## What changes were proposed in this pull request?

Add test case for scenarios where executor.cores is set as a
(non)divisor of spark.cores.max
This tests the change in
#17786

## How was this patch tested?

Ran the existing test suite with the new tests

dbtsai

Author: Davis Shepherd <dshepherd@netflix.com>

Closes #17788 from dgshep/add_mesos_test.

## What changes were proposed in this pull request?

Set maxCores to be a multiple of the smallest executor that can be launched. This ensures that we correctly detect the condition where no more executors will be launched when spark.cores.max is not a multiple of spark.executor.cores

## How was this patch tested?

This was manually tested with other sample frameworks measuring their incoming offers to determine if starvation would occur.

dbtsai mgummelt

Author: Davis Shepherd <dshepherd@netflix.com>

Closes #17786 from dgshep/fix_mesos_max_cores.

This change does a more thorough redaction of sensitive information from logs and UI
Add unit tests that ensure that no regressions happen that leak sensitive information to the logs.

The motivation for this change was appearance of password like so in `SparkListenerEnvironmentUpdate` in event logs under some JVM configurations:
`"sun.java.command":"org.apache.spark.deploy.SparkSubmit ... --conf spark.executorEnv.HADOOP_CREDSTORE_PASSWORD=secret_password ..."
`
Previously redaction logic was only checking if the key matched the secret regex pattern, it'd redact it's value. That worked for most cases. However, in the above case, the key (sun.java.command) doesn't tell much, so the value needs to be searched. This PR expands the check to check for values as well.

## How was this patch tested?

New unit tests added that ensure that no sensitive information is present in the event logs or the yarn logs. Old unit test in UtilsSuite was modified because the test was asserting that a non-sensitive property's value won't be redacted. However, the non-sensitive value had the literal "secret" in it which was causing it to redact. Simply updating the non-sensitive property's value to another arbitrary value (that didn't have "secret" in it) fixed it.

Author: Mark Grover <mark@apache.org>

Closes #17725 from markgrover/spark-20435.

This patch bumps the master branch version to `2.3.0-SNAPSHOT`.

Author: Josh Rosen <joshrosen@databricks.com>

Closes #17753 from JoshRosen/SPARK-20453.

[SPARK-20385][WEB-UI] Submitted Time' field, the date format needs to be formatted, in running Drivers table or Completed Drivers table in master web ui.

## What changes were proposed in this pull request?
Submitted Time' field, the date format **needs to be formatted**, in running Drivers table or Completed Drivers table in master web ui.
Before fix this problem  e.g.

Completed Drivers
Submission ID	             **Submitted Time**  	             Worker	                            State	   Cores	   Memory	       Main Class
driver-20170419145755-0005	 **Wed Apr 19 14:57:55 CST 2017**	 worker-20170419145250-zdh120-40412	FAILED	   1	       1024.0 MB	   cn.zte.HdfsTest

please see the  attachment:https://issues.apache.org/jira/secure/attachment/12863977/before_fix.png

After fix this problem e.g.

Completed Drivers
Submission ID	             **Submitted Time**  	             Worker	                            State	   Cores	   Memory	       Main Class
driver-20170419145755-0006	 **2017/04/19 16:01:25**	 worker-20170419145250-zdh120-40412	         FAILED	   1	       1024.0 MB	   cn.zte.HdfsTest

please see the  attachment:https://issues.apache.org/jira/secure/attachment/12863976/after_fix.png

'Submitted Time' field, the date format **has been formatted**, in running Applications table or Completed Applicationstable in master web ui, **it is correct.**
e.g.
Running Applications
Application ID	                Name	                Cores	Memory per Executor	   **Submitted Time**	      User	   State	        Duration
app-20170419160910-0000 (kill)	SparkSQL::10.43.183.120	1	    5.0 GB	               **2017/04/19 16:09:10**	  root	   RUNNING	    53 s

**Format after the time easier to observe, and consistent with the applications table,so I think it's worth fixing.**

## How was this patch tested?

(Please explain how this patch was tested. E.g. unit tests, integration tests, manual tests)
(If this patch involves UI changes, please attach a screenshot; otherwise, remove this)

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: 郭小龙 10207633 <guo.xiaolong1@zte.com.cn>
Author: guoxiaolong <guo.xiaolong1@zte.com.cn>
Author: guoxiaolongzte <guo.xiaolong1@zte.com.cn>

Closes #17682 from guoxiaolongzte/SPARK-20385.

## What changes were proposed in this pull request?

Typo fix: distitrbuted -> distributed

## How was this patch tested?

Existing tests

Author: Andrew Ash <andrew@andrewash.com>

Closes #17664 from ash211/patch-1.

[SPARK-19740][MESOS] Add support in Spark to pass arbitrary parameters into docker when running on mesos with docker containerizer

## What changes were proposed in this pull request?

Allow passing in arbitrary parameters into docker when launching spark executors on mesos with docker containerizer tnachen

## How was this patch tested?

Manually built and tested with passed in parameter

Author: Ji Yan <jiyan@Jis-MacBook-Air.local>

Closes #17109 from yanji84/ji/allow_set_docker_user.

## What changes were proposed in this pull request?

This PR proposes to run Spark unidoc to test Javadoc 8 build as Javadoc 8 is easily re-breakable.

There are several problems with it:

- It introduces little extra bit of time to run the tests. In my case, it took 1.5 mins more (`Elapsed :[94.8746569157]`). How it was tested is described in "How was this patch tested?".

- > One problem that I noticed was that Unidoc appeared to be processing test sources: if we can find a way to exclude those from being processed in the first place then that might significantly speed things up.

  (see  joshrosen's [comment](https://issues.apache.org/jira/browse/SPARK-18692?focusedCommentId=15947627&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15947627))

To complete this automated build, It also suggests to fix existing Javadoc breaks / ones introduced by test codes as described above.

There fixes are similar instances that previously fixed. Please refer https://github.com/apache/spark/pull/15999 and https://github.com/apache/spark/pull/16013

Note that this only fixes **errors** not **warnings**. Please see my observation https://github.com/apache/spark/pull/17389#issuecomment-288438704 for spurious errors by warnings.

## How was this patch tested?

Manually via `jekyll build` for building tests. Also, tested via running `./dev/run-tests`.

This was tested via manually adding `time.time()` as below:

```diff
     profiles_and_goals = build_profiles + sbt_goals

     print("[info] Building Spark unidoc (w/Hive 1.2.1) using SBT with these arguments: ",
           " ".join(profiles_and_goals))

+    import time
+    st = time.time()
     exec_sbt(profiles_and_goals)
+    print("Elapsed :[%s]" % str(time.time() - st))
```

produces

```
...
========================================================================
Building Unidoc API Documentation
========================================================================
...
[info] Main Java API documentation successful.
...
Elapsed :[94.8746569157]
...

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #17477 from HyukjinKwon/SPARK-18692.

[SPARK-20156][CORE][SQL][STREAMING][MLLIB] Java String toLowerCase "Turkish locale bug" causes Spark problems

## What changes were proposed in this pull request?

Add Locale.ROOT to internal calls to String `toLowerCase`, `toUpperCase`, to avoid inadvertent locale-sensitive variation in behavior (aka the "Turkish locale problem").

The change looks large but it is just adding `Locale.ROOT` (the locale with no country or language specified) to every call to these methods.

## How was this patch tested?

Existing tests.

Author: Sean Owen <sowen@cloudera.com>

Closes #17527 from srowen/SPARK-20156.

## What changes were proposed in this pull request?

Add spark.mesos.task.labels configuration option to add mesos key:value labels to the executor.

 "k1:v1,k2:v2" as the format, colons separating key-value and commas to list out more than one.

Discussion of labels with mgummelt at #17404

## How was this patch tested?

Added unit tests to verify labels were added correctly, with incorrect labels being ignored and added a test to test the name of the executor.

Tested with: `./build/sbt -Pmesos mesos/test`

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: Kalvin Chau <kalvin.chau@viasat.com>

Closes #17413 from kalvinnchau/mesos-labels.

Current test code tries to override the RackResolver used by setting
configuration params, but because YARN libs statically initialize the
resolver the first time it's used, that means that those configs don't
really take effect during Spark tests.

This change adds a wrapper class that easily allows tests to override the
behavior of the resolver for the Spark code that uses it.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #17508 from vanzin/SPARK-20191.

## What changes were proposed in this pull request?

Currently we use system classloader to find HBase jars, if it is specified by `--jars`, then it will be failed with ClassNotFound issue. So here changing to use child classloader.

Also putting added jars and main jar into classpath of submitted application in yarn cluster mode, otherwise HBase jars specified with `--jars` will never be honored in cluster mode, and fetching tokens in client side will always be failed.

## How was this patch tested?

Unit test and local verification.

Author: jerryshao <sshao@hortonworks.com>

Closes #17388 from jerryshao/SPARK-20059.

[SPARK-19995][YARN] Register tokens to current UGI to avoid re-issuing of tokens in yarn client mode

## What changes were proposed in this pull request?

In the current Spark on YARN code, we will obtain tokens from provided services, but we're not going to add these tokens to the current user's credentials. This will make all the following operations to these services still require TGT rather than delegation tokens. This is unnecessary since we already got the tokens, also this will lead to failure in user impersonation scenario, because the TGT is granted by real user, not proxy user.

So here changing to put all the tokens to the current UGI, so that following operations to these services will honor tokens rather than TGT, and this will further handle the proxy user issue mentioned above.

## How was this patch tested?

Local verified in secure cluster.

vanzin tgravescs mridulm  dongjoon-hyun please help to review, thanks a lot.

Author: jerryshao <sshao@hortonworks.com>

Closes #17335 from jerryshao/SPARK-19995.

## What changes were proposed in this pull request?
Adding additional information to existing logging messages:
  - YarnAllocator: log the executor ID together with the container id when a container for an executor is launched.
  - NettyRpcEnv: log the receiver address when there is a timeout waiting for an answer to a remote call.
  - ExecutorAllocationManager: fix a typo in the logging message for the list of executors to be removed.

## How was this patch tested?
Build spark and submit the word count example to a YARN cluster using cluster mode

Author: Juan Rodriguez Hortala <hortala@amazon.com>

Closes #17411 from juanrh/logging-improvements.

## What changes were proposed in this pull request?

Adding configurable mesos executor names and labels using `spark.mesos.task.name` and `spark.mesos.task.labels`.

Labels were defined as `k1:v1,k2:v2`.

mgummelt

## How was this patch tested?

Added unit tests to verify labels were added correctly, with incorrect labels being ignored and added a test to test the name of the executor.

Tested with: `./build/sbt -Pmesos mesos/test`

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: Kalvin Chau <kalvin.chau@viasat.com>

Closes #17404 from kalvinnchau/mesos-config.

This commit adds a killTaskAttempt method to SparkContext, to allow users to
kill tasks so that they can be re-scheduled elsewhere.

This also refactors the task kill path to allow specifying a reason for the task kill. The reason is propagated opaquely through events, and will show up in the UI automatically as `(N killed: $reason)` and `TaskKilled: $reason`. Without this change, there is no way to provide the user feedback through the UI.

Currently used reasons are "stage cancelled", "another attempt succeeded", and "killed via SparkContext.killTask". The user can also specify a custom reason through `SparkContext.killTask`.

cc rxin

In the stage overview UI the reasons are summarized:
![1](https://cloud.githubusercontent.com/assets/14922/23929209/a83b2862-08e1-11e7-8b3e-ae1967bbe2e5.png)

Within the stage UI you can see individual task kill reasons:
![2](https://cloud.githubusercontent.com/assets/14922/23929200/9a798692-08e1-11e7-8697-72b27ad8a287.png)

Existing tests, tried killing some stages in the UI and verified the messages are as expected.

Author: Eric Liang <ekl@databricks.com>
Author: Eric Liang <ekl@google.com>

Closes #17166 from ericl/kill-reason.

## What changes were proposed in this pull request?

Fixup typo in comment.

## How was this patch tested?

Don't need.

Author: Ye Yin <eyniy@qq.com>

Closes #17396 from hustcat/fix.

This fix removes deprecated support for config `SPARK_YARN_USER_ENV`, as is mentioned in SPARK-17979.
This fix also removes deprecated support for the following:
```
SPARK_YARN_USER_ENV
SPARK_JAVA_OPTS
SPARK_CLASSPATH
SPARK_WORKER_INSTANCES
```

Related JIRA:
[SPARK-14453]: https://issues.apache.org/jira/browse/SPARK-14453
[SPARK-12344]: https://issues.apache.org/jira/browse/SPARK-12344
[SPARK-15781]: https://issues.apache.org/jira/browse/SPARK-15781

Existing tests should pass.

Author: Yong Tang <yong.tang.github@outlook.com>

Closes #17212 from yongtang/SPARK-17979.

Add parentheses so that both lines form a single statement; also add
a log message so that the issue becomes more explicit if it shows up
again.

Tested manually with integration test that exercises the feature.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #17198 from vanzin/SPARK-19857.

## What changes were proposed in this pull request?

Increase default refuse_seconds timeout, and make it configurable.  See JIRA for details on how this reduces the risk of starvation.

## How was this patch tested?

Unit tests, Manual testing, and Mesos/Spark integration test suite

cc susanxhuynh skonto jmlvanre

Author: Michael Gummelt <mgummelt@mesosphere.io>

Closes #17031 from mgummelt/SPARK-19702-suppress-revive.

[SPARK-19373][MESOS] Base spark.scheduler.minRegisteredResourceRatio on registered cores rather than accepted cores

## What changes were proposed in this pull request?

See JIRA

## How was this patch tested?

Unit tests, Mesos/Spark integration tests

cc skonto susanxhuynh

Author: Michael Gummelt <mgummelt@mesosphere.io>

Closes #17045 from mgummelt/SPARK-19373-registered-resources.

[SPARK-15288][MESOS] Mesos dispatcher should handle gracefully when any thread gets UncaughtException

## What changes were proposed in this pull request?

Adding the default UncaughtExceptionHandler to the MesosClusterDispatcher.
## How was this patch tested?

I verified it manually, when any of the dispatcher thread gets uncaught exceptions then the default UncaughtExceptionHandler will handle those exceptions.

Author: Devaraj K <devaraj@apache.org>

Closes #13072 from devaraj-kavali/SPARK-15288.

## What changes were proposed in this pull request?
self.environment will be propagated to executor. Should set PYTHONHASHSEED as long as the python version is greater than 3.3

## How was this patch tested?
Manually tested it.

Author: Jeff Zhang <zjffdu@apache.org>

Closes #11211 from zjffdu/SPARK-13330.

## What changes were proposed in this pull request?

Because yarn#client will reset the `spark.yarn.keytab` configuration to point to the location in distributed file, so if user still uses the old `SparkConf` to create `SparkSession` with Hive enabled, it will read keytab from the path in distributed cached. This is OK for yarn cluster mode, but in yarn client mode where driver is running out of container, it will be failed to fetch the keytab.

So here we should avoid reseting this configuration in the `yarn#client` and only overwriting it for AM, so using `spark.yarn.keytab` could get correct keytab path no matter running in client (keytab in local fs) or cluster (keytab in distributed cache) mode.

## How was this patch tested?

Verified in security cluster.

Author: jerryshao <sshao@hortonworks.com>

Closes #16923 from jerryshao/SPARK-19038.

Allow an application to use the History Server URL as the tracking
URL in the YARN RM, so there's still a link to the web UI somewhere
in YARN even if the driver's UI is disabled. This is useful, for
example, if an admin wants to disable the driver UI by default for
applications, since it's harder to secure it (since it involves non
trivial ssl certificate and auth management that admins may not want
to expose to user apps).

This needs to be opt-in, because of the way the YARN proxy works, so
a new configuration was added to enable the option.

The YARN RM will proxy requests to live AMs instead of redirecting
the client, so pages in the SHS UI will not render correctly since
they'll reference invalid paths in the RM UI. The proxy base support
in the SHS cannot be used since that would prevent direct access to
the SHS.

So, to solve this problem, for the feature to work end-to-end, a new
YARN-specific filter was added that detects whether the requests come
from the proxy and redirects the client appropriatly. The SHS admin has
to add this filter manually if they want the feature to work.

Tested with new unit test, and by running with the documented configuration
set in a test cluster. Also verified the driver UI is used when it's
enabled.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #16946 from vanzin/SPARK-19554.

## What changes were proposed in this pull request?

In https://github.com/apache/spark/pull/14065, we introduced a configurable credential manager for Spark running on YARN. Also two configs `spark.yarn.credentials.renewalTime` and `spark.yarn.credentials.updateTime` were added, one is for the credential renewer and the other updater. But now we just query `spark.yarn.credentials.renewalTime` by mistake during CREDENTIALS UPDATING, where should be actually `spark.yarn.credentials.updateTime` .

This PR fixes this mistake.

## How was this patch tested?

existing test

cc jerryshao vanzin

Author: Kent Yao <yaooqinn@hotmail.com>

Closes #16955 from yaooqinn/cred_update.

## What changes were proposed in this pull request?

`askSync` is already added in `RpcEndpointRef` (see SPARK-19347 and https://github.com/apache/spark/pull/16690#issuecomment-276850068) and `askWithRetry` is marked as deprecated.
As mentioned SPARK-18113(https://github.com/apache/spark/pull/16503#event-927953218):

>askWithRetry is basically an unneeded API, and a leftover from the akka days that doesn't make sense anymore. It's prone to cause deadlocks (exactly because it's blocking), it imposes restrictions on the caller (e.g. idempotency) and other things that people generally don't pay that much attention to when using it.

Since `askWithRetry` is just used inside spark and not in user logic. It might make sense to replace all of them with `askSync`.

## How was this patch tested?
This PR doesn't change code logic, existing unit test can cover.

Author: jinxing <jinxing@meituan.com>

Closes #16790 from jinxing64/SPARK-19450.

- Move external/java8-tests tests into core, streaming, sql and remove
- Remove MaxPermGen and related options
- Fix some reflection / TODOs around Java 8+ methods
- Update doc references to 1.7/1.8 differences
- Remove Java 7/8 related build profiles
- Update some plugins for better Java 8 compatibility
- Fix a few Java-related warnings

For the future:

- Update Java 8 examples to fully use Java 8
- Update Java tests to use lambdas for simplicity
- Update Java internal implementations to use lambdas

## How was this patch tested?

Existing tests

Author: Sean Owen <sowen@cloudera.com>

Closes #16871 from srowen/SPARK-19493.

## What changes were proposed in this pull request?

As discussed in [JIRA](https://issues.apache.org/jira/browse/SPARK-19501), this patch addresses the problem where too many HDFS RPCs are made when there are many URIs specified in `spark.yarn.jars`, potentially adding hundreds of RTTs to YARN before the application launches. This becomes significant when submitting the application to a non-local YARN cluster (where the RTT may be in order of 100ms, for example). For each URI specified, the current implementation makes at least two HDFS RPCs, for:

- [Calling `getFileStatus()` before uploading each file to the distributed cache in `ClientDistributedCacheManager.addResource()`](https://github.com/apache/spark/blob/v2.1.0/yarn/src/main/scala/org/apache/spark/deploy/yarn/ClientDistributedCacheManager.scala#L71).
- [Resolving any symbolic links in each of the file URI](https://github.com/apache/spark/blob/v2.1.0/yarn/src/main/scala/org/apache/spark/deploy/yarn/Client.scala#L377-L379), which repeatedly makes HDFS RPCs until the all symlinks are resolved. (see [`FileContext.resolve(Path)`](https://github.com/apache/hadoop/blob/release-2.7.1/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileContext.java#L2189-L2195), [`FSLinkResolver.resolve(FileContext, Path)`](https://github.com/apache/hadoop/blob/release-2.7.1/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FSLinkResolver.java#L79-L112), and [`AbstractFileSystem.resolvePath()`](https://github.com/apache/hadoop/blob/release-2.7.1/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/AbstractFileSystem.java#L464-L468).)

The first `getFileStatus` RPC can be removed, using `statCache` populated with the file statuses retrieved with [the previous `globStatus` call](https://github.com/apache/spark/blob/v2.1.0/yarn/src/main/scala/org/apache/spark/deploy/yarn/Client.scala#L531).

The second one can be largely reduced by caching the symlink resolution results in a mutable.HashMap. This patch adds a local variable in `yarn.Client.prepareLocalResources()` and passes it as an additional parameter to `yarn.Client.copyFileToRemote`.  [The symlink resolution code was added in 2013](https://github.com/apache/spark/commit/a35472e1dd2ea1b5a0b1fb6b382f5a98f5aeba5a#diff-b050df3f55b82065803d6e83453b9706R187) and has not changed since. I am assuming that this is still required, but otherwise we can remove using `symlinkCache` and symlink resolution altogether.

## How was this patch tested?

This patch is based off 8e8afb3a, currently the latest YARN patch on master. All tests except a few in spark-hive passed with `./dev/run-tests` on my machine, using JDK 1.8.0_112 on macOS 10.12.3; also tested myself with this modified version of SPARK 2.2.0-SNAPSHOT which performed a normal deployment and execution on a YARN cluster without errors.

Author: Jong Wook Kim <jongwook@nyu.edu>

Closes #16916 from jongwook/SPARK-19501.

[SPARK-10748][MESOS] Log error instead of crashing Spark Mesos dispatcher when a job is misconfigured

## What changes were proposed in this pull request?

Now handling the spark exception which gets thrown for invalid job configuration, marking that job as failed and continuing to launch the other drivers instead of throwing the exception.
## How was this patch tested?

I verified manually, now the misconfigured jobs move to Finished Drivers section in UI and continue to launch the other jobs.

Author: Devaraj K <devaraj@apache.org>

Closes #13077 from devaraj-kavali/SPARK-10748.

## What changes were proposed in this pull request?

Due to the newly added API in Hadoop 2.6.4+, Spark builds against Hadoop 2.6.0~2.6.3 will meet compile error. So here still reverting back to use reflection to handle this issue.

## How was this patch tested?

Manual verification.

Author: jerryshao <sshao@hortonworks.com>

Closes #16884 from jerryshao/SPARK-19545.

[SPARK-19464][BUILD][HOTFIX][TEST-HADOOP2.6] Add back mockito test dep in YARN module, as it ends up being required in a Maven build

Add back mockito test dep in YARN module, as it ends up being required in a Maven build

## How was this patch tested?

PR builder again, but also a local `mvn` run using the command that the broken Jenkins job uses

Author: Sean Owen <sowen@cloudera.com>

Closes #16853 from srowen/SPARK-19464.2.

[SPARK-19409][BUILD][TEST-MAVEN] Fix ParquetAvroCompatibilitySuite failure due to test dependency on avro

## What changes were proposed in this pull request?

After using Apache Parquet 1.8.2, `ParquetAvroCompatibilitySuite` fails on **Maven** test. It is because `org.apache.parquet.avro.AvroParquetWriter` in the test code used new `avro 1.8.0` specific class, `LogicalType`. This PR aims to fix the test dependency of `sql/core` module to use avro 1.8.0.

https://amplab.cs.berkeley.edu/jenkins/view/Spark%20QA%20Test%20(Dashboard)/job/spark-master-test-maven-hadoop-2.7/2530/consoleFull

```
ParquetAvroCompatibilitySuite:
*** RUN ABORTED ***
  java.lang.NoClassDefFoundError: org/apache/avro/LogicalType
  at org.apache.parquet.avro.AvroParquetWriter.writeSupport(AvroParquetWriter.java:144)
```

## How was this patch tested?

Pass the existing test with **Maven**.

```
$ build/mvn -Pyarn -Phadoop-2.7 -Pkinesis-asl -Phive -Phive-thriftserver test
...
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 02:07 h
[INFO] Finished at: 2017-02-04T05:41:43+00:00
[INFO] Final Memory: 77M/987M
[INFO] ------------------------------------------------------------------------
```

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #16795 from dongjoon-hyun/SPARK-19409-2.

## What changes were proposed in this pull request?

- Remove support for Hadoop 2.5 and earlier
- Remove reflection and code constructs only needed to support multiple versions at once
- Update docs to reflect newer versions
- Remove older versions' builds and profiles.

## How was this patch tested?

Existing tests

Author: Sean Owen <sowen@cloudera.com>

Closes #16810 from srowen/SPARK-19464.

That method is prone to stack overflows when the input map is really
large; instead, use plain "map". Also includes a unit test that was
tested and caused stack overflows without the fix.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #16667 from vanzin/SPARK-18750.

This change introduces a new auth mechanism to the transport library,
to be used when users enable strong encryption. This auth mechanism
has better security than the currently used DIGEST-MD5.

The new protocol uses symmetric key encryption to mutually authenticate
the endpoints, and is very loosely based on ISO/IEC 9798.

The new protocol falls back to SASL when it thinks the remote end is old.
Because SASL does not support asking the server for multiple auth protocols,
which would mean we could re-use the existing SASL code by just adding a
new SASL provider, the protocol is implemented outside of the SASL API
to avoid the boilerplate of adding a new provider.

Details of the auth protocol are discussed in the included README.md
file.

This change partly undos the changes added in SPARK-13331; AES encryption
is now decoupled from SASL authentication. The encryption code itself,
though, has been re-used as part of this change.

## How was this patch tested?

- Unit tests
- Tested Spark 2.2 against Spark 1.6 shuffle service with SASL enabled
- Tested Spark 2.2 against Spark 2.2 shuffle service with SASL fallback disabled

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #16521 from vanzin/SPARK-19139.

## What changes were proposed in this pull request?
remove ununsed imports and outdated comments, and fix some minor code style issue.

## How was this patch tested?
existing ut

Author: uncleGen <hustyugm@gmail.com>

Closes #16591 from uncleGen/SPARK-19227.

## What changes were proposed in this pull request?

`spark.yarn.access.namenodes` configuration cannot actually reflects the usage of it, inside the code it is the Hadoop filesystems we get tokens, not NNs. So here propose to update the name of this configuration, also change the related code and doc.

## How was this patch tested?

Local verification.

Author: jerryshao <sshao@hortonworks.com>

Closes #16560 from jerryshao/SPARK-19179.

## What changes were proposed in this pull request?
#16092 moves YARN resource manager related code to resource-managers/yarn directory. The test case ```YarnSchedulerBackendSuite``` was added after that but with the wrong place. I move it to correct directory in this PR.

## How was this patch tested?
Existing test.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #16595 from yanboliang/yarn.

Currently Spark can only get token renewal interval from security HDFS (hdfs://), if Spark runs with other security file systems like webHDFS (webhdfs://), wasb (wasb://), ADLS, it will ignore these tokens and not get token renewal intervals from these tokens. These will make Spark unable to work with these security clusters. So instead of only checking HDFS token, we should generalize to support different DelegationTokenIdentifier.

## How was this patch tested?

Manually verified in security cluster.

Author: jerryshao <sshao@hortonworks.com>

Closes #16432 from jerryshao/SPARK-19021.