Allow files added through SparkContext.addFile() to be overwritten

This is useful for the cases when a file needs to be refreshed and downloaded
by the executors periodically.

Signed-off-by: Yinan Li <liyinan926@gmail.com>
Addressed comments from Reynold

Signed-off-by: Yinan Li <liyinan926@gmail.com>
Replace the code to check for Option != None with Option.isDefined call in Scala code.

This hopefully will make the code cleaner.
Fix for SPARK-1025: PySpark hang on missing files.
Increase JUnit test verbosity under SBT.

Upgrade junit-interface plugin from 0.9 to 0.10.

I noticed that the JavaAPISuite tests didn't
appear to display any output locally or under
Jenkins, making it difficult to know whether they
were running.  This change increases the verbosity
to more closely match the ScalaTest tests.
Fix ClassCastException in JavaPairRDD.collectAsMap() (SPARK-1040)

This fixes an issue where collectAsMap() could
fail when called on a JavaPairRDD that was derived
by transforming a non-JavaPairRDD.

The root problem was that we were creating the
JavaPairRDD's ClassTag by casting a
ClassTag[AnyRef] to a ClassTag[Tuple2[K2, V2]].
To fix this, I cast a ClassTag[Tuple2[_, _]]
instead, since this actually produces a ClassTag
of the appropriate type because ClassTags don't
capture type parameters:

scala> implicitly[ClassTag[Tuple2[_, _]]] == implicitly[ClassTag[Tuple2[Int, Int]]]
res8: Boolean = true

scala> implicitly[ClassTag[AnyRef]].asInstanceOf[ClassTag[Tuple2[Int, Int]]] == implicitly[ClassTag[Tuple2[Int, Int]]]
res9: Boolean = false
Merge pull request #511 from JoshRosen/SPARK-1040

Fix ClassCastException in JavaPairRDD.collectAsMap() (SPARK-1040)

This fixes [SPARK-1040](https://spark-project.atlassian.net/browse/SPARK-1040), an issue where JavaPairRDD.collectAsMap() could sometimes fail with ClassCastException.  I applied the same fix to the Spark Streaming Java APIs.  The commit message describes the fix in more detail.

I also increased the verbosity of JUnit test output under SBT to make it easier to verify that the Java tests are actually running.
Merge pull request #504 from JoshRosen/SPARK-1025

Fix PySpark hang when input files are deleted (SPARK-1025)

This pull request addresses [SPARK-1025](https://spark-project.atlassian.net/browse/SPARK-1025), an issue where PySpark could hang if its input files were deleted.
modified SparkPluginBuild.scala to use https protocol for accessing github.
Merge pull request #460 from srowen/RandomInitialALSVectors

Choose initial user/item vectors uniformly on the unit sphere

...rather than within the unit square to possibly avoid bias in the initial state and improve convergence.

The current implementation picks the N vector elements uniformly at random from [0,1). This means they all point into one quadrant of the vector space. As N gets just a little large, the vector tend strongly to point into the "corner", towards (1,1,1...,1). The vectors are not unit vectors either.

I suggest choosing the elements as Gaussian ~ N(0,1) and normalizing. This gets you uniform random choices on the unit sphere which is more what's of interest here. It has worked a little better for me in the past.

This is pretty minor but wanted to warm up suggesting a few tweaks to ALS.
Please excuse my Scala, pretty new to it.

Author: Sean Owen <sowen@cloudera.com>

== Merge branch commits ==

commit 492b13a7469e5a4ed7591ee8e56d8bd7570dfab6
Author: Sean Owen <sowen@cloudera.com>
Date:   Mon Jan 27 08:05:25 2014 +0000

    Style: spaces around binary operators

commit ce2b5b5a4fefa0356875701f668f01f02ba4d87e
Author: Sean Owen <sowen@cloudera.com>
Date:   Sun Jan 19 22:50:03 2014 +0000

    Generate factors with all positive components, per discussion in https://github.com/apache/incubator-spark/pull/460

commit b6f7a8a61643a8209e8bc662e8e81f2d15c710c7
Author: Sean Owen <sowen@cloudera.com>
Date:   Sat Jan 18 15:54:42 2014 +0000

    Choose initial user/item vectors uniformly on the unit sphere rather than within the unit square to possibly avoid bias in the initial state and improve convergence
Merge pull request #490 from hsaputra/modify_checkoption_with_isdefined

Replace the check for None Option with isDefined and isEmpty in Scala code

Propose to replace the Scala check for Option "!= None" with Option.isDefined and "=== None" with Option.isEmpty.

I think this, using method call if possible then operator function plus argument, will make the Scala code easier to read and understand.

Pass compile and tests.
Merge pull request #516 from sarutak/master

modified SparkPluginBuild.scala to use https protocol for accessing gith...

We cannot build Spark behind a proxy although we execute sbt with -Dhttp(s).proxyHost -Dhttp(s).proxyPort -Dhttp(s).proxyUser -Dhttp(s).proxyPassword options.
It's because of using git protocol to clone junit_xml_listener.git.
I could build after modifying SparkPluginBuild.scala.

I reported this issue to JIRA.
https://spark-project.atlassian.net/browse/SPARK-1046
Merge pull request #466 from liyinan926/file-overwrite-new

Allow files added through SparkContext.addFile() to be overwritten

This is useful for the cases when a file needs to be refreshed and downloaded by the executors periodically. For example, a possible use case is: the driver periodically renews a Hadoop delegation token and writes it to a token file. The token file needs to be downloaded by the executors whenever it gets renewed. However, the current implementation throws an exception when the target file exists and its contents do not match those of the new source. This PR adds an option to allow files to be overwritten to support use cases similar to the above.
Merge branch 'master' of github.com:apache/incubator-spark into lda-mahout