Connect to Yarn shuffle service only if it's enabled

Author: Andrew Or

yarn/stable/src/main/scala/org/apache/spark/deploy/yarn/ExecutorRunnable.scala

@@ -89,7 +89,11 @@ class ExecutorRunnable(
 
     ctx.setApplicationACLs(YarnSparkHadoopUtil.getApplicationAclsForYarn(securityMgr))
 
-    ctx.setServiceData(Map[String, ByteBuffer]("spark_shuffle" -> ByteBuffer.allocate(0)))
+    // If external shuffle service is enabled, register with the
+    // Yarn shuffle service already started on the node manager
+    if (sparkConf.getBoolean("spark.shuffle.service.enabled", false)) {
+      ctx.setServiceData(Map[String, ByteBuffer]("spark_shuffle" -> ByteBuffer.allocate(0)))
+    }
 
     // Send the start request to the ContainerManager
     nmClient.startContainer(container, ctx)