Summary: Before the fix we also marked the bottommost level for compaction. This is wrong because then RocksDB has N+1 levels instead of N as before the compaction.
Test Plan: SuggestCompactRangeTest in db_test
Reviewers: yhchiang, rven
Reviewed By: rven
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D37869
Summary:
CompactRange for universal compaction with num_levels > 1 seems to have a bug. The unit test also has a bug so it doesn't capture the problem.
Fix it. Revert the compact range to the logic equivalent to num_levels=1. Always compact all files together.
It should also fix DBTest.IncreaseUniversalCompactionNumLevels. The issue was that options.write_buffer_size = 100 << 10 and options.write_buffer_size = 100 << 10 are not used in later test scenarios. So write_buffer_size of 4MB was used. The compaction trigger condition is not anymore obvious as expected.
Test Plan: Run the new test and all test suites
Reviewers: yhchiang, rven, kradhakrishnan, anthony, igor
Reviewed By: igor
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D37551
Summary:
This diff implements a new `DB` method `PromoteL0` which moves all files in L0
to a given level skipping compaction, provided that the files have disjoint
ranges and all levels up to the target level are empty.
This method provides finer-grain control for trivial compactions, and it is
useful for bulk-loading pre-sorted keys. Compared to D34797, it does not change
the semantics of an existing operation, which can impact existing code.
PromoteL0 is designed to work well in combination with the proposed
`GetSstFileWriter`/`AddFile` interface, enabling to "design" the level structure
by populating one level at a time. Such fine-grained control can be very useful
for static or mostly-static databases.
Test Plan: `make check`
Reviewers: IslamAbdelRahman, philipp, MarkCallaghan, yhchiang, igor, sdong
Reviewed By: sdong
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D37107
Summary: To further distinguish the corruption cases were caused by storage media or in memory states when writing it, add a paranoid check after writing the file to iterate all the rows.
Test Plan: Add a new unit test for it
Reviewers: rven, igor
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D37335
Summary:
A couple of times on Travis, we have had the thread status say that there were no compactions done and since we assert for it, the test failed.
We now fix this by waiting till compaction started.
Test Plan:
run DBTEST::*PreShutdown*
d=/tmp/j; rm -rf $d; seq 200 | parallel --gnu --eta 'd=/tmp/j/d-{}; mkdir -p $d; TEST_TMPDIR=$d ./db_test --gtest_filter=DBTest.PreShutdown* >& '$d'/log-{}'
Reviewers: sdong, igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D37545
Summary:
Some Mongo+Rocks datasets in Parse's environment are not doing compactions very frequently. During the quiet period (with no IO), we'd like to schedule compactions so that our reads become faster. Also, aggressively compacting during quiet periods helps when write bursts happen. In addition, we also want to compact files that are containing deleted key ranges (like old oplog keys).
All of this is currently not possible with CompactRange() because it's single-threaded and blocks all other compactions from happening. Running CompactRange() risks an issue of blocking writes because we generate too much Level 0 files before the compaction is over. Stopping writes is very dangerous because they hold transaction locks. We tried running manual compaction once on Mongo+Rocks and everything fell apart.
MarkForCompaction() solves all of those problems. This is very light-weight manual compaction. It is lower priority than automatic compactions, which means it shouldn't interfere with background process keeping the LSM tree clean. However, if no automatic compactions need to be run (or we have extra background threads available), we will start compacting files that are marked for compaction.
Test Plan: added a new unit test
Reviewers: yhchiang, rven, MarkCallaghan, sdong
Reviewed By: sdong
Subscribers: yoshinorim, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D37083
Summary: D36669 introduces a bug that trivial moved data is not going to specific level but the next level, which will incorrectly be level 1 for level 0 compaciton if base level is not level 1. Fixing it by appreciating the output level
Test Plan: Run all tests
Reviewers: MarkCallaghan, rven, yhchiang, igor
Reviewed By: igor
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D37119
Summary:
Recent change of DBTest.DynamicLevelCompressionPerLevel2 has a bug that the second sync point is not enabled. Fix it. Also add an assert for that.
Also, flush compression is not tracked in the test. Add it.
Test Plan: Build everything
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D37101
Summary: When commiting the sync point interface change, didn't resolve the new occurance of the old interface in rebase. Fix it.
Test Plan: Build and see it pass
Reviewers: igor, yhchiang, rven, anthony, kradhakrishnan
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D37095
Summary:
Allow users to give a callback function with parameter using sync point, so more complicated verification can be done in tests.
Use it in DBTest.DynamicLevelCompressionPerLevel2 so that failures will be more easy to debug.
Test Plan: Run all tests. Run DBTest.DynamicLevelCompressionPerLevel2 with valgrind check.
Reviewers: rven, yhchiang, anthony, kradhakrishnan, igor
Reviewed By: igor
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D36999
Summary: https://reviews.facebook.net/D36963 made the debug build much faster and that triggered failures of CompactFilesOnLevelCompaction test. 3 out of 4 last tests on Jenkins failed. I'm disabling this test temporarily, since we likely know the reason why it's failing and there's already work in progress to address it -- https://reviews.facebook.net/D36225
Test Plan: none
Reviewers: sdong, rven, yhchiang, meyering
Reviewed By: meyering
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D36993
Summary:
The problem is that sometimes two memtables will be compacted together into a single file. In that case, our assertion
ASSERT_EQ(NumTableFilesAtLevel(0), 5);
fails because same amount of data is in 4 files instead of 5. We should wait for flush so that we prevent two memtables merging into a single file.
Test Plan: `for i in `seq 20`; do mrtest FIFOCompactionTest; done` -- fails at least once before. fails zero times after.
Reviewers: rven
Reviewed By: rven
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D36939
Summary:
The goal of this diff is to make Compaction class easier to use. This should also make new compaction algorithms easier to write (like CompactFiles from @yhchiang and dynamic leveled and multi-leveled universal from @sdong).
Here are couple of things demonstrating that Compaction class is hard to use:
1. we have two constructors of Compaction class
2. there's this thing called grandparents_, but it appears to only be setup for leveled compaction and not compactfiles
3. it's easy to introduce a subtle and dangerous bug like this: D36225
4. SetupBottomMostLevel() is hard to understand and it shouldn't be. See this comment: afbafeaeae/db/compaction.cc (L236-L241). It also made it harder for @yhchiang to write CompactFiles, as evidenced by this: afbafeaeae/db/compaction_picker.cc (L204-L210)
The problem is that we create Compaction object, which holds a lot of state, and then pass it around to some functions. After those functions are done mutating, then we call couple of functions on Compaction object, like SetupBottommostLevel() and MarkFilesBeingCompacted(). It is very hard to see what's happening with all that Compaction's state while it's travelling across different functions. If you're writing a new PickCompaction() function you need to try really hard to understand what are all the functions you need to run on Compaction object and what state you need to setup.
My proposed solution is to make important parts of Compaction immutable after construction. PickCompaction() should calculate compaction inputs and then pass them onto Compaction object once they are finalized. That makes it easy to create a new compaction -- just provide all the parameters to the constructor and you're done. No need to call confusing functions after you created your object.
This diff doesn't fully achieve that goal, but it comes pretty close. Here are some of the changes:
* have one Compaction constructor instead of two.
* inputs_ is constant after construction
* MarkFilesBeingCompacted() is now private to Compaction class and automatically called on construction/destruction.
* SetupBottommostLevel() is gone. Compaction figures it out on its own based on the input.
* CompactionPicker's functions are not passing around Compaction object anymore. They are only passing around the state that they need.
Test Plan:
make check
make asan_check
make valgrind_check
Reviewers: rven, anthony, sdong, yhchiang
Reviewed By: yhchiang
Subscribers: sdong, yhchiang, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D36687
Summary: Now trivial move is only triggered when moving from level n to n+1. With dynamic level base, it is possible that file is moved from level 0 to level n, while levels from 1 to n-1 are empty. Extend trivial move to this case.
Test Plan: Add a more unit test of sequential loading. Non-trivial compaction happened without the patch and now doesn't happen.
Reviewers: rven, yhchiang, MarkCallaghan, igor
Reviewed By: igor
Subscribers: leveldb, dhruba, IslamAbdelRahman
Differential Revision: https://reviews.facebook.net/D36669
Summary: Now we add warnings when user configures compression and the compression is not supported.
Test Plan:
Configured compression to non-supported values. Observed messages in my log:
2015/03/26-12:17:57.586341 7ffb8a496840 [WARN] Compression type chosen for level 2 is not supported: LZ4. RocksDB will not compress data on level 2.
2015/03/26-12:19:10.768045 7f36f15c5840 [WARN] Compression type chosen is not supported: LZ4. RocksDB will not compress data.
Reviewers: rven, sdong, yhchiang
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D35979
Summary:
Currently users have no idea a key is add, delete or merge from TablePropertiesCollector call back. Add a new function to add it.
Also refactor the codes so that
(1) make table property collector and internal table property collector two separate data structures with the later one now exposed
(2) table builders only receive internal table properties
Test Plan: Add cases in table_properties_collector_test to cover both of old and new ways of using TablePropertiesCollector.
Reviewers: yhchiang, igor.sugak, rven, igor
Reviewed By: rven, igor
Subscribers: meyering, yoshinorim, maykov, leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D35373
Summary: In some db_test tests sync points are not cleared which will cause unexpected results in the next tests. Clean them up in test cleaning up.
Test Plan:
Run the same tests that used to fail:
build using USE_CLANG=1 and run
./db_test --gtest_filter="DBTest.CompressLevelCompaction:*DBTestUniversalCompactionParallel*"
Reviewers: rven, yhchiang, igor
Reviewed By: igor
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D36429
Summary:
This diff fixes a crash found when an empty database is opened in readonly mode.
We now check the number of levels before we open the DB as a compacted DB.
Test Plan: DBTest.EmptyCompactedDB
Reviewers: igor, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D36327
Summary:
After recent change of DBTest.DynamicCompactionOptions, occasionally hit another non-deterministic case where L0 showdown is triggered while timeout should not triggered for hard limit.
Fix it by increasing L0 slowdown trigger at the same time.
Test Plan: Run the failed test.
Reviewers: igor, rven
Reviewed By: rven
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D36219
Summary:
With this change, we use L1 and up to store compaction outputs in universal compaction.
The compaction pick logic stays the same. Outputs are stored in the largest "level" as possible.
If options.num_levels=1, it behaves all the same as now.
Test Plan:
1) convert most of existing unit tests for universal comapaction to include the option of one level and multiple levels.
2) add a unit test to cover parallel compaction in universal compaction and run it in one level and multiple levels
3) add unit test to migrate from multiple level setting back to one level setting
4) add a unit test to insert keys to trigger multiple rounds of compactions and verify results.
Reviewers: rven, kradhakrishnan, yhchiang, igor
Reviewed By: igor
Subscribers: meyering, leveldb, MarkCallaghan, dhruba
Differential Revision: https://reviews.facebook.net/D34539
Summary:
Cleaning up log files can do heavy IO, since we call ftruncate() in the destructor. We don't want to call ftruncate() in user threads.
This diff moves cleaning to background threads (flush and compaction)
Test Plan: make check, will also run valgrind
Reviewers: yhchiang, rven, MarkCallaghan, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D36177
Summary:
We have addded new stats and perf_context for measuring the merge and filter operation time consumption.
We have bounded all the merge operations within the GUARD statment and collected the total time for these operations in the DB.
Test Plan: WIP
Reviewers: rven, yhchiang, kradhakrishnan, igor, sdong
Reviewed By: sdong
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D34377
Summary:
Improve ThreadStatusSingleCompaction in two ways:
1. Use SYNC_POINT to ensure compaction won't happen
before the test finishes its "Put Phase" instead of
using sleep.
2. In Put Phase, it continues until we have sufficient
number of L0 files. Note that during the put phase,
there won't be any compaction that consumes L0 files
because of item 1.
Test Plan: ./db_test --gtest_filter="*ThreadStatusSingleCompaction*"
Reviewers: sdong, igor, rven
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D35727
Summary: DBTest doesn't clean up wal directory. It might cause failure after a failure test run. Fix it.
Test Plan:
Run unit tests
Try open DB with non-empty db_path/wal.
Reviewers: rven, yhchiang, kradhakrishnan, igor
Reviewed By: igor
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D35559
Summary: This is a simple change to make db_test::MultiThreadedDBTest as value parameterized test. There is a value of creating a separate set of such tests later.
Test Plan:
```lang=bash
% make db_test
% ./make db_test
```
Also with the following command I can execute all db_test in 2:37.87 on my box
```
% ./db_test --gtest_list_tests | sed 's/\# GetParam.*//' | tr -d ' ' | env time parallel --gnu --eta --joblog=LOG -- 'TEST_TMPDIR=/dev/shm/rocksdb-{} ./db_test --gtest_filter="*{}"'
```
Reviewers: igor, rven, meyering, sdong
Reviewed By: meyering
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D35361
Summary: Add a DB property for number of deletions in memtables. It can sometimes help people debug slowness because of too many deletes.
Test Plan: Add test cases.
Reviewers: rven, yhchiang, kradhakrishnan, igor
Reviewed By: igor
Subscribers: leveldb, dhruba, yoshinorim
Differential Revision: https://reviews.facebook.net/D35247
Summary:
Our existing test notation is very similar to what is used in gtest. It makes it easy to adopt what is different.
In this diff I modify existing [[ https://code.google.com/p/googletest/wiki/Primer#Test_Fixtures:_Using_the_Same_Data_Configuration_for_Multiple_Te | test fixture ]] classes to inherit from `testing::Test`. Also for unit tests that use fixture class, `TEST` is replaced with `TEST_F` as required in gtest.
There are several custom `main` functions in our existing tests. To make this transition easier, I modify all `main` functions to fallow gtest notation. But eventually we can remove them and use implementation of `main` that gtest provides.
```lang=bash
% cat ~/transform
#!/bin/sh
files=$(git ls-files '*test\.cc')
for file in $files
do
if grep -q "rocksdb::test::RunAllTests()" $file
then
if grep -Eq '^class \w+Test {' $file
then
perl -pi -e 's/^(class \w+Test) {/${1}: public testing::Test {/g' $file
perl -pi -e 's/^(TEST)/${1}_F/g' $file
fi
perl -pi -e 's/(int main.*\{)/${1}::testing::InitGoogleTest(&argc, argv);/g' $file
perl -pi -e 's/rocksdb::test::RunAllTests/RUN_ALL_TESTS/g' $file
fi
done
% sh ~/transform
% make format
```
Second iteration of this diff contains only scripted changes.
Third iteration contains manual changes to fix last errors and make it compilable.
Test Plan:
Build and notice no errors.
```lang=bash
% USE_CLANG=1 make check -j55
```
Tests are still testing.
Reviewers: meyering, sdong, rven, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D35157
Summary:
gtest does not use exceptions to fail a unit test by design, and `ASSERT*`s are implemented using `return`. As a consequence we cannot use `ASSERT*` in a function that does not return `void` value ([[ https://code.google.com/p/googletest/wiki/AdvancedGuide#Assertion_Placement | 1]]), and have to fix our existing code. This diff does this in a generic way, with no manual changes.
In order to detect all existing `ASSERT*` that are used in functions that doesn't return void value, I change the code to generate compile errors for such cases.
In `util/testharness.h` I defined `EXPECT*` assertions, the same way as `ASSERT*`, and redefined `ASSERT*` to return `void`. Then executed:
```lang=bash
% USE_CLANG=1 make all -j55 -k 2> build.log
% perl -naF: -e 'print "-- -number=".$F[1]." ".$F[0]."\n" if /: error:/' \
build.log | xargs -L 1 perl -spi -e 's/ASSERT/EXPECT/g if $. == $number'
% make format
```
After that I reverted back change to `ASSERT*` in `util/testharness.h`. But preserved introduced `EXPECT*`, which is the same as `ASSERT*`. This will be deleted once switched to gtest.
This diff is independent and contains manual changes only in `util/testharness.h`.
Test Plan:
Make sure all tests are passing.
```lang=bash
% USE_CLANG=1 make check
```
Reviewers: igor, lgalanis, sdong, yufei.zhu, rven, meyering
Reviewed By: meyering
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D33333
Summary:
On RocksDB, when there are multiple instances doing
flushes/compactions in the background, the close call takes a long time
because the flushes/compactions need to complete before the database can
shut down. If another instance is using the background threads and the compaction for this instance is in the queue since it has been scheduled, we still cannot shutdown. We now remove the scheduled background tasks which have not yet started running, so that shutdown is speeded up.
Test Plan: DB Test added.
Reviewers: yhchiang, igor, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D33741
Summary:
The preshutdown tests check for stopped compactions/flushes.
Removing stalls on the write path.
Test Plan: DBTests.PreShutdown*
Reviewers: yhchiang, sdong, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D35037
Summary:
Improve the robustness of ThreadStatusSingleCompaction
by ensuring the number of files flushed in the test.
Test Plan:
export ROCKSDB_TESTS=ThreadStatus
./db_test
Reviewers: sdong, igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D35019
Summary:
Fix the deadlock issue in ThreadStatusSingleCompaction.
In the previous version of ThreadStatusSingleCompaction, the compaction
thread will wait for a SYNC_POINT while its db_mutex is held. However,
if the test hasn't finished its Put cycle while a compaction is running,
a deadlock will happen in the test.
Test Plan:
export ROCKSDB_TESTS=ThreadStatus
./db_test
Reviewers: sdong, igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D35001
Summary: The test depends on snappy to be used. Skip the test if it is not supported.
Test Plan: Run the test
Reviewers: meyering, igor
Reviewed By: igor
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D34995
Summary: Currently, we have `ifdef SNAPPY` around bunch of db_test code. Some tests that don't even use compression are also blocked when running system doesn't have snappy. This also causes hard-to-catch bugs, like D34983. We should dynamically figure out if compression is supported or not.
Test Plan: compiles
Reviewers: sdong, meyering
Reviewed By: meyering
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34989
Summary:
The tests using sync_point for intent to shutdown stop
compaction and this results in stalls if too many rows are written. We
now limit the number of rows written to prevent stalls, since the focus
of the test is to cancel background work, which is being correctly
tested. This fixes a Jenkins issue.
Test Plan: DBTest.PreShutdown*
Reviewers: sdong, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34893
Summary:
Change the way options.compression_per_level is used when options.level_compaction_dynamic_level_bytes=true so that options.compression_per_level[1] determines compression for the level L0 is merged to, options.compression_per_level[2] to the level after that, etc.
Test Plan: run all tests
Reviewers: rven, yhchiang, kradhakrishnan, igor
Reviewed By: igor
Subscribers: yoshinorim, leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D34431
Summary:
Provide an API which enables users to infor Rocksdb that it is
shutting down.
Test Plan: db_test
Reviewers: sdong, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34617
Summary: Got it working by some voodoo programming
Test Plan: works!
Reviewers: sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34611
Summary:
When having fixed max_bytes_for_level_base, the ratio of size of largest level and the second one can range from 0 to the multiplier. This makes LSM tree frequently irregular and unpredictable. It can also cause poor space amplification in some cases.
In this improvement (proposed by Igor Kabiljo), we introduce a parameter option.level_compaction_use_dynamic_max_bytes. When turning it on, RocksDB is free to pick a level base in the range of (options.max_bytes_for_level_base/options.max_bytes_for_level_multiplier, options.max_bytes_for_level_base] so that real level ratios are close to options.max_bytes_for_level_multiplier.
Test Plan: New unit tests and pass tests suites including valgrind.
Reviewers: MarkCallaghan, rven, yhchiang, igor, ikabiljo
Reviewed By: ikabiljo
Subscribers: yoshinorim, ikabiljo, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D31437
Summary:
Summary:
Added a new option to ColumnFamllyOptions - optimize_filters_for_hits. This option can be used in the case where most
accesses to the store are key hits and we dont need to optimize performance for key misses.
This is useful when you have a very large database and most of your lookups succeed. The option allows the store to
not store and use filters in the last level (the largest level which contains data). These filters can take a large amount of
space for large databases (in memory and on-disk). For the last level, these filters are only useful for key misses and not
for key hits. If we are not optimizing for key misses, we can choose to not store these filters for that level.
This option is only provided for BlockBasedTable. We skip the filters when we are compacting
Test Plan:
1. Modified db_test toalso run tests with an additonal option (skip_filters_on_last_level)
2. Added another unit test to db_test which specifically tests that filters are being skipped
Reviewers: rven, igor, sdong
Reviewed By: sdong
Subscribers: lgalanis, yoshinorim, MarkCallaghan, rven, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D33717
Summary:
When using latest clang (3.6 or 3.7/trunck) rocksdb is failing with many errors. Almost all of them are missing override errors. This diff adds missing override keyword. No manual changes.
Prerequisites: bear and clang 3.5 build with extra tools
```lang=bash
% USE_CLANG=1 bear make all # generate a compilation database http://clang.llvm.org/docs/JSONCompilationDatabase.html
% clang-modernize -p . -include . -add-override
% make format
```
Test Plan:
Make sure all tests are passing.
```lang=bash
% #Use default fb code clang.
% make check
```
Verify less error and no missing override errors.
```lang=bash
% # Have trunk clang present in path.
% ROCKSDB_NO_FBCODE=1 CC=clang CXX=clang++ make
```
Reviewers: igor, kradhakrishnan, rven, meyering, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34077
Summary: Add a DB property about live versions. It can be helpful to figure out whether there are files not live but not yet deleted, in some use cases.
Test Plan: make all check
Reviewers: rven, yhchiang, igor
Reviewed By: igor
Subscribers: yoshinorim, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D33327
