Export BackupEngine

Summary:
Lots of clients have problems with using StackableDB interface. It's nice to have BackupableDB as a layer on top of DB, but not necessary.

This diff exports BackupEngine, which can be used to create backups without forcing clients to use StackableDB interface.

Test Plan: backupable_db_test

Reviewers: dhruba, ljin, swk

Reviewed By: ljin

CC: leveldb, benj

Differential Revision: https://reviews.facebook.net/D15477
Better interface to create BackupEngine

Summary: I think it looks nicer. In RocksDB we have both styles, but I think that static method is the more common version.

Test Plan: backupable_db_test

Reviewers: ljin, benj, swk

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15519
Only get the manifest file size if there is no error

Summary:
I came across this while working on column families. CorruptionTest::RecoverWriteError threw a SIGSEG because the descriptor_log_->file() was nullptr. I'm not sure why it doesn't happen in master, but better safe than sorry.

@kailiu, can we get this in release, too?

Test Plan: make check

Reviewers: kailiu, dhruba, haobo

Reviewed By: haobo

CC: leveldb, kailiu

Differential Revision: https://reviews.facebook.net/D15513
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
Add history log and revise script

Summary:
* Add a change log for rocksdb releases.
* Remove the hacky parts of make_new_version.sh, which are either
  no longer useful or will be done in our dedicated 3rd-party release
  tool.

Test Plan: N/A

Reviewers: igor, haobo, sdong, dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15543
add include <atomic> to version_set.h
Installation instructions for CentOS
Improve make_new_version.sh
Canonicalize "RocksDB" in make_new_version.sh

Summary: Change all occurrences of "rocksdb" to its canonical form "RocksDB".

Test Plan: N/A

Reviewers: igor

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15549
LIBNAME in Makefile is not really configurable

Summary:
In new third-party release tool, `LIBNAME=<customized_library> make`
will not really change the LIBNAME.

However it's very odd that the same approach works with old third-party
release tools. I checked previous rocksdb version and both librocksdb.a
and librocksdb_debug.a were correctly generated and copied to the
right place.

Test Plan:
`LIBNAME=hello make -j32` generates hello.a
`make -j32` generates librocksdb.a

Reviewers: igor, sdong, haobo, dhruba

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15555
convert Tickers back to array with padding and alignment

Summary:
Pad each Ticker structure to be 64 bytes and make them align on 64 bytes
boundary to avoid cache line false sharing issue.
Please refer to task 3615553 for more details

Test Plan:
db_bench

LevelDB:    version 2.0s
Date:       Wed Jan 29 12:23:17 2014
CPU:        32 * Intel(R) Xeon(R) CPU E5-2660 0 @ 2.20GHz
CPUCache:   20480 KB
rocksdb.build.overwrite.qps 49638
rocksdb.build.overwrite.p50_micros 58.73
rocksdb.build.overwrite.p75_micros 210.56
rocksdb.build.overwrite.p99_micros 733.28
rocksdb.build.fillseq.qps 366729
rocksdb.build.fillseq.p50_micros 1.00
rocksdb.build.fillseq.p75_micros 1.00
rocksdb.build.fillseq.p99_micros 2.65
rocksdb.build.readrandom.qps 1152995
rocksdb.build.readrandom.p50_micros 11.27
rocksdb.build.readrandom.p75_micros 15.69
rocksdb.build.readrandom.p99_micros 33.59
rocksdb.build.readrandom_smallblockcache.qps 956047
rocksdb.build.readrandom_smallblockcache.p50_micros 15.23
rocksdb.build.readrandom_smallblockcache.p75_micros 17.31
rocksdb.build.readrandom_smallblockcache.p99_micros 31.49
rocksdb.build.readrandom_memtable_sst.qps 1105183
rocksdb.build.readrandom_memtable_sst.p50_micros 12.04
rocksdb.build.readrandom_memtable_sst.p75_micros 15.78
rocksdb.build.readrandom_memtable_sst.p99_micros 32.49
rocksdb.build.readrandom_fillunique_random.qps 487856
rocksdb.build.readrandom_fillunique_random.p50_micros 29.65
rocksdb.build.readrandom_fillunique_random.p75_micros 40.93
rocksdb.build.readrandom_fillunique_random.p99_micros 78.68
rocksdb.build.memtablefillrandom.qps 91304
rocksdb.build.memtablefillrandom.p50_micros 171.05
rocksdb.build.memtablefillrandom.p75_micros 196.12
rocksdb.build.memtablefillrandom.p99_micros 291.73
rocksdb.build.memtablereadrandom.qps 1340411
rocksdb.build.memtablereadrandom.p50_micros 9.48
rocksdb.build.memtablereadrandom.p75_micros 13.95
rocksdb.build.memtablereadrandom.p99_micros 30.36
rocksdb.build.readwhilewriting.qps 491004
rocksdb.build.readwhilewriting.p50_micros 29.58
rocksdb.build.readwhilewriting.p75_micros 40.34
rocksdb.build.readwhilewriting.p99_micros 76.78

Reviewers: igor, haobo

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15573
set bg_error_ when background flush goes wrong

Summary: as title

Test Plan: unit test

Reviewers: haobo, igor, sdong, kailiu, dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15435
InternalStatistics

Summary:
In DBImpl we keep track of some statistics internally and expose them via GetProperty(). This diff encapsulates all the internal statistics into a class InternalStatisics. Most of it is copy/paste.

Apart from cleaning up db_impl.cc, this diff is also necessary for Column families, since every column family should have its own CompactionStats, MakeRoomForWrite-stall stats, etc. It's much easier to keep track of it in every column family if it's nicely encapsulated in its own class.

Test Plan: make check

Reviewers: dhruba, kailiu, haobo, sdong, emayanke

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15273
Merge branch 'master' into performance

Conflicts:
	db/db_impl.h