[SPARK-4595][Core] Fix MetricsServlet not work issue

`MetricsServlet` handler should be added to the web UI after initialized by `MetricsSystem`, otherwise servlet handler cannot be attached.

Author: Saisai Shao <saisai.shao@intel.com>
Author: Josh Rosen <joshrosen@databricks.com>
Author: jerryshao <saisai.shao@intel.com>

Closes #3444 from jerryshao/SPARK-4595 and squashes the following commits:

434d17e [Saisai Shao] Merge pull request #10 from JoshRosen/metrics-system-cleanup
87a2292 [Josh Rosen] Guard against misuse of MetricsSystem methods.
f779fe0 [jerryshao] Fix MetricsServlet not work issue
[SPARK-4625] [SQL] Add sort by for DSL & SimpleSqlParser

Add `sort by` support for both DSL & SqlParser.

This PR is relevant with #3386, either one merged, will cause the other rebased.

Author: Cheng Hao <hao.cheng@intel.com>

Closes #3481 from chenghao-intel/sortby and squashes the following commits:

041004f [Cheng Hao] Add sort by for DSL & SimpleSqlParser
[SPARK-4694]Fix HiveThriftServer2  cann't stop In Yarn HA mode.

HiveThriftServer2 can not exit automactic when changing the standy resource manager in Yarn HA mode.
The scheduler backend was aware of the AM had been exited so it call sc.stop to exit the driver process but there was a user thread(HiveThriftServer2 ) which was still alive and cause this problem.
To fix it, make a demo thread to detect the sparkContext is null or not.If the sc is stopped, call the ThriftServer.stop to stop the user thread.

Author: carlmartin <carlmartinmax@gmail.com>

Closes #3576 from SaintBacchus/ThriftServer2ExitBug and squashes the following commits:

2890b4a [carlmartin] Use SparkListener instead of the demo thread to stop the hive server.
c15da0e [carlmartin] HiveThriftServer2 can not exit automactic when changing the standy resource manager in Yarn HA mode
[SPARK-3698][SQL] Fix case insensitive resolution of GetField.

Based on #2543.

Author: Michael Armbrust <michael@databricks.com>

Closes #3724 from marmbrus/resolveGetField and squashes the following commits:

0a47aae [Michael Armbrust] Fix case insensitive resolution of GetField.
[SPARK-4493][SQL] Don't pushdown Eq, NotEq, Lt, LtEq, Gt and GtEq predicates with nulls for Parquet

Predicates like `a = NULL` and `a < NULL` can't be pushed down since Parquet `Lt`, `LtEq`, `Gt`, `GtEq` doesn't accept null value. Note that `Eq` and `NotEq` can only be used with `null` to represent predicates like `a IS NULL` and `a IS NOT NULL`.

However, normally this issue doesn't cause NPE because any value compared to `NULL` results `NULL`, and Spark SQL automatically optimizes out `NULL` predicate in the `SimplifyFilters` rule. Only testing code that intentionally disables the optimizer may trigger this issue. (That's why this issue is not marked as blocker and I do **NOT** think we need to backport this to branch-1.1

This PR restricts `Lt`, `LtEq`, `Gt` and `GtEq` to non-null values only, and only uses `Eq` with null value to pushdown `IsNull` and `IsNotNull`. Also, added support for Parquet `NotEq` filter for completeness and (tiny) performance gain, it's also used to pushdown `IsNotNull`.

<!-- Reviewable:start -->
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Author: Cheng Lian <lian@databricks.com>

Closes #3367 from liancheng/filters-with-null and squashes the following commits:

cc41281 [Cheng Lian] Fixes several styling issues
de7de28 [Cheng Lian] Adds stricter rules for Parquet filters with null
[SPARK-4755] [SQL] sqrt(negative value) should return null

Author: Daoyuan Wang <daoyuan.wang@intel.com>

Closes #3616 from adrian-wang/sqrt and squashes the following commits:

d877439 [Daoyuan Wang] fix NULLTYPE
3effa2c [Daoyuan Wang] sqrt(negative value) should return null
[SPARK-3739] [SQL] Update the split num base on block size for table scanning

In local mode, Hadoop/Hive will ignore the "mapred.map.tasks", hence for small table file, it's always a single input split, however, SparkSQL doesn't honor that in table scanning, and we will get different result when do the Hive Compatibility test. This PR will fix that.

Author: Cheng Hao <hao.cheng@intel.com>

Closes #2589 from chenghao-intel/source_split and squashes the following commits:

dff38e7 [Cheng Hao] Remove the extra blank line
160a2b6 [Cheng Hao] fix the compiling bug
04d67f7 [Cheng Hao] Keep 1 split for small file in table scanning
[SPARK-4821] [mllib] [python] [docs] Fix for pyspark.mllib.rand doc

+ small doc edit
+ include edit to make IntelliJ happy

CC: davies  mengxr

Note to davies  -- this does not fix the "WARNING: Literal block expected; none found." warnings since that seems to involve spacing which IntelliJ does not like.  (Those warnings occur when generating the Python docs.)

Author: Joseph K. Bradley <joseph@databricks.com>

Closes #3669 from jkbradley/python-warnings and squashes the following commits:

4587868 [Joseph K. Bradley] fixed warning
8cb073c [Joseph K. Bradley] Updated based on davies recommendation
c51eca4 [Joseph K. Bradley] Updated rst file for pyspark.mllib.rand doc.  Small doc edit.  Small include edit to make IntelliJ happy.
[HOTFIX][SQL] Fix parquet filter suite

Author: Michael Armbrust <michael@databricks.com>

Closes #3727 from marmbrus/parquetNotEq and squashes the following commits:

2157bfc [Michael Armbrust] Fix parquet filter suite
[SPARK-4856] [SQL] NullType instead of StringType when sampling against empty string or nul...

```
TestSQLContext.sparkContext.parallelize(
  """{"ip":"27.31.100.29","headers":{"Host":"1.abc.com","Charset":"UTF-8"}}""" ::
  """{"ip":"27.31.100.29","headers":{}}""" ::
  """{"ip":"27.31.100.29","headers":""}""" :: Nil)
```
As empty string (the "headers") will be considered as String in the beginning (in line 2 and 3), it ignores the real nested data type (struct type "headers" in line 1), and also take the line 1 (the "headers") as String Type, which is not our expected.

Author: Cheng Hao <hao.cheng@intel.com>

Closes #3708 from chenghao-intel/json and squashes the following commits:

e7a72e9 [Cheng Hao] add more concise unit test
853de51 [Cheng Hao] NullType instead of StringType when sampling against empty string or null value
[SPARK-3891][SQL] Add array support to percentile, percentile_approx and constant inspectors support

Supported passing array to percentile and percentile_approx UDAFs
To support percentile_approx,  constant inspectors are supported for GenericUDAF
Constant folding support added to CreateArray expression
Avoided constant udf expression re-evaluation

Author: Venkata Ramana G <ramana.gollamudihuawei.com>

Author: Venkata Ramana Gollamudi <ramana.gollamudi@huawei.com>

Closes #2802 from gvramana/percentile_array_support and squashes the following commits:

a0182e5 [Venkata Ramana Gollamudi] fixed review comment
a18f917 [Venkata Ramana Gollamudi] avoid constant udf expression re-evaluation - fixes failure due to return iterator and value type mismatch
c46db0f [Venkata Ramana Gollamudi] Removed TestHive reset
4d39105 [Venkata Ramana Gollamudi] Unified inspector creation, style check fixes
f37fd69 [Venkata Ramana Gollamudi] Fixed review comments
47f6365 [Venkata Ramana Gollamudi] fixed test
cb7c61e [Venkata Ramana Gollamudi] Supported ConstantInspector for UDAF Fixed HiveUdaf wrap object issue.
7f94aff [Venkata Ramana Gollamudi] Added foldable support to CreateArray
MAINTENANCE: Automated closing of pull requests.

This commit exists to close the following pull requests on Github:

Closes #3137 (close requested by 'marmbrus')
Closes #3362 (close requested by 'marmbrus')
Closes #2979 (close requested by 'JoshRosen')
Closes #2223 (close requested by 'JoshRosen')
Closes #2998 (close requested by 'marmbrus')
Closes #3202 (close requested by 'marmbrus')
Closes #3079 (close requested by 'marmbrus')
Closes #3210 (close requested by 'marmbrus')
Closes #2764 (close requested by 'marmbrus')
Closes #3618 (close requested by 'marmbrus')
Closes #3501 (close requested by 'marmbrus')
Closes #2768 (close requested by 'marmbrus')
Closes #3381 (close requested by 'marmbrus')
Closes #3510 (close requested by 'marmbrus')
Closes #3703 (close requested by 'marmbrus')
Closes #2543 (close requested by 'marmbrus')
Closes #2876 (close requested by 'marmbrus')
Closes #1281 (close requested by 'JoshRosen')
[SPARK-4822] Use sphinx tags for Python doc annotations

Modify python annotations for sphinx. There is no change to build process from.
https://github.com/apache/spark/blob/master/docs/README.md

Author: lewuathe <lewuathe@me.com>

Closes #3685 from Lewuathe/sphinx-tag-for-pydoc and squashes the following commits:

88a0fd9 [lewuathe] [SPARK-4822] Fix DevelopApi and WARN tags
3d7a398 [lewuathe] [SPARK-4822] Use sphinx tags for Python doc annotations
[SPARK-4461][YARN] pass extra java options to yarn application master

Currently, there is no way to pass yarn am specific java options. It cause some potential issues when reading classpath from hadoop configuration file. Hadoop configuration actually replace variables in its property with the system property passed in java options. How to specify the value depends on different hadoop distribution.

The new options are SPARK_YARN_JAVA_OPTS or spark.yarn.extraJavaOptions. I make it as spark global level, because typically we don't want user to specify this in their command line each time submitting spark job after it is setup in spark-defaults.conf.

In addition, with this new extra options enabled to be passed to AM, it provides more flexibility.

For example int the following valid mapred-site.xml file, we have the class path which specify values using system property. Hadoop can correctly handle it because it has java options passed in.

This is the example, currently spark will break due to hadoop.version is not passed in.
  <property>
    <name>mapreduce.application.classpath</name>
    <value>/etc/hadoop/${hadoop.version}/mapreduce/*</value>
  </property>

In the meantime, we cannot relies on  mapreduce.admin.map.child.java.opts in mapred-site.xml, because it has its own extra java options specified, which does not apply to Spark.

Author: Zhan Zhang <zhazhan@gmail.com>

Closes #3409 from zhzhan/Spark-4461 and squashes the following commits:

daec3d0 [Zhan Zhang] solve review comments
08f44a7 [Zhan Zhang] add warning in driver mode if spark.yarn.am.extraJavaOptions is configured
5a505d3 [Zhan Zhang] solve review comments
4ed43ad [Zhan Zhang] solve review comments
ad777ed [Zhan Zhang] Merge branch 'master' into Spark-4461
3e9e574 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
e3f9abe [Zhan Zhang] solve review comments
8963552 [Zhan Zhang] rebase
f8f6700 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
dea1692 [Zhan Zhang] change the option key name to client mode specific
90d5dff [Zhan Zhang] rebase
8ac9254 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
092a25f [Zhan Zhang] solve review comments
bc5a9ae [Zhan Zhang] solve review comments
782b014 [Zhan Zhang] add new configuration to docs/running-on-yarn.md and remove it from spark-defaults.conf.template
6faaa97 [Zhan Zhang] solve review comments
369863f [Zhan Zhang] clean up unnecessary var
733de9c [Zhan Zhang] Merge branch 'master' into Spark-4461
a68e7f0 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
864505a [Zhan Zhang] Add extra java options to be passed to Yarn application master
15830fc [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
685d911 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
03ebad3 [Zhan Zhang] Merge branch 'master' of https://github.com/zhzhan/spark
46d9e3d [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
ebb213a [Zhan Zhang] revert
b983ef3 [Zhan Zhang] test
c4efb9b [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
779d67b [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
4daae6d [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
12e1be5 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
ce0ca7b [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
93f3081 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
3764505 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
a9d372b [Zhan Zhang] Merge branch 'master' of https://github.com/zhzhan/spark
a00f60f [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
497b0f4 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
4a2e36d [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
a72c0d4 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
301eb4a [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
cedcc6f [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
adf4924 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
d10bf00 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
7e0cc36 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
68deb11 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
3ee3b2b [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
2b0d513 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
1ccd7cc [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
af9feb9 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
e4c1982 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
921e914 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
789ea21 [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
cb53a2c [Zhan Zhang] Merge branch 'master' of https://github.com/apache/spark
f6a8a40 [Zhan Zhang] revert
ba14f28 [Zhan Zhang] test
SPARK-3779. yarn spark.yarn.applicationMaster.waitTries config should be...

... changed to a time period

Author: Sandy Ryza <sandy@cloudera.com>

Closes #3471 from sryza/sandy-spark-3779 and squashes the following commits:

20b9887 [Sandy Ryza] Deprecate old property
42b5df7 [Sandy Ryza] Review feedback
9a959a1 [Sandy Ryza] SPARK-3779. yarn spark.yarn.applicationMaster.waitTries config should be changed to a time period
Add mesos specific configurations into doc

Author: Timothy Chen <tnachen@gmail.com>

Closes #3349 from tnachen/mesos_doc and squashes the following commits:

737ef49 [Timothy Chen] Add TOC
5ca546a [Timothy Chen] Update description around cores requested.
26283a5 [Timothy Chen] Add mesos specific configurations into doc
[SPARK-3607] ConnectionManager threads.max configs on the thread pools don't work

Hi all - cleaned up the code to get rid of the unused parameter and added some discussion of the ThreadPoolExecutor parameters to explain why we can use a single threadCount instead of providing a min/max.

Author: Ilya Ganelin <ilya.ganelin@capitalone.com>

Closes #3664 from ilganeli/SPARK-3607C and squashes the following commits:

3c05690 [Ilya Ganelin] Updated documentation and refactored code to extract shared variables
[SPARK-4887][MLlib] Fix a bad unittest in LogisticRegressionSuite

The original test doesn't make sense since if you step in, the lossSum is already NaN,
and the coefficients are diverging. That's because the step size is too large for SGD,
so it doesn't work.

The correct behavior is that you should get smaller coefficients than the one
without regularization. Comparing the values using 20000.0 relative error doesn't
make sense as well.

Author: DB Tsai <dbtsai@alpinenow.com>

Closes #3735 from dbtsai/mlortestfix and squashes the following commits:

b1a3c42 [DB Tsai] first commit
[SPARK-4880] remove spark.locality.wait in Analytics

spark.locality.wait set to 100000 in examples/graphx/Analytics.scala.
Should be left to the user.

Author: Ernest <earneyzxl@gmail.com>

Closes #3730 from Earne/SPARK-4880 and squashes the following commits:

d79ed04 [Ernest] remove spark.locality.wait in Analytics
[SPARK-4884]: Improve Partition docs

Rewording was based on this discussion: http://apache-spark-developers-list.1001551.n3.nabble.com/RDD-data-flow-td9804.html
This is the associated JIRA ticket: https://issues.apache.org/jira/browse/SPARK-4884

Author: Madhu Siddalingaiah <madhu@madhu.com>

Closes #3722 from msiddalingaiah/master and squashes the following commits:

79e679f [Madhu Siddalingaiah] [DOC]: improve documentation
51d14b9 [Madhu Siddalingaiah] Merge remote-tracking branch 'upstream/master'
38faca4 [Madhu Siddalingaiah] Merge remote-tracking branch 'upstream/master'
cbccbfe [Madhu Siddalingaiah] Documentation: replace <b> with <code> (again)
332f7a2 [Madhu Siddalingaiah] Documentation: replace <b> with <code>
cd2b05a [Madhu Siddalingaiah] Merge remote-tracking branch 'upstream/master'
0fc12d7 [Madhu Siddalingaiah] Documentation: add description for repartitionAndSortWithinPartitions