[SPARK-3952] [Streaming] [PySpark] add Python examples in Streaming Programming Guide

Having Python examples in Streaming Programming Guide.

Also add RecoverableNetworkWordCount example.

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

Closes #2808 from davies/pyguide and squashes the following commits:

8d4bec4 [Davies Liu] update readme
26a7e37 [Davies Liu] fix format
3821c4d [Davies Liu] address comments, add missing file
7e4bb8a [Davies Liu] add Python examples in Streaming Programming Guide
[SPARK-2546] Clone JobConf for each task (branch-1.0 / 1.1 backport)

This patch attempts to fix SPARK-2546 in `branch-1.0` and `branch-1.1`.  The underlying problem is that thread-safety issues in Hadoop Configuration objects may cause Spark tasks to get stuck in infinite loops.  The approach taken here is to clone a new copy of the JobConf for each task rather than sharing a single copy between tasks.  Note that there are still Configuration thread-safety issues that may affect the driver, but these seem much less likely to occur in practice and will be more complex to fix (see discussion on the SPARK-2546 ticket).

This cloning is guarded by a new configuration option (`spark.hadoop.cloneConf`) and is disabled by default in order to avoid unexpected performance regressions for workloads that are unaffected by the Configuration thread-safety issues.

Author: Josh Rosen <joshrosen@apache.org>

Closes #2684 from JoshRosen/jobconf-fix-backport and squashes the following commits:

f14f259 [Josh Rosen] Add configuration option to control cloning of Hadoop JobConf.
b562451 [Josh Rosen] Remove unused jobConfCacheKey field.
dd25697 [Josh Rosen] [SPARK-2546] [1.0 / 1.1 backport] Clone JobConf for each task.

(cherry picked from commit 2cd40db2b3ab5ddcb323fd05c171dbd9025f9e71)
Signed-off-by: Josh Rosen <joshrosen@databricks.com>

Conflicts:
	core/src/main/scala/org/apache/spark/rdd/HadoopRDD.scala
[SPARK-3902] [SPARK-3590] Stabilize AsynRDDActions and add Java API

This PR adds a Java API for AsyncRDDActions and promotes the API from `Experimental` to stable.

Author: Josh Rosen <joshrosen@apache.org>
Author: Josh Rosen <joshrosen@databricks.com>

Closes #2760 from JoshRosen/async-rdd-actions-in-java and squashes the following commits:

0d45fbc [Josh Rosen] Whitespace fix.
ad3ae53 [Josh Rosen] Merge remote-tracking branch 'origin/master' into async-rdd-actions-in-java
c0153a5 [Josh Rosen] Remove unused variable.
e8e2867 [Josh Rosen] Updates based on Marcelo's review feedback
7a1417f [Josh Rosen] Removed unnecessary java.util import.
6f8f6ac [Josh Rosen] Fix import ordering.
ff28e49 [Josh Rosen] Add MiMa excludes and fix a scalastyle error.
346e46e [Josh Rosen] [SPARK-3902] Stabilize AsyncRDDActions; add Java API.
[SPARK-3948][Shuffle]Fix stream corruption bug in sort-based shuffle

Kernel 2.6.32 bug will lead to unexpected behavior of transferTo in copyStream, and this will corrupt the shuffle output file in sort-based shuffle, which will somehow introduce PARSING_ERROR(2), deserialization error or offset out of range. Here fix this by adding append flag, also add some position checking code. Details can be seen in [SPARK-3948](https://issues.apache.org/jira/browse/SPARK-3948).

Author: jerryshao <saisai.shao@intel.com>

Closes #2824 from jerryshao/SPARK-3948 and squashes the following commits:

be0533a [jerryshao] Address the comments
a82b184 [jerryshao] add configuration to control the NIO way of copying stream
e17ada2 [jerryshao] Fix kernel 2.6.32 bug led unexpected behavior of transferTo
[SPARK-4010][Web UI]Spark UI returns 500 in yarn-client mode

The problem caused by #1966
CC YanTangZhai andrewor14

Author: GuoQiang Li <witgo@qq.com>

Closes #2858 from witgo/SPARK-4010 and squashes the following commits:

9866fbf [GuoQiang Li] Spark UI returns 500 in yarn-client mode
[SPARK-3986][SQL] Fix package names to fit their directory names.

Package names of 2 test suites are different from their directory names.
- `GeneratedEvaluationSuite`
- `GeneratedMutableEvaluationSuite`

Author: Takuya UESHIN <ueshin@happy-camper.st>

Closes #2835 from ueshin/issues/SPARK-3986 and squashes the following commits:

fa2cc05 [Takuya UESHIN] Fix package names to fit their directory names.
[SPARK-3736] Workers reconnect when disassociated from the master.

Before, if the master node is killed and restarted, the worker nodes
would not attempt to reconnect to the Master. Therefore, when the Master
node was restarted, the worker nodes needed to be restarted as well.

Now, when the Master node is disconnected, the worker nodes will
continuously ping the master node in attempts to reconnect to it. Once
the master node restarts, it will detect one of the registration
requests from its former workers. The result is that the cluster
re-enters a healthy state.

In addition, when the master does not receive a heartbeat from the
worker, the worker was removed; however, when the worker sent a
heartbeat to the master, the master used to ignore the heartbeat. Now,
a master that receives a heartbeat from a worker that had been
disconnected will request the worker to re-attempt the registration
process, at which point the worker will send a RegisterWorker request
and be re-connected accordingly.

Re-connection attempts per worker are submitted every N seconds, where N
is configured by the property spark.worker.reconnect.interval - this has
a default of 60 seconds right now.

Author: mcheah <mcheah@palantir.com>

Closes #2828 from mccheah/reconnect-dead-workers and squashes the following commits:

83f8bc9 [mcheah] [SPARK-3736] More informative log message, and fixing some indentation.
fe0e02f [mcheah] [SPARK-3736] Moving reconnection logic to registerWithMaster().
94ddeca [mcheah] [SPARK-3736] Changing a log warning to a log info.
a698e35 [mcheah] [SPARK-3736] Addressing PR comment to make some defs private.
b9a3077 [mcheah] [SPARK-3736] Addressing PR comments related to reconnection.
2ad5ed5 [mcheah] [SPARK-3736] Cancel attempts to reconnect if the master changes.
b5b34af [mcheah] [SPARK-3736] Workers reconnect when disassociated from the master.
[SPARK-3207][MLLIB]Choose splits for continuous features in DecisionTree more adaptively

DecisionTree splits on continuous features by choosing an array of values from a subsample of the data.
Currently, it does not check for identical values in the subsample, so it could end up having multiple copies of the same split. In this PR, we choose splits for a continuous feature in 3 steps:

1. Sort sample values for this feature
2. Get number of occurrence of each distinct value
3. Iterate the value count array computed in step 2 to choose splits.

After find splits, `numSplits` and `numBins` in metadata will be updated.

CC: mengxr manishamde jkbradley, please help me review this, thanks.

Author: Qiping Li <liqiping1991@gmail.com>
Author: chouqin <liqiping1991@gmail.com>
Author: liqi <liqiping1991@gmail.com>
Author: qiping.lqp <qiping.lqp@alibaba-inc.com>

Closes #2780 from chouqin/dt-findsplits and squashes the following commits:

18d0301 [Qiping Li] check explicitly findsplits return distinct splits
8dc28ab [chouqin] remove blank lines
ffc920f [chouqin] adjust code based on comments and add more test cases
9857039 [chouqin] Merge branch 'master' of https://github.com/apache/spark into dt-findsplits
d353596 [qiping.lqp] fix pyspark doc test
9e64699 [Qiping Li] fix random forest unit test
3c72913 [Qiping Li] fix random forest unit test
092efcb [Qiping Li] fix bug
f69f47f [Qiping Li] fix bug
ab303a4 [Qiping Li] fix bug
af6dc97 [Qiping Li] fix bug
2a8267a [Qiping Li] fix bug
c339a61 [Qiping Li] fix bug
369f812 [Qiping Li] fix style
8f46af6 [Qiping Li] add comments and unit test
9e7138e [Qiping Li] Merge branch 'dt-findsplits' of https://github.com/chouqin/spark into dt-findsplits
1b25a35 [Qiping Li] Merge branch 'master' of https://github.com/apache/spark into dt-findsplits
0cd744a [liqi] fix bug
3652823 [Qiping Li] fix bug
af7cb79 [Qiping Li] Choose splits for continuous features in DecisionTree more adaptively
[SPARK-3906][SQL] Adds multiple join support for SQLContext

Author: Cheng Lian <lian.cs.zju@gmail.com>

Closes #2767 from liancheng/multi-join and squashes the following commits:

9dc0d18 [Cheng Lian] Adds multiple join support for SQLContext
[SPARK-3800][SQL] Clean aliases from grouping expressions

Author: Michael Armbrust <michael@databricks.com>

Closes #2658 from marmbrus/nestedAggs and squashes the following commits:

862b763 [Michael Armbrust] Merge remote-tracking branch 'origin/master' into nestedAggs
3234521 [Michael Armbrust] Merge remote-tracking branch 'origin/master' into nestedAggs
8b06fdc [Michael Armbrust] possible fix for grouping on nested fields
[SPARK-3966][SQL] Fix nullabilities of Cast related to DateType.

Author: Takuya UESHIN <ueshin@happy-camper.st>

Closes #2820 from ueshin/issues/SPARK-3966 and squashes the following commits:

ca4a745 [Takuya UESHIN] Fix nullabilities of Cast related to DateType.
[SPARK-3945]Properties of hive-site.xml is invalid in running the Thrift JDBC server

Write properties of hive-site.xml to HiveContext when initilize session state in SparkSQLEnv.scala.

The method of SparkSQLEnv.init() in HiveThriftServer2.scala can not write the properties of hive-site.xml to HiveContext. Such as: add configuration property spark.sql.shuffle.partititions in the hive-site.xml.

Author: luogankun <luogankun@gmail.com>

Closes #2800 from luogankun/SPARK-3945 and squashes the following commits:

3679efc [luogankun] [SPARK-3945]Write properties of hive-site.xml to HiveContext when initilize session state In SparkSQLEnv.scala
[SPARK-3969][SQL] Optimizer should have a super class as an interface.

Some developers want to replace `Optimizer` to fit their projects but can't do so because currently `Optimizer` is an `object`.

Author: Takuya UESHIN <ueshin@happy-camper.st>

Closes #2825 from ueshin/issues/SPARK-3969 and squashes the following commits:

abbc53c [Takuya UESHIN] Re-rename Optimizer object.
4d2e1bc [Takuya UESHIN] Rename Optimizer object.
9547a23 [Takuya UESHIN] Extract abstract class from Optimizer for developers to be able to replace Optimizer.
[SPARK-3940][SQL] Avoid console printing error messages three times

If  wrong sql,the console print error one times。
eg：
<pre>
spark-sql> show tabless;
show tabless;
14/10/13 21:03:48 INFO ParseDriver: Parsing command: show tabless
............
	at org.apache.spark.sql.hive.thriftserver.SparkSQLCLIDriver.processCmd(SparkSQLCLIDriver.scala:274)
	at org.apache.hadoop.hive.cli.CliDriver.processLine(CliDriver.java:413)
	at org.apache.spark.sql.hive.thriftserver.SparkSQLCLIDriver$.main(SparkSQLCLIDriver.scala:209)
	at org.apache.spark.sql.hive.thriftserver.SparkSQLCLIDriver.main(SparkSQLCLIDriver.scala)
Caused by: org.apache.hadoop.hive.ql.parse.ParseException: line 1:5 cannot recognize input near 'show' 'tabless' '<EOF>' in ddl statement

	at org.apache.hadoop.hive.ql.parse.ParseDriver.parse(ParseDriver.java:193)
	at org.apache.hadoop.hive.ql.parse.ParseDriver.parse(ParseDriver.java:161)
	at org.apache.spark.sql.hive.HiveQl$.getAst(HiveQl.scala:218)
	at org.apache.spark.sql.hive.HiveQl$.createPlan(HiveQl.scala:226)
	... 47 more
Time taken: 4.35 seconds
14/10/13 21:03:51 INFO CliDriver: Time taken: 4.35 seconds
</pre>

Author: wangxiaojing <u9jing@gmail.com>

Closes #2790 from wangxiaojing/spark-3940 and squashes the following commits:

e2e5c14 [wangxiaojing] sql Print the error code three times
Update Building Spark link.
[SPARK-3958] TorrentBroadcast cleanup / debugging improvements.

This PR makes several changes to TorrentBroadcast in order to make
it easier to reason about, which should help when debugging SPARK-3958.
The key changes:

- Remove all state from the global TorrentBroadcast object.  This state
  consisted mainly of configuration options, like the block size and
  compression codec, and was read by the blockify / unblockify methods.
  Unfortunately, the use of `lazy val` for `BLOCK_SIZE` meant that the block
  size was always determined by the first SparkConf that TorrentBroadast was
  initialized with; as a result, unit tests could not properly test
  TorrentBroadcast with different block sizes.

  Instead, blockifyObject and unBlockifyObject now accept compression codecs
  and blockSizes as arguments.  These arguments are supplied at the call sites
  inside of TorrentBroadcast instances.  Each TorrentBroadcast instance
  determines these values from SparkEnv's SparkConf.  I was careful to ensure
  that we do not accidentally serialize CompressionCodec or SparkConf objects
  as part of the TorrentBroadcast object.

- Remove special-case handling of local-mode in TorrentBroadcast.  I don't
  think that broadcast implementations should know about whether we're running
  in local mode.  If we want to optimize the performance of broadcast in local
  mode, then we should detect this at a higher level and use a dummy
  LocalBroadcastFactory implementation instead.

  Removing this code fixes a subtle error condition: in the old local mode
  code, a failure to find the broadcast in the local BlockManager would lead
  to an attempt to deblockify zero blocks, which could lead to confusing
  deserialization or decompression errors when we attempted to decompress
  an empty byte array.  This should never have happened, though: a failure to
  find the block in local mode is evidence of some other error.  The changes
  here will make it easier to debug those errors if they ever happen.

- Add a check that throws an exception when attempting to deblockify an
  empty array.

- Use ScalaCheck to add a test to check that TorrentBroadcast's
  blockifyObject and unBlockifyObject methods are inverses.

- Misc. cleanup and logging improvements.

Author: Josh Rosen <joshrosen@databricks.com>

Closes #2844 from JoshRosen/torrentbroadcast-bugfix and squashes the following commits:

1e8268d [Josh Rosen] Address Reynold's review comments
2a9fdfd [Josh Rosen] Address Reynold's review comments.
c3b08f9 [Josh Rosen] Update TorrentBroadcast tests to reflect removal of special local-mode optimizations.
5c22782 [Josh Rosen] Store broadcast variable's value in the driver.
33fc754 [Josh Rosen] Change blockify/unblockifyObject to accept serializer as argument.
618a872 [Josh Rosen] [SPARK-3958] TorrentBroadcast cleanup / debugging improvements.
[SPARK-4023] [MLlib] [PySpark] convert rdd into RDD of Vector

Convert the input rdd to RDD of Vector.

cc mengxr

Author: Davies Liu <davies@databricks.com>

Closes #2870 from davies/fix4023 and squashes the following commits:

1eac767 [Davies Liu] address comments
0871576 [Davies Liu] convert rdd into RDD of Vector
replace awaitTransformation with awaitTermination in scaladoc/javadoc

Author: Holden Karau <holden@pigscanfly.ca>

Closes #2861 from holdenk/SPARK-4015-Documentation-in-the-streaming-context-references-non-existent-function and squashes the following commits:

081db8a [Holden Karau] fix pyspark streaming doc too
0e03863 [Holden Karau] replace awaitTransformation with awaitTermination
[SPARK-4035] Fix a wrong format specifier

Just found a typo. Should not use "%f" for Long.

Author: zsxwing <zsxwing@gmail.com>

Closes #2875 from zsxwing/SPARK-4035 and squashes the following commits:

ce347e2 [zsxwing] Fix a wrong format specifier
[SPARK-4020] Do not rely on timeouts to remove failed block managers

If an executor fails without being scheduled to run any tasks, then `DAGScheduler` won't notify `BlockManagerMasterActor` that the associated block manager should be removed. Instead, the associated block manager will be expired only after a few rounds of heartbeat timeouts. In terms of removal treatment, there should really be no distinction between executors that have been scheduled tasks and those that have not.

The fix, then, is to add all known executors to `TaskSchedulerImpl`'s `activeExecutorIds` whether or not it has been scheduled a task. In fact, the existing comment above `activeExecutorIds` is
```
// Which executor IDs we have executors on
val activeExecutorIds = new HashSet[String]
```
not  "Which executors have been scheduled tasks thus far."

Author: Andrew Or <andrewor14@gmail.com>

Closes #2865 from andrewor14/active-executors and squashes the following commits:

ff3172b [Andrew Or] Add all known executors to `activeExecutorIds`