Summary:
Rename PickCompactionHybrid to PickCompactionUniversal.
Changed a few LOG message from "Hybrid:" to "Universal:".

Test Plan:

Reviewers:

CC:

Task ID: #

Blame Rev:

Summary:
There is a new option called hybrid_mode which, when switched on,
causes HBase style compactions.  Files from L0 are
compacted back into L0. This meat of this compaction algorithm
is in PickCompactionHybrid().

All files reside in L0. That means all files have overlapping
keys. Each file has a time-bound, i.e. each file contains a
range of keys that were inserted around the same time. The
start-seqno and the end-seqno refers to the timeframe when
these keys were inserted.  Files that have contiguous seqno
are compacted together into a larger file. All files are
ordered from most recent to the oldest.

The current compaction algorithm starts to look for
candidate files starting from the most recent file. It continues to
add more files to the same compaction run as long as the
sum of the files chosen till now is smaller than the next
candidate file size. This logic needs to be debated
and validated.

The above logic should reduce write amplification to a
large extent... will publish numbers shortly.

Test Plan: dbstress runs for 6 hours with no data corruption (tested so far).

Differential Revision: https://reviews.facebook.net/D11289

Summary:
There is a new option called hybrid_mode which, when switched on,
causes HBase style compactions.  Files from L0 are
compacted back into L0. This meat of this compaction algorithm
is in PickCompactionHybrid().

All files reside in L0. That means all files have overlapping
keys. Each file has a time-bound, i.e. each file contains a
range of keys that were inserted around the same time. The
start-seqno and the end-seqno refers to the timeframe when
these keys were inserted.  Files that have contiguous seqno
are compacted together into a larger file. All files are
ordered from most recent to the oldest.

The current compaction algorithm starts to look for
candidate files starting from the most recent file. It continues to
add more files to the same compaction run as long as the
sum of the files chosen till now is smaller than the next
candidate file size. This logic needs to be debated
and validated.

The above logic should reduce write amplification to a
large extent... will publish numbers shortly.

Test Plan: dbstress runs for 6 hours with no data corruption (tested so far).

Differential Revision: https://reviews.facebook.net/D11289

Summary:
This diff simplifies EnvOptions by treating it as POD, similar to Options.
- virtual functions are removed and member fields are accessed directly.
- StorageOptions is removed.
- Options.allow_readahead and Options.allow_readahead_compactions are deprecated.
- Unused global variables are removed: useOsBuffer, useFsReadAhead, useMmapRead, useMmapWrite

Test Plan: make check; db_stress

Reviewers: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D11175

Summary: Added the 'score' column to the compaction stats output, which shows the level total size devided by level target size. Could be useful when monitoring compaction decisions...

Test Plan: make check; db_bench

Reviewers: dhruba

CC: leveldb, MarkCallaghan

Differential Revision: https://reviews.facebook.net/D11025

Summary:
This diff introduces a new Merge operation into rocksdb.
The purpose of this review is mostly getting feedback from the team (everyone please) on the design.

Please focus on the four files under include/leveldb/, as they spell the client visible interface change.
include/leveldb/db.h
include/leveldb/merge_operator.h
include/leveldb/options.h
include/leveldb/write_batch.h

Please go over local/my_test.cc carefully, as it is a concerete use case.

Please also review the impelmentation files to see if the straw man implementation makes sense.

Note that, the diff does pass all make check and truly supports forward iterator over db and a version
of Get that's based on iterator.

Future work:
- Integration with compaction
- A raw Get implementation

I am working on a wiki that explains the design and implementation choices, but coding comes
just naturally and I think it might be a good idea to share the code earlier. The code is
heavily commented.

Test Plan: run all local tests

Reviewers: dhruba, heyongqiang

Reviewed By: dhruba

CC: leveldb, zshao, sheki, emayanke, MarkCallaghan

Differential Revision: https://reviews.facebook.net/D9651

Summary: Simplified level_ptrs by using a std:vector

Test Plan: make check

Reviewers: sheki, emayanke

Reviewed By: emayanke

CC: leveldb

Differential Revision: https://reviews.facebook.net/D10245

Summary:
FindObsoleteFiles was slow, holding the single big lock, resulted in bad p99 behavior.
Didn't profile anything, but several things could be improved:
1. VersionSet::AddLiveFiles works with std::set, which is by itself slow (a tree).
   You also don't know how many dynamic allocations occur just for building up this tree.
   switched to std::vector, also added logic to pre-calculate total size and do just one allocation
2. Don't see why env_->GetChildren() needs to be mutex proteced, moved to PurgeObsoleteFiles where
   mutex could be unlocked.
3. switched std::set to std:unordered_set, the conversion from vector is also inside PurgeObsoleteFiles
I have a feeling this should pretty much fix it.

Test Plan: make check;  db_stress

Reviewers: dhruba, heyongqiang, MarkCallaghan

Reviewed By: dhruba

CC: leveldb, zshao

Differential Revision: https://reviews.facebook.net/D10197

Summary:
This patch allows an application to specify whether to use bufferedio,
reads-via-mmaps and writes-via-mmaps per database. Earlier, there
was a global static variable that was used to configure this functionality.

The default setting remains the same (and is backward compatible):
 1. use bufferedio
 2. do not use mmaps for reads
 3. use mmap for writes
 4. use readaheads for reads needed for compaction

I also added a parameter to db_bench to be able to explicitly specify
whether to do readaheads for compactions or not.

Test Plan: make check

Reviewers: sheki, heyongqiang, MarkCallaghan

Reviewed By: sheki

CC: leveldb

Differential Revision: https://reviews.facebook.net/D9429

Summary: Makefile had options to ignore sign-comparisons and unused-parameters, which should be there. Also fixed the specific errors in the code-base

Test Plan: make

Reviewers: chip, dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D9531

Summary:
SizeBeingCompacted was called without any lock protection. This causes
crashes, especially when running db_bench with value_size=128K.
The fix is to compute SizeUnderCompaction while holding the mutex and
passing in these values into the call to Finalize.

(gdb) where
#4  leveldb::VersionSet::SizeBeingCompacted (this=this@entry=0x7f0b490931c0, level=level@entry=4) at db/version_set.cc:1827
#5  0x000000000043a3c8 in leveldb::VersionSet::Finalize (this=this@entry=0x7f0b490931c0, v=v@entry=0x7f0b3b86b480) at db/version_set.cc:1420
#6  0x00000000004418d1 in leveldb::VersionSet::LogAndApply (this=0x7f0b490931c0, edit=0x7f0b3dc8c200, mu=0x7f0b490835b0, new_descriptor_log=<optimized out>) at db/version_set.cc:1016
#7  0x00000000004222b2 in leveldb::DBImpl::InstallCompactionResults (this=this@entry=0x7f0b49083400, compact=compact@entry=0x7f0b2b8330f0) at db/db_impl.cc:1473
#8  0x0000000000426027 in leveldb::DBImpl::DoCompactionWork (this=this@entry=0x7f0b49083400, compact=compact@entry=0x7f0b2b8330f0) at db/db_impl.cc:1757
#9  0x0000000000426690 in leveldb::DBImpl::BackgroundCompaction (this=this@entry=0x7f0b49083400, madeProgress=madeProgress@entry=0x7f0b41bf2d1e, deletion_state=...) at db/db_impl.cc:1268
#10 0x0000000000428f42 in leveldb::DBImpl::BackgroundCall (this=0x7f0b49083400) at db/db_impl.cc:1170
#11 0x000000000045348e in BGThread (this=0x7f0b49023100) at util/env_posix.cc:941
#12 leveldb::(anonymous namespace)::PosixEnv::BGThreadWrapper (arg=0x7f0b49023100) at util/env_posix.cc:874
#13 0x00007f0b4a7cf10d in start_thread (arg=0x7f0b41bf3700) at pthread_create.c:301
#14 0x00007f0b49b4b11d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:115

Test Plan:
make check

I am running db_bench with a value size of 128K to see if the segfault is fixed.

Reviewers: MarkCallaghan, sheki, emayanke

Reviewed By: sheki

CC: leveldb

Differential Revision: https://reviews.facebook.net/D9279

Summary:
This adds the rate_delay_limit_milliseconds option to make the delay
configurable in MakeRoomForWrite when the max compaction score is too high.
This delay is called the Ln slowdown. This change also counts the Ln slowdown
per level to make it possible to see where the stalls occur.

From IO-bound performance testing, the Level N stalls occur:
* with compression -> at the largest uncompressed level. This makes sense
                      because compaction for compressed levels is much
                      slower. When Lx is uncompressed and Lx+1 is compressed
                      then files pile up at Lx because the (Lx,Lx+1)->Lx+1
                      compaction process is the first to be slowed by
                      compression.
* without compression -> at level 1

Task ID: #1832108

Blame Rev:

Test Plan:
run with real data, added test

Revert Plan:

Database Impact:

Memcache Impact:

Other Notes:

EImportant:

- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -

Reviewers: dhruba

Reviewed By: dhruba

Differential Revision: https://reviews.facebook.net/D9045

Summary:
scripted NULL to nullptr in
* include/leveldb/
* db/
* table/
* util/

Test Plan: make all check

Reviewers: dhruba, emayanke

Reviewed By: emayanke

CC: leveldb

Differential Revision: https://reviews.facebook.net/D9003

Summary:
On some filesystems, pre-allocation can be a considerable
amount of space.  xfs in our production environment pre-allocates by
1GB, for instance.  By using fallocate to inform the kernel of our
expected file sizes, we eliminate this wasteage (that isn't recovered
until the file is closed which, in the case of LOG files, can be a
considerable amount of time).

Test Plan:
created an xfs loopback filesystem, mounted with
allocsize=4M, and ran db_stress.  LOG file without this change was 4M,
and with it it was 128k then grew to normal size.

Reviewers: dhruba

Reviewed By: dhruba

CC: adsharma, leveldb

Differential Revision: https://reviews.facebook.net/D7953

Summary:
Replace manual memory management with std::unique_ptr in a
number of places; not exhaustive, but this fixes a few leaks with file
handles as well as clarifies semantics of the ownership of file handles
with log classes.

Test Plan: db_stress, make check

Reviewers: dhruba

Reviewed By: dhruba

CC: zshao, leveldb, heyongqiang

Differential Revision: https://reviews.facebook.net/D8043

Summary:
Check in LogAndApply if the file size is more than the limit set in
Options.
Things to consider : will this be expensive?

Test Plan: make all check. Inputs on a new unit test?

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D7701

Summary: Due to how the code handled compactions in Level 0 in `PickCompaction()` it could be the case that two compactions on level 0 ran that produced tables in level 1 that overlap. However, this case seems like it would only occur on a seek compaction which is unlikely on level 0. Furthermore, level 0 and level 1 had to have a certain arrangement of files.

Test Plan:
make check

Reviewers: dhruba, vamsi

Reviewed By: dhruba

CC: leveldb, sheki

Differential Revision: https://reviews.facebook.net/D7923

Summary:
Pretty much a blind copy of the patch in open source.
Hope to get this in before we make a release

Test Plan: make clean check

Reviewers: dhruba, heyongqiang

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D7809

Summary: Without this option, manifest_dump does not print binary keys for files in a human-readable way.

Test Plan:
./manifest_dump --hex=1 --verbose=0 --file=/data/users/zshao/fdb_comparison/leveldb/fbobj.apprequest-0_0_original/MANIFEST-000002
manifest_file_number 589 next_file_number 590 last_sequence 2311567 log_number 543  prev_log_number 0
--- level 0 --- version# 0 ---
 532:1300357['0000455BABE20000' @ 2183973 : 1 .. 'FFFCA5D7ADE20000' @ 2184254 : 1]
 536:1308170['000198C75CE30000' @ 2203313 : 1 .. 'FFFCF94A79E30000' @ 2206463 : 1]
 542:1321644['0002931AA5E50000' @ 2267055 : 1 .. 'FFF77B31C5E50000' @ 2270754 : 1]
 544:1286390['000410A309E60000' @ 2278592 : 1 .. 'FFFE470A73E60000' @ 2289221 : 1]
 538:1298778['0006BCF4D8E30000' @ 2217050 : 1 .. 'FFFD77DAF7E30000' @ 2220489 : 1]
 540:1282353['00090D5356E40000' @ 2231156 : 1 .. 'FFFFF4625CE40000' @ 2231969 : 1]
--- level 1 --- version# 0 ---
 510:2112325['000007F9C2D40000' @ 1782099 : 1 .. '146F5B67B8D80000' @ 1905458 : 1]
 511:2121742['146F8A3023D60000' @ 1824388 : 1 .. '28BC8FBB9CD40000' @ 1777993 : 1]
 512:801631['28BCD396F1DE0000' @ 2080191 : 1 .. '3082DBE9ADDB0000' @ 1989927 : 1]

Reviewers: dhruba, sheki, emayanke

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D7425

Summary:
A compaction is picked based on its score. It is useful to
print the compaction score in the LOG because it aids in
debugging. If one looks at the logs, one can find out why
a compaction was preferred over another.

Test Plan: make clean check

Differential Revision: https://reviews.facebook.net/D7137

Summary:
Scripted and removed all trailing spaces and converted all tabs to
spaces.

Also fixed other lint errors.
All lint errors from this point of time should be taken seriously.

Test Plan: make all check

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D7059

Summary:
When we expand the range of keys for a level 0 compaction, we
need to invoke ParentFilesInCompaction() only once for the
entire range of keys that is being compacted. We were invoking
it for each file that was being compacted, but this triggers
an assertion because each file's range were contiguous but
non-overlapping.

I renamed ParentFilesInCompaction to ParentRangeInCompaction
to adequately represent that it is the range-of-keys and
not individual files that we compact in a single compaction run.

Here is the assertion that is fixed by this patch.
db_test: db/version_set.cc:585: void leveldb::Version::ExtendOverlappingInputs(int, const leveldb::Slice&, const leveldb::Slice&, std::vector<leveldb::FileMetaData*, std::allocator<leveldb::FileMetaData*> >*, int): Assertion `user_cmp->Compare(flimit, user_begin) >= 0' failed.

Test Plan: make clean check OPT=-g

Reviewers: sheki

Reviewed By: sheki

CC: MarkCallaghan, emayanke, leveldb

Differential Revision: https://reviews.facebook.net/D6963

Summary:
The manifest file contains a series of edits. If the verbose
option is switched on, then print each individual edit in the
manifest file. This helps in debugging.

Test Plan: make clean manifest_dump

Reviewers: emayanke, sheki

Reviewed By: sheki

CC: leveldb

Differential Revision: https://reviews.facebook.net/D6807

Summary:
The manifest file contains a series of edits. If the verbose
option is switched on, then print each individual edit in the
manifest file. This helps in debugging.

Test Plan: make clean manifest_dump

Reviewers: emayanke, sheki

Reviewed By: sheki

CC: leveldb

Differential Revision: https://reviews.facebook.net/D6807

Summary:
When a new version is created, we sort all the files at every
level based on their size. This is necessary because we want
to compact the largest file first. The sorting takes quite a
bit of CPU.

Moved the sorting code to be outside the mutex. Also, the
earlier code was sorting files at all levels but we do not
need to sort the highest-number level because those files
are never the cause of any compaction. To reduce sorting
costs, we sort only the first few files in each level
because it is likely that those are the only files in that
level that will be picked for compaction.

At steady state, I have seen that this patch increase
throughout from 1500 writes/sec to 1700 writes/sec at the
end of a 72 hour run. The cpu saving by not sorting the
last level was not distinctive in this test run because
there were only 100K files in the highest numbered level.
I expect the cpu saving to be significant when the number of
files is much higher.

This is mostly an early preview and not ready for rigorous review.

With this patch, the writs/sec is now bottlenecked not by the sorting code but by GetOverlappingInputs. I am working on a patch to optimize GetOverlappingInputs.

Test Plan: make check

Reviewers: MarkCallaghan, heyongqiang

Reviewed By: heyongqiang

Differential Revision: https://reviews.facebook.net/D6411

Summary:
Fixed compilation error in previous merge.

Test Plan:

Reviewers:

CC:

Task ID: #

Blame Rev:

Summary:
The Version::GetOverlappingInputs() is called multiple times in
the compaction code path. Eack invocation does a binary search
for overlapping files in the specified key range.
This patch remembers the offset of an overlapped file when
GetOverlappingInputs() is called the first time within
a compaction run. Suceeding calls to GetOverlappingInputs()
uses the remembered index to avoid the binary search.

I measured that 1000 iterations of GetOverlappingInputs
takes around 4500 microseconds without this patch. If I use
this patch with the hint on every invocation, then 1000
iterations take about 3900 microsecond.

Test Plan: make check OPT=-g

Reviewers: heyongqiang

Reviewed By: heyongqiang

CC: MarkCallaghan, emayanke, sheki

Differential Revision: https://reviews.facebook.net/D6513

Summary:
The method Version::GetOverlappingInputs used a sequential search
to map a kay-range to a set of files. But the files are arranged
in ascending order of key, so a biary search is more effective.

This patch implements Version::GetOverlappingInputsBinarySearch
that finds one file that corresponds to the specified key range
and then iterates backwards and forwards to find all overlapping
files.

This patch is critical for making compactions efficient, especially
when there are thousands of files in a single level.

I measured that 1000 iterations of TEST_MaxNextLevelOverlappingBytes
takes 16000 microseconds without this patch. With this patch, the
same method takes about 4600 microseconds.

Test Plan: Almost all unit tests in db_test uses this method to lookup keys.

Reviewers: heyongqiang

Reviewed By: heyongqiang

CC: MarkCallaghan, emayanke, sheki

Differential Revision: https://reviews.facebook.net/D6465

Summary: as subject.

Test Plan: manually test it, will add a testcase

Reviewers: dhruba, MarkCallaghan

Differential Revision: https://reviews.facebook.net/D6345

Summary:
Adds a method that returns the score for the next level that most
needs compaction. That method is then used by db_bench to rate limit threads.
Threads are put to sleep at the end of each stats interval until the score
is less than the limit. The limit is set via the --rate_limit=$double option.
The specified value must be > 1.0. Also adds the option --stats_per_interval
to enable additional metrics reported every stats interval.

Task ID: #

Blame Rev:

Test Plan:
run db_bench

Revert Plan:

Database Impact:

Memcache Impact:

Other Notes:

EImportant:

- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -

Reviewers: dhruba

Reviewed By: dhruba

Differential Revision: https://reviews.facebook.net/D6243

Summary:
It is best if we pick the largest file to compact in a level.
This reduces the write amplification factor for compactions.
Each level has an auxiliary data structure called files_by_size_
that sorts all files by their size. This data structure is
updated when a new version is created.

Test Plan: make check

Differential Revision: https://reviews.facebook.net/D6195

Summary: as subject

Test Plan: compile

Reviewers: dhruba

Reviewed By: dhruba

CC: MarkCallaghan

Differential Revision: https://reviews.facebook.net/D6117

published in https://reviews.facebook.net/D5997.

Summary:
This patch allows compaction to occur in multiple background threads
concurrently.

If a manual compaction is issued, the system falls back to a
single-compaction-thread model. This is done to ensure correctess
and simplicity of code. When the manual compaction is finished,
the system resumes its concurrent-compaction mode automatically.

The updates to the manifest are done via group-commit approach.

Test Plan: run db_bench

Summary:
The GetLiveFiles() api lists the set of sst files and the current
MANIFEST file. But the database continues to append new data to the
MANIFEST file even when the application is backing it up to the
backup location. This means that the database-version that is
stored in the MANIFEST FILE in the backup location
does not correspond to the sst files returned by GetLiveFiles.

This API adds a new parameter to GetLiveFiles. This new parmeter
returns the current size of the MANIFEST file.

Test Plan: Unit test attached.

Reviewers: heyongqiang

Reviewed By: heyongqiang

Differential Revision: https://reviews.facebook.net/D5631

Summary:
A set of apis that allows an application to backup data from the
leveldb database based on a set of files.

Test Plan: unint test attached. more coming soon.

Reviewers: heyongqiang

Reviewed By: heyongqiang

Differential Revision: https://reviews.facebook.net/D5439

Summary:
Clean up compiler warnings generated by -Wall option.
make clean all OPT=-Wall

This is a pre-requisite before making a new release.

Test Plan: compile and run unit tests

Reviewers: heyongqiang

Reviewed By: heyongqiang

Differential Revision: https://reviews.facebook.net/D5019

Summary:

as subject

Test Plan:

db_test table_test

Reviewers: dhruba

Summary:
as subject.

A new log is written to scribe via thrift client when a new db is opened and when there is
a compaction.

a new option var scribe_log_db_stats is added.

Test Plan: manually checked using command "ptail -time 0 leveldb_deploy_stats"

Reviewers: dhruba

Differential Revision: https://reviews.facebook.net/D4659

Summary:
./manifest_dump --file=/tmp/dbbench/MANIFEST-000002

Output looks like

manifest_file_number 30 next_file_number 31 last_sequence 388082 log_number 28  prev_log_number 0
--- level 0 ---
--- level 1 ---
--- level 2 ---
 5:3244155['0000000000000000' @ 1 : 1 .. '0000000000028220' @ 28221 : 1]
 7:3244177['0000000000028221' @ 28222 : 1 .. '0000000000056441' @ 56442 : 1]
 9:3244156['0000000000056442' @ 56443 : 1 .. '0000000000084662' @ 84663 : 1]
 11:3244178['0000000000084663' @ 84664 : 1 .. '0000000000112883' @ 112884 : 1]
 13:3244158['0000000000112884' @ 112885 : 1 .. '0000000000141104' @ 141105 : 1]
 15:3244176['0000000000141105' @ 141106 : 1 .. '0000000000169325' @ 169326 : 1]
 17:3244156['0000000000169326' @ 169327 : 1 .. '0000000000197546' @ 197547 : 1]
 19:3244178['0000000000197547' @ 197548 : 1 .. '0000000000225767' @ 225768 : 1]
 21:3244155['0000000000225768' @ 225769 : 1 .. '0000000000253988' @ 253989 : 1]
 23:3244179['0000000000253989' @ 253990 : 1 .. '0000000000282209' @ 282210 : 1]
 25:3244157['0000000000282210' @ 282211 : 1 .. '0000000000310430' @ 310431 : 1]
 27:3244176['0000000000310431' @ 310432 : 1 .. '0000000000338651' @ 338652 : 1]
 29:3244156['0000000000338652' @ 338653 : 1 .. '0000000000366872' @ 366873 : 1]
--- level 3 ---
--- level 4 ---
--- level 5 ---
--- level 6 ---

Test Plan: run on test directory created by dbbench

Reviewers: heyongqiang

Reviewed By: heyongqiang

CC: hustliubo

Differential Revision: https://reviews.facebook.net/D4743

Summary:
add compaction summary to log

log looks like:

2012/08/17-18:18:32.557334 7fdcaa2bb700 Compaction summary: Base level 0, input file:[11 9 7 ],[]

Test Plan: tested via db_test

Reviewers: dhruba

Differential Revision: https://reviews.facebook.net/D4749