Summary:
On some platforms like MacOS, a second 'make check' can lead to
/bin/rm: Argument list too long

This is fixed by replacing with a 'find'. Also, using '-f' for more rm calls
to avoid prompt.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7095

Test Plan: 'make check' on Linux and MacOS

Reviewed By: riversand963

Differential Revision: D22415808

Pulled By: pdillinger

fbshipit-source-id: 0fd1ebae13739c9d81f9e813e99b062715604d6b

Summary:
by tracking and linking against runtime dependent libraries in
Makefile

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7098

Test Plan: look for fix in CircleCI

Reviewed By: riversand963

Differential Revision: D22420860

Pulled By: pdillinger

fbshipit-source-id: d211d709214bf5306db68e43b7a2f18169281022

Summary:
Primarily, this change adds a way to work around a bug limiting the effective output (and therefore debugability) of the Linux builds using parallel make. We would get
make[1]: write error: stdout
probably due to a kernel bug, apparently affecting both available ubuntu 16 machine images (maybe not affecting docker images, less horsepower). https://bugs.launchpad.net/ubuntu/+source/linux-signed/+bug/1814393

Now in the CircleCI config, make output on Ubuntu is piped through a custom 'cat' that ignores EAGAIN errors, which seems to fix the problem.

Significant other changes:
* Add another linux build that combines
  * LIB_MODE=shared, to ensure this works with compile and unit test execution
  * Alternative rocksdb namespace, to ensure this works (not rely on Travis)
  * ASSERT_STATUS_CHECKED=1, but with building all unit tests and running those expected to pass with it
* Run release build with and without gflags. (Was running only without, ignore large swaths of code in a normal release build! Two regressions in this build, only with gflags, in the last week not caught by CI!)
* Use gflags with unity and LITE build, as typical case.

Debugability improvements:
* Use V=1 to show commands being executed (thanks to EAGAIN work-around)
* Print kernel version and compiler versions as part of V=1 output from Makefile

Cosmetic other changes:
* Put more commands on one line, for less clutter in CircleCI output pages
* Remove redundant "all" in "make all check" and put make command options before targets
* Change some recursive "make clean" into dependency on "clean," toward minimizing unnecessary overhead (detect platform, build version, etc.) of extra recursive makes

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7078

Reviewed By: siying

Differential Revision: D22391647

Pulled By: pdillinger

fbshipit-source-id: d446fccf5a8c568b37dc8748621c8a5c546fe135

Summary:
(a) use STRESS_LIBRARY for db_stress and make sure
STRESS_LIBRARY has other stress test dependencies (as in buck build)

(b) fix rpath option to be accepted on MacOS. It still doesn't fully work
for me e.g. to run a LIB_MODE=shared unit test binary from another
directory, as it does on Linux, but the option is now accepted, and running
unit tests from current directory works for me.

Also adding LIB_MODE=shared to Travis. (Later TBD where best to fit in
in CircleCI.)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7066

Test Plan: manual

Reviewed By: cheng-chang

Differential Revision: D22364068

Pulled By: pdillinger

fbshipit-source-id: 6fa98a222f89f808ee786474de1100d92c1adec3

Summary:
Follow-up to https://github.com/facebook/rocksdb/issues/6660. Release build had linker error. fbcode+clang+shared build was erroring on unused parameter '-nostdinc'.

Fixes https://github.com/facebook/rocksdb/issues/7061

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7062

Test Plan: make release, USE_CLANG=1 LIB_MODE=shared make check, etc.

Reviewed By: siying

Differential Revision: D22335663

Pulled By: pdillinger

fbshipit-source-id: 261cd959ca1f6c273dc763a70020a535ba8e81de

Summary:
Change the linking of tests/tools to be against a library rather than a list of objects.  This change substantially reduces the size of the objects produced.

peterd clean repo size: 264M
Before this change, with make all: 40G
After this change, with make all: 28G
With make LIB_MODE=shared all: 7.0G

The list of TESTS was changed from being hard-coded to generated from the test sources variable.  Note that there are some test sources that are not built as tests (though the set of tests is identical to the previous version).

Added OBJ_DIR option to Makefile to allow objects to be placed in an alternative location.  By default, OBJ_DIR is the same as before ("./").

This change is a precursor to being able to build/run the tests/tools linked against static libraries.  Additionally, it should be possible to clean up and merge some of the rules for building tests and the like if so desired.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6660

Reviewed By: riversand963

Differential Revision: D22244463

Pulled By: pdillinger

fbshipit-source-id: db9c6341d81ed62c2270374f4ede02fb9604c754

Summary:
We are still keeping unity build working. So it's a good idea to add to a pre-commit CI.
A latest GCC docker image just to get a little bit more coverage. Fix three small issues to make it pass.
Also make unity_test to run db_basic_test rather than db_test to cut the test time. There is no point to run expensive tests here. It was set to run db_test before db_basic_test was separated out.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7026

Test Plan: watch tests to pass.

Reviewed By: zhichao-cao

Differential Revision: D22223197

fbshipit-source-id: baa3b6cbb623bf359829b63ce35715c75bcb0ed4

Summary:
We don't need them.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7008

Test Plan: "make check" and ensure "make crash_test" starts

Reviewed By: ajkr

Differential Revision: D22143838

Pulled By: pdillinger

fbshipit-source-id: 72c8e16603abc59f4954e304466bc4dc1f58f94e

Summary:
1. As part of IOTracing project, Add a class IOTracer,
IOTraceReader and IOTracerWriter that writes the file operations
information in a binary file. IOTrace Record contains record information
and right now it contains access_timestamp, file_operation, file_name,
io_status, len, offset and later other options will be added when file
system APIs will be call IOTracer.

2. Add few unit test cases that verify that reading and writing to a IO
Trace file is working properly and before start trace and after ending
trace nothing is added to the binary file.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6958

Test Plan:
1. make check -j64
                 2. New testcases for IOTracer.

Reviewed By: anand1976

Differential Revision: D21943375

Pulled By: akankshamahajan15

fbshipit-source-id: 3532204e2a3eab0104bf411ab142e3fdd4fbce54

Summary:
Add crash test for the case of best-efforts recovery.
After a certain amount of time, we kill the db_stress process, randomly delete some certain table files and restart db_stress. Given the randomness of file deletion, it is difficult to verify against a reference for data correctness. Therefore, we just check that the db can restart successfully.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6819

Test Plan:
```
./db_stress -best_efforts_recovery=true -disable_wal=1 -reopen=0
./db_stress -best_efforts_recovery=true -disable_wal=0 -skip_verifydb=1 -verify_db_one_in=0 -continuous_verification_interval=0
make crash_test_with_best_efforts_recovery
```

Reviewed By: anand1976

Differential Revision: D21436753

Pulled By: riversand963

fbshipit-source-id: 0b3605c922a16c37ed17d5ab6682ca4240e47926

Summary:
Moving towards the long term goal of moving most CI build to CircleCI when possible, add some Linux tests in CircleCI. This is not all what we can include to CircleCI. For example, Java builds are not includ
ed.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6937

Test Plan: Watch CI build results.

Reviewed By: pdillinger

Differential Revision: D21941605

fbshipit-source-id: db6aead3c45f523386d4fb30d224cfde573cccad

Summary:
Currently, `DeleteDir` only deletes the directory if there are no other directories under the target dir. This PR makes it delete directories recursively.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6934

Test Plan:
Added a new unit test in testutil_test.cc.
`make testutil_test`

Reviewed By: zhichao-cao

Differential Revision: D21884211

Pulled By: cheng-chang

fbshipit-source-id: 0b9a48a200f494ee007aef5d1763b4aa331f8b5a

Summary:
This reverts commit 8d87e9ce.

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:
People keep breaking the gcc 4.8 compilation due to different
warnings for shadowing member functions with locals. Adding to Travis
to keep compatibility. (gcc 4.8 is default on CentOS 7.)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6915

Test Plan: local and Travis

Reviewed By: siying

Differential Revision: D21842894

Pulled By: pdillinger

fbshipit-source-id: bdcd4385127ee5d1cc222d87e53fb3695c32a9d4

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/6808

Reviewed By: anand1976

Differential Revision: D21483984

Pulled By: pdillinger

fbshipit-source-id: 70c5eff2bd54ddba469761d95e4cd4611fb8e598

Summary:
RocksDB Makefile was assuming existence of 'python' command,
which is not present in CentOS 8. We avoid using 'python' if 'python3' is available.

Also added fancy logic to format-diff.sh to make clang-format-diff.py for Python2 work even with Python3 only (as some CentOS 8 FB machines come equipped)

Also, now use just 'python3' for PYTHON if not found so that an informative
"command not found" error will result rather than something weird.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6883

Test Plan: manually tried some variants, 'make check' on a fresh CentOS 8 machine without 'python' executable or Python2 but with clang-format-diff.py for Python2.

Reviewed By: gg814

Differential Revision: D21767029

Pulled By: pdillinger

fbshipit-source-id: 54761b376b140a3922407bdc462f3572f461d0e9

Summary:
* Print stack trace on status checked failure
* Make folly_synchronization_distributed_mutex_test a parallel test
* Disable ldb_test.py and rocksdb_dump_test.sh with
  ASSERT_STATUS_CHECKED (broken)
* Fix shadow warning in random_access_file_reader.h reported by gcc
  4.8.5 (ROCKSDB_NO_FBCODE), also https://github.com/facebook/rocksdb/issues/6866
* Work around compiler bug on max_align_t for gcc < 4.9
* Remove an apparently wrong comment in status.h
* Use check_some in Travis config (for proper diagnostic output)
* Fix ignored Status in loop in options_helper.cc
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6871

Test Plan: manual, CI

Reviewed By: ajkr

Differential Revision: D21706619

Pulled By: pdillinger

fbshipit-source-id: daf6364173d6689904eb394461a69a11f5bee2cb

Summary:
Fixed some option handling code that recently broke the
ASSERT_STATUS_CHECKED build for options_test.

Added all other existing tests that pass under ASSERT_STATUS_CHECKED to
the whitelist.

Added a Travis configuration to run all whitelisted tests with
ASSERT_STATUS_CHECKED. (Someday we might enable this check by default in
debug builds.)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6870

Test Plan: ASSERT_STATUS_CHECKED=1 make check, Travis

Reviewed By: ajkr

Differential Revision: D21704374

Pulled By: pdillinger

fbshipit-source-id: 15daef98136a19d7a6843fa0c9ec08738c2ac693

Summary:
... so that we have freedom to upgrade it (see https://github.com/facebook/rocksdb/issues/6808).

As a side benefit, gtest will no longer be linked into main library in
buck build.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6858

Test Plan: fb internal build & link

Reviewed By: riversand963

Differential Revision: D21652061

Pulled By: pdillinger

fbshipit-source-id: 6018104af944debde576b5beda6c134e737acedb

Summary:
Added status check enforcement for io_posix_test and options_settable_test
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6857

Test Plan: ASSERT_STATUS_CHECKED=1 make -j48 check

Reviewed By: ajkr

Differential Revision: D21647904

Pulled By: akankshamahajan15

fbshipit-source-id: b7f2321eb6c141a88cd5e1270ecb7d58f00341af

Summary:
Currently, in direct IO mode, `MultiGet` retrieves the data blocks one by one instead of in parallel, see `BlockBasedTable::RetrieveMultipleBlocks`.

Since direct IO is supported in `RandomAccessFileReader::MultiRead` in https://github.com/facebook/rocksdb/pull/6446, this PR applies `MultiRead` to `MultiGet` so that the data blocks can be retrieved in parallel.

Also, in direct IO mode and when data blocks are compressed and need to uncompressed, this PR only allocates one continuous aligned buffer to hold the data blocks, and then directly uncompress the blocks to insert into block cache, there is no longer intermediate copies to scratch buffers.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6815

Test Plan:
1. added a new unit test `BlockBasedTableReaderTest::MultiGet`.
2. existing unit tests and stress tests  contain tests against `MultiGet` in direct IO mode.

Reviewed By: anand1976

Differential Revision: D21426347

Pulled By: cheng-chang

fbshipit-source-id: b8446ae0e74152444ef9111e97f8e402ac31b24f

Summary:
Tried making Status object enforce that it is checked in some way. In cases it is not checked, `PermitUncheckedError()` must be called explicitly.

Added a way to run tests (`ASSERT_STATUS_CHECKED=1 make -j48 check`) on a
whitelist. The effort appears significant to get each test to pass with
this assertion, so I only fixed up enough to get one test (`options_test`)
working and added it to the whitelist.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6798

Reviewed By: pdillinger

Differential Revision: D21377404

Pulled By: ajkr

fbshipit-source-id: 73236f9c8df38f01cf24ecac4a6d1661b72d077e

Summary:
Add Github Action to perform some basic sanity check for PR, inclding the
following.
1) Buck TARGETS file.
On the one hand, The TARGETS file is used for internal buck, and we do not
manually update it. On the other hand, we need to run the buckifier scripts to
update TARGETS whenever new files are added, etc. With this Github Action, we
make sure that every PR does not forget this step. The GH Action uses
a Makefile target called check-buck-targets. Users can manually run `make
check-buck-targets` on local machine.

2) Code format
We use clang-format-diff.py to format our code. The GH Action in this PR makes
sure this step is not skipped. The checking script build_tools/format-diff.sh assumes that `clang-format-diff.py` is executable.
On host running GH Action, it is difficult to download `clang-format-diff.py` and make it
executable. Therefore, we modified build_tools/format-diff.sh to handle the case in which there is a non-executable clang-format-diff.py file in the top-level rocksdb repo directory.

Test Plan (Github and devserver):
Watch for Github Action result in the `Checks` tab.
On dev server
```
make check-format
make check-buck-targets
make check
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6761

Test Plan: Watch for Github Action result in the `Checks` tab.

Reviewed By: pdillinger

Differential Revision: D21260209

Pulled By: riversand963

fbshipit-source-id: c646e2f37c6faf9f0614b68aa0efc818cff96787

Summary:
Some common build variables like USE_CLANG and
COMPILE_WITH_UBSAN did not work if specified as make variables, as in
`make USE_CLANG=1 check` etc. rather than (in theory less hygienic)
`USE_CLANG=1 make check`. This patches Makefile to export some commonly
used ones to build_detect_platform so that they work. (I'm skeptical of
a broad `export` in Makefile because it's hard to predict how random
make variables might affect various invoked tools.)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6740

Test Plan: manual / CI

Reviewed By: siying

Differential Revision: D21229011

Pulled By: pdillinger

fbshipit-source-id: b00c69b23eb2a13105bc8d860ce2d1e61ac5a355

Summary:
In https://github.com/facebook/rocksdb/pull/6455, we modified the interface of `RandomAccessFileReader::Read` to be able to get rid of memcpy in direct IO mode.
This PR applies the new interface to `BlockFetcher` when reading blocks from SST files in direct IO mode.

Without this PR, in direct IO mode, when fetching and uncompressing compressed blocks, `BlockFetcher` will first copy the raw compressed block into `BlockFetcher::compressed_buf_` or `BlockFetcher::stack_buf_` inside `RandomAccessFileReader::Read` depending on the block size. then during uncompressing, it will copy the uncompressed block into `BlockFetcher::heap_buf_`.

In this PR, we get rid of the first memcpy and directly uncompress the block from `direct_io_buf_` to `heap_buf_`.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6689

Test Plan: A new unit test `block_fetcher_test` is added.

Reviewed By: anand1976

Differential Revision: D21006729

Pulled By: cheng-chang

fbshipit-source-id: 2370b92c24075692423b81277415feb2aed5d980

Summary:
Updates the version of bzip2 used for RocksJava static builds.

Please, can we also get this cherry-picked to:

1. 6.7.fb
2. 6.8.fb
3. 6.9.fb
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6714

Reviewed By: cheng-chang

Differential Revision: D21067233

Pulled By: pdillinger

fbshipit-source-id: 8164b7eb99c5ca7b2021ab8c371ba9ded4cb4f7e

Summary:
This PR implements a fault injection mechanism for injecting errors in reads in db_stress. The FaultInjectionTestFS is used for this purpose. A thread local structure is used to track the errors, so that each db_stress thread can independently enable/disable error injection and verify observed errors against expected errors. This is initially enabled only for Get and MultiGet, but can be extended to iterator as well once its proven stable.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6538

Test Plan:
crash_test
make check

Reviewed By: riversand963

Differential Revision: D20714347

Pulled By: anand1976

fbshipit-source-id: d7598321d4a2d72bda0ced57411a337a91d87dc7

Summary:
Towards making compaction logic compatible with user timestamp.
When computing boundaries and overlapping ranges for inputs of compaction, We need to compare SSTs by user key without timestamp.

Test plan (devserver):
```
make check
```
Several individual tests:
```
./version_set_test --gtest_filter=VersionStorageInfoTimestampTest.GetOverlappingInputs
./db_with_timestamp_compaction_test
./db_with_timestamp_basic_test
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6645

Reviewed By: ltamasi

Differential Revision: D20960012

Pulled By: riversand963

fbshipit-source-id: ad377fa9eb481bf7a8a3e1824aaade48cdc653a4

Summary:
New memory technologies are being developed by various hardware vendors (Intel DCPMM is one such technology currently available). These new memory types require different libraries for allocation and management (such as PMDK and memkind). The high capacities available make it possible to provision large caches (up to several TBs in size), beyond what is achievable with DRAM.
The new allocator provided in this PR uses the memkind library to allocate memory on different media.

**Performance**

We tested the new allocator using db_bench.
- For each test, we vary the size of the block cache (relative to the size of the uncompressed data in the database).
- The database is filled sequentially. Throughput is then measured with a readrandom benchmark.
- We use a uniform distribution as a worst-case scenario.

The plot shows throughput (ops/s) relative to a configuration with no block cache and default allocator.
For all tests, p99 latency is below 500 us.

![image](https://user-images.githubusercontent.com/26400080/71108594-42479100-2178-11ea-8231-8a775bbc92db.png)

**Changes**

- Add MemkindKmemAllocator
- Add --use_cache_memkind_kmem_allocator db_bench option (to create an LRU block cache with the new allocator)
- Add detection of memkind library with KMEM DAX support
- Add test for MemkindKmemAllocator

**Minimum Requirements**

- kernel 5.3.12
- ndctl v67 - https://github.com/pmem/ndctl
- memkind v1.10.0 - https://github.com/memkind/memkind

**Memory Configuration**

The allocator uses the MEMKIND_DAX_KMEM memory kind. Follow the instructions on[ memkind’s GitHub page](https://github.com/memkind/memkind) to set up NVDIMM memory accordingly.

Note on memory allocation with NVDIMM memory exposed as system memory.
- The MemkindKmemAllocator will only allocate from NVDIMM memory (using memkind_malloc with MEMKIND_DAX_KMEM kind).
- The default allocator is not restricted to RAM by default. Based on NUMA node latency, the kernel should allocate from local RAM preferentially, but it’s a kernel decision. numactl --preferred/--membind can be used to allocate preferentially/exclusively from the local RAM node.

**Usage**

When creating an LRU cache, pass a MemkindKmemAllocator object as argument.
For example (replace capacity with the desired value in bytes):

```
#include "rocksdb/cache.h"
#include "memory/memkind_kmem_allocator.h"

NewLRUCache(
    capacity /*size_t*/,
    6 /*cache_numshardbits*/,
    false /*strict_capacity_limit*/,
    false /*cache_high_pri_pool_ratio*/,
    std::make_shared<MemkindKmemAllocator>());
```

Refer to [RocksDB’s block cache documentation](https://github.com/facebook/rocksdb/wiki/Block-Cache) to assign the LRU cache as block cache for a database.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6214

Reviewed By: cheng-chang

Differential Revision: D19292435

fbshipit-source-id: 7202f47b769e7722b539c86c2ffd669f64d7b4e1

Summary:
Although there are tests related to locking in transaction_test, this new test directly tests against TransactionLockMgr.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6599

Test Plan: make transaction_lock_mgr_test && ./transaction_lock_mgr_test

Reviewed By: lth

Differential Revision: D20673749

Pulled By: cheng-chang

fbshipit-source-id: 1fa4a13218e68d785f5a99924556751a8c5c0f31

Summary:
Adding a simple timer support to schedule work at a fixed time.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6543

Test Plan: TODO: clean up the unit tests, and make them better.

Reviewed By: siying

Differential Revision: D20465390

Pulled By: sagar0

fbshipit-source-id: cba143f70b6339863e1d0f8b8bf92e51c2b3d678

Summary:
When Travis times out, it's hard to determine whether
the last executing thing took an excessively long time or the
sum of all the work just exceeded the time limit. This
change inserts some timestamps in the output that should
make this easier to determine.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6643

Test Plan: CI (Travis mostly)

Reviewed By: anand1976

Differential Revision: D20843901

Pulled By: pdillinger

fbshipit-source-id: e7aae5434b0c609931feddf238ce4355964488b7

Summary:
This PR adds support for pipelined & parallel compression optimization for `BlockBasedTableBuilder`. This optimization makes block building, block compression and block appending a pipeline, and uses multiple threads to accelerate block compression. Users can set `CompressionOptions::parallel_threads` greater than 1 to enable compression parallelism.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6262

Reviewed By: ajkr

Differential Revision: D20651306

fbshipit-source-id: 62125590a9c15b6d9071def9dc72589c1696a4cb

Summary:
There are a few scripts with python3 compatibility issues that were not
detected by automated tool before. Update them now.

Test Plan (devserver):
python2 tools/ldb_test.py
python3 tools/ldb_test.py

python2 tools/write_stress_runner.py --runtime_sec=30
python3 tools/write_stress_runner.py --runtime_sec=30

python2 tools/db_crashtest.py --simple --interval=2 --duration=10 blackbox
python3 tools/db_crashtest.py --simple --interval=2 --duration=10 blackbox

python2 tools/db_crashtest.py --simple --duration=10 --random_kill_odd=1000 --ops_per_thread=1000 whitebox
python3 tools/db_crashtest.py --simple --duration=10 --random_kill_odd=1000 --ops_per_thread=1000 whitebox
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6525

Reviewed By: cheng-chang

Differential Revision: D20627820

Pulled By: riversand963

fbshipit-source-id: 4b25a7bd4d001c7f868be8b640ef876523be6ca3

Summary:
By supporting direct IO in RandomAccessFileReader::MultiRead, the benefits of parallel IO (IO uring) and direct IO can be combined.

In direct IO mode, read requests are aligned and merged together before being issued to RandomAccessFile::MultiRead, so blocks in the original requests might share the same underlying buffer, the shared buffers are returned in `aligned_bufs`, which is a new parameter of the `MultiRead` API.

For example, suppose alignment requirement for direct IO is 4KB, one request is (offset: 1KB, len: 1KB), another request is (offset: 3KB, len: 1KB), then since they all belong to page (offset: 0, len: 4KB), `MultiRead` only reads the page with direct IO into a buffer on heap, and returns 2 Slices referencing regions in that same buffer. See `random_access_file_reader_test.cc` for more examples.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6446

Test Plan: Added a new test `random_access_file_reader_test.cc`.

Reviewed By: anand1976

Differential Revision: D20097518

Pulled By: cheng-chang

fbshipit-source-id: ca48a8faf9c3af146465c102ef6b266a363e78d1

Summary:
In some of the test, db_basic_test may cause time out due to its long running time. Separate the timestamp related test from db_basic_test to avoid the potential issue.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6516

Test Plan: pass make asan_check

Differential Revision: D20423922

Pulled By: zhichao-cao

fbshipit-source-id: d6306f89a8de55b07bf57233e4554c09ef1fe23a

Summary:
In the `.travis.yml` file the `jdk: openjdk7` element is ignored when `language: cpp`. So whatever version of the JDK that was installed in the Travis container was used - typically JDK 11.

To ensure our RocksJava builds are working, we now instead install and use OpenJDK 8. Ideally we would use OpenJDK 7, as RocksJava supports Java 7, but many of the newer Travis containers don't support Java 7, so Java 8 is the next best thing.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6512

Differential Revision: D20388296

Pulled By: pdillinger

fbshipit-source-id: 8bbe6b59b70cfab7fe81ff63867d907fefdd2df1

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/6519

Test Plan:
```
make all
make check
```

Differential Revision: D20400691

Pulled By: ltamasi

fbshipit-source-id: 20ef911cf1c2c92c7f71ef0b493f9be64f2eef94

Summary:
In Linux, when reopening DB with many SST files, profiling shows that 100% system cpu time spent for a couple of seconds for `GetLogicalBufferSize`. This slows down MyRocks' recovery time when site is down.

This PR introduces two new APIs:
1. `Env::RegisterDbPaths` and `Env::UnregisterDbPaths` lets `DB` tell the env when it starts or stops using its database directories . The `PosixFileSystem` takes this opportunity to set up a cache from database directories to the corresponding logical block sizes.
2. `LogicalBlockSizeCache` is defined only for OS_LINUX to cache the logical block sizes.

Other modifications:
1. rename `logical buffer size` to `logical block size` to be consistent with Linux terms.
2. declare `GetLogicalBlockSize` in `PosixHelper` to expose it to `PosixFileSystem`.
3. change the functions `IOError` and `IOStatus` in `env/io_posix.h` to have external linkage since they are used in other translation units too.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6457

Test Plan:
1. A new unit test is added for `LogicalBlockSizeCache` in `env/io_posix_test.cc`.
2. A new integration test is added for `DB` operations related to the cache in `db/db_logical_block_size_cache_test.cc`.

`make check`

Differential Revision: D20131243

Pulled By: cheng-chang

fbshipit-source-id: 3077c50f8065c0bffb544d8f49fb10bba9408d04

Summary:
* **macOS version:** 10.15.2 (Catalina)
* **XCode/Clang version:** Apple clang version 11.0.0 (clang-1100.0.33.16)

Before this bugfix the error generated is:

```
In file included from ./util/compression.h:23:
./snappy-1.1.7/snappy.h:76:59: error: unknown type name 'string'; did you mean 'std::string'?
  size_t Compress(const char* input, size_t input_length, string* output);
                                                          ^~~~~~
                                                          std::string
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/iosfwd:211:65: note: 'std::string' declared here
typedef basic_string<char, char_traits<char>, allocator<char> > string;
                                                                ^
In file included from db/builder.cc:10:
In file included from ./db/builder.h:12:
In file included from ./db/range_tombstone_fragmenter.h:15:
In file included from ./db/pinned_iterators_manager.h:12:
In file included from ./table/internal_iterator.h:13:
In file included from ./table/format.h:25:
In file included from ./options/cf_options.h:14:
In file included from ./util/compression.h:23:
./snappy-1.1.7/snappy.h:85:19: error: unknown type name 'string'; did you mean 'std::string'?
                  string* uncompressed);
                  ^~~~~~
                  std::string
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1/iosfwd:211:65: note: 'std::string' declared here
typedef basic_string<char, char_traits<char>, allocator<char> > string;
                                                                ^
2 errors generated.
make: *** [jls/db/builder.o] Error 1
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6496

Differential Revision: D20389254

Pulled By: pdillinger

fbshipit-source-id: 2864245c8d0dba7b2ab81294241a62f2adf02e20