[SPARK-11019] [STREAMING] [FLUME] Gracefully shutdown Flume receiver th…

…reads.

Wait for a minute for the receiver threads to shutdown before interrupting them.

Author: Hari Shreedharan <hshreedharan@apache.org>

Closes #9041 from harishreedharan/flume-graceful-shutdown.

external/flume/src/main/scala/org/apache/spark/streaming/flume/FlumePollingInputDStream.scala

@@ -18,7 +18,7 @@ package org.apache.spark.streaming.flume
 
 
 import java.net.InetSocketAddress
-import java.util.concurrent.{LinkedBlockingQueue, Executors}
+import java.util.concurrent.{Executors, LinkedBlockingQueue, TimeUnit}
 
 import scala.collection.JavaConverters._
 import scala.reflect.ClassTag
@@ -93,7 +93,11 @@ private[streaming] class FlumePollingReceiver(
 
   override def onStop(): Unit = {
     logInfo("Shutting down Flume Polling Receiver")
-    receiverExecutor.shutdownNow()
+    receiverExecutor.shutdown()
+    // Wait upto a minute for the threads to die
+    if (!receiverExecutor.awaitTermination(60, TimeUnit.SECONDS)) {
+      receiverExecutor.shutdownNow()
+    }
     connections.asScala.foreach(_.transceiver.close())
     channelFactory.releaseExternalResources()
   }