[SPARK-4601][Streaming] Set correct call site for streaming jobs so that it is displayed correctly on the Spark UI

When running the NetworkWordCount, the description of the word count jobs are set as "getCallsite at DStream:xxx" . This should be set to the line number of the streaming application that has the output operation that led to the job being created. This is because the callsite is incorrectly set in the thread launching the jobs. This PR fixes that.

Author: Tathagata Das <tathagata.das1565@gmail.com>

Closes #3455 from tdas/streaming-callsite-fix and squashes the following commits:

69fc26f [Tathagata Das] Set correct call site for streaming jobs so that it is displayed correctly on the Spark UI

streaming/src/main/scala/org/apache/spark/streaming/dstream/ForEachDStream.scala

@@ -38,6 +38,7 @@ class ForEachDStream[T: ClassTag] (
     parent.getOrCompute(time) match {
       case Some(rdd) =>
         val jobFunc = () => {
+          ssc.sparkContext.setCallSite(creationSite)
           foreachFunc(rdd, time)
         }
         Some(new Job(time, jobFunc))

streaming/src/test/scala/org/apache/spark/streaming/StreamingContextSuite.scala

@@ -336,16 +336,20 @@ package object testPackage extends Assertions {
 
       // Verify creation site of generated RDDs
       var rddGenerated = false
-      var rddCreationSiteCorrect = true
+      var rddCreationSiteCorrect = false
+      var foreachCallSiteCorrect = false
 
       inputStream.foreachRDD { rdd =>
         rddCreationSiteCorrect = rdd.creationSite == creationSite
+        foreachCallSiteCorrect =
+          rdd.sparkContext.getCallSite().shortForm.contains("StreamingContextSuite")
         rddGenerated = true
       }
       ssc.start()
 
       eventually(timeout(10000 millis), interval(10 millis)) {
         assert(rddGenerated && rddCreationSiteCorrect, "RDD creation site was not correct")
+        assert(rddGenerated && foreachCallSiteCorrect, "Call site in foreachRDD was not correct")
       }
     } finally {
       ssc.stop()