[SPARK-2468] Netty based block server / client module

Previous pull request (#1907) was reverted. This brings it back. Still looking into the hang.

Author: Reynold Xin <rxin@apache.org>

Closes #1971 from rxin/netty1 and squashes the following commits:

b0be96f [Reynold Xin] Added test to make sure outstandingRequests are cleaned after firing the events.
4c6d0ee [Reynold Xin] Pass callbacks cleanly.
603dce7 [Reynold Xin] Upgrade Netty to 4.0.23 to fix the DefaultFileRegion bug.
88be1d4 [Reynold Xin] Downgrade to 4.0.21 to work around a bug in writing DefaultFileRegion.
002626a [Reynold Xin] Remove netty-test-file.txt.
db6e6e0 [Reynold Xin] Revert "Revert "[SPARK-2468] Netty based block server / client module""
[MLLIB] minor update to word2vec

very minor update Ishiihara

Author: Xiangrui Meng <meng@databricks.com>

Closes #2043 from mengxr/minor-w2v and squashes the following commits:

be649fd [Xiangrui Meng] remove map because we only need append
eccefcc [Xiangrui Meng] minor updates to word2vec
[SPARK-3112][MLLIB] Add documentation and example for StreamingLR

Added a documentation section on StreamingLR to the ``MLlib - Linear Methods``, including a worked example.

mengxr tdas

Author: freeman <the.freeman.lab@gmail.com>

Closes #2047 from freeman-lab/streaming-lr-docs and squashes the following commits:

568d250 [freeman] Tweaks to wording / formatting
05a1139 [freeman] Added documentation and example for StreamingLR
[SQL] add note of use synchronizedMap in SQLConf

Refer to:
http://stackoverflow.com/questions/510632/whats-the-difference-between-concurrenthashmap-and-collections-synchronizedmap
Collections.synchronizedMap(map) creates a blocking Map which will degrade performance, albeit ensure consistency. So use ConcurrentHashMap(a more effective thread-safe hashmap) instead.

also update HiveQuerySuite to fix test error when changed to ConcurrentHashMap.

Author: wangfei <wangfei_hello@126.com>
Author: scwf <wangfei1@huawei.com>

Closes #1996 from scwf/sqlconf and squashes the following commits:

93bc0c5 [wangfei] revert change of HiveQuerySuite
0cc05dd [wangfei] add note for use synchronizedMap
3c224d31 [scwf] fix formate
a7bcb98 [scwf] use ConcurrentHashMap in sql conf, intead synchronizedMap
[SPARK-3130][MLLIB] detect negative values in naive Bayes

because NB treats feature values as term frequencies. jkbradley

Author: Xiangrui Meng <meng@databricks.com>

Closes #2038 from mengxr/nb-neg and squashes the following commits:

52c37c3 [Xiangrui Meng] address comments
65f892d [Xiangrui Meng] detect negative values in nb
[HOTFIX][Streaming][MLlib] use temp folder for checkpoint

or Jenkins will complain about no Apache header in checkpoint files. tdas rxin

Author: Xiangrui Meng <meng@databricks.com>

Closes #2046 from mengxr/tmp-checkpoint and squashes the following commits:

0d3ec73 [Xiangrui Meng] remove ssc.stop
9797843 [Xiangrui Meng] change checkpointDir to lazy val
89964ab [Xiangrui Meng] use temp folder for checkpoint
[SPARK-3119] Re-implementation of TorrentBroadcast.

This is a re-implementation of TorrentBroadcast, with the following changes:

1. Removes most of the mutable, transient state from TorrentBroadcast (e.g. totalBytes, num of blocks fetched).
2. Removes TorrentInfo and TorrentBlock
3. Replaces the BlockManager.getSingle call in readObject with a getLocal, resuling in one less RPC call to the BlockManagerMasterActor to find the location of the block.
4. Removes the metadata block, resulting in one less block to fetch.
5. Removes an extra memory copy for deserialization (by using Java's SequenceInputStream).

Basically for a regular broadcasted object with only one block, the number of RPC calls goes from 5+1 to 2+1).

Old TorrentBroadcast for object of a single block:
1 RPC to ask for location of the broadcast variable
1 RPC to ask for location of the metadata block
1 RPC to fetch the metadata block
1 RPC to ask for location of the first data block
1 RPC to fetch the first data block
1 RPC to tell the driver we put the first data block in
i.e. 5 + 1

New TorrentBroadcast for object of a single block:
1 RPC to ask for location of the first data block
1 RPC to get the first data block
1 RPC to tell the driver we put the first data block in
i.e. 2 + 1

Author: Reynold Xin <rxin@apache.org>

Closes #2030 from rxin/torrentBroadcast and squashes the following commits:

5bacb9d [Reynold Xin] Always add the object to driver's block manager.
0d8ed5b [Reynold Xin] Added getBytes to BlockManager and uses that in TorrentBroadcast.
2d6a5fb [Reynold Xin] Use putBytes/getRemoteBytes throughout.
3670f00 [Reynold Xin] Code review feedback.
c1185cd [Reynold Xin] [SPARK-3119] Re-implementation of TorrentBroadcast.
[SPARK-3142][MLLIB] output shuffle data directly in Word2Vec

Sorry I didn't realize this in #2043. Ishiihara

Author: Xiangrui Meng <meng@databricks.com>

Closes #2049 from mengxr/more-w2v and squashes the following commits:

050b1c5 [Xiangrui Meng] output shuffle data directly
[SPARK-2974] [SPARK-2975] Fix two bugs related to spark.local.dirs

This PR fixes two bugs related to `spark.local.dirs` and `SPARK_LOCAL_DIRS`, one where `Utils.getLocalDir()` might return an invalid directory (SPARK-2974) and another where the `SPARK_LOCAL_DIRS` override didn't affect the driver, which could cause problems when running tasks in local mode (SPARK-2975).

This patch fixes both issues: the new `Utils.getOrCreateLocalRootDirs(conf: SparkConf)` utility method manages the creation of local directories and handles the precedence among the different configuration options, so we should see the same behavior whether we're running in local mode or on a worker.

It's kind of a pain to mock out environment variables in tests (no easy way to mock System.getenv), so I added a `private[spark]` method to SparkConf for accessing environment variables (by default, it just delegates to System.getenv).  By subclassing SparkConf and overriding this method, we can mock out SPARK_LOCAL_DIRS in tests.

I also fixed a typo in PySpark where we used `SPARK_LOCAL_DIR` instead of `SPARK_LOCAL_DIRS` (I think this was technically innocuous, but it seemed worth fixing).

Author: Josh Rosen <joshrosen@apache.org>

Closes #2002 from JoshRosen/local-dirs and squashes the following commits:

efad8c6 [Josh Rosen] Address review comments:
1dec709 [Josh Rosen] Minor updates to Javadocs.
7f36999 [Josh Rosen] Use env vars to detect if running in YARN container.
399ac25 [Josh Rosen] Update getLocalDir() documentation.
bb3ad89 [Josh Rosen] Remove duplicated YARN getLocalDirs() code.
3e92d44 [Josh Rosen] Move local dirs override logic into Utils; fix bugs:
b2c4736 [Josh Rosen] Add failing tests for SPARK-2974 and SPARK-2975.
007298b [Josh Rosen] Allow environment variables to be mocked in tests.
6d9259b [Josh Rosen] Fix typo in PySpark: SPARK_LOCAL_DIR should be SPARK_LOCAL_DIRS
 [DOCS] Fixed wrong links

Author: Ken Takagiwa <ugw.gi.world@gmail.com>

Closes #2042 from giwa/patch-1 and squashes the following commits:

216fe0e [Ken Takagiwa] Fixed wrong links
[SPARK-3141] [PySpark] fix sortByKey() with take()

Fix sortByKey() with take()

The function `f` used in mapPartitions should always return an iterator.

Author: Davies Liu <davies.liu@gmail.com>

Closes #2045 from davies/fix_sortbykey and squashes the following commits:

1160f59 [Davies Liu] fix sortByKey() with take()
[SPARK-3054][STREAMING] Add unit tests for Spark Sink.

This patch adds unit tests for Spark Sink.

It also removes the private[flume] for Spark Sink,
since the sink is instantiated from Flume configuration (looks like this is ignored by reflection which is used by
Flume, but we should still remove it anyway).

Author: Hari Shreedharan <hshreedharan@apache.org>
Author: Hari Shreedharan <hshreedharan@cloudera.com>

Closes #1958 from harishreedharan/spark-sink-test and squashes the following commits:

e3110b9 [Hari Shreedharan] Add a sleep to allow sink to commit the transactions
120b81e [Hari Shreedharan] Fix complexity in threading model in test
4df5be6 [Hari Shreedharan] Merge remote-tracking branch 'asf/master' into spark-sink-test
c9190d1 [Hari Shreedharan] Indentation and spaces changes
7fedc5a [Hari Shreedharan] Merge remote-tracking branch 'asf/master' into spark-sink-test
abc20cb [Hari Shreedharan] Minor test changes
7b9b649 [Hari Shreedharan] Merge branch 'master' into spark-sink-test
f2c56c9 [Hari Shreedharan] Update SparkSinkSuite.scala
a24aac8 [Hari Shreedharan] Remove unused var
c86d615 [Hari Shreedharan] [SPARK-3054][STREAMING] Add unit tests for Spark Sink.
Merge branch 'master' into sort

Conflicts:
	python/pyspark/rdd.py
	python/pyspark/shuffle.py