingOutputs()
```

should be before

```
versions_->NewFileNumber()
```
Right now we are not actually protecting the file from being deleted

Test Plan: make check

Reviewers: sdong, anthony, yhchiang

Reviewed By: yhchiang

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D54645

Summary: We always put compaction to level0_compactions_in_progress_ for universal compaction, so we should also remove it. The bug causes assert failure when running manual compaction.

Test Plan:
TEST_TMPDIR=/dev/shm/ ./db_bench --benchmarks=fillrandom,compact --subcompactions=16 --compaction_style=1
always fails on my host. After the fix, it doesn't fail any more.

Reviewers: IslamAbdelRahman, andrewkr, kradhakrishnan, yhchiang

Reviewed By: yhchiang

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D55017

Summary: We want to provide a way to detect whether an iterator is stale and needs to be recreated. Add a iterator property to return version number.

Test Plan: Add two unit tests for it.

Reviewers: IslamAbdelRahman, yhchiang, anthony, kradhakrishnan, andrewkr

Reviewed By: andrewkr

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D54921

Summary: Now we skip to add boundary keys to subcompaction candidates since we see an empty level. This makes subcompaction almost disabled for universal compaction. We should consider all files instead.

Test Plan: Run existing tests.

Reviewers: IslamAbdelRahman, andrewkr, yhchiang

Reviewed By: yhchiang

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D55005

Summary: Rename iterator property to folow property naming convention.

Test Plan: Run all existing tests.

Reviewers: andrewkr, anthony, yhchiang, kradhakrishnan, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D54957

Summary:
In some situations the DB will scan all existing files in the DB path and delete the ones that are Obsolete.
If this happen during adding an external sst file. this could cause the file to be deleted while we are adding it.
This diff fix this issue

Test Plan:
unit test to reproduce the bug
existing unit tests

Reviewers: sdong, yhchiang, andrewkr

Reviewed By: andrewkr

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D54627

Summary: Add a DB Property "rocksdb.current_version_number" for users to monitor version changes and stale iterators.

Test Plan: Add a unit test.

Reviewers: andrewkr, yhchiang, kradhakrishnan, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D54927

Summary: After we made manual compaction runnable concurrently with automaticallly compaction, we need to run ComputeCompactionScore() to prepare a coming compaction picking call before the compaction finishes.

Test Plan: Run existing tests.

Reviewers: yhchiang, IslamAbdelRahman, andrewkr, kradhakrishnan, anthony, igor

Reviewed By: igor

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D54891

Summary:
Add Iterator::GetProperty(), a way for users to communicate with iterator, and turn Iterator::IsKeyPinned() with it.
As a follow-up, I'll ask a property as the version number attached to the iterator

Test Plan: Rerun existing tests and add a negative test case.

Reviewers: yhchiang, andrewkr, kradhakrishnan, anthony, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D54783

Summary:
Fixed two related race conditions in backup creation.

(1) CreateNewBackup() uses DB::DisableFileDeletions() to prevent table files
from being deleted while it is copying; however, the MANIFEST file could still
rotate during this time. The fix is to stop deleting the old manifest in the
rotation logic. It will be deleted safely later when PurgeObsoleteFiles() runs
(can only happen when file deletions are enabled).

(2) CreateNewBackup() did not account for the CURRENT file being mutable.
This is significant because the files returned by GetLiveFiles() contain a
particular manifest filename, but the manifest to which CURRENT refers can
change at any time. This causes problems when CURRENT changes between the call
to GetLiveFiles() and when it's copied to the backup directory. To workaround this, I
manually forge a CURRENT file referring to the manifest filename returned in
GetLiveFiles().

(2) also applies to the checkpointing code, so let me know if this approach is
good and I'll make the same change there.

Test Plan:
new test for roll manifest during backup creation.

running the test before this change:

  $ ./backupable_db_test --gtest_filter=BackupableDBTest.ChangeManifestDuringBackupCreation
  ...
  IO error: /tmp/rocksdbtest-9383/backupable_db/MANIFEST-000001: No such file or directory

running the test after this change:

  $ ./backupable_db_test --gtest_filter=BackupableDBTest.ChangeManifestDuringBackupCreation
  ...
  [ RUN      ] BackupableDBTest.ChangeManifestDuringBackupCreation
  [       OK ] BackupableDBTest.ChangeManifestDuringBackupCreation (2836 ms)

Reviewers: IslamAbdelRahman, anthony, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D54711

Summary:
Based on thread scheduling, DBTestUniversalCompaction.IncreaseUniversalCompactionNumLevels can fail to flush enough files to trigger expected compactions. Fix it by waiting for flush after inserting each key.
There are failrue reported:

db/db_universal_compaction_test.cc:1134: Failure
Expected: (NumTableFilesAtLevel(options.num_levels - 1, 1)) > (0), actual: 0 vs 0

but I can't repro it. Try to fix the bug and see whether it goes away.

Test Plan: Run the test multiple time.

Reviewers: IslamAbdelRahman, anthony, andrewkr, kradhakrishnan, yhchiang

Reviewed By: yhchiang

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D54747

Summary: Add a test case in ColumnFamilyTest.ReadDroppedColumnFamily to make sure existing iterator is not impacted by column family dropping.

Test Plan: N/A

Reviewers: igor, yhchiang, anthony, andrewkr, kradhakrishnan, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D54657

Summary: DBImpl::SyncWAL() releases db mutex before calling DBImpl::MarkLogsSynced(), while inside DBImpl::MarkLogsSynced() we assert there is none or one outstanding log file. However, a memtable switch can happen in between and causing two or outstanding logs there, failing the assert. The diff adds a unit test that repros the issue and fix the assert so that the unit test passes.

Test Plan: Run the new tests.

Reviewers: anthony, kolmike, yhchiang, IslamAbdelRahman, kradhakrishnan, andrewkr

Reviewed By: andrewkr

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D54621

Summary:
There was a race condition in the test where the rolling thread
acquired the mutex before the flush thread pinned the logger. Rather than add
more complicated synchronization to fix it, I followed Siying's suggestion to
use SyncPoint in the test code.

Comments in the LoadDependency() invocation explain the reason for each of the
sync points.

Test Plan:
Ran test 1000 times for tsan/asan. Will wait for all sandcastle tests
to finish before committing since this is a tricky test.

Reviewers: IslamAbdelRahman, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D54615

Summary:
We started getting two kinds of crashes since we started using `DB::CompactFiles()`:
(1) `CompactFiles()` fails saying something like "/data/logdevice/4440/shard12/012302.sst: No such file or directory", and presumably makes DB read-only,
(2) DB fails to open saying "Corruption: Can't access /267000.sst: IO error: /data/logdevice/4440/shard1/267000.sst: No such file or directory".

AFAICT, both can be explained by background thread deleting compaction output as "obsolete" while it's being written, before it's committed to manifest. If it ends up committed to the manifest, we get (2); if compaction notices the disappearance and fails, we get (1). The internal tasks t10068021 and t10134177 have some details about the investigation that led to this.

Test Plan: `make -j check`; the new test fails to reopen the DB without the fix

Reviewers: yhchiang

Reviewed By: yhchiang

Subscribers: dhruba, sdong

Differential Revision: https://reviews.facebook.net/D54561

 https://github.com/facebook/rocksdb/issues/1002

Summary:
Previously I just slept until the flush_thread was "probably" ready
since proper synchronization in test cases seemed like overkill. But then tsan
complained about it, so I did the synchronization (mostly) properly now.

Test Plan:
  $ COMPILE_WITH_TSAN=1 make -j32 auto_roll_logger_test
  $ ./auto_roll_logger_test

Reviewers: anthony, IslamAbdelRahman, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D54399

Summary:
Introude SstFileManager::SetMaxAllowedSpaceUsage() that can be used to limit the maximum space usage allowed for RocksDB.
When this limit is exceeded WriteImpl() will fail and return Status::Aborted()

Test Plan: unit testing

Reviewers: yhchiang, anthony, andrewkr, sdong

Reviewed By: sdong

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D53763

Summary:
For GetLogFileSize() and Flush(), they previously did not follow the
synchronization pattern for accessing logger_. This meant ResetLogger() could
cause logger_ destruction while the unsynchronized functions were accessing it,
causing a segfault.

Also made the mutex instance variable mutable so we can preserve
GetLogFileSize()'s const-ness.

Test Plan:
new test case, it's quite ugly because both threads need to access
one of the functions with SyncPoints (PosixLogger::Flush()), and also special
handling is needed to prevent the mutex and sync points from conflicting.

Reviewers: kradhakrishnan, IslamAbdelRahman, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D54237

Summary: Currently write_with_callback_test does not test with WAL syncing enabled. This addresses that.

Test Plan: write_with_callback_test

Reviewers: anthony

Reviewed By: anthony

Subscribers: leveldb, dhruba, hermanlee4

Differential Revision: https://reviews.facebook.net/D54255

Summary: There is an issue in DBImpl::WriteImpl where if an empty writebatch comes in and sync=true then the logs will be marked as being synced yet the sync never actually happens because there is no data in the writebatch. This causes the next incoming batch to hang while waiting for the logs to complete syncing. This fix syncs logs even if the writebatch is empty.

Test Plan: DoubleEmptyBatch unit test in transaction_test.

Reviewers: yoshinorim, hermanlee4, sdong, ngbronson, anthony

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D54057

Summary: We've hit it today.

Test Plan: `make -j check`; didn't reproduce the issue

Reviewers: yhchiang

Reviewed By: yhchiang

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D54219

Summary: Isolate db_bench functionality from main so custom benchmark code can be written and managed

Test Plan:
Tested commands
./build_tools/regression_build_test.sh
./db_bench --db=/tmp/rocksdbtest-12321/dbbench --stats_interval_seconds=1 --num=1000
./db_bench --db=/tmp/rocksdbtest-12321/dbbench --stats_interval_seconds=1 --num=1000 --reads=500 --writes=500
./db_bench --db=/tmp/rocksdbtest-12321/dbbench --stats_interval_seconds=1 --num=1000 --merge_keys=100 --numdistinct=100 --num_column_families=3 --num_hot_column_families=1
./db_bench --stats_interval_seconds=1 --num=1000 --bloom_locality=1 --seed=5 --threads=5
./db_bench --duration=60 --value_size=50 --seek_nexts=10 --reverse_iterator=true --usee_uint64_comparator=true --batch-size=5
./db_bench --duration=60 --value_size=50 --seek_nexts=10 --reverse_iterator=true --use_uint64_comparator=true --batch_size=5
./db_bench --duration=60 --value_size=50 --seek_nexts=10 --reverse_iterator=true --usee_uint64_comparator=true --batch-size=5

Test Results - https://phabricator.fb.com/P56130387

Additional tests for:
./db_bench --duration=60 --value_size=50 --seek_nexts=10 --reverse_iterator=true --use_uint64_comparator=true --batch_size=5 --key_size=8 --merge_operator=put
./db_bench --stats_interval_seconds=1 --num=1000 --bloom_locality=1 --seed=5 --threads=5 --merge_operator=uint64add

Results: https://phabricator.fb.com/P56130607

Reviewers: yhchiang, sdong

Reviewed By: sdong

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D53991

Summary:
Add a new compaction priority as following:
For every file, we calculate total size of files overalapping with the file in the next level, over the file's size itself. The file with smallest ratio will be picked first.
My "db_bench --fillrandom" shows about 5% less compaction than kOldestSmallestSeqFirst if --hard_pending_compaction_bytes_limit value to keep LSM tree in shape. If not limiting hard_pending_compaction_bytes_limit, improvement is only 1% or 2%.

Test Plan: Add a unit test

Reviewers: andrewkr, kradhakrishnan, anthony, IslamAbdelRahman, yhchiang

Reviewed By: yhchiang

Subscribers: MarkCallaghan, leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D54075

Fixes #983.

Summary:
Add kSstFileTier to ReadTier, which allows Get and MultiGet to
read only directly from SST files and skip mem-tables.

    kSstFileTier = 0x2      // data in SST files.
                          // Note that this ReadTier currently only supports
                          // Get and MultiGet and does not support iterators.

Test Plan: add new test in db_test.

Reviewers: anthony, IslamAbdelRahman, rven, kradhakrishnan, sdong

Reviewed By: sdong

Subscribers: igor, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D53511

Summary: Previous commit introduces a test that is not supported in LITE. Fix it.

Test Plan: Build the test with ROCKSDB_LITE.

Reviewers: kradhakrishnan, IslamAbdelRahman, anthony, yhchiang, andrewkr

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D53901

Summary: If users turn on concurrent insert but the memtable doesn't support it, they might see unexcepted crash. Fix it by explicitly fail.

Test Plan:
Run different setting of stress_test and make sure it fails correctly.
Will add a unit test too.

Reviewers: anthony, kradhakrishnan, IslamAbdelRahman, yhchiang, andrewkr, ngbronson

Reviewed By: ngbronson

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D53895

Summary:
copy from task 8196669:

1) Optimistic transactions do not support batching writes from different threads.
2) Pessimistic transactions do not support batching writes if an expiration time is set.

In these 2 cases, we currently do not do any write batching in DBImpl::WriteImpl() because there is a WriteCallback that could decide at the last minute to abort the write.  But we could support batching write operations with callbacks if we make sure to process the callbacks correctly.

To do this, we would first need to modify write_thread.cc to stop preventing writes with callbacks from being batched together.  Then we would need to change DBImpl::WriteImpl() to call all WriteCallback's in a batch, only write the batches that succeed, and correctly set the state of each batch's WriteThread::Writer.

Test Plan: Added test WriteWithCallbackTest to write_callback_test.cc which creates multiple client threads and verifies that writes are batched and executed properly.

Reviewers: hermanlee4, anthony, ngbronson

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D52863

Summary: Add a new option to BlockBasedTableOptions that will allow us to change the restart interval for the index block

Test Plan: unit tests

Reviewers: yhchiang, anthony, andrewkr, sdong

Reviewed By: sdong

Subscribers: march, dhruba

Differential Revision: https://reviews.facebook.net/D53721

Summary:
InlineSkipList::InsertConcurrently should invalidate the
sequential-insertion cache prev_[] for all inserts of multi-level nodes,
not just those that increase the height of the skip list.  The invariant
for prev_ is that prev_[i] (i > 0) is supposed to be the predecessor of
prev_[0] at level i.  Before this diff InsertConcurrently could violate
this constraint when inserting a multi-level node after prev_[i] but
before prev_[0].

This diff also reenables kConcurrentSkipList as db_test's
MultiThreaded/MultiThreadedDBTest.MultiThreaded/29.

Test Plan:
1. unit tests
2. temporarily hack kConcurrentSkipList timing so that it is fast but has a 1.5% failure rate on my dev box (1ms stagger on thread launch, 1s test duration, failure rate baseline over 1000 runs)
3. observe 1000 passes post-fix

Reviewers: igor, sdong

Reviewed By: sdong

Subscribers: MarkCallaghan, dhruba

Differential Revision: https://reviews.facebook.net/D53751

Summary:
Before this diff, there were duplicated constants to refer to properties (user-
facing API had strings and InternalStats had an enum). I noticed these were
inconsistent in terms of which constants are provided, names of constants, and
documentation of constants. Overall it seemed annoying/error-prone to maintain
these duplicated constants.

So, this diff gets rid of InternalStats's constants and replaces them with a map
keyed on the user-facing constant. The value in that map contains a function
pointer to get the property value, so we don't need to do string matching while
holding db->mutex_. This approach has a side benefit of making many small
handler functions rather than a giant switch-statement.

Test Plan: db_properties_test passes, running "make commit-prereq -j32"

Reviewers: sdong, yhchiang, kradhakrishnan, IslamAbdelRahman, rven, anthony

Reviewed By: anthony

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D53253

Summary: Disable test that is intermittently failing

Test Plan: unit tests

Reviewers: igor, andrewkr, sdong

Reviewed By: sdong

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D53715

break compatibility with Windows 7. The issue with rotated logs
was fixed other way.

Summary:
Concurrent memtable adds were incorrectly computing
the last sequence number for a write batch group when the
write batches were not solitary.  This is the cause of
https://github.com/facebook/mysql-5.6/issues/155

Test Plan:
1. unit tests
2. new unit test
3. parallel db_bench stress tests with batch size of 10 and asserts enabled

Reviewers: igor, sdong

Reviewed By: sdong

Subscribers: IslamAbdelRahman, MarkCallaghan, dhruba

Differential Revision: https://reviews.facebook.net/D53595

Summary:
Fix current clang failure
https://ci-builds.fb.com/view/rocksdb/job/rocksdb_clang_build/1398/console

Test Plan:
make sure that both clang and g++ compilation succeed

USE_CLANG=1 make check -j64
make check -j64

Reviewers: anthony, yhchiang, sdong

Reviewed By: sdong

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D53667