## What changes were proposed in this pull request?

After SPARK-6990, `dev/lint-java` keeps Java code healthy and helps PR review by saving much time.
This issue aims remove unused imports from Java/Scala code and add `UnusedImports` checkstyle rule to help developers.

## How was this patch tested?
```
./dev/lint-java
./build/sbt compile
```

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #11438 from dongjoon-hyun/SPARK-13583.

## What changes were proposed in this pull request?
As the title says, this moves the three modules currently in network/ into common/network-*. This removes one top level, non-user-facing folder.

## How was this patch tested?
Compilation and existing tests. We should run both SBT and Maven.

Author: Reynold Xin <rxin@databricks.com>

Closes #11409 from rxin/SPARK-13529.

## What changes were proposed in this pull request?

Add support for SPARK_DAEMON_JAVA_OPTS with MesosClusterDispatcher.

## How was the this patch tested?

Manual testing by launching dispatcher with SPARK_DAEMON_JAVA_OPTS

Author: Timothy Chen <tnachen@gmail.com>

Closes #11277 from tnachen/cluster_dispatcher_opts.

See http://openjdk.java.net/jeps/223 for more information about the JDK 9 version string scheme.

Author: Claes Redestad <claes.redestad@gmail.com>

Closes #11160 from cl4es/master.

This patch changes Spark's build to make Scala 2.11 the default Scala version. To be clear, this does not mean that Spark will stop supporting Scala 2.10: users will still be able to compile Spark for Scala 2.10 by following the instructions on the "Building Spark" page; however, it does mean that Scala 2.11 will be the default Scala version used by our CI builds (including pull request builds).

The Scala 2.11 compiler is faster than 2.10, so I think we'll be able to look forward to a slight speedup in our CI builds (it looks like it's about 2X faster for the Maven compile-only builds, for instance).

After this patch is merged, I'll update Jenkins to add new compile-only jobs to ensure that Scala 2.10 compilation doesn't break.

Author: Josh Rosen <joshrosen@databricks.com>

Closes #10608 from JoshRosen/SPARK-6363.

…spark/sparkR

Author: Jeff Zhang <zjffdu@apache.org>

Closes #10658 from zjffdu/SPARK-12707.

Include the following changes:

1. Close `java.sql.Statement`
2. Fix incorrect `asInstanceOf`.
3. Remove unnecessary `synchronized` and `ReentrantLock`.

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #10440 from zsxwing/findbugs.

Author: Reynold Xin <rxin@databricks.com>

Closes #10395 from rxin/SPARK-11808.

Author: Reynold Xin <rxin@databricks.com>

Closes #10387 from rxin/version-bump.

Please help to review, thanks a lot.

Author: jerryshao <sshao@hortonworks.com>

Closes #10195 from jerryshao/SPARK-10123.

This change abstracts the code that serves jars / files to executors so that
each RpcEnv can have its own implementation; the akka version uses the existing
HTTP-based file serving mechanism, while the netty versions uses the new
stream support added to the network lib, which makes file transfers benefit
from the easier security configuration of the network library, and should also
reduce overhead overall.

The change includes a small fix to TransportChannelHandler so that it propagates
user events to downstream handlers.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #9530 from vanzin/SPARK-11140.

Exception details can be seen here (https://issues.apache.org/jira/browse/SPARK-11744).

Author: jerryshao <sshao@hortonworks.com>

Closes #9721 from jerryshao/SPARK-11744.

The stop() callback was trying to close the launcher connection in the
same thread that handles connection data, which ended up causing a
deadlock. So avoid that by dispatching the stop() request in its own
thread.

On top of that, add some exception safety to a few parts of the code,
and use "destroyForcibly" from Java 8 if it's available, to force
kill the child process. The flip side is that "kill()" may not actually
work if running Java 7.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #9633 from vanzin/SPARK-11655.

Java 8 javadoc does not like self closing tags: ```<p/>```, ```<br/>```, ...

This PR fixes those.

Author: Herman van Hovell <hvanhovell@questtec.nl>

Closes #9339 from hvanhovell/SPARK-11388.

The test could fail depending on scheduling of the various threads
involved; the change removes some sources of races, while making the
test a little more resilient by trying a few times before giving up.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #9079 from vanzin/SPARK-11071.

Please help review it. Thanks

Author: Jeff Zhang <zjffdu@apache.org>

Closes #9114 from zjffdu/SPARK-11099.

This change adds an API that encapsulates information about an app
launched using the library. It also creates a socket-based communication
layer for apps that are launched as child processes; the launching
application listens for connections from launched apps, and once
communication is established, the channel can be used to send updates
to the launching app, or to send commands to the child app.

The change also includes hooks for local, standalone/client and yarn
masters.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #7052 from vanzin/SPARK-8673.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #8775 from vanzin/SPARK-10300.

This makes YARN containers behave like all other processes launched by
Spark, which launch with a default perm gen size of 256m unless
overridden by the user (or not needed by the vm).

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #8970 from vanzin/SPARK-10916.

This reverts commit 8abef21d.

This change does two things:

- tag a few tests and adds the mechanism in the build to be able to disable those tags,
  both in maven and sbt, for both junit and scalatest suites.
- add some logic to run-tests.py to disable some tags depending on what files have
  changed; that's used to disable expensive tests when a module hasn't explicitly
  been changed, to speed up testing for changes that don't directly affect those
  modules.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #8437 from vanzin/test-tags.

Author: Reynold Xin <rxin@databricks.com>

Closes #8350 from rxin/1.6.

This change aims at speeding up the dev cycle a little bit, by making
sure that all tests behave the same w.r.t. where the code to be tested
is loaded from. Namely, that means that tests don't rely on the assembly
anymore, rather loading all needed classes from the build directories.

The main change is to make sure all build directories (classes and test-classes)
are added to the classpath of child processes when running tests.

YarnClusterSuite required some custom code since the executors are run
differently (i.e. not through the launcher library, like standalone and
Mesos do).

I also found a couple of tests that could leak a SparkContext on failure,
and added code to handle those.

With this patch, it's possible to run the following command from a clean
source directory and have all tests pass:

  mvn -Pyarn -Phadoop-2.4 -Phive-thriftserver install

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #7629 from vanzin/SPARK-9284.

Tiny modification to a few comments ```sbt publishLocal``` work again.

Author: Herman van Hovell <hvanhovell@questtec.nl>

Closes #8209 from hvanhovell/SPARK-9980.

This change allows any Spark argument to be added to the app to
be started using SparkLauncher. Known arguments are properly
validated, while unknown arguments are allowed so that the
library can launch newer Spark versions (in case SPARK_HOME points
at one).

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #7975 from vanzin/SPARK-9074 and squashes the following commits:

b5e451a [Marcelo Vanzin] [SPARK-9074] [launcher] Allow arbitrary Spark args to be set.

While the functionality is there to exclude packages, there are no flags that allow users to exclude dependencies, in case of dependency conflicts. We should provide users with a flag to add dependency exclusions in case the packages are not resolved properly (or not available due to licensing).

The flag I added was --packages-exclude, but I'm open on renaming it. I also added property flags in case people would like to use a conf file to provide dependencies, which is possible if there is a long list of dependencies or exclusions.

cc andrewor14 vanzin pwendell

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #7599 from brkyvz/packages-exclusions and squashes the following commits:

636f410 [Burak Yavuz] addressed nits
6e54ede [Burak Yavuz] is this the culprit
b5e508e [Burak Yavuz] Merge branch 'master' of github.com:apache/spark into packages-exclusions
154f5db [Burak Yavuz] addressed initial comments
1536d7a [Burak Yavuz] Added flags to exclude packages using --packages-exclude

This patch builds directly on #7820, which is largely written by tnachen. The only addition is one commit for cleaning up the code. There should be no functional differences between this and #7820.

Author: Timothy Chen <tnachen@gmail.com>
Author: Andrew Or <andrew@databricks.com>

Closes #7881 from andrewor14/tim-cleanup-mesos-shuffle and squashes the following commits:

8894f7d [Andrew Or] Clean up code
2a5fa10 [Andrew Or] Merge branch 'mesos_shuffle_clean' of github.com:tnachen/spark into tim-cleanup-mesos-shuffle
fadff89 [Timothy Chen] Address comments.
e4d0f1d [Timothy Chen] Clean up external shuffle data on driver exit with Mesos.

These are minor corrections in the documentation of several classes that are preventing:

```bash
build/sbt publish-local
```

I believe this might be an issue associated with running JDK8 as ankurdave does not appear to have this issue in JDK7.

Author: Joseph Gonzalez <joseph.e.gonzalez@gmail.com>

Closes #7354 from jegonzal/FixingJavadocErrors and squashes the following commits:

6664b7e [Joseph Gonzalez] making requested changes
2e16d89 [Joseph Gonzalez] Fixing errors in javadocs that prevents build/sbt publish-local from completing.

I am increasing the perm gen size to 256m.

https://issues.apache.org/jira/browse/SPARK-8776

Author: Yin Huai <yhuai@databricks.com>

Closes #7196 from yhuai/SPARK-8776 and squashes the following commits:

60901b4 [Yin Huai] Fix test.
d44b713 [Yin Huai] Make sparkShell and hiveConsole use 256m PermGen size.
30aaf8e [Yin Huai] Increase the default PermGen size to 256m.

I've updated default values in comments, documentation, and in the command line builder to be 1g based on comments in the JIRA. I've also updated most usages to point at a single variable defined in the Utils.scala and JavaUtils.java files. This wasn't possible in all cases (R, shell scripts etc.) but usage in most code is now pointing at the same place.

Please let me know if I've missed anything.

Will the spark-shell use the value within the command line builder during instantiation?

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

Closes #7132 from ilganeli/SPARK-3071 and squashes the following commits:

4074164 [Ilya Ganelin] String fix
271610b [Ilya Ganelin] Merge branch 'SPARK-3071' of github.com:ilganeli/spark into SPARK-3071
273b6e9 [Ilya Ganelin] Test fix
fd67721 [Ilya Ganelin] Update JavaUtils.java
26cc177 [Ilya Ganelin] test fix
e5db35d [Ilya Ganelin] Fixed test failure
39732a1 [Ilya Ganelin] merge fix
a6f7deb [Ilya Ganelin] Created default value for DRIVER MEM in Utils that's now used in almost all locations instead of setting manually in each
09ad698 [Ilya Ganelin] Update SubmitRestProtocolSuite.scala
19b6f25 [Ilya Ganelin] Missed one doc update
2698a3d [Ilya Ganelin] Updated default value for driver memory

This patch excludes `hadoop-client`'s dependency on `mockito-all`.  As of #7061, Spark depends on `mockito-core` instead of `mockito-all`, so the dependency from Hadoop was leading to test compilation failures for some of the Hadoop 2 SBT builds.

Author: Josh Rosen <joshrosen@databricks.com>

Closes #7090 from JoshRosen/SPARK-8709 and squashes the following commits:

e190122 [Josh Rosen] [SPARK-8709] Exclude hadoop-client's mockito-all dependency.

Spark's tests currently depend on `mockito-all`, which bundles Hamcrest and Objenesis classes. Instead, it should depend on `mockito-core`, which declares those libraries as Maven dependencies. This is necessary in order to fix a dependency conflict that leads to a NoSuchMethodError when using certain Hamcrest matchers.

See https://github.com/mockito/mockito/wiki/Declaring-mockito-dependency for more details.

Author: Josh Rosen <joshrosen@databricks.com>

Closes #7061 from JoshRosen/mockito-core-instead-of-all and squashes the following commits:

70eccbe [Josh Rosen] Depend on mockito-core instead of mockito-all.

SPARK_JAVA_OPTS was missed in reconstructing the launcher part, we should add it back so process launched by spark-class could read it properly. And so does `SPARK_DRIVER_MEMORY`.

The missing part is [here](https://github.com/apache/spark/blob/1c30afdf94b27e1ad65df0735575306e65d148a1/bin/spark-class#L97).

Author: WangTaoTheTonic <wangtao111@huawei.com>
Author: Tao Wang <wangtao111@huawei.com>

Closes #6741 from WangTaoTheTonic/SPARK-8290 and squashes the following commits:

bd89f0f [Tao Wang] make sure the memory setting is right too
e313520 [WangTaoTheTonic] spark class command builder need read SPARK_JAVA_OPTS

Reorganize code so that the launcher library handles most of the work
of printing usage messages, instead of having an awkward protocol between
the library and the scripts for that.

This mostly applies to SparkSubmit, since the launcher lib does not do
command line parsing for classes invoked in other ways, and thus cannot
handle failures for those. Most scripts end up going through SparkSubmit,
though, so it all works.

The change adds a new, internal command line switch, "--usage-error",
which prints the usage message and exits with a non-zero status. Scripts
can override the command printed in the usage message by setting an
environment variable - this avoids having to grep the output of
SparkSubmit to remove references to the "spark-submit" script.

The only sub-optimal part of the change is the special handling for the
spark-sql usage, which is now done in SparkSubmitArguments.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #5841 from vanzin/SPARK-6324 and squashes the following commits:

2821481 [Marcelo Vanzin] Merge branch 'master' into SPARK-6324
bf139b5 [Marcelo Vanzin] Filter output of Spark SQL CLI help.
c6609bf [Marcelo Vanzin] Fix exit code never being used when printing usage messages.
6bc1b41 [Marcelo Vanzin] [SPARK-6324] [core] Centralize handling of script usage messages.

Author: Patrick Wendell <patrick@databricks.com>

Closes #6328 from pwendell/spark-1.5-update and squashes the following commits:

2f42d02 [Patrick Wendell] A few more excludes
4bebcf0 [Patrick Wendell] Update to RC4
61aaf46 [Patrick Wendell] Using new release candidate
55f1610 [Patrick Wendell] Another exclude
04b4f04 [Patrick Wendell] More issues with transient 1.4 changes
36f549b [Patrick Wendell] [SPARK-7801] [BUILD] Updating versions to SPARK 1.5.0

I found this by chance while building spark and think it is better to keep its name consistent with other sub-projects (Spark Project *).

I am not gonna file JIRA as it is a pretty small issue.

Author: WangTaoTheTonic <wangtao111@huawei.com>

Closes #6603 from WangTaoTheTonic/projName and squashes the following commits:

994b3ba [WangTaoTheTonic] make the project name consistent

https://issues.apache.org/jira/browse/SPARK-7945

Now applications submited by org.apache.spark.launcher.Main read properties file without doing trim to values in it.
If user left a space after a value(say spark.driver.extraClassPath) then it probably affect global functions(like some jar could not be included in the classpath), so we should do it like Utils.getPropertiesFromFile.

Author: WangTaoTheTonic <wangtao111@huawei.com>
Author: Tao Wang <wangtao111@huawei.com>

Closes #6496 from WangTaoTheTonic/SPARK-7945 and squashes the following commits:

bb41b4b [Tao Wang] indent 4 to 2
6dd1cf2 [WangTaoTheTonic] use a simpler way
2c053a1 [WangTaoTheTonic] Do trim to values in properties file

IBM's Java VM doesn't have the concept of a permgen, so this option shouldn't be passed when the vendor property shows it is an IBM JDK.

Author: Tim Ellison <t.p.ellison@gmail.com>
Author: Tim Ellison <tellison@users.noreply.github.com>

Closes #6055 from tellison/MaxPermSize and squashes the following commits:

3a0fb66 [Tim Ellison] Convert tabs back to spaces
6ad4266 [Tim Ellison] Remove unnecessary else clauses to reduce nesting.
d27174b [Tim Ellison] Merge branch 'master' of https://github.com/apache/spark into MaxPermSize
42a8c3f [Tim Ellison] [MINOR] Avoid passing the PermGenSize option to IBM JVMs.

We should let Thrift Server take these two parameters as it is a daemon. And it is better to read driver-related configs as an app submited by spark-submit.

https://issues.apache.org/jira/browse/SPARK-7031

Author: WangTaoTheTonic <wangtao111@huawei.com>

Closes #5609 from WangTaoTheTonic/SPARK-7031 and squashes the following commits:

8d3fc16 [WangTaoTheTonic] indent
035069b [WangTaoTheTonic] better code style
d3ddfb6 [WangTaoTheTonic] revert the unnecessary changes in suite
624e652 [WangTaoTheTonic] fix break tests
0565831 [WangTaoTheTonic] fix failed tests
4fb25ed [WangTaoTheTonic] let thrift server take SPARK_DAEMON_MEMORY and SPARK_DAEMON_JAVA_OPTS

Take 2. Does the same thing as #4688, but fixes Hadoop-1 build.

Author: Hari Shreedharan <hshreedharan@apache.org>

Closes #5823 from harishreedharan/kerberos-longrunning and squashes the following commits:

3c86bba [Hari Shreedharan] Import fixes. Import postfixOps explicitly.
4d04301 [Hari Shreedharan] Minor formatting fixes.
b5e7a72 [Hari Shreedharan] Remove reflection, use a method in SparkHadoopUtil to update the token renewer.
7bff6e9 [Hari Shreedharan] Make sure all required classes are present in the jar. Fix import order.
e851f70 [Hari Shreedharan] Move the ExecutorDelegationTokenRenewer to yarn module. Use reflection to use it.
36eb8a9 [Hari Shreedharan] Change the renewal interval config param. Fix a bunch of comments.
611923a [Hari Shreedharan] Make sure the namenodes are listed correctly for creating tokens.
09fe224 [Hari Shreedharan] Use token.renew to get token's renewal interval rather than using hdfs-site.xml
6963bbc [Hari Shreedharan] Schedule renewal in AM before starting user class. Else, a restarted AM cannot access HDFS if the user class tries to.
072659e [Hari Shreedharan] Fix build failure caused by thread factory getting moved to ThreadUtils.
f041dd3 [Hari Shreedharan] Merge branch 'master' into kerberos-longrunning
42eead4 [Hari Shreedharan] Remove RPC part. Refactor and move methods around, use renewal interval rather than max lifetime to create new tokens.
ebb36f5 [Hari Shreedharan] Merge branch 'master' into kerberos-longrunning
bc083e3 [Hari Shreedharan] Overload RegisteredExecutor to send tokens. Minor doc updates.
7b19643 [Hari Shreedharan] Merge branch 'master' into kerberos-longrunning
8a4f268 [Hari Shreedharan] Added docs in the security guide. Changed some code to ensure that the renewer objects are created only if required.
e800c8b [Hari Shreedharan] Restore original RegisteredExecutor message, and send new tokens via NewTokens message.
0e9507e [Hari Shreedharan] Merge branch 'master' into kerberos-longrunning
7f1bc58 [Hari Shreedharan] Minor fixes, cleanup.
bcd11f9 [Hari Shreedharan] Refactor AM and Executor token update code into separate classes, also send tokens via akka on executor startup.
f74303c [Hari Shreedharan] Move the new logic into specialized classes. Add cleanup for old credentials files.
2f9975c [Hari Shreedharan] Ensure new tokens are written out immediately on AM restart. Also, pikc up the latest suffix from HDFS if the AM is restarted.
61b2b27 [Hari Shreedharan] Account for AM restarts by making sure lastSuffix is read from the files on HDFS.
62c45ce [Hari Shreedharan] Relogin from keytab periodically.
fa233bd [Hari Shreedharan] Adding logging, fixing minor formatting and ordering issues.
42813b4 [Hari Shreedharan] Remove utils.sh, which was re-added due to merge with master.
0de27ee [Hari Shreedharan] Merge branch 'master' into kerberos-longrunning
55522e3 [Hari Shreedharan] Fix failure caused by Preconditions ambiguity.
9ef5f1b [Hari Shreedharan] Added explanation of how the credentials refresh works, some other minor fixes.
f4fd711 [Hari Shreedharan] Fix SparkConf usage.
2debcea [Hari Shreedharan] Change the file structure for credentials files. I will push a followup patch which adds a cleanup mechanism for old credentials files. The credentials files are small and few enough for it to cause issues on HDFS.
af6d5f0 [Hari Shreedharan] Cleaning up files where changes weren't required.
f0f54cb [Hari Shreedharan] Be more defensive when updating the credentials file.
f6954da [Hari Shreedharan] Got rid of Akka communication to renew, instead the executors check a known file's modification time to read the credentials.
5c11c3e [Hari Shreedharan] Move tests to YarnSparkHadoopUtil to fix compile issues.
b4cb917 [Hari Shreedharan] Send keytab to AM via DistributedCache rather than directly via HDFS
0985b4e [Hari Shreedharan] Write tokens to HDFS and read them back when required, rather than sending them over the wire.
d79b2b9 [Hari Shreedharan] Make sure correct credentials are passed to FileSystem#addDelegationTokens()
8c6928a [Hari Shreedharan] Fix issue caused by direct creation of Actor object.
fb27f46 [Hari Shreedharan] Make sure principal and keytab are set before CoarseGrainedSchedulerBackend is started. Also schedule re-logins in CoarseGrainedSchedulerBackend#start()
41efde0 [Hari Shreedharan] Merge branch 'master' into kerberos-longrunning
d282d7a [Hari Shreedharan] Fix ClientSuite to set YARN mode, so that the correct class is used in tests.
bcfc374 [Hari Shreedharan] Fix Hadoop-1 build by adding no-op methods in SparkHadoopUtil, with impl in YarnSparkHadoopUtil.
f8fe694 [Hari Shreedharan] Handle None if keytab-login is not scheduled.
2b0d745 [Hari Shreedharan] [SPARK-5342][YARN] Allow long running Spark apps to run on secure YARN/HDFS.
ccba5bc [Hari Shreedharan] WIP: More changes wrt kerberos
77914dd [Hari Shreedharan] WIP: Add kerberos principal and keytab to YARN client.