Summary:
Especially after updating to C++17, I don't see a compelling case for
*requiring* any folly components in RocksDB. I was able to purge the existing
hard dependencies, and it can be quite difficult to strip out non-trivial components
from folly for use in RocksDB. (The prospect of doing that on F14 has changed
my mind on the best approach here.)
But this change creates an optional integration where we can plug in
components from folly at compile time, starting here with F14FastMap to replace
std::unordered_map when possible (probably no public APIs for example). I have
replaced the biggest CPU users of std::unordered_map with compile-time
pluggable UnorderedMap which will use F14FastMap when USE_FOLLY is set.
USE_FOLLY is always set in the Meta-internal buck build, and a simulation of
that is in the Makefile for public CI testing. A full folly build is not needed, but
checking out the full folly repo is much simpler for getting the dependency,
and anything else we might want to optionally integrate in the future.
Some picky details:
* I don't think the distributed mutex stuff is actually used, so it was easy to remove.
* I implemented an alternative to `folly::constexpr_log2` (which is much easier
in C++17 than C++11) so that I could pull out the hard dependencies on
`ConstexprMath.h`
* I had to add noexcept move constructors/operators to some types to make
F14's complainUnlessNothrowMoveAndDestroy check happy, and I added a
macro to make that easier in some common cases.
* Updated Meta-internal buck build to use folly F14Map (always)
No updates to HISTORY.md nor INSTALL.md as this is not (yet?) considered a
production integration for open source users.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9546
Test Plan:
CircleCI tests updated so that a couple of them use folly.
Most internal unit & stress/crash tests updated to use Meta-internal latest folly.
(Note: they should probably use buck but they currently use Makefile.)
Example performance improvement: when filter partitions are pinned in cache,
they are tracked by PartitionedFilterBlockReader::filter_map_ and we can build
a test that exercises that heavily. Build DB with
```
TEST_TMPDIR=/dev/shm/rocksdb ./db_bench -benchmarks=fillrandom -num=10000000 -disable_wal=1 -write_buffer_size=30000000 -bloom_bits=16 -compaction_style=2 -fifo_compaction_max_table_files_size_mb=10000 -fifo_compaction_allow_compaction=0 -partition_index_and_filters
```
and test with (simultaneous runs with & without folly, ~20 times each to see
convergence)
```
TEST_TMPDIR=/dev/shm/rocksdb ./db_bench_folly -readonly -use_existing_db -benchmarks=readrandom -num=10000000 -bloom_bits=16 -compaction_style=2 -fifo_compaction_max_table_files_size_mb=10000 -fifo_compaction_allow_compaction=0 -partition_index_and_filters -duration=40 -pin_l0_filter_and_index_blocks_in_cache
```
Average ops/s no folly: 26229.2
Average ops/s with folly: 26853.3 (+2.4%)
Reviewed By: ajkr
Differential Revision: D34181736
Pulled By: pdillinger
fbshipit-source-id: ffa6ad5104c2880321d8a1aa7187e00ab0d02e94
Summary:
* Fix LIB_MODE=shared for Meta-internal builds (use PIC libraries
appropriately)
* Fix gnu_parallel to recognize CircleCI and Travis builds as not
connected to a terminal (was previously relying on the
`| cat_ignore_eagain` stuff for Ubuntu 16). This problem could cause
timeouts that should be 10m to balloon to 5h.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9553
Test Plan: manual and CI
Reviewed By: jay-zhuang
Differential Revision: D34182886
Pulled By: pdillinger
fbshipit-source-id: e95fd8002d94c8dc414bae1975e4fd348589f2b5
Summary:
For internal build enviroment only. Developer could run the
microbenchmark without `ROCKSDB_NO_FBCODE=1`.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8954
Test Plan: `$ make microbench` on dev server
Reviewed By: ajkr
Differential Revision: D31163717
Pulled By: jay-zhuang
fbshipit-source-id: 1ff59f660ca05afd0fd5c7c7dcdfd831ac365462
Summary:
Required for platform009, which is incompat with the centos
assembler.
author: pbrady@fb.com D29099768
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8733
Test Plan: CI
Reviewed By: pixelb
Differential Revision: D30687156
Pulled By: jay-zhuang
fbshipit-source-id: 796f90842cbf0ca11bad07e7d654bce1fafc4ba0
Summary:
DistributedMutex hasn't been used in the code base and enabling
`USE_FOLLY_DISTRIBUTED_MUTEX` only runs the mutex tests from third-party
lib. So disabling it for now.
The implementation may also out of date, should re-sync with folly before
using.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8584
Test Plan: CI
Reviewed By: ajkr
Differential Revision: D29888960
Pulled By: jay-zhuang
fbshipit-source-id: 3e75f73386c6ed03efb96a1400258d602a724f17
Summary:
Was seeing
./cache_test: error while loading shared libraries: libasan.so.5: cannot open shared object file: No such file or directory
etc. using COMPILE_WITH_ASAN=1 without USE_CLANG=1
Now including compiler libs in runtime ld path.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8402
Test Plan: reproduced with local builds
Reviewed By: akankshamahajan15
Differential Revision: D29107729
Pulled By: pdillinger
fbshipit-source-id: 13805b87b846b39522c9dd6a231ca245c58f1c71
Summary:
Internal builds failing
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8399
Test Plan:
I can reproduce a failure by putting a bad version of `as` in
my PATH. This indicates that before this change, the custom compiler is
falsely relying on host `as`. This change fixes that, ignoring the bad
`as` on PATH.
Reviewed By: akankshamahajan15
Differential Revision: D29094159
Pulled By: pdillinger
fbshipit-source-id: c432e90404ea4d39d885a685eebbb08be9eda1c8
Summary:
Upgrade tool chain to the latest. It is done mostly manually as build_tools/build_detect_platform fails to update many of them.
Try to fix a new clang analyze warning with the new tool chain.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7251
Test Plan: "make all", "USE_CLANG=1 make all"
Reviewed By: riversand963
Differential Revision: D23091090
fbshipit-source-id: 732e5a30137837431438f85f36296406b641f975
Summary:
`USE_LTO=1` in `make` commands now enables LTO. The archiver (`ar`) needed
to change in this PR to use a wrapper that enables the LTO plugin.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7181
Test Plan:
build a few ways
```
$ make clean && USE_LTO=1 make -j48 db_bench
$ make clean && USE_CLANG=1 USE_LTO=1 make -j48 db_bench
$ make clean && ROCKSDB_NO_FBCODE=1 USE_LTO=1 make -j48 db_bench
```
Reviewed By: cheng-chang
Differential Revision: D22784994
Pulled By: ajkr
fbshipit-source-id: 9c45333bd49bf4615aa04c85b7c6fd3925421152
Summary:
Right now, PosixRandomAccessFile::MultiRead() executes read requests in parallel. In this PR, it leverages I/O Uring library to run it in parallel, even when page cache is enabled. This function will fall back if the kernel version doesn't support it.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5881
Test Plan: Run the unit test on a kernel version supporting it and make sure all tests pass, and run a unit test on kernel version supporting it and see it pass. Before merging, will also run stress test and see it passes.
Differential Revision: D17742266
fbshipit-source-id: e05699c925ac04fdb42379456a4e23e4ebcb803a
Summary:
In preparing to utilize a new Intel instruction extension, I
noticed problems with the existing build script in regard to the
existing utilized extensions, either with USE_SSE or PORTABLE flags.
* PORTABLE=0 was interpreted the same as PORTABLE=1. Now empty and 0
mean the same. (I guess you were not supposed to set PORTABLE= if you
wanted non-portable--except that...)
* The Facebook build script extensions would set PORTABLE=1 even if
it's already set in a make var or environment. Now it does not override
a non-empty setting, so use PORTABLE=0 for fully optimized build,
overriding Facebook environment default.
* Put in an explanation of the USE_SSE flag where it's used by
build_detect_platform, and cleaned up some confusing/redundant
associated logic.
* If USE_SSE was set and expected intrinsics were not available,
build_detect_platform would exit early but build would proceed with
broken, incomplete configuration. Now warning is gracefully recovered.
* If USE_SSE was set and expected intrinsics were not available,
build would still try to use flags like -msse4.2 etc. which could lead
to unexpected compilation failure or binary incompatibility. Now those
flags are not used if the warning is issued.
This should not break or change existing, valid build scripts.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5800
Test Plan: manual case testing
Differential Revision: D17369543
Pulled By: pdillinger
fbshipit-source-id: 4ee244911680ae71144d272c40aceea548e3ce88
Summary:
This ports `folly::DistributedMutex` into RocksDB. The PR includes everything else needed to compile and use DistributedMutex as a component within folly. Most files are unchanged except for some portability stuff and includes.
For now, I've put this under `rocksdb/third-party`, but if there is a better folder to put this under, let me know. I also am not sure how or where to put unit tests for third-party stuff like this. It seems like gtest is included already, but I need to link with it from another third-party folder.
This also includes some other common components from folly
- folly/Optional
- folly/ScopeGuard (In particular `SCOPE_EXIT`)
- folly/synchronization/ParkingLot (A portable futex-like interface)
- folly/synchronization/AtomicNotification (The standard C++ interface for futexes)
- folly/Indestructible (For singletons that don't get destroyed without allocations)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5642
Differential Revision: D16544439
fbshipit-source-id: 179b98b5dcddc3075926d31a30f92fd064245731
Summary:
- When building with internal dependencies, specify this toolchain by setting `ROCKSDB_FBCODE_BUILD_WITH_PLATFORM007=1`
- It is not enabled by default. However, it is enabled for TSAN builds in CI since there is a known problem with TSAN in gcc-5: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71090
- I did not add support for Lua since (1) we agreed to deprecate it, and (2) we only have an internal build for v5.3 with this toolchain while that has breaking changes compared to our current version (v5.2).
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4923
Differential Revision: D13827226
Pulled By: ajkr
fbshipit-source-id: 9aa3388ed3679777cfb15ef8cbcb83c07f62f947
Summary:
- If block cache disabled or not used for meta-blocks, `BlockBasedTableReader::Rep::uncompression_dict` owns the `UncompressionDict`. It is preloaded during `PrefetchIndexAndFilterBlocks`.
- If block cache is enabled and used for meta-blocks, block cache owns the `UncompressionDict`, which holds dictionary and digested dictionary when needed. It is never prefetched though there is a TODO for this in the code. The cache key is simply the compression dictionary block handle.
- New stats for compression dictionary accesses in block cache: "BLOCK_CACHE_COMPRESSION_DICT_*" and "compression_dict_block_read_count"
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4881
Differential Revision: D13663801
Pulled By: ajkr
fbshipit-source-id: bdcc54044e180855cdcc57639b493b0e016c9a3f
Summary:
TSAN requires the code is built with -fPIC. This PR links against a libzstd built with -fPIC when necessary, which enables ZSTD compression to be used in TSAN builds.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4249
Differential Revision: D9244746
Pulled By: ajkr
fbshipit-source-id: 8c6a8fadd6c8643b2077afcbc3626779e1d73b63
Summary:
We forgot to add the new flag in internal build script. Add it.
Closes https://github.com/facebook/rocksdb/pull/2360
Differential Revision: D5121428
Pulled By: siying
fbshipit-source-id: af72d48cd855b37df1ce3c1fbb00c80377ba6e4f
Summary:
- added a feature test in build_detect_platform to check whether sched_getcpu() is available. glibc offers it only on some platforms (e.g., linux but not mac); this way should be easier than maintaining a list of platforms on which it's available.
- refactored PhysicalCoreID() to be simpler / less repetitive. ordered the conditional compilation clauses from most-to-least preferred
Closes https://github.com/facebook/rocksdb/pull/2272
Differential Revision: D5038093
Pulled By: ajkr
fbshipit-source-id: 81d7db3cc620250de220bdeb3194b2b3d7673de7
Summary:
This diff includes an implementation of CompactionFilter that allows
users to write CompactionFilter in Lua. With this ability, users can
dynamically change compaction filter logic without requiring building
the rocksdb binary and restarting the database.
To compile, WITH_LUA_PATH must be specified to the base directory
of lua.
Closes https://github.com/facebook/rocksdb/pull/1478
Differential Revision: D4150138
Pulled By: yhchiang
fbshipit-source-id: ed84222
Summary: Splitting the makefile part of D55581.
Test Plan:
make all check -j32
ROCKSDB_FBCODE_BUILD_WITH_481=1 make all check -j32
ROCKSDB_NO_FBCODE=1 make all check -j32
export TBB_BASE=/mnt/gvfs/third-party2/tbb/afa54b33cfcf93f1d90a3160cdb894d6d63d5dca/4.0_update2/gcc-4.9-glibc-2.20/e9936bf;
ROCKSDB_NO_FBCODE=1 CFLAGS="-I $TBB_BASE/include" LDFLAGS="-L $TBB_BASE/lib -Wl,-rpath=$TBB_BASE/lib" make all check -j32
Reviewers: IslamAbdelRahman, sdong
Reviewed By: sdong
Subscribers: kradhakrishnan, yhchiang, IslamAbdelRahman, andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D56979
Summary: current libgcc lib path is broken, update it and make sure the new one exists
Test Plan:
verify that the new path exists
make check -j64
Reviewers: yiwu, sdong, andrewkr
Reviewed By: andrewkr
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D59535
Summary: current clang_analyze path is broken, update it
Test Plan:
USE_CLANG=1 TEST_TMPDIR=/dev/shm/rocksdb OPT=-g make J=64 analyze -j64
make sure it works
Reviewers: yiwu, sdong, andrewkr
Reviewed By: andrewkr
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D59505
Summary: clang was removed from tp2 so change to llvm-fb.
Test Plan:
USE_CLANG=1 make all -j64
Reviewers: yhchiang, andrewkr, kradhakrishnan, sdong, lightmark, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D59259
Summary: Warning is printed out with USE_CLANG=1 when including jemalloc.h. Disable it in that case.
Test Plan: Run db_bench with USE_CLANG=1 and not. Make sure they can all build and jemalloc status is printed out in the case where USE_CLANG is not set.
Reviewers: andrewkr, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: leveldb, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D57399
Summary: It looks like we mistakenly enable JEMALLOC even if it's not available on the machine, that's why travis is failing
Test Plan:
check on my devserver
check on my mac
Reviewers: sdong
Reviewed By: sdong
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D57345
Summary:
This diff
- Include the rest of the dependencies (kernel-headers, binutils, valgrind) in dependencies.sh
- updtade zst to 0.4.7
- It also fix a problem in clang scan build
Test Plan:
make check
USE_CLANG=1 make check
USE_CLANG=1 make analyze
coverage_test.sh
Reviewers: sdong, yhchiang, rven, andrewkr, kradhakrishnan
Reviewed By: kradhakrishnan
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D53301
Summary:
Update fbcode_config.sh so that It try to use the latest version for dependencies that we are using, after updating the code these libraries where updated
```
Snappy: 1.0.3 => 1.1.3
GFLAGS: 1.6 => 2.1.1
JEMALLOC: 3.6.0 => 4.0.3
```
I have also updated clang from 3.7 to 3.7.1
```
Clang 3.7 => 3.7.1
```
Another change is that we use the same tp2 directory as fbcode, so we dont need to keep changing commit hash every time we need to change a version of a compiler or a library
Test Plan:
make check -j64
USE_CLANG=1 make check -j64
DISABLE_JEMALLOC=1 OPT=-g make all valgrind_check -j32 (make sure it's running)
Reviewers: yhchiang, anthony, rven, kradhakrishnan, andrewkr, sdong
Reviewed By: sdong
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D53037
Summary: update internal build scripts to use zstd 0.4.5.
Test Plan: built and ran tests with and without ROCKSDB_FBCODE_BUILD_WITH_481
Reviewers: yhchiang, rven, kradhakrishnan, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D52833
Summary:
It was already built in third-party2 but the include/library paths in
rocksdb hadn't been updated accordingly.
Test Plan:
verified build works
$ make clean && make -j32 all
$ make clean && USE_CLANG=1 make -j32 all
Reviewers: cyan, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D52299
Summary: Change to call the new compression function.
Test Plan: build and run db_bench with the compression to make sure it compresses.
Reviewers: anthony, rven, kradhakrishnan, IslamAbdelRahman, igor, yhchiang
Reviewed By: yhchiang
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D51603
Summary:
Reverting c745f1d2c4 because it
was based on an incorrect understanding of the correct way to enable
TSAN tests (it assumes "make COMPILE_WITH_TSAN=1 check" but in fact only
"COMPILE_WITH_TSAN=1 make check" is supported).
Test Plan: COMPILE_WITH_TSAN=1 make check
Reviewers: kradhakrishnan
Reviewed By: kradhakrishnan
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D50445
Summary:
TSAN builds for gcc 4.9 need a PIC version of the libraries
taken from the fbcode platform. This is accomplished by assuming every
.a has a _pic.a sibling, and by fixing the third-party2 zlib build.
Test Plan: make COMPILE_WITH_TSAN=1 check
Reviewers: sdong, igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D50331
Summary: This patch splits the posix storage backend into Env and
the actual *File implementations. The motivation is to allow other Envs
to use posix as a library. This enables a storage backend different from
posix to split its secondary storage between a normal file system
partition managed by posix, and it own media.
Test Plan: No new functionality is added to posix Env or the library,
thus the current tests should suffice.
Summary: Add ZSTD compression type. The same way as adding LZ4.
Test Plan: run all tests. Generate files in db_bench. Make sure reads succeed. But the SST files cannot be opened in older versions. Also some other adhoc tests.
Reviewers: rven, anthony, IslamAbdelRahman, kradhakrishnan, igor
Reviewed By: igor
Subscribers: MarkCallaghan, maykov, yoshinorim, leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D45747
Summary:
Currently, when we insert something into block cache, we say that the block cache capacity decreased by the size of the block. However, size of the block might be less than the actual memory used by this object. For example, 4.5KB block will actually use 8KB of memory. So even if we configure block cache to 10GB, our actually memory usage of block cache will be 20GB!
This problem showed up a lot in testing and just recently also showed up in MongoRocks production where we were using 30GB more memory than expected.
This diff will fix the problem. Instead of counting the block size, we will count memory used by the block. That way, a block cache configured to be 10GB will actually use only 10GB of memory.
I'm using non-portable function and I couldn't find info on portability on Google. However, it seems to work on Linux, which will cover majority of our use-cases.
Test Plan:
1. fill up mongo instance with 80GB of data
2. restart mongo with block cache size configured to 10GB
3. do a table scan in mongo
4. memory usage before the diff: 12GB. memory usage after the diff: 10.5GB
Reviewers: sdong, MarkCallaghan, rven, yhchiang
Reviewed By: yhchiang
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D40635
Summary:
Added a script that will compile MongoRocks with the same flags as RocksDB binary. On FB infra, we can now do:
cd ~/rocksdb; make static_lib
cd ~/mongo; ~/rocksdb/build_tools/fb_compile_mongo.sh
No need to upgrade the g++ on the devbox (like Aaron and I did) or maintain a separate script to compile (like Mark did)
fb_compile_mongo.sh gets the settings from fbcode_config.sh, so it also makes it easier to upgrade the environment one day.
Test Plan: Compiled mongod with new script. Also, ldd output looks good: https://phabricator.fb.com/P19891602
Reviewers: AaronFeldman, MarkCallaghan, anthony
Reviewed By: anthony
Subscribers: anthony, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D40659
Summary:
This lets the production toolchain libraries get used on devservers and
in production.
Task ID: #6849362
Blame Rev:
Test Plan:
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D37533
Summary: I don't think we need to use whole-archive to include jemalloc. This change only affects our development builds -- it does not affect our open source builds (which don't support jemalloc) or our fbcode third-party2 builds (which use open-source build codepaths).
Test Plan:
make
verify that jemalloc is running by running `MALLOC_CONF="prof:true" ./cache_test` and observing that file was created
Reviewers: MarkCallaghan
Reviewed By: MarkCallaghan
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D36783
Summary: Updated reference to the latest clang dev in fbcode. Since RocksDB already uses recent version of clang dev no code changes need.
Test Plan:
Make sure can be build with clang.
```lang=bash
% USE_CLANG=1 make all
```
Reviewers: meyering, sdong, rven, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D35121
Summary: Current clang path in fbcode points to clang 3.5. This diff updates clang path to clang 3.7.
Test Plan:
Make sure clang 3.7 is in use and all tests are passing.
```lang=bash
% USE_CLANG make check
```
Reviewers: meyering, sdong, rven, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D34119
Summary:
This changes the RocksDB build to share headers provided by MongoDB. It is invoked as:
ROCKSDB_FOR_MONGO=/path/to/mongodb/root make static_lib
Task ID: #
Blame Rev:
Test Plan:
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D34071
Summary:
Added new target ##make analyze## into Makefile. This command runs clang static analyzer and builds the sources as ##make all##. The result report is put into ##$(RocksDbSourceRoot)/can_build_report/##
If the development environment is a Facebook devserver and ##ROCKSDB_NO_FBCODE## is not set, then scan-build is used from fbcode. If it is run not on a Facebook devserver, scan-build should be available in ##$PATH##. I'll add details to wiki how to install scan-build on a non Facebook devserver environment.
Test Plan:
Run the fallowing commands on a Facebook devserver and Mac OS, and ensure no build or test errors.
```
% make all check -j32
% make clean
% USE_CLANG=1 make all -j32
% make analyze
% USE_CLANG=1 make analyze
```
Reviewers: sdong, lgalanis, leveldb, igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D32799
Peter Dillinger