Summary:
Ran `find ./db/ -type f | xargs clang-format -i`. Excluded minor changes it tried to make on db/db_impl/. Everything else it changed was directly under db/ directory. Included minor manual touchups mentioned in PR commit history.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10910
Reviewed By: riversand963
Differential Revision: D40880683
Pulled By: ajkr
fbshipit-source-id: cfe26cda05b3fb9a72e3cb82c286e21d8c5c4174
Summary:
For regular db instance and secondary instance, we return error and refuse to open DB if Logger creation fails.
Our current code allows it, but it is really difficult to debug because
there will be no LOG files. The same for OPTIONS file, which will be explored in another PR.
Furthermore, Arena::AllocateAligned(size_t bytes, size_t huge_page_size, Logger* logger) has an
assertion as the following:
```cpp
#ifdef MAP_HUGETLB
if (huge_page_size > 0 && bytes > 0) {
assert(logger != nullptr);
}
#endif
```
It can be removed.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9984
Test Plan: make check
Reviewed By: jay-zhuang
Differential Revision: D36347754
Pulled By: riversand963
fbshipit-source-id: 529798c0511d2eaa2f0fd40cf7e61c4cbc6bc57e
Summary:
This PR adds timestamp support to the secondary DB instance.
With this, these timestamp related APIs are supported:
ReadOptions.timestamp : read should return the latest data visible to this specified timestamp
Iterator::timestamp() : returns the timestamp associated with the key, value
DB:Get(..., std::string* timestamp) : returns the timestamp associated with the key, value in timestamp
Test plan (on devserver):
```
$COMPILE_WITH_ASAN=1 make -j24 all
$./db_secondary_test --gtest_filter=DBSecondaryTestWithTimestamp*
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10061
Reviewed By: riversand963
Differential Revision: D36722915
Pulled By: jowlyzhang
fbshipit-source-id: 644ada39e4e51164a759593478c38285e0c1a666
Summary:
Start tracking SST unique id in MANIFEST, which is used to verify with
SST properties to make sure the SST file is not overwritten or
misplaced. A DB option `try_verify_sst_unique_id` is introduced to
enable/disable the verification, if enabled, it opens all SST files
during DB-open to read the unique_id from table properties (default is
false), so it's recommended to use it with `max_open_files = -1` to
pre-open the files.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9990
Test Plan: unittests, format-compatible test, mini-crash
Reviewed By: anand1976
Differential Revision: D36381863
Pulled By: jay-zhuang
fbshipit-source-id: 89ea2eb6b35ed3e80ead9c724eb096083eaba63f
Summary:
ToString() is created as some platform doesn't support std::to_string(). However, we've already used std::to_string() by mistake for 16 months (in db/db_info_dumper.cc). This commit just remove ToString().
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9955
Test Plan: Watch CI tests
Reviewed By: riversand963
Differential Revision: D36176799
fbshipit-source-id: bdb6dcd0e3a3ab96a1ac810f5d0188f684064471
Summary:
Add the ability to cancel remote compaction on the remote side by
setting `OpenAndCompactOptions.canceled` to true.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9725
Test Plan: added unittest
Reviewed By: ajkr
Differential Revision: D35018800
Pulled By: jay-zhuang
fbshipit-source-id: be3652f9645e0347df429e42a5614d5a9b3a1ec4
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:
Original unit test fail to test the case of multi-cf mode switching to new manifest. The assertion
failure will trigger when the primary instance reopens and secondary continues to tail the
newly-created MANIFEST. Fix the assertion failure and update existing unit tests.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9143
Test Plan: make check
Reviewed By: ltamasi
Differential Revision: D32574233
Pulled By: riversand963
fbshipit-source-id: 857ddbe994019091276458abebcf8e2b65340468
Summary:
Directory fsync might be expensive on btrfs and it may not be needed.
Here are 4 directory fsync cases:
1. creating a new file: dir-fsync is not needed on btrfs, as long as the
new file itself is synced.
2. renaming a file: dir-fsync is not needed if the renamed file is
synced. So an API `FsyncAfterFileRename(filename, ...)` is provided
to sync the file on btrfs. By default, it just calls dir-fsync.
3. deleting files: dir-fsync is forced by set
`IOOptions.force_dir_fsync = true`
4. renaming multiple files (like backup and checkpoint): dir-fsync is
forced, the same as above.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8903
Test Plan: run tests on btrfs and non btrfs
Reviewed By: ajkr
Differential Revision: D30885059
Pulled By: jay-zhuang
fbshipit-source-id: dd2730b31580b0bcaedffc318a762d7dbf25de4a
Summary:
This PR does the following:
-> Makes the MemTableRepFactory into a Customizable class and creatable/configurable via CreateFromString
-> Makes the existing implementations compatible with configurations
-> Moves the "SpecialRepFactory" test class into testutil, accessible via the ObjectRegistry or a NewSpecial API
New tests were added to validate the functionality and all existing tests pass. db_bench and memtablerep_bench were hand-tested to verify the functionality in those tools.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8419
Reviewed By: zhichao-cao
Differential Revision: D29558961
Pulled By: mrambacher
fbshipit-source-id: 81b7229636e4e649a0c914e73ac7b0f8454c931c
Summary:
Recent refactor of `ReactiveVersionSet::ReadAndApply()` uses
`ManifestTailer` whose `Iterate()` method can cause the db's
`last_sequence_` to go backward. Consequently, read requests can see
out-dated data. For example, latest changes to the primary will not be
seen on the secondary even after a `TryCatchUpWithPrimary()` if no new
write batches are read from the WALs and no new MANIFEST entries are
read from the MANIFEST.
Fix the bug so that `VersionEditHandler::CheckIterationResult` will
never decrease `last_sequence_`, `last_allocated_sequence_` and
`last_published_sequence_`.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8653
Test Plan: make check
Reviewed By: jay-zhuang
Differential Revision: D30272084
Pulled By: riversand963
fbshipit-source-id: c6a49c534b2509b93ef62d8936ed0acd5b860eaa
Summary:
The PerThreadDBPath has already specified a slash. It does not need to be specified when initializing the test path.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8555
Reviewed By: ajkr
Differential Revision: D29758399
Pulled By: jay-zhuang
fbshipit-source-id: 6d2b878523e3e8580536e2829cb25489844d9011
Summary:
If the primary's CURRENT file is missing or inaccessible, the secondary should not hang
trying repeatedly to switch to the next MANIFEST.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8200
Test Plan: make check
Reviewed By: jay-zhuang
Differential Revision: D27840627
Pulled By: riversand963
fbshipit-source-id: 071fed97cbab1bc5cdefd1dc235e5cd406c174e1
Summary:
When db is open as secondary, there are basically 2 step process:
1) Collect column families from wal log
2) Apply changes to Memtable
In case primary db is TransactionDB instance, wal log will contain some additional data, like noop, etc. ColumnFamilyCollector doesn't implement methods to handle these, so it fails to open a wal log written by TransactionDB. (Everything works fine with standard DB::Open).
Memtable recovery process knows how to handle such wal logs, so only missing piece seems to be ColumnFamilyCollector.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8456
Reviewed By: ajkr
Differential Revision: D29455945
Pulled By: mrambacher
fbshipit-source-id: 5b29560fcbc008e17e95d0dc4b07558f3d63e26f
Summary:
Add compaction API for secondary instance, which compact the files to a secondary DB path without installing to the LSM tree.
The API will be used to remote compaction.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8171
Test Plan: `make check`
Reviewed By: ajkr
Differential Revision: D27694545
Pulled By: jay-zhuang
fbshipit-source-id: 8ff3ec1bffdb2e1becee994918850c8902caf731
Summary:
This PR
- adds a class `ManifestTailer` that inherits from `VersionEditHandlerPointInTime`. `ManifestTailer::Iterate()` can be called multiple times to tail the primary instance's MANIFEST and apply the changes to the secondary,
- updates the implementation of `ReactiveVersionSet::ReadAndApply` to use this class,
- removes unused code in version_set.cc,
- updates existing tests, e.g. removing deleted sync points from unit tests,
- adds a new test to address the bug in https://github.com/facebook/rocksdb/issues/7815.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7998
Test Plan:
make check
Existing and newly-added tests in version_set_test.cc and db_secondary_test.cc
Reviewed By: jay-zhuang
Differential Revision: D26926641
Pulled By: riversand963
fbshipit-source-id: 8d4dd15db0ba863c213f743e33b5a207e948c980
Summary:
https://github.com/facebook/rocksdb/issues/7340 reports and reproduces an assertion failure caused by a combination of the following:
- atomic flush is disabled.
- a column family can appear multiple times in the flush queue at the same time. This behavior was introduced in release 5.17.
Consequently, it is possible that two flushes race with each other. One bg flush thread flushes all memtables. The other thread calls `FlushMemTableToOutputFile()` afterwards, and hits the assertion error below.
```
assert(cfd->imm()->NumNotFlushed() != 0);
assert(cfd->imm()->IsFlushPending());
```
Fix this by reverting the behavior. In non-atomic-flush case, a column family can appear in the flush queue at most once at the same time.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7362
Test Plan:
make check
Also run stress test successfully for 10 times.
```
make crash_test
```
Reviewed By: ajkr
Differential Revision: D25172996
Pulled By: riversand963
fbshipit-source-id: f1559b6366cc609e961e3fc83fae548f1fad08ce
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:
As suggested by pdillinger ,The name of kLogFile is misleading, in some tests, kLogFile is defined as info log. Replace it with kWalFile and move it to public, which will be used in https://github.com/facebook/rocksdb/issues/7523
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7580
Test Plan: make check
Reviewed By: riversand963
Differential Revision: D24485420
Pulled By: zhichao-cao
fbshipit-source-id: 955e3dacc1021bb590fde93b0a568ffe9ad80799
Summary:
After https://github.com/facebook/rocksdb/pull/7036, we still see extra DBTest that can timeout when running 10 or 20 in parallel. Expand skip-fsync mode in whole DBTest. Still preserve other tests from doing this mode to be conservative.
This commit reinstates https://github.com/facebook/rocksdb/issues/7049, whose un-revert was lost in an automatic
infrastructure mis-merge.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7274
Test Plan: Run all existing files.
Reviewed By: pdillinger
Differential Revision: D23177444
fbshipit-source-id: 1f61690b2ac6333c3b2c87176fef6b2cba086b33
Summary:
Cleans up some of the dependencies on test code in the Makefile while building tools:
- Moves the test::RandomString, DBBaseTest::RandomString into Random
- Moves the test::RandomHumanReadableString into Random
- Moves the DestroyDir method into file_utils
- Moves the SetupSyncPointsToMockDirectIO into sync_point.
- Moves the FaultInjection Env and FS classes under env
These changes allow all of the tools to build without dependencies on test_util, thereby simplifying the build dependencies. By moving the FaultInjection code, the dependency in db_stress on different libraries for debug vs release was eliminated.
Tested both release and debug builds via Make and CMake for both static and shared libraries.
More work remains to clean up how the tools are built and remove some unnecessary dependencies. There is also more work that should be done to get the Makefile and CMake to align in their builds -- what is in the libraries and the sizes of the executables are different.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7097
Reviewed By: riversand963
Differential Revision: D22463160
Pulled By: pdillinger
fbshipit-source-id: e19462b53324ab3f0b7c72459dbc73165cc382b2
Summary:
After https://github.com/facebook/rocksdb/pull/7036, we still see extra DBTest that can timeout when running 10 or 20 in parallel. Expand skip-fsync mode in whole DBTest. Still preserve other tests from doing this mode to be conservative.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7049
Test Plan: Run all existing files.
Reviewed By: pdillinger
Differential Revision: D22301700
fbshipit-source-id: f9a9e3b3b26ce640665a47cb8bff33ba0c89b565
Summary:
With consistency check enabled, VersionBuilder::SaveTo() may return error once
corruption is detected while building versions. We should handle these errors.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6801
Test Plan: make check
Reviewed By: siying
Differential Revision: D21385045
Pulled By: riversand963
fbshipit-source-id: 98f6424e2a4699b62befa21e9fe00e70a771118e
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:
db_stress_tool.cc now is a giant file. In order to main it easier to improve and maintain, break it down to multiple source files.
Most classes are turned into their own files. Separate .h and .cc files are created for gflag definiations. Another .h and .cc files are created for some common functions. Some test execution logic that is only loosely related to class StressTest is moved to db_stress_driver.h and db_stress_driver.cc. All the files are located under db_stress_tool/. The directory name is created as such because if we end it with either stress or test, .gitignore will ignore any file under it and makes it prone to issues in developements.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6134
Test Plan: Build under GCC7 with and without LITE on using GNU Make. Build with GCC 4.8. Build with cmake with -DWITH_TOOL=1
Differential Revision: D18876064
fbshipit-source-id: b25d0a7451840f31ac0f5ebb0068785f783fdf7d
Summary:
After secondary instance replays the logs from primary, certain files become
obsolete. The secondary should find these files, evict their table readers from
table cache and close them. If this is not done, the secondary will hold on to
these files and prevent their space from being freed.
Test plan (devserver):
```
$./db_secondary_test --gtest_filter=DBSecondaryTest.SecondaryCloseFiles
$make check
$./db_stress -ops_per_thread=100000 -enable_secondary=true -threads=32 -secondary_catch_up_one_in=10000 -clear_column_family_one_in=1000 -reopen=100
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6114
Differential Revision: D18769998
Pulled By: riversand963
fbshipit-source-id: 5d1f151567247196164e1b79d8402fa2045b9120
Summary:
Further apply formatter to more recent commits.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5830
Test Plan: Run all existing tests.
Differential Revision: D17488031
fbshipit-source-id: 137458fd94d56dd271b8b40c522b03036943a2ab
Summary:
While the secondary is replaying after the primary, the primary may switch to a new MANIFEST. The secondary is already able to detect and follow the primary to the new MANIFEST. However, the current implementation has a bug, described as follows.
The new MANIFEST's first records have been generated by VersionSet::WriteSnapshot to describe the current state of the column families and the db as of the MANIFEST creation. Since the secondary instance has already finished recovering upon start, there is no need for the secondary to process these records. Actually, if the secondary were to replay these records, the secondary may end up adding the same SST files **again** to each column family, causing consistency checks done by VersionBuilder to fail. Therefore, we record the number of records to skip at the beginning of the new MANIFEST and ignore them.
Test plan (on dev server)
```
$make clean && make -j32 all
$./db_secondary_test
```
All existing unit tests must pass as well.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5472
Differential Revision: D15866771
Pulled By: riversand963
fbshipit-source-id: a1eec4837fb2ad13059398efb0f437e74fd53bed
Summary:
`DBImplSecondary` calls `CheckConsistency()` during open. In the past, `DBImplSecondary` did not override this function thus `DBImpl::CheckConsistency()` is called.
The following can happen. The secondary instance is performing consistency check which calls `GetFileSize(file_path)` but the file at `file_path` is deleted by the primary instance. `DBImpl::CheckConsistency` does not account for this and fails the consistency check. This is undesirable. The solution is that, we call `DBImpl::CheckConsistency()` first. If it passes, then we are good. If not, we give it a second chance and handles the case of file(s) being deleted.
Test plan (on dev server):
```
$make clean && make -j20 all
$./db_secondary_test
```
All other existing unit tests must pass as well.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5469
Differential Revision: D15861845
Pulled By: riversand963
fbshipit-source-id: 507d72392508caed3cd003bb2e2aa43f993dd597
Summary:
In regular RocksDB instance, `MemTable::earliest_seqno_` is "db sequence number at the time of creation". However, we cannot use the db sequence number to set the value of `MemTable::earliest_seqno_` for secondary instance, i.e. `DBImplSecondary` due to the logic of MANIFEST and WAL replay.
When replaying the log files of the primary, the secondary instance first replays MANIFEST and updates the db sequence number if necessary. Next, the secondary replays WAL files, creates new memtables if necessary and inserts key-value pairs into memtables. The following can occur when the db has two or more column families.
Assume the db has column family "default" and "cf1". At a certain in time, both "default" and "cf1" have data in memtables.
1. Primary triggers a flush and flushes "cf1". "default" is **not** flushed.
2. Secondary replays the MANIFEST updates its db sequence number to the latest value learned from the MANIFEST.
3. Secondary starts to replay WAL that contains the writes to "default". It is possible that the write batches' sequence numbers are smaller than the db sequence number. In this case, these write batches will be skipped, and these updates will not be visible to reader until "default" is later flushed.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5413
Differential Revision: D15637407
Pulled By: riversand963
fbshipit-source-id: 3de3fe35cfc6f1b9f844f3f926f0df29717b6580
Summary:
With this commit, RocksDB secondary instance respects atomic groups in version edits.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5411
Differential Revision: D15617512
Pulled By: HaoyuHuang
fbshipit-source-id: 913f4ede391d772dcaf5649e3cd2099fa292d120
Summary:
1. Fix a bug in WAL replay in which write batches with old sequence numbers are mistakenly inserted into memtables.
2. Add support for benchmarking secondary instance to db_bench_tool.
With changes made in this PR, we can start benchmarking secondary instance
using two processes. It is also possible to vary the frequency at which the
secondary instance tries to catch up with the primary. The info log of the
secondary can be found in a directory whose path can be specified with
'-secondary_path'.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5170
Differential Revision: D15564608
Pulled By: riversand963
fbshipit-source-id: ce97688ed3d33f69d3a0b9266ebbbbf887aa0ec8
Summary:
There are too many types of files under util/. Some test related files don't belong to there or just are just loosely related. Mo
ve them to a new directory test_util/, so that util/ is cleaner.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5377
Differential Revision: D15551366
Pulled By: siying
fbshipit-source-id: 0f5c8653832354ef8caa31749c0143815d719e2c
Summary:
RocksDB secondary can replay both MANIFEST and WAL now.
On the one hand, the memory usage by memtables will grow after replaying WAL for sometime. On the other hand, replaying the MANIFEST can bring the database persistent data to a more recent point in time, giving us the opportunity to discard some memtables containing out-dated data.
This PR coordinates the MANIFEST and WAL replay, using the updates from MANIFEST replay to update the active memtable and immutable memtable list of each column family.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5305
Differential Revision: D15386512
Pulled By: riversand963
fbshipit-source-id: a3ea6fc415f8382d8cf624f52a71ebdcffa3e355
Summary:
Previously in PR https://github.com/facebook/rocksdb/pull/5161 we have added the capability to do WAL tailing in `OpenAsSecondary`, in this PR we extend such feature to `TryCatchUpWithPrimary` which is useful for an secondary RocksDB instance to retrieve and apply the latest updates and refresh log readers if needed.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5282
Differential Revision: D15261011
Pulled By: miasantreble
fbshipit-source-id: a15c94471e8c3b3b1f7f47c3135db1126e936949
Summary: PR https://github.com/facebook/rocksdb/pull/4899 implemented the general framework for RocksDB secondary instances. This PR adds the support for WAL tailing in `OpenAsSecondary`, which means after the `OpenAsSecondary` call, the secondary is now able to see primary's writes that are yet to be flushed. The secondary can see primary's writes in the WAL up to the moment of `OpenAsSecondary` call starts.
Differential Revision: D15059905
Pulled By: miasantreble
fbshipit-source-id: 44f71f548a30b38179a7940165e138f622de1f10
Summary:
This PR allows RocksDB to run in single-primary, multi-secondary process mode.
The writer is a regular RocksDB (e.g. an `DBImpl`) instance playing the role of a primary.
Multiple `DBImplSecondary` processes (secondaries) share the same set of SST files, MANIFEST, WAL files with the primary. Secondaries tail the MANIFEST of the primary and apply updates to their own in-memory state of the file system, e.g. `VersionStorageInfo`.
This PR has several components:
1. (Originally in #4745). Add a `PathNotFound` subcode to `IOError` to denote the failure when a secondary tries to open a file which has been deleted by the primary.
2. (Similar to #4602). Add `FragmentBufferedReader` to handle partially-read, trailing record at the end of a log from where future read can continue.
3. (Originally in #4710 and #4820). Add implementation of the secondary, i.e. `DBImplSecondary`.
3.1 Tail the primary's MANIFEST during recovery.
3.2 Tail the primary's MANIFEST during normal processing by calling `ReadAndApply`.
3.3 Tailing WAL will be in a future PR.
4. Add an example in 'examples/multi_processes_example.cc' to demonstrate the usage of secondary RocksDB instance in a multi-process setting. Instructions to run the example can be found at the beginning of the source code.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4899
Differential Revision: D14510945
Pulled By: riversand963
fbshipit-source-id: 4ac1c5693e6012ad23f7b4b42d3c374fecbe8886
Andrew Kryczka