Summary:
Allows the Env to have options (Configurable) and loads like other Customizable classes.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9293
Reviewed By: pdillinger, zhichao-cao
Differential Revision: D33181591
Pulled By: mrambacher
fbshipit-source-id: 55e823886c654d214eda9eedd45ccdc54dac14d7
Summary:
Made SystemClock into a Customizable class, complete with CreateFromString.
Cleaned up some of the existing SystemClock implementations that were redundant (NoSleep was the same as the internal one for MockEnv).
Changed MockEnv construction to allow Clock to be passed to the Memory/MockFileSystem.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8636
Reviewed By: zhichao-cao
Differential Revision: D30483360
Pulled By: mrambacher
fbshipit-source-id: cd0e3a876c39f8c98fe13374c06e8edbd5b9f2a1
Summary:
Currently, we only truncate the latest alive WAL files when the DB is opened. If the latest WAL file is empty or was flushed during Open, its not truncated since the file will be deleted later on in the Open path. However, before deletion, a new WAL file is created, and if the process crash loops between the new WAL file creation and deletion of the old WAL file, the preallocated space will keep accumulating and eventually use up all disk space. To prevent this, always truncate the latest WAL file, even if its empty or the data was flushed.
Tests:
Add unit tests to db_wal_test
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8122
Reviewed By: riversand963
Differential Revision: D27366132
Pulled By: anand1976
fbshipit-source-id: f923cc03ef033ccb32b140d36c6a63a8152f0e8e
Summary:
For performance purposes, the lower level routines were changed to use a SystemClock* instead of a std::shared_ptr<SystemClock>. The shared ptr has some performance degradation on certain hardware classes.
For most of the system, there is no risk of the pointer being deleted/invalid because the shared_ptr will be stored elsewhere. For example, the ImmutableDBOptions stores the Env which has a std::shared_ptr<SystemClock> in it. The SystemClock* within the ImmutableDBOptions is essentially a "short cut" to gain access to this constant resource.
There were a few classes (PeriodicWorkScheduler?) where the "short cut" property did not hold. In those cases, the shared pointer was preserved.
Using db_bench readrandom perf_level=3 on my EC2 box, this change performed as well or better than 6.17:
6.17: readrandom : 28.046 micros/op 854902 ops/sec; 61.3 MB/s (355999 of 355999 found)
6.18: readrandom : 32.615 micros/op 735306 ops/sec; 52.7 MB/s (290999 of 290999 found)
PR: readrandom : 27.500 micros/op 871909 ops/sec; 62.5 MB/s (367999 of 367999 found)
(Note that the times for 6.18 are prior to revert of the SystemClock).
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8033
Reviewed By: pdillinger
Differential Revision: D27014563
Pulled By: mrambacher
fbshipit-source-id: ad0459eba03182e454391b5926bf5cdd45657b67
Summary:
Removed confusing, awkward, and undocumented internal API
ReadOneLine and replaced with very simple LineFileReader.
In refactoring backupable_db.cc, this has the side benefit of
removing the arbitrary cap on the size of backup metadata files.
Also added Status::MustCheck to make it easy to mark a Status as
"must check." Using this, I can ensure that after
LineFileReader::ReadLine returns false the caller checks GetStatus().
Also removed some excessive conditional compilation in status.h
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8026
Test Plan: added unit test, and running tests with ASSERT_STATUS_CHECKED
Reviewed By: mrambacher
Differential Revision: D26831687
Pulled By: pdillinger
fbshipit-source-id: ef749c265a7a26bb13cd44f6f0f97db2955f6f0f
Summary:
Since the hashes should not be persisted in output_validator
nor mock_env.
Also updated NPHash64 to use 64-bit seed, and comments.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7632
Test Plan:
make check, and new build setting that enables modification
to NPHash64, to check for behavior depending on specific values. Added
that setting to one of the CircleCI configurations.
Reviewed By: jay-zhuang
Differential Revision: D24833780
Pulled By: pdillinger
fbshipit-source-id: 02a57652ccf1ac105fbca79e77875bb7bf7c071f
Summary:
Consider the following sequence of events:
1. Db flushed an SST with file number N, appended to MANIFEST, and tried to sync the MANIFEST.
2. Syncing MANIFEST failed and db crashed.
3. Db tried to recover with this MANIFEST. In the meantime, no entry about the newly-flushed SST was found in the MANIFEST. Therefore, RocksDB replayed WAL and tried to flush to an SST file reusing the same file number N. This failed because file system does not support overwrite. Then Db deleted this file.
4. Db crashed again.
5. Db tried to recover. When db read the MANIFEST, there was an entry referencing N.sst. This could happen probably because the append in step 1 finally reached the MANIFEST and became visible. Since N.sst had been deleted in step 3, recovery failed.
It is possible that N.sst created in step 1 is valid. Although step 3 would still fail since the MANIFEST was not synced properly in step 1 and 2, deleting N.sst would make it impossible for the db to recover even if the remaining part of MANIFEST was appended and visible after step 5.
After this PR, in step 3, immediately after recovering from MANIFEST, a new MANIFEST is created, then we find that N.sst is not referenced in the MANIFEST, so we delete it, and we'll not reuse N as file number. Then in step 5, since the new MANIFEST does not contain N.sst, the recovery failure situation in step 5 won't happen.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7621
Test Plan:
1. some tests are updated, because these tests assume that new MANIFEST is created after WAL recovery.
2. a new unit test is added in db_basic_test to simulate step 3.
Reviewed By: riversand963
Differential Revision: D24668144
Pulled By: cheng-chang
fbshipit-source-id: 90d7487fbad2bc3714f5ede46ea949895b15ae3b
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:
Make (most of) the env*_test pass when ASSERT_STATUS_CHECKED is enabled.
One test that opens a database is currently disabled in this mode, as there are many errors that need revisited for DB tests and status checks.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7176
Reviewed By: cheng-chang
Differential Revision: D22799278
Pulled By: ajkr
fbshipit-source-id: 16d8a02eaeecd6df1060249b6a5811292801f2ed
Summary:
The dynamic_cast in the filter benchmark causes release mode to fail due to
no-rtti. Replace with static_cast_with_check.
Signed-off-by: Derrick Pallas <derrick@pallas.us>
Addition by peterd: Remove unnecessary 2nd template arg on all static_cast_with_check
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6732
Reviewed By: ltamasi
Differential Revision: D21304260
Pulled By: pdillinger
fbshipit-source-id: 6e8eb437c4ca5a16dbbfa4053d67c4ad55f1608c
Summary:
There are situations when RocksDB tries to recover, but the db is in an inconsistent state due to SST files referenced in the MANIFEST being missing. In this case, previous RocksDB will just fail the recovery and return a non-ok status.
This PR enables another possibility. During recovery, RocksDB checks possible MANIFEST files, and try to recover to the most recent state without missing table file. `VersionSet::Recover()` applies version edits incrementally and "materializes" a version only when this version does not reference any missing table file. After processing the entire MANIFEST, the version created last will be the latest version.
`DBImpl::Recover()` calls `VersionSet::Recover()`. Afterwards, WAL replay will *not* be performed.
To use this capability, set `options.best_efforts_recovery = true` when opening the db. Best-efforts recovery is currently incompatible with atomic flush.
Test plan (on devserver):
```
$make check
$COMPILE_WITH_ASAN=1 make all && make check
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6334
Reviewed By: anand1976
Differential Revision: D19778960
Pulled By: riversand963
fbshipit-source-id: c27ea80f29bc952e7d3311ecf5ee9c54393b40a8
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:
Use delete to disable automatic generated methods instead of private, and put the constructor together for more clear.This modification cause the unused field warning, so add unused attribute to disable this warning.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5009
Differential Revision: D17288733
fbshipit-source-id: 8a767ce096f185f1db01bd28fc88fef1cdd921f3
Summary:
Ran the following commands to recursively change all the files under RocksDB:
```
find . -type f -name "*.cc" -exec sed -i 's/ unique_ptr/ std::unique_ptr/g' {} +
find . -type f -name "*.cc" -exec sed -i 's/<unique_ptr/<std::unique_ptr/g' {} +
find . -type f -name "*.cc" -exec sed -i 's/ shared_ptr/ std::shared_ptr/g' {} +
find . -type f -name "*.cc" -exec sed -i 's/<shared_ptr/<std::shared_ptr/g' {} +
```
Running `make format` updated some formatting on the files touched.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4638
Differential Revision: D12934992
Pulled By: sagar0
fbshipit-source-id: 45a15d23c230cdd64c08f9c0243e5183934338a8
Summary:
Currently statistics are supposed to be dumped to info log at intervals of `options.stats_dump_period_sec`. However the implementation choice was to bind it with compaction thread, meaning if the database has been serving very light traffic, the stats may not get dumped at all.
We decided to separate stats dumping into a new timed thread using `TimerQueue`, which is already used in blob_db. This will allow us schedule new timed tasks with more deterministic behavior.
Tested with db_bench using `--stats_dump_period_sec=20` in command line:
> LOG:2018/09/17-14:07:45.575025 7fe99fbfe700 [WARN] [db/db_impl.cc:605] ------- DUMPING STATS -------
LOG:2018/09/17-14:08:05.643286 7fe99fbfe700 [WARN] [db/db_impl.cc:605] ------- DUMPING STATS -------
LOG:2018/09/17-14:08:25.691325 7fe99fbfe700 [WARN] [db/db_impl.cc:605] ------- DUMPING STATS -------
LOG:2018/09/17-14:08:45.740989 7fe99fbfe700 [WARN] [db/db_impl.cc:605] ------- DUMPING STATS -------
LOG content:
> 2018/09/17-14:07:45.575025 7fe99fbfe700 [WARN] [db/db_impl.cc:605] ------- DUMPING STATS -------
2018/09/17-14:07:45.575080 7fe99fbfe700 [WARN] [db/db_impl.cc:606]
** DB Stats **
Uptime(secs): 20.0 total, 20.0 interval
Cumulative writes: 4447K writes, 4447K keys, 4447K commit groups, 1.0 writes per commit group, ingest: 5.57 GB, 285.01 MB/s
Cumulative WAL: 4447K writes, 0 syncs, 4447638.00 writes per sync, written: 5.57 GB, 285.01 MB/s
Cumulative stall: 00:00:0.012 H:M:S, 0.1 percent
Interval writes: 4447K writes, 4447K keys, 4447K commit groups, 1.0 writes per commit group, ingest: 5700.71 MB, 285.01 MB/s
Interval WAL: 4447K writes, 0 syncs, 4447638.00 writes per sync, written: 5.57 MB, 285.01 MB/s
Interval stall: 00:00:0.012 H:M:S, 0.1 percent
** Compaction Stats [default] **
Level Files Size Score Read(GB) Rn(GB) Rnp1(GB) Write(GB) Wnew(GB) Moved(GB) W-Amp Rd(MB/s) Wr(MB/s) Comp(sec) Comp(cnt) Avg(sec) KeyIn KeyDrop
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4382
Differential Revision: D9933051
Pulled By: miasantreble
fbshipit-source-id: 6d12bb1e4977674eea4bf2d2ac6d486b814bb2fa
Summary:
As you know, almost all compilers support "pragma once" keyword instead of using include guards. To be keep consistency between header files, all header files are edited.
Besides this, try to fix some warnings about loss of data.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4339
Differential Revision: D9654990
Pulled By: ajkr
fbshipit-source-id: c2cf3d2d03a599847684bed81378c401920ca848
Summary:
This change adds a virtual `Truncate` method to `Env`, which truncates
the named file to the specified size. At the moment, this is only
supported for `MockEnv`, but other `Env's` could be extended to override
the method too. This is the same approach that methods like `LinkFile` and
`AreSameFile` have taken.
This is useful for any user of the in-memory `Env`. The implementation's
header is not exported, so before this change, it was impossible to
access it's already existing `Truncate` method.
Closes https://github.com/facebook/rocksdb/pull/3779
Differential Revision: D7785789
Pulled By: ajkr
fbshipit-source-id: 3bcdaeea7b7180529f7d9b496dc67b791a00bbf0
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 attempting to build a static lib for use in iOS, I ran in to lots of type errors between uint64_t and size_t. This PR contains the changes I made to get `TARGET_OS=IOS make static_lib` to succeed while also getting Xcode to build successfully with the resulting `librocksdb.a` library imported.
This also compiles for me on macOS and tests fine, but I'm really not sure if I made the correct decisions about where to `static_cast` and where to change types.
Also up for discussion: is iOS worth supporting? Getting the static lib is just part one, we aren't providing any bridging headers or wrappers like the ObjectiveRocks project, it won't be a great experience.
Closes https://github.com/facebook/rocksdb/pull/3503
Differential Revision: D7106457
Pulled By: gfosco
fbshipit-source-id: 82ac2073de7e1f09b91f6b4faea91d18bd311f8e
Summary:
MSVC does not support unused attribute at this time. A separate assignment line fixes the issue probably by being counted as usage for MSVC and it no longer complains about unused var.
Closes https://github.com/facebook/rocksdb/pull/3048
Differential Revision: D6126272
Pulled By: maysamyabandeh
fbshipit-source-id: 4907865db45fd75a39a15725c0695aaa17509c1f
Summary:
Replace dynamic_cast<> so that users can choose to build with RTTI off, so that they can save several bytes per object, and get tiny more memory available.
Some nontrivial changes:
1. Add Comparator::GetRootComparator() to get around the internal comparator hack
2. Add the two experiemental functions to DB
3. Add TableFactory::GetOptionString() to avoid unnecessary casting to get the option string
4. Since 3 is done, move the parsing option functions for table factory to table factory files too, to be symmetric.
Closes https://github.com/facebook/rocksdb/pull/2645
Differential Revision: D5502723
Pulled By: siying
fbshipit-source-id: fd13cec5601cf68a554d87bfcf056f2ffa5fbf7c
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:
Valgrind had false positive complaints about the initialization pattern for `GetCurrentTime()`'s argument in #2480. We can instead have the client initialize the time variable before calling `GetCurrentTime()`, and have `GetCurrentTime()` promise to only overwrite it in success case.
Closes https://github.com/facebook/rocksdb/pull/2526
Differential Revision: D5358689
Pulled By: ajkr
fbshipit-source-id: 857b189f24c19196f6bb299216f3e23e7bc4be42
Summary:
initialize 2 additional fields tm_gmtoff and tm_zone,
otherwise under strict warnings for initialization, we get errors
in myrocks.
Closes https://github.com/facebook/rocksdb/pull/2439
Differential Revision: D5229013
Pulled By: yiwu-arbug
fbshipit-source-id: 9fc1615a1919656f36064791706ed41e10e9db84
Summary:
/home/travis/build/facebook/rocksdb/env/mock_env.cc: In member function ‘virtual void rocksdb::{anonymous}::TestMemLogger::Logv(const char*, va_list)’:
/home/travis/build/facebook/rocksdb/env/mock_env.cc:391:53: error: ‘t.tm::tm_year’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
static_cast<int>(now_tv.tv_usec));
Closes https://github.com/facebook/rocksdb/pull/2418
Differential Revision: D5193597
Pulled By: maysamyabandeh
fbshipit-source-id: 8801a3ef27f33eb419d534f7de747702cdf504a0
Summary:
This is a manual commit of this PR:
Retire InMemoryEnv in favor of MockEnv #2082
With MockEnv doing the same yet being more mature, InMemoryEnv is redundant.
Reviewed By: IslamAbdelRahman
Differential Revision: D5162323
fbshipit-source-id: 59fd0082a891dc99cc531e4da9d68bf891eae3f5
Summary:
Move some files under util/ to new directories env/, monitoring/ options/ and cache/
Closes https://github.com/facebook/rocksdb/pull/2090
Differential Revision: D4833681
Pulled By: siying
fbshipit-source-id: 2fd8bef
Summary:
Fixing some bugs in MockEnv so it be actually used.
Closes https://github.com/facebook/rocksdb/pull/1914
Differential Revision: D4609923
Pulled By: maysamyabandeh
fbshipit-source-id: ca25735
Summary:
It'd be nice to use the error status type to distinguish
between user error and system error. For example, GetChildren can fail
listing a backup directory's contents either because a bad path was provided
(user error) or because an operation failed, e.g., a remote storage service
call failed (system error). In the former case, we want to continue and treat
the backup directory as empty; in the latter case, we want to immediately
propagate the error to the caller.
This diff uses NotFound to indicate user error and IOError to indicate
system error. Previously IOError indicated both.
Closes https://github.com/facebook/rocksdb/pull/1644
Differential Revision: D4312157
Pulled By: ajkr
fbshipit-source-id: 51b4f24
Summary:
Made it consistent with posix Env, which uses pread() that returns 0
(success) when an offset is given beyond EOF. The purpose of making these Envs
behave consistently is I am repurposing the in-memory Envs' tests for the basic
Env tests in D58635.
Test Plan: ran mock_env_test and memenv_test
Reviewers: IslamAbdelRahman, lightmark, sdong
Reviewed By: sdong
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D58845
Summary. A change https://reviews.facebook.net/differential/diff/224721/
Has attempted to move common functionality out of platform dependent
code to a new facility called file_reader_writer.
This includes:
- perf counters
- Buffering
- RateLimiting
However, the change did not attempt to refactor Windows code.
To mitigate, we introduce new quering interfaces such as UseOSBuffer(),
GetRequiredBufferAlignment() and ReaderWriterForward()
for pure forwarding where required.
Introduce WritableFile got a new method Truncate(). This is to communicate
to the file as to how much data it has on close.
- When space is pre-allocated on Linux it is filled with zeros implicitly,
no such thing exist on Windows so we must truncate file on close.
- When operating in unbuffered mode the last page is filled with zeros but we still want to truncate.
Previously, Close() would take care of it but now buffer management is shifted to the wrappers and the file has
no idea about the file true size.
This means that Close() on the wrapper level must always include
Truncate() as well as wrapper __dtor should call Close() and
against double Close().
Move buffered/unbuffered write logic to the wrapper.
Utilize Aligned buffer class.
Adjust tests and implement Truncate() where necessary.
Come up with reasonable defaults for new virtual interfaces.
Forward calls for RandomAccessReadAhead class to avoid double
buffering and locking (double locking in unbuffered mode on WIndows).
Summary: RandomRWFile is not used anywhere in out code base, this patch remove RandomRWFile
Test Plan:
make check -j64
USE_CLANG=1 make all -j64
OPT=-DROCKSDB_LITE make release -j64
Reviewers: sdong, yhchiang, anthony, kradhakrishnan, rven, igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D44091
Summary: Add new CheckFileExists method. Considered changing the FileExists api but didn't want to break anyone's builds.
Test Plan: unit tests
Reviewers: yhchiang, igor, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D42003
Summary: Make RocksDb build and run on Windows to be functionally
complete and performant. All existing test cases run with no
regressions. Performance numbers are in the pull-request.
Test plan: make all of the existing unit tests pass, obtain perf numbers.
Co-authored-by: Praveen Rao praveensinghrao@outlook.com
Co-authored-by: Sherlock Huang baihan.huang@gmail.com
Co-authored-by: Alex Zinoviev alexander.zinoviev@me.com
Co-authored-by: Dmitri Smirnov dmitrism@microsoft.com
Summary: We should use mocked-out env for these tests to make it more realiable. Added benefit is that instead of actually sleeping for 3 seconds, we can instead pretend to sleep and just increase time counters.
Test Plan: for i in `seq 100`; do ./wal_manager_test --gtest_filter=WalManagerTest.WALArchivalTtl ;done
Reviewers: rven, meyering
Reviewed By: meyering
Subscribers: meyering, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D36951
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
mrambacher