Commit Graph

101 Commits

Author SHA1 Message Date
Aaron Feldman
a69bc91e37 Multithreaded backup and restore in BackupEngineImpl
Summary:
Add a new field: BackupableDBOptions.max_background_copies.
CreateNewBackup() and RestoreDBFromBackup() will use this number of threads to perform copies.
If there is a backup rate limit, then max_background_copies must be 1.
Update backupable_db_test.cc to test multi-threaded backup and restore.
Update backupable_db_test.cc to test backups when the backup environment is not the same as the database environment.

Test Plan:
Run ./backupable_db_test
Run valgrind ./backupable_db_test
Run with TSAN and ASAN

Reviewers: yhchiang, rven, anthony, sdong, igor

Reviewed By: igor

Subscribers: yhchiang, anthony, sdong, leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D40725
2015-07-02 11:35:51 -07:00
sdong
e409d3d745 Make "make all" work for CYGWIN
Summary: Some test and benchmark codes don't build for CYGWIN. Fix it.

Test Plan: Build "make all" with TARGET_OS=Cygwin on cygwin and make sure it passes.

Reviewers: rven, yhchiang, anthony, igor, kradhakrishnan

Reviewed By: igor, kradhakrishnan

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D39711
2015-06-09 16:36:07 -07:00
Igor Canadi
50eab9cf30 Fix BackupEngine
Summary:
In D28521 we removed GarbageCollect() from BackupEngine's constructor. The reason was that opening BackupEngine on HDFS was very slow and in most cases we didn't have any garbage. We allowed the user to call GarbageCollect() when it detects some garbage files in his backup directory.

Unfortunately, this left us vulnerable to an interesting issue. Let's say we started a backup and copied files {1, 3} but the backup failed. On another host, we restore DB from backup and generate {1, 3, 5}. Since {1, 3} is already there, we will not overwrite. However, these files might be from a different database so their contents might be different. See internal task t6781803 for more info.

Now, when we're copying files and we discover a file already there, we check:
1. if the file is not referenced from any backups, we overwrite the file.
2. if the file is referenced from other backups AND the checksums don't match, we fail the backup. This will only happen if user is using a single backup directory for backing up two different databases.
3. if the file is referenced from other backups AND the checksums match, it's all good. We skip the copy and go copy the next file.

Test Plan: Added new test to backupable_db_test. The test fails before this patch.

Reviewers: sdong, rven, yhchiang

Reviewed By: yhchiang

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D37599
2015-05-07 17:39:19 -07:00
Jim Meyering
acf8a4141d maint: use ASSERT_TRUE, not ASSERT_EQ(true; same for false
Summary:
The usage I'm fixing here caused trouble on Fedora 21 when
compiling with the current gcc version 4.9.2 20150212 (Red Hat 4.9.2-6) (GCC):

  db/write_controller_test.cc: In member function ‘virtual void rocksdb::WriteControllerTest_SanityTest_Test::TestBody()’:
  db/write_controller_test.cc:23:165: error: converting ‘false’ to pointer type for argument 1 of ‘char testing::internal::IsNullLiteralHelper(testing::internal::Secret*)’ [-Werror=conversion-null]
     ASSERT_EQ(false, controller.IsStopped());
                                                                                                                                                                          ^

This change was induced mechanically via:

  git grep -l -E 'ASSERT_EQ\(false'|xargs perl -pi -e 's/ASSERT_EQ\(false, /ASSERT_FALSE(/'
  git grep -l -E 'ASSERT_EQ\(true'|xargs perl -pi -e 's/ASSERT_EQ\(true, /ASSERT_TRUE(/'

Except for the three in utilities/backupable/backupable_db_test.cc for which
I ended up reformatting (joining lines) in the result.

As for why this problem is exhibited with that version of gcc, and none
of the others I've used (from 4.8.1 through gcc-5.0.0 and newer), I suspect
it's a bug in F21's gcc that has been fixed in gcc-5.0.0.

Test Plan:
  "make" now succeed on Fedora 21

Reviewers: ljin, rven, igor.sugak, yhchiang, sdong, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D37329
2015-04-17 14:54:17 -07:00
Igor Sugak
b4b69e4f77 rocksdb: switch to gtest
Summary:
Our existing test notation is very similar to what is used in gtest. It makes it easy to adopt what is different.
In this diff I modify existing [[ https://code.google.com/p/googletest/wiki/Primer#Test_Fixtures:_Using_the_Same_Data_Configuration_for_Multiple_Te | test fixture ]] classes to inherit from `testing::Test`. Also for unit tests that use fixture class, `TEST` is replaced with `TEST_F` as required in gtest.

There are several custom `main` functions in our existing tests. To make this transition easier, I modify all `main` functions to fallow gtest notation. But eventually we can remove them and use implementation of `main` that gtest provides.

```lang=bash
% cat ~/transform
#!/bin/sh
files=$(git ls-files '*test\.cc')
for file in $files
do
  if grep -q "rocksdb::test::RunAllTests()" $file
  then
    if grep -Eq '^class \w+Test {' $file
    then
      perl -pi -e 's/^(class \w+Test) {/${1}: public testing::Test {/g' $file
      perl -pi -e 's/^(TEST)/${1}_F/g' $file
    fi
    perl -pi -e 's/(int main.*\{)/${1}::testing::InitGoogleTest(&argc, argv);/g' $file
    perl -pi -e 's/rocksdb::test::RunAllTests/RUN_ALL_TESTS/g' $file
  fi
done
% sh ~/transform
% make format
```

Second iteration of this diff contains only scripted changes.

Third iteration contains manual changes to fix last errors and make it compilable.

Test Plan:
Build and notice no errors.
```lang=bash
% USE_CLANG=1 make check -j55
```
Tests are still testing.

Reviewers: meyering, sdong, rven, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D35157
2015-03-17 14:08:00 -07:00
Igor Sugak
9fd6edf81c rocksdb: Replace ASSERT* with EXPECT* in functions that does not return void value
Summary:
gtest does not use exceptions to fail a unit test by design, and `ASSERT*`s are implemented using `return`. As a consequence we cannot use `ASSERT*` in a function that does not return `void` value ([[ https://code.google.com/p/googletest/wiki/AdvancedGuide#Assertion_Placement | 1]]), and have to fix our existing code. This diff does this in a generic way, with no manual changes.

In order to detect all existing `ASSERT*` that are used in functions that doesn't return void value, I change the code to generate compile errors for such cases.

In `util/testharness.h` I defined `EXPECT*` assertions, the same way as `ASSERT*`, and redefined `ASSERT*` to return `void`. Then executed:

```lang=bash
% USE_CLANG=1 make all -j55 -k 2> build.log
% perl -naF: -e 'print "-- -number=".$F[1]." ".$F[0]."\n" if  /: error:/' \
build.log | xargs -L 1 perl -spi -e 's/ASSERT/EXPECT/g if $. == $number'
% make format
```
After that I reverted back change to `ASSERT*` in `util/testharness.h`. But preserved introduced `EXPECT*`, which is the same as `ASSERT*`. This will be deleted once switched to gtest.

This diff is independent and contains manual changes only in `util/testharness.h`.

Test Plan:
Make sure all tests are passing.
```lang=bash
% USE_CLANG=1 make check
```

Reviewers: igor, lgalanis, sdong, yufei.zhu, rven, meyering

Reviewed By: meyering

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D33333
2015-03-16 20:52:32 -07:00
Igor Canadi
b9ff6b050d Fix a bug in ReadOnlyBackupEngine
Summary:
This diff fixes a bug introduced by D28521. Read-only backup engine can delete a backup that is later than the latest -- we never check the condition.

I also added a bunch of logging that will help with debugging cases like this in the future.

See more discussion at t6218248.

Test Plan: Added a unit test that was failing before the change. Also, see new LOG file contents: https://phabricator.fb.com/P19738984

Reviewers: benj, sanketh, sumeet, yhchiang, rven, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D33897
2015-02-27 14:03:56 -08:00
Igor Sugak
62247ffa3b rocksdb: Add missing override
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
2015-02-26 11:28:41 -08:00
Hasnain Lakhani
373c665edf Fix broken test in 31b02d.
Summary:
CorruptionTest for backupable_db_test did not call
GarbageCollect() after deleting a corrupt backup,
which sometimes lead to test failures as the newly created backup
would reuse the same backup ID and files and fail the consistency
check.

Moved around some of the test logic to ensure that GarbageCollect()
is called at the right time.

Test Plan:
Run backupable_db_test eight times and make sure
it passes repeatedly. Also run make check to make sure other
tests don't fail.

Reviewers: igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D28863
2014-11-13 14:46:30 -08:00
Hasnain Lakhani
31b02dc21d Improve Backup Engine.
Summary:
Improve the backup engine by not deleting the corrupted
backup when it is detected; instead leaving it to the client
to delete the corrupted backup.

Also add a BackupEngine::Open() call.

Test Plan:
Add check to CorruptionTest inside backupable_db_test
to check that the corrupt backups are not deleted. The previous
version of the code failed this test as backups were deleted,
but after the changes in this commit, this test passes.

Run make check to ensure that no other tests fail.

Reviewers: sdong, benj, sanketh, sumeet, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D28521
2014-11-13 09:51:41 -08:00
Danny Al-Gaaf
9d6f380866 backupable_db_test.cc: pass const string param by reference
Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
2014-10-01 11:57:01 +02:00
Igor Canadi
a4816269f1 Relax backupable rate limiting test 2014-09-04 10:22:58 -07:00
Igor Canadi
0ff183a0d9 Move include/utilities/*.h to include/rocksdb/utilities/*.h
Summary:
All public headers need to be under `include/rocksdb` directory. Otherwise, clients include our header files like this:

    #include <rocksdb/db.h>
    #include <utilities/backupable_db.h> // still our public header!

Also, internally, we include:

    #include "utilities/backupable/backupable_db.h" // internal header
    #include "utilities/backupable_db.h" // public header

which is confusing.

This way, when we install rocksdb as a system library, we can just copy `include/rocksdb` directory to system's header files. We can't really copy `utilities` directory to system's header files.

Test Plan: compiles

Reviewers: dhruba, ljin, yhchiang, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D20409
2014-07-23 10:21:38 -04:00
Igor Canadi
552c49f0f4 Remove upper bound for rate limiting unit test 2014-06-03 13:58:44 -07:00
Igor Canadi
f725e4fe1f Make RateLimiting unit test less flakey 2014-05-20 17:09:38 -07:00
Igor Canadi
7984b9bbb0 BackupableDBTest thread-safe
Summary: We need to lock accesses to some TestEnv variables. Otherwise we get failures like http://ci-builds.fb.com/job/rocksdb_asan_check/657/console

Test Plan: make check

Reviewers: dhruba, haobo, sdong

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18489
2014-05-05 14:30:24 -07:00
Benjamin Renard
41e5cf2392 Add share_files_with_cheksum option to BackupEngine
Summary: added a new option to BackupEngine: if share_files_with_checksum is set to true, sst files are stored in shared_checksum/ and are identified by the triple (file name, checksum, file size) instead of just the file name. This option is targeted at distributed databases that want to backup their primary replica.

Test Plan: unit tests and tested backup and restore on a distributed rocksdb

Reviewers: igor

Reviewed By: igor

Differential Revision: https://reviews.facebook.net/D18393
2014-05-02 17:08:55 -07:00
Igor Canadi
d6d67c0efe More s/us fixes 2014-04-30 07:04:36 -07:00
Igor Canadi
a618691a3b Read-only BackupEngine
Summary: Read-only BackupEngine can connect to the same backup directory that is already running BackupEngine. That enables some interesting use-cases (i.e. restoring replica from primary's backup directory)

Test Plan: added a unit test

Reviewers: dhruba, haobo, ljin

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18297
2014-04-25 15:49:29 -04:00
Igor Canadi
3d2fe844ab Merge branch 'master' into columnfamilies
Conflicts:
	db/db_impl.cc
	db/db_impl.h
	db/memtable_list.cc
	db/version_set.cc
2014-04-07 11:31:11 -07:00
Igor Canadi
acdc6a1a0d relax backupable db rate limit tests 2014-04-04 16:27:47 -07:00
Igor Canadi
ddbd1ece88 Merge branch 'master' into columnfamilies
Conflicts:
	db/db_impl.cc
	db/db_test.cc
	db/internal_stats.cc
	db/internal_stats.h
	db/version_edit.cc
	db/version_edit.h
	db/version_set.cc
	include/rocksdb/options.h
	util/options.cc
2014-03-31 13:39:24 -07:00
Igor Canadi
5826f9528f Make rate limiting unit test more robust 2014-03-27 11:53:05 -07:00
Igor Canadi
e8168382c4 Merge branch 'master' into columnfamilies
Conflicts:
	db/db_impl.cc
	include/rocksdb/options.h
	util/options.cc
2014-03-25 11:09:40 -07:00
Igor Canadi
e6d4b006b6 Relax backupable RateLimiter unit test for slow environments 2014-03-24 11:59:42 -07:00
Igor Canadi
b253f24403 Rate limiter for BackupableDB
Summary: Might be useful if client doesn't want to effect running system during backup too much.

Test Plan: added a test case

Reviewers: dhruba, haobo, ljin

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17091
2014-03-24 11:38:44 -07:00
Igor Canadi
64904b39a0 Merge branch 'master' into columnfamilies
Conflicts:
	utilities/backupable/backupable_db.cc
2014-03-17 17:57:14 -07:00
Igor Canadi
9caeff516e keep_log_files option in BackupableDB
Summary:
Added an option to BackupableDB implementation that allows users to persist in-memory databases. When the restore happens with keep_log_files = true, it will
*) Not delete existing log files in wal_dir
*) Move log files from archive directory to wal_dir, so that DB can replay them if necessary

Test Plan: Added an unit test

Reviewers: dhruba, ljin

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16941
2014-03-17 15:39:23 -07:00
Igor Canadi
ee4b9966bc DeleteLogFiles in FailOverwritingBackups 2014-03-12 13:47:07 -07:00
Igor Canadi
25c8a1a20f More bug fixed introduced by code cleanup 2014-03-12 12:28:23 -07:00
Igor Canadi
0738ae6dc9 Merge branch 'master' into columnfamilies
Conflicts:
	db/db_impl.cc
2014-03-05 12:25:05 -08:00
Igor Canadi
2b5155fb29 CloseDB in BackupableDBTest to make valgrind happy 2014-03-05 09:00:53 -08:00
Igor Canadi
e3f396f1ea Some fixes to BackupableDB
Summary:
(1) Report corruption if backup meta file has tailing data that was not read. This should fix: https://github.com/facebook/rocksdb/issues/81 (also, @sdong reported similar issue)
(2) Don't use OS buffer when copying file to backup directory. We don't need the file in cache since we won't be reading it twice
(3) Don't delete newer backups when somebody tries to backup the diverged DB (restore from older backup, add new data, try to backup). Rather, just fail the new backup.

Test Plan: backupable_db_test

Reviewers: ljin, dhruba, sdong

Reviewed By: ljin

CC: leveldb, sdong

Differential Revision: https://reviews.facebook.net/D16287
2014-03-04 17:02:25 -08:00
Igor Canadi
ccdb93e775 Merge branch 'master' into columnfamilies
Conflicts:
	db/db_impl.cc
	db/db_impl.h
	db/memtable_list.cc
	db/memtable_list.h
	db/version_set.cc
	db/version_set.h
2014-02-12 14:01:30 -08:00
Igor Canadi
b06840aa7d [CF] Rethinking ColumnFamilyHandle and fix to dropping column families
Summary:
The change to the public behavior:
* When opening a DB or creating new column family client gets a ColumnFamilyHandle.
* As long as column family handle is alive, client can do whatever he wants with it, even drop it
* Dropped column family can still be read from (using the column family handle)
* Added a new call CloseColumnFamily(). Client has to close all column families that he has opened before deleting the DB
* As soon as column family is closed, any calls to DB using that column family handle will fail (also any outstanding calls)

Internally:
* Ref-counting ColumnFamilyData
* New thread-safety for ColumnFamilySet
* Dropped column families are now completely dropped and their memory cleaned-up

Test Plan: added some tests to column_family_test

Reviewers: dhruba, haobo, kailiu, sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16101
2014-02-12 13:47:09 -08:00
Lei Jin
994c327b86 IOError cleanup
Summary: Clean up IOErrors so that it only indicates errors talking to device.

Test Plan: make all check

Reviewers: igor, haobo, dhruba, emayanke

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15831
2014-02-12 11:42:54 -08:00
Igor Canadi
73f62255c1 [CF] Split SanitizeOptions into two
Summary:
There are three SanitizeOption-s now : one for DBOptions, one for ColumnFamilyOptions and one for Options (which just calls the other two)

I have also reshuffled some options -- table_cache options and info_log should live in DBOptions, for example.

Test Plan: make check doesn't complain

Reviewers: dhruba, haobo, kailiu, sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15873
2014-02-04 17:26:51 -08:00
Igor Canadi
20b231d712 Merge branch 'master' into columnfamilies 2014-01-29 11:47:43 -08:00
Igor Canadi
c1071ed95c Merge branch 'master' into columnfamilies 2014-01-28 16:04:00 -08:00
Lei Jin
9a126ba3b3 only corrupt private file checksum in backupable_db_test
Summary:
if it happens (randomly) to corrupt shared file in the test, then the
    checksum will be inconsistent between meta files from different backup.
    BackupEngine will then detect this issue and fail. But in reality, this
    does not happen since the checksum is checked on every backup. So here,
    only corrupt checksum of private file to let BackupEngine to construct
    properly (but fail during restore).

Test Plan: run test with valgrind

Reviewers: igor

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15531
2014-01-28 16:03:55 -08:00
Lei Jin
9dc29414e3 add checksum for backup files
Summary: Keep checksum of each backuped file in meta file. When it restores these files, compute their checksum on the fly and compare against what is in the meta file. Fail the restore process if checksum mismatch.

Test Plan: unit test

Reviewers: haobo, igor, sdong, kailiu

Reviewed By: igor

CC: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D15381
2014-01-28 09:43:36 -08:00
Igor Canadi
151f9e144f Merge branch 'master' into columnfamilies 2014-01-13 09:09:51 -08:00
Igor Canadi
cb37ddf229 Feature requests for BackupableDB
Summary:
This diff introduces some features that were requested by two internal customers:
* Ability for backups not to share table files, because we can't guarantee that equal filename means equal content accross replicas
* Ability for two threads to call EnableFileDeletions() and DisableFileDeletions()
* Ability to stop backup from another thread and not slow down the DB close
* Copy the files to the temporary folder first and then atomically rename

Test Plan: Added some tests to backupable_db_test

Reviewers: dhruba, sanketh, muthu, sdong, haobo

Reviewed By: haobo

CC: leveldb, sanketh, muthu

Differential Revision: https://reviews.facebook.net/D14769
2014-01-09 12:24:28 -08:00
Igor Canadi
6de1b5b83e Merge branch 'master' into columnfamilies 2014-01-02 04:18:07 -08:00
Igor Canadi
b60c14f6ee Support multi-threaded DisableFileDeletions() and EnableFileDeletions()
Summary:
We don't want two threads to clash if they concurrently call DisableFileDeletions() and EnableFileDeletions(). I'm adding a counter that will enable file deletions only after all DisableFileDeletions() calls have been negated with EnableFileDeletions().

However, we also don't want to break the old behavior, so I added a parameter force to EnableFileDeletions(). If force is true, we will still enable file deletions after every call to EnableFileDeletions(), which is what is happening now.

Test Plan: make check

Reviewers: dhruba, haobo, sanketh

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14781
2014-01-02 03:33:42 -08:00
Igor Canadi
9385a5247e [RocksDB] [Column Family] Interface proposal
Summary:
<This diff is for Column Family branch>

Sharing some of the work I've done so far. This diff compiles and passes the tests.

The biggest change is in options.h - I broke down Options into two parts - DBOptions and ColumnFamilyOptions. DBOptions is DB-specific (env, create_if_missing, block_cache, etc.) and ColumnFamilyOptions is column family-specific (all compaction options, compresion options, etc.). Note that this does not break backwards compatibility at all.

Further, I created DBWithColumnFamily which inherits DB interface and adds new functions with column family support. Clients can transparently switch to DBWithColumnFamily and it will not break their backwards compatibility.
There are few methods worth checking out: ListColumnFamilies(), MultiNewIterator(), MultiGet() and GetSnapshot(). [GetSnapshot() returns the snapshot across all column families for now - I think that's what we agreed on]

Finally, I made small changes to WriteBatch so we are able to atomically insert data across column families.

Please provide feedback.

Test Plan: make check works, the code is backward compatible

Reviewers: dhruba, haobo, sdong, kailiu, emayanke

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14445
2013-12-18 13:08:22 -08:00
Igor Canadi
5e4ab767cf BackupableDB delete backups with newer seq number
Summary: We now delete backups with newer sequence number, so the clients don't have to handle confusing situations when they restore from backup.

Test Plan: added a unit test

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14547
2013-12-10 20:49:28 -08:00
Siying Dong
4815468be4 Fix another sign and unsign comparison in test 2013-12-10 10:52:47 -08:00
Igor Canadi
cbe7ffef9a fix comparison between signed and unsigned 2013-12-10 10:48:49 -08:00
Igor Canadi
7cf5728440 Cleaning up BackupableDB + fix valgrind errors
Summary: Valgrind complained about BackupableDB. This fixes valgrind errors. Also, I cleaned up some code.

Test Plan: valgrind does not complain anymore

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14529
2013-12-10 10:35:06 -08:00
Igor Canadi
fb9fce4fc3 [RocksDB] BackupableDB
Summary:
In this diff I present you BackupableDB v1. You can easily use it to backup your DB and it will do incremental snapshots for you.
Let's first describe how you would use BackupableDB. It's inheriting StackableDB interface so you can easily construct it with your DB object -- it will add a method RollTheSnapshot() to the DB object. When you call RollTheSnapshot(), current snapshot of the DB will be stored in the backup dir. To restore, you can just call RestoreDBFromBackup() on a BackupableDB (which is a static method) and it will restore all files from the backup dir. In the next version, it will even support automatic backuping every X minutes.

There are multiple things you can configure:
1. backup_env and db_env can be different, which is awesome because then you can easily backup to HDFS or wherever you feel like.
2. sync - if true, it *guarantees* backup consistency on machine reboot
3. number of snapshots to keep - this will keep last N snapshots around if you want, for some reason, be able to restore from an earlier snapshot. All the backuping is done in incremental fashion - if we already have 00010.sst, we will not copy it again. *IMPORTANT* -- This is based on assumption that 00010.sst never changes - two files named 00010.sst from the same DB will always be exactly the same. Is this true? I always copy manifest, current and log files.
4. You can decide if you want to flush the memtables before you backup, or you're fine with backing up the log files -- either way, you get a complete and consistent view of the database at a time of backup.
5. More things you can find in BackupableDBOptions

Here is the directory structure I use:

   backup_dir/CURRENT_SNAPSHOT - just 4 bytes holding the latest snapshot
               0, 1, 2, ... - files containing serialized version of each snapshot - containing a list of files
               files/*.sst - sst files shared between snapshots - if one snapshot references 00010.sst and another one needs to backup it from the DB, it will just reference the same file
               files/ 0/, 1/, 2/, ... - snapshot directories containing private snapshot files - current, manifest and log files

All the files are ref counted and deleted immediatelly when they get out of scope.

Some other stuff in this diff:
1. Added GetEnv() method to the DB. Discussed with @haobo and we agreed that it seems right thing to do.
2. Fixed StackableDB interface. The way it was set up before, I was not able to implement BackupableDB.

Test Plan:
I have a unittest, but please don't look at this yet. I just hacked it up to help me with debugging. I will write a lot of good tests and update the diff.

Also, `make asan_check`

Reviewers: dhruba, haobo, emayanke

Reviewed By: dhruba

CC: leveldb, haobo

Differential Revision: https://reviews.facebook.net/D14295
2013-12-09 14:06:52 -08:00