Summary:
This PR does a few things:
1. The MockFileSystem class was split out from the MockEnv. This change would theoretically allow a MockFileSystem to be used by other Environments as well (if we created a means of constructing one). The MockFileSystem implements a FileSystem in its entirety and does not rely on any Wrapper implementation.
2. Make the RocksDB test suite work when MOCK_ENV=1 and ENCRYPTED_ENV=1 are set. To accomplish this, a few things were needed:
- The tests that tried to use the "wrong" environment (Env::Default() instead of env_) were updated
- The MockFileSystem was changed to support the features it was missing or mishandled (such as recursively deleting files in a directory or supporting renaming of a directory).
3. Updated the test framework to have a ROCKSDB_GTEST_SKIP macro. This can be used to flag tests that are skipped. Currently, this defaults to doing nothing (marks the test as SUCCESS) but will mark the tests as SKIPPED when RocksDB is upgraded to a version of gtest that supports this (gtest-1.10).
I have run a full "make check" with MEM_ENV, ENCRYPTED_ENV, both, and neither under both MacOS and RedHat. A few tests were disabled/skipped for the MEM/ENCRYPTED cases. The error_handler_fs_test fails/hangs for MEM_ENV (presumably a timing problem) and I will introduce another PR/issue to track that problem. (I will also push a change to disable those tests soon). There is one more test in DBTest2 that also fails which I need to investigate or skip before this PR is merged.
Theoretically, this PR should also allow the test suite to run against an Env loaded from the registry, though I do not have one to try it with currently.
Finally, once this is accepted, it would be nice if there was a CircleCI job to run these tests on a checkin so this effort does not become stale. I do not know how to do that, so if someone could write that job, it would be appreciated :)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7566
Reviewed By: zhichao-cao
Differential Revision: D24408980
Pulled By: jay-zhuang
fbshipit-source-id: 911b1554a4d0da06fd51feca0c090a4abdcb4a5f
Summary:
After https://github.com/facebook/rocksdb/pull/7036, we still see extra DBTest that can timeout when running 10 or 20 in parallel. Expand skip-fsync mode in whole DBTest. Still preserve other tests from doing this mode to be conservative.
This commit reinstates https://github.com/facebook/rocksdb/issues/7049, whose un-revert was lost in an automatic
infrastructure mis-merge.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7274
Test Plan: Run all existing files.
Reviewed By: pdillinger
Differential Revision: D23177444
fbshipit-source-id: 1f61690b2ac6333c3b2c87176fef6b2cba086b33
Summary:
We have a number of tests hanging on MacOS and windows due to
mishandling of code for mock sleeps. In addition, the code was in
terrible shape because the same variable (addon_time_) would sometimes
refer to microseconds and sometimes to seconds. One test even assumed it
was nanoseconds but was written to pass anyway.
This has been cleaned up so that DB tests generally use a SpecialEnv
function to mock sleep, for either some number of microseconds or seconds
depending on the function called. But to call one of these, the test must first
call SetMockSleep (precondition enforced with assertion), which also turns
sleeps in RocksDB into mock sleeps. To also removes accounting for actual
clock time, call SetTimeElapseOnlySleepOnReopen, which implies
SetMockSleep (on DB re-open). This latter setting only works by applying
on DB re-open, otherwise havoc can ensue if Env goes back in time with
DB open.
More specifics:
Removed some unused test classes, and updated comments on the general
problem.
Fixed DBSSTTest.GetTotalSstFilesSize using a sync point callback instead
of mock time. For this we have the only modification to production code,
inserting a sync point callback in flush_job.cc, which is not a change to
production behavior.
Removed unnecessary resetting of mock times to 0 in many tests. RocksDB
deals in relative time. Any behaviors relying on absolute date/time are likely
a bug. (The above test DBSSTTest.GetTotalSstFilesSize was the only one
clearly injecting a specific absolute time for actual testing convenience.) Just
in case I misunderstood some test, I put this note in each replacement:
// NOTE: Presumed unnecessary and removed: resetting mock time in env
Strengthened some tests like MergeTestTime, MergeCompactionTimeTest, and
FilterCompactionTimeTest in db_test.cc
stats_history_test and blob_db_test are each their own beast, rather deeply
dependent on MockTimeEnv. Each gets its own variant of a work-around for
TimedWait in a mock time environment. (Reduces redundancy and
inconsistency in stats_history_test.)
Intended follow-up:
Remove TimedWait from the public API of InstrumentedCondVar, and only
make that accessible through Env by passing in an InstrumentedCondVar and
a deadline. Then the Env implementations mocking time can fix this problem
without using sync points. (Test infrastructure using sync points interferes
with individual tests' control over sync points.)
With that change, we can simplify/consolidate the scattered work-arounds.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7101
Test Plan: make check on Linux and MacOS
Reviewed By: zhichao-cao
Differential Revision: D23032815
Pulled By: pdillinger
fbshipit-source-id: 7f33967ada8b83011fb54e8279365c008bd6610b
Summary:
Cleans up some of the dependencies on test code in the Makefile while building tools:
- Moves the test::RandomString, DBBaseTest::RandomString into Random
- Moves the test::RandomHumanReadableString into Random
- Moves the DestroyDir method into file_utils
- Moves the SetupSyncPointsToMockDirectIO into sync_point.
- Moves the FaultInjection Env and FS classes under env
These changes allow all of the tools to build without dependencies on test_util, thereby simplifying the build dependencies. By moving the FaultInjection code, the dependency in db_stress on different libraries for debug vs release was eliminated.
Tested both release and debug builds via Make and CMake for both static and shared libraries.
More work remains to clean up how the tools are built and remove some unnecessary dependencies. There is also more work that should be done to get the Makefile and CMake to align in their builds -- what is in the libraries and the sizes of the executables are different.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7097
Reviewed By: riversand963
Differential Revision: D22463160
Pulled By: pdillinger
fbshipit-source-id: e19462b53324ab3f0b7c72459dbc73165cc382b2
Summary:
After https://github.com/facebook/rocksdb/pull/7036, we still see extra DBTest that can timeout when running 10 or 20 in parallel. Expand skip-fsync mode in whole DBTest. Still preserve other tests from doing this mode to be conservative.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7049
Test Plan: Run all existing files.
Reviewed By: pdillinger
Differential Revision: D22301700
fbshipit-source-id: f9a9e3b3b26ce640665a47cb8bff33ba0c89b565
Summary:
This reverts commit 8d87e9cea1.
Based on offline discussions, it's too early to upgrade to gtest 1.10, as it prevents some developers from using an older version of gtest to integrate to some other systems. Revert it for now.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6923
Reviewed By: pdillinger
Differential Revision: D21864799
fbshipit-source-id: d0726b1ff649fc911b9378f1763316200bd363fc
Summary:
This very old test code bug was causing a new valgrind failure
in MultiGetDeadlineExceeded
Also fix hang in MultiGetDeadlineExceeded by unifying with some logic from another test.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6803
Test Plan: run that unit test under valgrind, make check
Reviewed By: siying
Differential Revision: D21388470
Pulled By: pdillinger
fbshipit-source-id: 0ce99d6d5eb8cd3195b17406892c8c5cff5fa5dd
Summary:
When dynamically linking two binaries together, different builds of RocksDB from two sources might cause errors. To provide a tool for user to solve the problem, the RocksDB namespace is changed to a flag which can be overridden in build time.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6433
Test Plan: Build release, all and jtest. Try to build with ROCKSDB_NAMESPACE with another flag.
Differential Revision: D19977691
fbshipit-source-id: aa7f2d0972e1c31d75339ac48478f34f6cfcfb3e
Summary:
In `DBSSTTest.SSTsWithLdbSuffixHandling`, some sst files are renamed to ldb files, the original intention of the test is to test that the ldb files can be loaded along with the sst files.
The original test checks this by `ASSERT_NE("NOT_FOUND", Get(Key(k)))`, but the problem is `Get(Key(k))` returns IO error due to path not found instead of NOT_FOUND, so the success of ASSERT_NE does not mean the key can be retrieved.
This PR updates the test to make sure Get(Key(k)) returns the original value.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6370
Test Plan: make db_sst_test && ./db_sst_test
Differential Revision: D19726278
Pulled By: cheng-chang
fbshipit-source-id: 993127f56457b315e669af4eeb92d6f956b7a4b7
Summary:
When paranoid_checks is on, DBImpl::CheckConsistency() iterates over all sst files and calls Env::GetFileSize() for each of them. As far as I could understand, this is pretty arbitrary and doesn't affect correctness - if filesystem doesn't corrupt fsynced files, the file sizes will always match; if it does, it may as well corrupt contents as well as sizes, and rocksdb doesn't check contents on open.
If there are thousands of sst files, getting all their sizes takes a while. If, on top of that, Env is overridden to use some remote storage instead of local filesystem, it can be *really* slow and overload the remote storage service. This PR adds an option to not do GetFileSize(); instead it does GetChildren() for parent directory to check that all the expected sst files are at least present, but doesn't check their sizes.
We can't just disable paranoid_checks instead because paranoid_checks do a few other important things: make the DB read-only on write errors, print error messages on read errors, etc.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6353
Test Plan: ran the added sanity check unit test. Will try it out in a LogDevice test cluster where the GetFileSize() calls are causing a lot of trouble.
Differential Revision: D19656425
Pulled By: al13n321
fbshipit-source-id: c2c421b367633033760d1f56747bad206d1fbf82
Summary:
1. Cleanup WAL trash files on open
2. Don't apply deletion rate limit if WAL dir is different from db dir
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5520
Test Plan: Add new unit tests and make check
Differential Revision: D16096750
Pulled By: anand1976
fbshipit-source-id: 6f07858ad864b754b711db416f0389c45ede599b
Summary:
By increasing the ratio, we ensure that all files go through background deletion and eliminate flakiness due to timing of deletions.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5366
Differential Revision: D15549992
Pulled By: anand1976
fbshipit-source-id: d137375cd791fc1a802841412755d6e2b8fd7688
Summary:
util/ means for lower level libraries, so it's a good idea to move the files which requires knowledge to DB out. Create a file/ and move some files there.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5375
Differential Revision: D15550935
Pulled By: siying
fbshipit-source-id: 61a9715dcde5386eebfb43e93f847bba1ae0d3f2
Summary:
Depending on the config, manual compaction (leveled compaction style) does following compactions:
L0->L1
L1->L2
...
Ln-1 -> Ln
Ln -> Ln
The final Ln -> Ln compaction is partly unnecessary as it recompacts all the files that were just generated by the Ln-1 -> Ln. We should avoid recompacting such files. This rule should be applied to Lmax only.
Resolves issue https://github.com/facebook/rocksdb/issues/4995
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5138
Differential Revision: D14940106
Pulled By: miasantreble
fbshipit-source-id: 8d3cf5507a17e76f3333cfd4bac5256d005636e5
Summary:
**This PR updates RepeatableThread::wait, breaking some tests on OS X. The rest of the PR fixes the tests on OS X.**
`RepeatableThreadTest.MockEnvTest` uses `MockTimeEnv` and `RepeatableThread`. If `RepeatableThread::wait` calls `TimedWait` with a time smaller than or equal to the current (real) time, `TimedWait` returns immediately on certain platforms, e.g. OS X. #4560 addresses this issue by replacing `TimedWait` with `Wait` in test. This fixes the test but makes test/production code diverge, which is not optimal for test coverage. This PR proposes an alternative fix which unifies test and production code path for `RepeatableThread::wait`. We obtain the current (real) time in seconds and add 10 extra seconds to ensure that `RepeatableThread::wait` invokes `TimedWait` with a time greater than (real) current time. This is to prevent the `TimedWait` function from returning immediately without sleeping and releasing the mutex. If `TimedWait` returns immediately, the mutex will not be released, and `RepeatableThread::TEST_WaitForRun` never has a chance to execute the callback which, in this case, updates the result returned by `mock_env->NowMicros()`. Consequently, `RepeatableThread::wait` cannot break out of the loop, causing test to hang. The extra 10 seconds is a best-effort approach because there seems no reliable and deterministic way to provide the aforementioned guarantee. By the time `RepeatableThread::wait` is called, there is no guarantee that the `delay + mock_env->NowMicros()` will be greater than the current real time. However, 10 seconds should be sufficient in most cases. We will keep an eye for possible flakiness of this test.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5107
Differential Revision: D14680885
Pulled By: riversand963
fbshipit-source-id: d1ecbe10e1dacd110bd464cd01e188bfee72b89e
Summary:
WAL files are currently not subject to deletion rate limiting by DeleteScheduler. If the size of the WAL files is significant, this can cause a high delete rate on SSDs that may affect other operations. To fix it, force WAL file deletions to go through the SstFileManager. Original PR for this is #2768
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5116
Differential Revision: D14669437
Pulled By: anand1976
fbshipit-source-id: c5f62d0640cebaa1574de841a1d01e4ce2faadf0
Summary:
DBSSTTest.RateLimitedDelete is flakey. The root cause is not completely identified, but
the compaction waiting in the test doesn't strictly wait for compaction cleaning to finish, which
may cause test flakiness. Fix it first and see whether the failures still happen.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4840
Differential Revision: D13567273
Pulled By: siying
fbshipit-source-id: 6fce38b912aff92a925231e7aa9bb0fef892761a
Summary:
The test has become complicated over the years and hard to reason about the corner cases that makes the test flaky. The patch simplifies the test and also fixes some probable synchronization issues.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4235
Differential Revision: D9187995
Pulled By: maysamyabandeh
fbshipit-source-id: 53c7b060f14367e5a9e361014578c26debfe3d27
Summary:
Fix a minor data race in DBSSTTest.DeleteSchedulerMultipleDBPaths reported by TSAN
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4146
Differential Revision: D8880945
Pulled By: siying
fbshipit-source-id: 25c632f685757735c59ad4ff26b2f346a443a446
Summary:
This PR comments out the rest of the unused arguments which allow us to turn on the -Wunused-parameter flag. This is the second part of a codemod relating to https://github.com/facebook/rocksdb/pull/3557.
Closes https://github.com/facebook/rocksdb/pull/3662
Differential Revision: D7426121
Pulled By: Dayvedde
fbshipit-source-id: 223994923b42bd4953eb016a0129e47560f7e352
Summary:
In this change, an option to set different paths for different column families is added.
This option is set via cf_paths setting of ColumnFamilyOptions. This option will work in a similar fashion to db_paths setting. Cf_paths is a vector of Dbpath values which contains a pair of the absolute path and target size. Multiple levels in a Column family can go to different paths if cf_paths has more than one path.
To maintain backward compatibility, if cf_paths is not specified for a column family, db_paths setting will be used. Note that, if db_paths setting is also not specified, RocksDB already has code to use db_name as the only path.
Changes :
1) A new member "cf_paths" is added to ImmutableCfOptions. This is set, based on cf_paths setting of ColumnFamilyOptions and db_paths setting of ImmutableDbOptions. This member is used to identify the path information whenever files are accessed.
2) Validation checks are added for cf_paths setting based on existing checks for db_paths setting.
3) DestroyDB, PurgeObsoleteFiles etc. are edited to support multiple cf_paths.
4) Unit tests are added appropriately.
Closes https://github.com/facebook/rocksdb/pull/3102
Differential Revision: D6951697
Pulled By: ajkr
fbshipit-source-id: 60d2262862b0a8fd6605b09ccb0da32bb331787d
Summary:
currently rocksdb lite build fails due to the following errors:
> db/db_sst_test.cc:29:51: error: ‘FlushJobInfo’ does not name a type
virtual void OnFlushCompleted(DB* /*db*/, const FlushJobInfo& info) override {
^
db/db_sst_test.cc:29:16: error: ‘virtual void rocksdb::FlushedFileCollector::OnFlushCompleted(rocksdb::DB*, const int&)’ marked ‘override’, but does not override
virtual void OnFlushCompleted(DB* /*db*/, const FlushJobInfo& info) override {
^
db/db_sst_test.cc:24:7: error: ‘class rocksdb::FlushedFileCollector’ has virtual functions and accessible non-virtual destructor [-Werror=non-virtual-dtor]
class FlushedFileCollector : public EventListener {
^
db/db_sst_test.cc: In member function ‘virtual void rocksdb::FlushedFileCollector::OnFlushCompleted(rocksdb::DB*, const int&)’:
db/db_sst_test.cc:31:35: error: request for member ‘file_path’ in ‘info’, which is of non-class type ‘const int’
flushed_files_.push_back(info.file_path);
^
cc1plus: all warnings being treated as errors
make: *** [db/db_sst_test.o] Error 1
Closes https://github.com/facebook/rocksdb/pull/3676
Differential Revision: D7493006
Pulled By: miasantreble
fbshipit-source-id: 77dff0a5b23e27db51be9b9798e3744e6fdec64f
Summary:
Manual compactions should be cancelled, just like scheduled compactions are cancelled, if sfm->EnoughRoomForCompaction is not true.
Closes https://github.com/facebook/rocksdb/pull/3670
Differential Revision: D7457683
Pulled By: amytai
fbshipit-source-id: 669b02fdb707f75db576d03d2c818fb98d1876f5
Summary:
I landed #3544 which made this test flaky. The reason was the files scheduled for deletion sometimes went through the trash-marking process, and sometimes were deleted directly. Our counter only bumped on the former code path, so if the latter code path was used, we'd miss counting a file deleted by deletion scheduler. This PR also bumps the counter in the latter code path.
Closes https://github.com/facebook/rocksdb/pull/3593
Differential Revision: D7226173
Pulled By: yiwu-arbug
fbshipit-source-id: 81ab44c60834df6ff88db1d73ea34e26c6e93c39
Summary:
Added a stat that counts the number of cancelled compactions.
Closes https://github.com/facebook/rocksdb/pull/3574
Differential Revision: D7190259
Pulled By: amytai
fbshipit-source-id: d5ce82dc9398da6d6d34023ad4ed8cec909852a3
Summary:
This diff handles cases where compaction causes an ENOSPC error.
This does not handle corner cases where another background job is started while compaction is running, and the other background job triggers ENOSPC, although we do allow the user to provision for these background jobs with SstFileManager::SetCompactionBufferSize.
It also does not handle the case where compaction has finished and some other background job independently triggers ENOSPC.
Usage: Functionality is inside SstFileManager. In particular, users should set SstFileManager::SetMaxAllowedSpaceUsage, which is the reference highwatermark for determining whether to cancel compactions.
Closes https://github.com/facebook/rocksdb/pull/3449
Differential Revision: D7016941
Pulled By: amytai
fbshipit-source-id: 8965ab8dd8b00972e771637a41b4e6c645450445
Summary:
Now that files scheduled for deletion are kept in the same directory, we don't need to constrain deletion scheduler to `db_paths[0]`. Previously this was done because there was a separate trash directory, and this constraint prevented files from being accidentally copied to another filesystem when they're scheduled for deletion.
Closes https://github.com/facebook/rocksdb/pull/3544
Differential Revision: D7093786
Pulled By: ajkr
fbshipit-source-id: 202f5c92d925eafebec1281fb95bb5828d33414f
Summary:
DeleteScheduler::MarkAsTrash() don't handle existing .trash files correctly
This cause rocksdb to not being able to delete existing .trash files on restart
Closes https://github.com/facebook/rocksdb/pull/3261
Differential Revision: D6548003
Pulled By: IslamAbdelRahman
fbshipit-source-id: c3800639412e587a690062c63076a5a08881e0e6
Summary:
Allow users to configure the trash-to-DB size ratio limit, so
that ratelimits for deletes can be enforced even when larger portions of
the database are being deleted.
Closes https://github.com/facebook/rocksdb/pull/3158
Differential Revision: D6304897
Pulled By: gdavidsson
fbshipit-source-id: a28dd13059ebab7d4171b953ed91ce383a84d6b3
Summary:
We don't propagate TableProperty::oldest_key_time on compaction and just write the default value to SST files. It is more natural to default the value to 0.
Also revert db_sst_test back to before #2842.
Closes https://github.com/facebook/rocksdb/pull/3079
Differential Revision: D6165702
Pulled By: yiwu-arbug
fbshipit-source-id: ca3ce5928d96ae79a5beb12bb7d8c640a71478a0
Summary:
SstFileManager move files that need to be deleted into a trash directory.
Deprecate this behaviour and instead add ".trash" extension to files that need to be deleted
Closes https://github.com/facebook/rocksdb/pull/2970
Differential Revision: D5976805
Pulled By: IslamAbdelRahman
fbshipit-source-id: 27374ece4315610b2792c30ffcd50232d4c9a343
Summary:
With FIFO compaction we would like to get the oldest data time for monitoring. The problem is we don't have timestamp for each key in the DB. As an approximation, we expose the earliest of sst file "creation_time" property.
My plan is to override the property with a more accurate value with blob db, where we actually have timestamp.
Closes https://github.com/facebook/rocksdb/pull/2842
Differential Revision: D5770600
Pulled By: yiwu-arbug
fbshipit-source-id: 03833c8f10bbfbee62f8ea5c0d03c0cafb5d853a
Summary:
This reverts the previous commit 1d7048c598, which broke the build.
Did a `git revert 1d7048c`.
Closes https://github.com/facebook/rocksdb/pull/2627
Differential Revision: D5476473
Pulled By: sagar0
fbshipit-source-id: 4756ff5c0dfc88c17eceb00e02c36176de728d06
Summary: This uses `clang-tidy` to comment out unused parameters (in functions, methods and lambdas) in fbcode. Cases that the tool failed to handle are fixed manually.
Reviewed By: igorsugak
Differential Revision: D5454343
fbshipit-source-id: 5dee339b4334e25e963891b519a5aa81fbf627b2
Summary:
Replacement of #2147
The change was squashed due to a lot of conflicts.
Closes https://github.com/facebook/rocksdb/pull/2194
Differential Revision: D4929799
Pulled By: siying
fbshipit-source-id: 5cd49c254737a1d5ac13f3c035f128e86524c581
Summary:
Level-based L0->L0 compaction operates on spans of files that aren't currently being compacted. It reduces the number of L0 files, thus making write stall conditions harder to reach.
- L0->L0 is triggered when base level is unavailable due to pending compactions
- L0->L0 always outputs one file of at most `max_level0_burst_file_size` bytes.
- Subcompactions are disabled for L0->L0 since we want to output one file.
- Input files are chosen as the longest span of available files that will fit within the size limit. This minimizes number of files in L0.
Closes https://github.com/facebook/rocksdb/pull/2027
Differential Revision: D4760318
Pulled By: ajkr
fbshipit-source-id: 9d07183
Summary:
db_sst_test had been flaky occasionally in the following way: reached_max_space_on_compaction can in very rare cases be 0. This happens when the limit on maximum allowable space set using SetMaxAllowedSpaceUsage is hit during flush for all test db sizes (1,2,4,8 and 10MB).The fix clears the error returned when the the space limit is reached during flush. This ensures that the compaction call back will always be called. The runtime is increased slightly because the 1MB loop writes more data and hits the limit during multiple flushes until compaction is scheduled.
Closes https://github.com/facebook/rocksdb/pull/1861
Differential Revision: D4557396
Pulled By: lgalanis
fbshipit-source-id: ff778d1
Summary:
If the WriteOptions.no_slowdown flag is set AND we need to wait or sleep for
the write request, then fail immediately with Status::Incomplete().
Closes https://github.com/facebook/rocksdb/pull/1527
Differential Revision: D4191405
Pulled By: maysamyabandeh
fbshipit-source-id: 7f3ce3f
Summary: Using real clock causes failures of DBSSTTest.RateLimitedDelete in some cases. Turn away from the real time. Use fake time instead.
Test Plan: Run the tests and all existing tests.
Reviewers: yiwu, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: leveldb, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D65145
mrambacher