From 66be9adf5a74eeba203e842719466b061925abd9 Mon Sep 17 00:00:00 2001
From: Devaraj K <devaraj@apache.org>
Date: Wed, 1 Jul 2015 15:14:02 +0530
Subject: [PATCH] https://issues.apache.org/jira/browse/SPARK-8754
 YarnClientSchedulerBackend doesn't stop gracefully in failure conditions

In YarnClientSchedulerBackend.stop(), added a check for monitorThread.
---
 .../spark/scheduler/cluster/YarnClientSchedulerBackend.scala  | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/yarn/src/main/scala/org/apache/spark/scheduler/cluster/YarnClientSchedulerBackend.scala b/yarn/src/main/scala/org/apache/spark/scheduler/cluster/YarnClientSchedulerBackend.scala
index 1c8d7ec57635f..dd8c4fdb549ed 100644
--- a/yarn/src/main/scala/org/apache/spark/scheduler/cluster/YarnClientSchedulerBackend.scala
+++ b/yarn/src/main/scala/org/apache/spark/scheduler/cluster/YarnClientSchedulerBackend.scala
@@ -148,7 +148,9 @@ private[spark] class YarnClientSchedulerBackend(
    */
   override def stop() {
     assert(client != null, "Attempted to stop this scheduler before starting it!")
-    monitorThread.interrupt()
+    if (monitorThread != null) {
+      monitorThread.interrupt()
+    }
     super.stop()
     client.stop()
     logInfo("Stopped")