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`
SPARK-3770: Make userFeatures accessible from python

https://issues.apache.org/jira/browse/SPARK-3770

We need access to the underlying latent user features from python. However, the userFeatures RDD from the MatrixFactorizationModel isn't accessible from the python bindings. I've added a method to the underlying scala class to turn the RDD[(Int, Array[Double])] to an RDD[String]. This is then accessed from the python recommendation.py

Author: Michelangelo D'Agostino <mdagostino@civisanalytics.com>

Closes #2636 from mdagost/mf_user_features and squashes the following commits:

c98f9e2 [Michelangelo D'Agostino] Added unit tests for userFeatures and productFeatures and merged master.
d5eadf8 [Michelangelo D'Agostino] Merge branch 'master' into mf_user_features
2481a2a [Michelangelo D'Agostino] Merged master and resolved conflict.
a6ffb96 [Michelangelo D'Agostino] Eliminated a function from our first approach to this problem that is no longer needed now that we added the fromTuple2RDD function.
2aa1bf8 [Michelangelo D'Agostino] Implemented a function called fromTuple2RDD in PythonMLLibAPI and used it to expose the MF userFeatures and productFeatures in python.
34cb2a2 [Michelangelo D'Agostino] A couple of lint cleanups and a comment.
cdd98e3 [Michelangelo D'Agostino] It's working now.
e1fbe5e [Michelangelo D'Agostino] Added scala function to stringify userFeatures for access in python.
[SPARK-3994] Use standard Aggregator code path for countByKey and countByValue

See [JIRA](https://issues.apache.org/jira/browse/SPARK-3994) for more information. Also adds
a note which warns against using these methods.

Author: Aaron Davidson <aaron@databricks.com>

Closes #2839 from aarondav/countByKey and squashes the following commits:

d6fdb2a [Aaron Davidson] Respond to comments
e1f06d3 [Aaron Davidson] [SPARK-3994] Use standard Aggregator code path for countByKey and countByValue
SPARK-3568 [mllib] add ranking metrics

Add common metrics for ranking algorithms (http://www-nlp.stanford.edu/IR-book/), including:
 - Mean Average Precision
 - Precisionn: top-n precision
 - Discounted cumulative gain (DCG) and NDCG

The following methods and the corresponding tests are implemented:

```
class RankingMetrics[T](predictionAndLabels: RDD[(Array[T], Array[T])]) {
  /* Returns the precsionk for each query */
  lazy val precAtK: RDD[Array[Double]]

  /**
   * param k the position to compute the truncated precision
   * return the average precision at the first k ranking positions
   */
  def precision(k: Int): Double

  /* Returns the average precision for each query */
  lazy val avePrec: RDD[Double]

  /*Returns the mean average precision (MAP) of all the queries*/
  lazy val meanAvePrec: Double

  /*Returns the normalized discounted cumulative gain for each query */
  lazy val ndcgAtK: RDD[Array[Double]]

  /**
   * param k the position to compute the truncated ndcg
   * return the average ndcg at the first k ranking positions
   */
  def ndcg(k: Int): Double
}
```

Author: coderxiang <shuoxiangpub@gmail.com>

Closes #2667 from coderxiang/rankingmetrics and squashes the following commits:

d881097 [coderxiang] update doc
14d9cd9 [coderxiang] remove unexpected files
d7fb93f [coderxiang] style change and remove ignored files
f113ee1 [coderxiang] modify doc for displaying superscript and subscript
f626896 [coderxiang] improve doc and remove unnecessary computation while labSet is empty
be6645e [coderxiang] set the precision of empty labset to 0.0
d64c120 [coderxiang] add logWarning for empty ground truth set
dfae292 [coderxiang] handle empty labSet for map. add test
62047c4 [coderxiang] style change and add documentation
f66612d [coderxiang] add additional test of precisionAt
b794cb2 [coderxiang] move private members precAtK, ndcgAtK into public methods. style change
77c9e5d [coderxiang] set precAtK and ndcgAtK as private member. Improve documentation
5f87bce [coderxiang] add API to calculate precision and ndcg at each ranking position
b7851cc [coderxiang] Use generic type to represent IDs
e443fee [coderxiang] change style and use alternative builtin methods
3a5a6ff [coderxiang] add ranking metrics
[SQL]redundant methods for broadcast

redundant methods for broadcast in ```TableReader```

Author: wangfei <wangfei1@huawei.com>

Closes #2862 from scwf/TableReader and squashes the following commits:

414cc24 [wangfei] unnecessary methods for broadcast
SPARK-1813. Add a utility to SparkConf that makes using Kryo really easy

Author: Sandy Ryza <sandy@cloudera.com>

Closes #789 from sryza/sandy-spark-1813 and squashes the following commits:

48b05e9 [Sandy Ryza] Simplify
b824932 [Sandy Ryza] Allow both spark.kryo.classesToRegister and spark.kryo.registrator at the same time
6a15bb7 [Sandy Ryza] Small fix
a2278c0 [Sandy Ryza] Respond to review comments
6ef592e [Sandy Ryza] SPARK-1813. Add a utility to SparkConf that makes using Kryo really easy
Update JavaCustomReceiver.java

Changed the usage string to correctly reflect the file name.

Author: Karthik <karthik.gomadam@gmail.com>

Closes #2699 from namelessnerd/patch-1 and squashes the following commits:

8570e33 [Karthik] Update JavaCustomReceiver.java
use isRunningLocally rather than runningLocally

runningLocally is deprecated now

Author: CrazyJvm <crazyjvm@gmail.com>

Closes #2879 from CrazyJvm/runningLocally and squashes the following commits:

bec0b3e [CrazyJvm] use isRunningLocally rather than runningLocally
Fix for sampling error in NumPy v1.9 [SPARK-3995][PYSPARK]

Change maximum value for default seed during RDD sampling so that it is strictly less than 2 ** 32. This prevents a bug in the most recent version of NumPy, which cannot accept random seeds above this bound.

Adds an extra test that uses the default seed (instead of setting it manually, as in the docstrings).

mengxr

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

Closes #2889 from freeman-lab/pyspark-sampling and squashes the following commits:

dc385ef [freeman] Change maximum value for default seed
[SPARK-3426] Fix sort-based shuffle error when spark.shuffle.compress and spark.shuffle.spill.compress settings are different

This PR fixes SPARK-3426, an issue where sort-based shuffle crashes if the
`spark.shuffle.spill.compress` and `spark.shuffle.compress` settings have
different values.

The problem is that sort-based shuffle's read and write paths use different
settings for determining whether to apply compression.  ExternalSorter writes
runs to files using `TempBlockId` ids, which causes
`spark.shuffle.spill.compress` to be used for enabling compression, but these
spilled files end up being shuffled over the network and read as shuffle files
using `ShuffleBlockId` by BlockStoreShuffleFetcher, which causes
`spark.shuffle.compress` to be used for enabling decompression.  As a result,
this leads to errors when these settings disagree.

Based on the discussions in #2247 and #2178, it sounds like we don't want to
remove the `spark.shuffle.spill.compress` setting.  Therefore, I've tried to
come up with a fix where `spark.shuffle.spill.compress` is used to compress
data that's read and written locally and `spark.shuffle.compress` is used to
compress any data that will be fetched / read as shuffle blocks.

To do this, I split `TempBlockId` into two new id types, `TempLocalBlockId` and
`TempShuffleBlockId`, which map to `spark.shuffle.spill.compress` and
`spark.shuffle.compress`, respectively.  ExternalAppendOnlyMap also used temp
blocks for spilling data.  It looks like ExternalSorter was designed to be
a generic sorter but its configuration already happens to be tied to sort-based
shuffle, so I think it's fine if we use `spark.shuffle.compress` to compress
its spills; we can move the compression configuration to the constructor in
a later commit if we find that ExternalSorter is being used in other contexts
where we want different configuration options to control compression.  To
summarize:

**Before:**

|       | ExternalAppendOnlyMap        | ExternalSorter               |
|-------|------------------------------|------------------------------|
| Read  | spark.shuffle.spill.compress | spark.shuffle.compress       |
| Write | spark.shuffle.spill.compress | spark.shuffle.spill.compress |

**After:**

|       | ExternalAppendOnlyMap        | ExternalSorter         |
|-------|------------------------------|------------------------|
| Read  | spark.shuffle.spill.compress | spark.shuffle.compress |
| Write | spark.shuffle.spill.compress | spark.shuffle.compress |

Thanks to andrewor14 for debugging this with me!

Author: Josh Rosen <joshrosen@databricks.com>

Closes #2890 from JoshRosen/SPARK-3426 and squashes the following commits:

1921cf6 [Josh Rosen] Minor edit for clarity.
c8dd8f2 [Josh Rosen] Add comment explaining use of createTempShuffleBlock().
2c687b9 [Josh Rosen] Fix SPARK-3426.
91e7e40 [Josh Rosen] Combine tests into single test of all combinations
76ca65e [Josh Rosen] Add regression test for SPARK-3426.
[SPARK-3877][YARN] Throw an exception when application is not successful so that the exit code wil be set to 1

When an yarn application fails (yarn-cluster mode), the exit code of spark-submit is still 0. It's hard for people to write some automatic scripts to run spark jobs in yarn because the failure can not be detected in these scripts.

This PR added a status checking after `monitorApplication`. If an application is not successful, `run()` will throw an `SparkException`, so that Client.scala will exit with code 1. Therefore, people can use the exit code of `spark-submit` to write some automatic scripts.

Author: zsxwing <zsxwing@gmail.com>

Closes #2732 from zsxwing/SPARK-3877 and squashes the following commits:

1f89fa5 [zsxwing] Fix the unit test
a0498e1 [zsxwing] Update the docs and the error message
e1cb9ef [zsxwing] Fix the hacky way of calling Client
ff16fec [zsxwing] Remove System.exit in Client.scala and add a test
6a2c103 [zsxwing] [SPARK-3877] Throw an exception when application is not successful so that the exit code wil be set to 1
[SPARK-3812] [BUILD] Adapt maven build to publish effective pom.

I have tried maven help plugin first but that published all projects in top level pom. So I was left with no choice but to roll my own trivial plugin. This patch basically installs an effective pom after maven install is finished.

The problem it fixes is described as follows:
If you install using maven
` mvn install -DskipTests -Dhadoop.version=2.2.0 -Phadoop-2.2 `
Then without this patch the published pom(s) will have hadoop version as 1.0.4. This can be a problem at some point.

Author: Prashant Sharma <prashant.s@imaginea.com>

Closes #2673 from ScrapCodes/build-changes-effective-pom and squashes the following commits:

aa7b91d [Prashant Sharma] used an unused dep.
0300dac [Prashant Sharma] improved comment messages..
28f891e [Prashant Sharma] Added a useless dependency, so that we can shade it. And realized fake shading works for us.
553d96b [Prashant Sharma] Shaded some unused class of an unused dep, to generate effective pom(s)
[BUILD] Fixed resolver for scalastyle plugin and upgrade sbt version.

Author: Prashant Sharma <prashant.s@imaginea.com>

Closes #2877 from ScrapCodes/scalastyle-fix and squashes the following commits:

a17b9fe [Prashant Sharma] [BUILD] Fixed resolver for scalastyle plugin.
[SPARK-4055][MLlib] Inconsistent spelling 'MLlib' and 'MLLib'

Thare are some inconsistent spellings 'MLlib' and 'MLLib' in some documents and source codes.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #2903 from sarutak/SPARK-4055 and squashes the following commits:

b031640 [Kousuke Saruta] Fixed inconsistent spelling "MLlib and MLLib"
[SPARK-4006] In long running contexts, we encountered the situation of double registe...

...r without a remove in between. The cause for that is unknown, and assumed a temp network issue.

However, since the second register is with a BlockManagerId on a different port, blockManagerInfo.contains() returns false, while blockManagerIdByExecutor returns Some. This inconsistency is caught in a conditional statement that does System.exit(1), which is a huge robustness issue for us.

The fix - simply remove the old id from both maps during register when this happens. We are mimicking the behavior of expireDeadHosts(), by doing local cleanup of the maps before trying to add new ones.

Also - added some logging for register and unregister.

This is just like https://github.com/apache/spark/pull/2854 except it's on master

Author: Tal Sliwowicz <tal.s@taboola.com>

Closes #2886 from tsliwowicz/master-block-mgr-removal and squashes the following commits:

094d508 [Tal Sliwowicz] some more white space change undone
41a2217 [Tal Sliwowicz] some more whitspaces change undone
7bcfc3d [Tal Sliwowicz] whitspaces fix
df9d98f [Tal Sliwowicz] Code review comments fixed
f48bce9 [Tal Sliwowicz] In long running contexts, we encountered the situation of double register without a remove in between. The cause for that is unknown, and assumed a temp network issue.