hdfs cleanup and compile test against CDH 4.4.

- fix compile error with env_test; static casts added

Summary: Per request from @nkg-, temporarily print thread ID when a thread terminates. It is a temp solution as we try to minimized stderr messages.

Test Plan: env_test

Reviewers: haobo, igor, dhruba

Reviewed By: igor

CC: nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D18753

ThreadPool to allow decrease number of threads and increase of number of threads is to be instantly scheduled

Summary:
Add a feature to decrease the number of threads in thread pool.
Also instantly schedule more threads if number of threads is increased.

Here is the way it is implemented: each background thread needs its thread ID. After decreasing number of threads, all threads are woken up. The thread with the largest thread ID will terminate. If there are more threads to terminate, the thread will wake up all threads again.

Another change is made so that when number of threads is increased, more threads are created and all previous excessive threads are woken up to do the work.

Test Plan: Add a unit test.

Reviewers: haobo, dhruba

Reviewed By: haobo

CC: yhchiang, igor, nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D18675

Summary:
This diff adds rapidjson (https://code.google.com/p/rapidjson/) to RocksDB repository. First step to adding JSON is to add a JSON parser :)

I'm not sure if rapidjson is the right choice. I only considered folly as an alternative. Using folly JSON parser has serious downsides. I tried extracting folly::json from the folly library. However, it depends on folly::dynamic, which basically depends on everything else. I would prefer to avoid adding complete folly library as RocksDB dependency. Folly has a lot of its own dependencies (https://github.com/facebook/folly) and also looks like open source world has some trouble installing it (https://groups.google.com/forum/#!forum/facebook-folly -- 60% of the posts are compile errors). We can discuss this if you think otherwise.

RapidJSON does not have any dependencies whatsoever. No boost, no STL. We don't need to compile it since it's all header files. The performance results are also impressive: https://code.google.com/p/rapidjson/wiki/Performance. However, I'll make sure to write code in a way that we can easily switch JSON implementations going forward. Quora thread has some alternatives: http://www.quora.com/What-is-the-best-C-JSON-library

Test Plan: none

Reviewers: dhruba, haobo, yhchiang, sdong, jamesgpearce

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18729

Summary:
Materialize the hash index to avoid the soaring cpu/flash usage
when initializing the database.

Test Plan: existing unit tests passed

Reviewers: sdong, haobo

Reviewed By: sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18339

Summary: Key size limit doesn't seem to be applicable anymore. Remove it.

Test Plan: run a couple of tests in db_bench

Reviewers: haobo, igor, yhchiang, dhruba

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18723

Fix errors while building with clang (against libc++) under linux

This reverts commit 35a8873a.

Summary: Copy improvements from fbcode's version of EnvHdfs to our open-source version. Some very important bug fixes in there.

Test Plan: compiles

Reviewers: dhruba, haobo, sdong

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18711

Summary: Cleaned up compaction logging a little bit. Now file sizes are easier to read. Also, removed the trailing space.

Test Plan:
verified that i'm happy with logging output:

        files_size[#33(seq=101,sz=98KB,0) #31(seq=81,sz=159KB,0) #26(seq=0,sz=637KB,0)]

Reviewers: sdong, haobo, dhruba

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18549

Summary:
In order to use arena to a use case that the total allocation size might be small (LogBuffer is already such a case), inline 1KB of data in it, so that it can be mostly in stack or inline in another class.

If always inlining 2KB is a concern, I could make it a template to determine what to inline. However, dependents need to changes. Doesn't go with it for now

Test Plan: make all check.

Reviewers: haobo, igor, yhchiang, dhruba

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18609

Travis CI

Summary: As title

Test Plan: make all check.

Reviewers: haobo, igor, yhchiang

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18705

Summary: Fixed a bug in Java DB Benchmark where random reads does not consider full key range.

Test Plan:
make rocksdbjava
make jdb_bench
cd java
jdb_bench.sh --db=/tmp/rocksdb-test --benchmarks=fillseq --use_existing_db=false --num=100000
jdb_bench.sh --db=/tmp/rocksdb-test --benchmarks=readrandom --use_existing_db=true --num=100000 --reads=1000000

Reviewers: haobo, sdong

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18693

Summary: Make read benchmarks print out found / not-found information.

Test Plan:
make rocksdbjava
make jdb_bench
cd java
./jdb_bench.sh

Reviewers: haobo, sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18699

Summary:
This diff addresses task #4296714 and rethinks how users provide us with TablePropertiesCollectors as part of Options.

Here's description of task #4296714:
       I'm debugging #4295529 and noticed that our count of user properties kDeletedKeys is wrong. We're sharing one single InternalKeyPropertiesCollector with all Table Builders. In LOG Files, we're outputting number of kDeletedKeys as connected with a single table, while it's actually the total count of deleted keys since creation of the DB.

       For example, this table has 3155 entries and 1391828 deleted keys.

The problem with current approach that we call methods on a single TablePropertiesCollector for all the tables we create. Even worse, we could do it from multiple threads at the same time and TablePropertiesCollector has no way of knowing which table we're calling it for.

Good part: Looks like nobody inside Facebook is using Options::table_properties_collectors. This means we should be able to painfully change the API.

In this change, I introduce TablePropertiesCollectorFactory. For every table we create, we call `CreateTablePropertiesCollector`, which creates a TablePropertiesCollector for a single table. We then use it sequentially from a single thread, which means it doesn't have to be thread-safe.

Test Plan:
Added a test in table_properties_collector_test that fails on master (build two tables, assert that kDeletedKeys count is correct for the second one).
Also, all other tests

Reviewers: sdong, dhruba, haobo, kailiu

Reviewed By: kailiu

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18579

Summary:
Before the Java binding for Env is ready, Java developers have no way to
control the number of background threads.  This diff provides a temporary
solution where RocksDB.setMaxBackgroundCompactions() will affect the
number of background threads.

Note that once Env is ready.  Changes made in this diff should be reverted.

Test Plan:
make rocksdbjava
make jtest
make jdb_bench
java/jdb_bench.sh

Reviewers: haobo, sdong

Reviewed By: sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18681

Summary:
Fixed a file-not-found issue when a log file is moved to archive
by doing a missing retry.

Test Plan:
make db_test
export ROCKSDB_TEST=TransactionLogIteratorRace
./db_test

Reviewers: sdong, haobo

Reviewed By: sdong

CC: igor, leveldb

Differential Revision: https://reviews.facebook.net/D18669

Summary:
Renamed Iterator to RocksIterator to avoid potential confliction with
the Java built-in Iterator.

Test Plan:
make rocksdbjava
make jtest

Reviewers: haobo, dhruba, sdong, ankgup87

Reviewed By: sdong

CC: leveldb, rsumbaly, swapnilghike, zzbennett

Differential Revision: https://reviews.facebook.net/D18615

Fix building RocksDB in paths containing spaces

only use MAP_HUGETLB when the kernel supports it

Add a minimal .travis.yml for Travis CI. Some ugly hacks needed to get RocksDB building in Travis' OpenVZ Ubuntu 12.04 environment.

Fix building RocksDB in paths containing spaces -- quote path names in Makefile and build_detect_platform.

Summary:
This diff is addressing multiple things with a single goal -- to make RocksDB easier to use:
* Add some functions to Options that make RocksDB easier to tune.
* Add example code for both simple RocksDB and RocksDB with Column Families.
* Rewrite our README.md

Regarding Options, I took a stab at something we talked about for a long time:
* https://www.facebook.com/groups/rocksdb.dev/permalink/563169950448190/

I added functions:
* IncreaseParallelism() -- easy, increases the thread pool and max_background_compactions
* OptimizeLevelStyleCompaction(memtable_memory_budget) -- the easiest way to optimize rocksdb for less stalls with level style compaction. This is very likely not ideal configuration. Feel free to suggest improvements. I used some of Mark's suggestions from here: https://github.com/facebook/rocksdb/issues/54
* OptimizeUniversalStyleCompaction(memtable_memory_budget) -- optimize for universal compaction.

Test Plan: compiled rocksdb. ran examples.

Reviewers: dhruba, MarkCallaghan, haobo, sdong, yhchiang

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18621