[SPARK-12466] Fix harmless NPE in tests

Andrew Or · Andrew Or · commit ca3998512dd7 · 2015-12-21T14:09:11.000-08:00
``` [info] ReplayListenerSuite: [info] - Simple replay (58 milliseconds) java.lang.NullPointerException at org.apache.spark.deploy.master.Master$$anonfun$asyncRebuildSparkUI$1.applyOrElse(Master.scala:982) at org.apache.spark.deploy.master.Master$$anonfun$asyncRebuildSparkUI$1.applyOrElse(Master.scala:980) ``` https://amplab.cs.berkeley.edu/jenkins/view/Spark-QA-Test/job/Spark-Master-SBT/4316/AMPLAB_JENKINS_BUILD_PROFILE=hadoop2.2,label=spark-test/consoleFull This was introduced in apache#10284. It's harmless because the NPE is caused by a race that occurs mainly in `local-cluster` tests (but don't actually fail the tests). Tested locally to verify that the NPE is gone. Author: Andrew Or <andrew@databricks.com> Closes apache#10417 from andrewor14/fix-harmless-npe. (cherry picked from commit d655d37) Signed-off-by: Andrew Or <andrew@databricks.com>
diff --git a/core/src/main/scala/org/apache/spark/deploy/master/Master.scala b/core/src/main/scala/org/apache/spark/deploy/master/Master.scala
@@ -979,7 +979,11 @@ private[deploy] class Master(
 
     futureUI.onSuccess { case Some(ui) =>
       appIdToUI.put(app.id, ui)
-      self.send(AttachCompletedRebuildUI(app.id))
+      // `self` can be null if we are already in the process of shutting down
+      // This happens frequently in tests where `local-cluster` is used
+      if (self != null) {
+        self.send(AttachCompletedRebuildUI(app.id))
+      }
       // Application UI is successfully rebuilt, so link the Master UI to it
       // NOTE - app.appUIUrlAtHistoryServer is volatile
       app.appUIUrlAtHistoryServer = Some(ui.basePath)
