Memory issue fix in c_simple_example

Valgrind report prior to this fix:
==20829== Memcheck, a memory error detector
==20829== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==20829== Using Valgrind-3.10.0.SVN and LibVEX; rerun with -h for copyright info
==20829== Command: ./c_simple_example
==20829==
==20829== Invalid read of size 1
==20829==    at 0x4C2F1C8: strcmp (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==20829==    by 0x422522: main (in /home/user/rocksgit/transfer/rocksdb-git/examples/c_simple_example)
==20829==  Address 0x5f60df5 is 0 bytes after a block of size 5 alloc'd
==20829==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==20829==    by 0x4226D5: CopyString (c.cc:498)
==20829==    by 0x423032: rocksdb_get (c.cc:730)
==20829==    by 0x4224EB: main (in /home/user/rocksgit/transfer/rocksdb-git/examples/c_simple_example)
==20829==
==20829==
==20829== HEAP SUMMARY:
==20829==     in use at exit: 77 bytes in 5 blocks
==20829==   total heap usage: 4,491 allocs, 4,486 frees, 839,216 bytes allocated
==20829==
==20829== LEAK SUMMARY:
==20829==    definitely lost: 5 bytes in 1 blocks
==20829==    indirectly lost: 0 bytes in 0 blocks
==20829==      possibly lost: 0 bytes in 0 blocks
==20829==    still reachable: 72 bytes in 4 blocks
==20829==         suppressed: 0 bytes in 0 blocks
==20829== Rerun with --leak-check=full to see details of leaked memory
==20829==
==20829== For counts of detected and suppressed errors, rerun with: -v
==20829== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

Summary: I'm tired of double-tab when opening build_tools/<something>. This change will make bu<tab> fully complete my path :)

Test Plan: `vi bu<tab>` gives me `vi build_tools/` yay!

Reviewers: yhchiang, rven, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D30639

Summary:
Create a benchmark for testing memtablereps. This diff is a bit rough, but it should do the trick until other bootcampers can clean it up.

Addressing comments
Removed the mutexes
Changed ReadWriteBenchmark to fix number of reads and count the number of writes we can perform in that time.

Test Plan:
Run it.

Below runs pass
./memtablerep_bench --benchmarks fillrandom,readrandom --memtablerep skiplist

./memtablerep_bench --benchmarks fillseq,readseq --memtablerep skiplist

./memtablerep_bench --benchmarks readwrite,seqreadwrite --memtablerep skiplist --num_operations 200 --num_threads 5

./memtablerep_bench --benchmarks fillrandom,readrandom --memtablerep hashskiplist

./memtablerep_bench --benchmarks fillseq,readseq --memtablerep hashskiplist
 --num_scans 2

./memtablerep_bench --benchmarks fillseq,readseq --memtablerep vector

Reviewers: jpaton, ikabiljo, sdong

Reviewed By: sdong

Subscribers: dhruba, ameyag

Differential Revision: https://reviews.facebook.net/D22683

Summary: Add comments in db.h to help users discover their options.

Test Plan: Compile

Reviewers: rven, yhchiang, igor

Reviewed By: igor

Subscribers: MarkCallaghan, yoshinorim, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D31077

Fixed negative numbers comparison in DocumentDB

Summary: Add an extra assert to make sure current version is included in VersionSet::AddLiveFiles().

Test Plan: make all check

Reviewers: yhchiang, rven, igor

Reviewed By: igor

Subscribers: dhruba, hermanlee4, leveldb

Differential Revision: https://reviews.facebook.net/D30819

Summary: During recovery, VersionBuilder::Apply() was called multiple times. If the DB is open for long enough, most of files added earlier will be deleted by later deletes. In current solution, sorting added file happens first and then deletes are applied. In this patch, deletes are applied when possible inside Apply(), which can significantly reduce the sorting time in some cases.

Test Plan:
Add unit tests in version_builder
valgrind_check
Open a manifest of 50MB, with 9K live files. The manifest read time reduced from 1.6 seconds to 0.7 seconds.

Reviewers: rven, yhchiang, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D30765

Summary:
This patch changes concurrency guarantees around ColumnFamilySet::column_families_ and ColumnFamilySet::column_families_data_.

Before:
* When mutating: lock DB mutex and spin lock
* When reading: lock DB mutex OR spin lock

After:
* When mutating: lock DB mutex and be in write thread
* When reading: lock DB mutex or be in write thread

That way, we eliminate the spin lock that protects these hash maps and  simplify concurrency. That means we don't need to lock the spin lock during writing, since writing is mutually exclusive with column family create/drop (the only operations that mutate those hash maps).

With these new restrictions, I also needed to move column family create to the write thread (column family drop was already in the write thread).

Even though we don't need to lock the spin lock during write, impact on performance should be minimal -- the spin lock is almost never busy, so locking it is almost free.

This addresses task t5116919.

Test Plan:
make check

Stress test with lots and lots of column family drop and create:

   time ./db_stress --threads=30 --ops_per_thread=5000000 --max_key=5000 --column_families=200 --clear_column_family_one_in=100000 --verify_before_write=0  --reopen=15 --max_background_compactions=10 --max_background_flushes=10 --db=/fast-rocksdb-tmp/db_stress/

Reviewers: yhchiang, rven, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D30651

Summary: When trivial move commit is done, we log the summary of the input version instead of current. This is inconsistent with other log messages and confusing.

Test Plan: compiles

Reviewers: sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D30939

benchmark.sh won't run through all tests properly if one specifies wal_dir to be different than db directory.

Summary:
A command line like this to run all the tests:
source benchmark.config.sh && nohup ./benchmark.sh 'bulkload,fillseq,overwrite,filluniquerandom,readrandom,readwhilewriting'
where
benchmark.config.sh is:
export DB_DIR=/data/mysql/rocksdata
export WAL_DIR=/txlogs/rockswal
export OUTPUT_DIR=/root/rocks_benchmarking/output

Will fail for the tests that need a new DB .

Also 1) set disable_data_sync=0 and 2) add debug mode to run through all the tests more quickly

Test Plan: run ./benchmark.sh 'debug,bulkload,fillseq,overwrite,filluniquerandom,readrandom,readwhilewriting' and verify that there are no complaints about WAL dir not being empty.

Reviewers: sdong, yhchiang, rven, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D30909

Summary:
Since https://reviews.facebook.net/D16119, we ignore partial tailing writes. Because of that, we no longer need skip_log_error_on_recovery.

The documentation says "Skip log corruption error on recovery (If client is ok with losing most recent changes)", while the option actually ignores any corruption of the WAL (not only just the most recent changes). This is very dangerous and can lead to DB inconsistencies. This was originally set up to ignore partial tailing writes, which we now do automatically (after D16119). I have digged up old task t2416297 which confirms my findings.

Test Plan: There was actually no tests that verified correct behavior of skip_log_error_on_recovery.

Reviewers: yhchiang, rven, dhruba, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D30603

Summary:
This is a serious bug. If paranod_check == true and WAL is corrupted, we don't fail DB::Open(). I tried going into history and it seems we've been doing this for a long long time.

I found this when investigating t5852041.

Test Plan: Added unit test to verify correct behavior.

Reviewers: yhchiang, rven, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D30597

Improve backupable db performance on loading BackupMeta

* Use strtoul() and strtoull() instead of sscanf().
  glibc's sscanf() will do a implicit strlen().

* Move implicit construction of Slice("crc32 ") out of loop.

Summary: CLANG was broken for a recent change in db_ench. Fix it.

Test Plan: Build db_bench using CLANG.

Reviewers: rven, igor, yhchiang

Reviewed By: yhchiang

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D30801

Summary:
Add structures for exposing events and operations.  Event describes
high-level action about a thread such as doing compaciton or
doing flush, while an operation describes lower-level action
of a thread such as reading / writing a SST table, waiting for
mutex.  Events and operations are designed to be independent.
One thread would typically involve in one event and one operation.

Code instrument will be in a separate diff.

Test Plan:
Add unit-tests in thread_list_test
make dbg -j32
./thread_list_test
export ROCKSDB_TESTS=ThreadList
./db_test

Reviewers: ljin, igor, sdong

Reviewed By: sdong

Subscribers: rven, jonahcohen, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D29781

Summary: Having --num_hot_column_families default on fails some existing regression tests. By default turn it off

Test Plan: Run db_bench to make sure it is default off.

Reviewers: yhchiang, rven, igor

Reviewed By: igor

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D30705

Summary: Fixed valgrind issue

Test Plan: valgrind check done

Reviewers: rven, sdong

Reviewed By: sdong

Subscribers: sdong, dhruba

Differential Revision: https://reviews.facebook.net/D30699

Summary:
Add option --num_hot_column_families in db_bench. If it is set, write options will first write to that number of column families, and then move on to next set of hot column families. The working set of column families can be smaller than total number of CFs.

It is to test how RocksDB can handle cold column families

Test Plan: Run db_bench with  --num_hot_column_families set and not set.

Reviewers: yhchiang, rven, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D30663

Summary: Added necessary routines for dumping block based SST with block filter

Test Plan: Added "raw" mode to utility sst_dump

Reviewers: sdong, rven

Reviewed By: rven

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D29679

Fix the Java API build on Mac OS X

Fix the build with -DNDEBUG.

Summary:
Add support to allow nested config for block-based table factory. The format looks like this:

"write_buffer_size=1024;block_based_table_factory={block_size=4k};max_write_buffer_num=2"

Test Plan: unit test

Reviewers: yhchiang, rven, igor, ljin, jonahcohen

Reviewed By: jonahcohen

Subscribers: jonahcohen, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D29223

Dike out the body of VerifyCompactionResult.  With assert() compiled out, the
loop index variable in the inner loop was unused, breaking the build when
-Werror is enabled.

Summary:
GetThreadList() feature depends on the thread creation and destruction, which is currently handled under Env.
This patch moves GetThreadList() feature under Env to better manage the dependency of GetThreadList() feature
on thread creation and destruction.

Renamed ThreadStatusImpl to ThreadStatusUpdater.  Add ThreadStatusUtil, which is a static class contains
utility functions for ThreadStatusUpdater.

Test Plan: run db_test, thread_list_test and db_bench and verify the life cycle of Env and ThreadStatusUpdater is properly managed.

Reviewers: igor, sdong

Reviewed By: sdong

Subscribers: ljin, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D30057

Summary: As title. We shouldn't need to execute flush from compaction if there are dedicated threads doing flushes.

Test Plan: make check

Reviewers: rven, yhchiang, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D30579

Summary:
There are two versions of FindObsoleteFiles():
* full scan, which is executed every 6 hours (and it's terribly slow)
* no full scan, which is executed every time a background process finishes and iterator is deleted

This diff is optimizing the second case (no full scan). Here's what we do before the diff:
* Get the list of obsolete files (files with ref==0). Some files in obsolete_files set might actually be live.
* Get the list of live files to avoid deleting files that are live.
* Delete files that are in obsolete_files and not in live_files.

After this diff:
* The only files with ref==0 that are still live are files that have been part of move compaction. Don't include moved files in obsolete_files.
* Get the list of obsolete files (which exclude moved files).
* No need to get the list of live files, since all files in obsolete_files need to be deleted.

I'll post the benchmark results, but you can get the feel of it here: https://reviews.facebook.net/D30123

This depends on D30123.

P.S. We should do full scan only in failure scenarios, not every 6 hours. I'll do this in a follow-up diff.

Test Plan:
One new unit test. Made sure that unit test fails if we don't have a `if (!f->moved)` safeguard in ~Version.

make check

Big number of compactions and flushes:

  ./db_stress --threads=30 --ops_per_thread=20000000 --max_key=10000 --column_families=20 --clear_column_family_one_in=10000000 --verify_before_write=0  --reopen=15 --max_background_compactions=10 --max_background_flushes=10 --db=/fast-rocksdb-tmp/db_stress --prefixpercent=0 --iterpercent=0 --writepercent=75 --db_write_buffer_size=2000000

Reviewers: yhchiang, rven, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D30249

fix really trivial typo in column families example

Summary:
This one wasn't easy to find :)

What happens is we go through all cfds on flush_queue_ and find no cfds to flush, *but* the cfd is set to the last CF we looped through and following code assumes we want it flushed.

BTW @sdong do you think we should also make BackgroundFlush() only check a single cfd for flushing instead of doing this `while (!flush_queue_.empty())`?

Test Plan: regression test no longer fails

Reviewers: sdong, rven, yhchiang

Reviewed By: yhchiang

Subscribers: sdong, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D30591

Summary: This is a feature request from rocksdb's user. I didn't even realize we don't support multigets on TTL DB :)

Test Plan: added a unit test

Reviewers: yhchiang, rven, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D30561