YARN-2857. ConcurrentModificationException in ContainerLogAppender. Contributed by Mohammad Kamrul Islam

hadoop-yarn-project/CHANGES.txt

@@ -87,6 +87,9 @@ Release 2.7.0 - UNRELEASED
     YARN-2856. Fixed RMAppImpl to handle ATTEMPT_KILLED event at ACCEPTED state
     on app recovery. (Rohith Sharmaks via jianhe)
 
+    YARN-2857. ConcurrentModificationException in ContainerLogAppender
+    (Mohammad Kamrul Islam via jlowe)
+
 Release 2.6.0 - 2014-11-18
 
   INCOMPATIBLE CHANGES

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/ContainerLogAppender.java

@@ -41,6 +41,7 @@ public class ContainerLogAppender extends FileAppender
   //so that log4j can configure it from the configuration(log4j.properties). 
   private int maxEvents;
   private Queue<LoggingEvent> tail = null;
+  private boolean closing = false;
 
   @Override
   public void activateOptions() {
@@ -57,6 +58,9 @@ public class ContainerLogAppender extends FileAppender
   @Override
   public void append(LoggingEvent event) {
     synchronized (this) {
+      if (closing) { // When closing drop any new/transitive CLA appending
+        return;
+      }
       if (tail == null) {
         super.append(event);
       } else {
@@ -77,8 +81,9 @@ public class ContainerLogAppender extends FileAppender
 
   @Override
   public synchronized void close() {
+    closing = true;
     if (tail != null) {
-      for(LoggingEvent event: tail) {
+      for (LoggingEvent event : tail) {
         super.append(event);
       }
     }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/TestContainerLogAppender.java

@@ -0,0 +1,46 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.yarn;
+
+import org.apache.log4j.Logger;
+import org.apache.log4j.PatternLayout;
+import org.junit.Test;
+
+public class TestContainerLogAppender {
+
+  @Test
+  public void testAppendInClose() throws Exception {
+    final ContainerLogAppender claAppender = new ContainerLogAppender();
+    claAppender.setName("testCLA");
+    claAppender.setLayout(new PatternLayout("%-5p [%t]: %m%n"));
+    claAppender.setContainerLogDir("target/testAppendInClose/logDir");
+    claAppender.setTotalLogFileSize(1000);
+    claAppender.activateOptions();
+    final Logger claLog = Logger.getLogger("testAppendInClose-catergory");
+    claLog.setAdditivity(false);
+    claLog.addAppender(claAppender);
+    claLog.info(new Object() {
+      public String toString() {
+        claLog.info("message1");
+        return "return message1";
+      }
+    });
+    claAppender.close();
+  }
+}