[SPARK-25778] WriteAheadLogBackedBlockRDD in YARN Cluster Mode Fails …

…due lack of access to tmpDir from $PWD to HDFS

WriteAheadLogBackedBlockRDD usage of java.io.tmpdir will fail if $PWD resolves to a folder in HDFS and the Spark YARN Cluster job does not have the correct access to this folder in regards to the dummy folder. So this patch provides an option to set spark.streaming.receiver.blockStore.tmpdir to override java.io.tmpdir which sets $PWD from YARN Cluster mode.

## What changes were proposed in this pull request?
This change provides an option to override the java.io.tmpdir option so that when $PWD is resolved in YARN Cluster mode Spark does not attempt to use this folder and instead use the folder provided with the following option: spark.streaming.receiver.blockStore.tmpdir

## How was this patch tested?
Patch was manually tested on a Spark Streaming Job with Write Ahead logs in Cluster mode.

Closes apache#22867 from gss2002/SPARK-25778.

Authored-by: gss2002 <greg@senia.org>
Signed-off-by: Marcelo Vanzin <vanzin@cloudera.com>
(cherry picked from commit 2b671e7)
Signed-off-by: Marcelo Vanzin <vanzin@cloudera.com>

Author: gss2002

streaming/src/main/scala/org/apache/spark/streaming/rdd/WriteAheadLogBackedBlockRDD.scala

@@ -136,7 +136,7 @@ class WriteAheadLogBackedBlockRDD[T: ClassTag](
         // this dummy directory should not already exist otherwise the WAL will try to recover
         // past events from the directory and throw errors.
         val nonExistentDirectory = new File(
-          System.getProperty("java.io.tmpdir"), UUID.randomUUID().toString).getAbsolutePath
+          System.getProperty("java.io.tmpdir"), UUID.randomUUID().toString).toURI.toString
         writeAheadLog = WriteAheadLogUtils.createLogForReceiver(
           SparkEnv.get.conf, nonExistentDirectory, hadoopConf)
         dataRead = writeAheadLog.read(partition.walRecordHandle)