MAPREDUCE-5957. AM throws ClassNotFoundException with job classloader enabled if custom output format/committer is used. Contributed by Sangjin Lee

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1612358 13f79535-47bb-0310-9956-ffa450edef68

hadoop-mapreduce-project/CHANGES.txt

@@ -169,6 +169,9 @@ Release 2.6.0 - UNRELEASED
     MAPREDUCE-5956. Made MR AM not use maxAttempts to determine if the current
     attempt is the last retry. (Wangda Tan via zjshen)
 
+    MAPREDUCE-5957. AM throws ClassNotFoundException with job classloader
+    enabled if custom output format/committer is used (Sangjin Lee via jlowe)
+
 Release 2.5.0 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/MRAppMaster.java

@@ -41,7 +41,6 @@ import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FSDataInputStream;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.Path;
-import org.apache.hadoop.http.HttpConfig;
 import org.apache.hadoop.mapred.FileOutputCommitter;
 import org.apache.hadoop.mapred.JobConf;
 import org.apache.hadoop.mapred.LocalContainerLauncher;
@@ -200,6 +199,7 @@ public class MRAppMaster extends CompositeService {
       new JobTokenSecretManager();
   private JobId jobId;
   private boolean newApiCommitter;
+  private ClassLoader jobClassLoader;
   private OutputCommitter committer;
   private JobEventDispatcher jobEventDispatcher;
   private JobHistoryEventHandler jobHistoryEventHandler;
@@ -250,6 +250,9 @@ public class MRAppMaster extends CompositeService {
 
   @Override
   protected void serviceInit(final Configuration conf) throws Exception {
+    // create the job classloader if enabled
+    createJobClassLoader(conf);
+
     conf.setBoolean(Dispatcher.DISPATCHER_EXIT_ON_ERROR_KEY, true);
 
     initJobCredentialsAndUGI(conf);
@@ -387,8 +390,13 @@ public class MRAppMaster extends CompositeService {
       addIfService(committerEventHandler);
 
       //policy handling preemption requests from RM
-      preemptionPolicy = createPreemptionPolicy(conf);
-      preemptionPolicy.init(context);
+      callWithJobClassLoader(conf, new Action<Void>() {
+        public Void call(Configuration conf) {
+          preemptionPolicy = createPreemptionPolicy(conf);
+          preemptionPolicy.init(context);
+          return null;
+        }
+      });
 
       //service to handle requests to TaskUmbilicalProtocol
       taskAttemptListener = createTaskAttemptListener(context, preemptionPolicy);
@@ -453,33 +461,37 @@ public class MRAppMaster extends CompositeService {
   }
 
   private OutputCommitter createOutputCommitter(Configuration conf) {
-    OutputCommitter committer = null;
-
-    LOG.info("OutputCommitter set in config "
-        + conf.get("mapred.output.committer.class"));
-
-    if (newApiCommitter) {
-      org.apache.hadoop.mapreduce.v2.api.records.TaskId taskID = MRBuilderUtils
-          .newTaskId(jobId, 0, TaskType.MAP);
-      org.apache.hadoop.mapreduce.v2.api.records.TaskAttemptId attemptID = MRBuilderUtils
-          .newTaskAttemptId(taskID, 0);
-      TaskAttemptContext taskContext = new TaskAttemptContextImpl(conf,
-          TypeConverter.fromYarn(attemptID));
-      OutputFormat outputFormat;
-      try {
-        outputFormat = ReflectionUtils.newInstance(taskContext
-            .getOutputFormatClass(), conf);
-        committer = outputFormat.getOutputCommitter(taskContext);
-      } catch (Exception e) {
-        throw new YarnRuntimeException(e);
+    return callWithJobClassLoader(conf, new Action<OutputCommitter>() {
+      public OutputCommitter call(Configuration conf) {
+        OutputCommitter committer = null;
+
+        LOG.info("OutputCommitter set in config "
+            + conf.get("mapred.output.committer.class"));
+
+        if (newApiCommitter) {
+          org.apache.hadoop.mapreduce.v2.api.records.TaskId taskID =
+              MRBuilderUtils.newTaskId(jobId, 0, TaskType.MAP);
+          org.apache.hadoop.mapreduce.v2.api.records.TaskAttemptId attemptID =
+              MRBuilderUtils.newTaskAttemptId(taskID, 0);
+          TaskAttemptContext taskContext = new TaskAttemptContextImpl(conf,
+              TypeConverter.fromYarn(attemptID));
+          OutputFormat outputFormat;
+          try {
+            outputFormat = ReflectionUtils.newInstance(taskContext
+                .getOutputFormatClass(), conf);
+            committer = outputFormat.getOutputCommitter(taskContext);
+          } catch (Exception e) {
+            throw new YarnRuntimeException(e);
+          }
+        } else {
+          committer = ReflectionUtils.newInstance(conf.getClass(
+              "mapred.output.committer.class", FileOutputCommitter.class,
+              org.apache.hadoop.mapred.OutputCommitter.class), conf);
+        }
+        LOG.info("OutputCommitter is " + committer.getClass().getName());
+        return committer;
       }
-    } else {
-      committer = ReflectionUtils.newInstance(conf.getClass(
-          "mapred.output.committer.class", FileOutputCommitter.class,
-          org.apache.hadoop.mapred.OutputCommitter.class), conf);
-    }
-    LOG.info("OutputCommitter is " + committer.getClass().getName());
-    return committer;
+    });
   }
 
   protected AMPreemptionPolicy createPreemptionPolicy(Configuration conf) {
@@ -667,38 +679,42 @@ public class MRAppMaster extends CompositeService {
     return new StagingDirCleaningService();
   }
 
-  protected Speculator createSpeculator(Configuration conf, AppContext context) {
-    Class<? extends Speculator> speculatorClass;
-
-    try {
-      speculatorClass
-          // "yarn.mapreduce.job.speculator.class"
-          = conf.getClass(MRJobConfig.MR_AM_JOB_SPECULATOR,
-                          DefaultSpeculator.class,
-                          Speculator.class);
-      Constructor<? extends Speculator> speculatorConstructor
-          = speculatorClass.getConstructor
-               (Configuration.class, AppContext.class);
-      Speculator result = speculatorConstructor.newInstance(conf, context);
-
-      return result;
-    } catch (InstantiationException ex) {
-      LOG.error("Can't make a speculator -- check "
-          + MRJobConfig.MR_AM_JOB_SPECULATOR, ex);
-      throw new YarnRuntimeException(ex);
-    } catch (IllegalAccessException ex) {
-      LOG.error("Can't make a speculator -- check "
-          + MRJobConfig.MR_AM_JOB_SPECULATOR, ex);
-      throw new YarnRuntimeException(ex);
-    } catch (InvocationTargetException ex) {
-      LOG.error("Can't make a speculator -- check "
-          + MRJobConfig.MR_AM_JOB_SPECULATOR, ex);
-      throw new YarnRuntimeException(ex);
-    } catch (NoSuchMethodException ex) {
-      LOG.error("Can't make a speculator -- check "
-          + MRJobConfig.MR_AM_JOB_SPECULATOR, ex);
-      throw new YarnRuntimeException(ex);
-    }
+  protected Speculator createSpeculator(Configuration conf,
+      final AppContext context) {
+    return callWithJobClassLoader(conf, new Action<Speculator>() {
+      public Speculator call(Configuration conf) {
+        Class<? extends Speculator> speculatorClass;
+        try {
+          speculatorClass
+              // "yarn.mapreduce.job.speculator.class"
+              = conf.getClass(MRJobConfig.MR_AM_JOB_SPECULATOR,
+                              DefaultSpeculator.class,
+                              Speculator.class);
+          Constructor<? extends Speculator> speculatorConstructor
+              = speculatorClass.getConstructor
+                   (Configuration.class, AppContext.class);
+          Speculator result = speculatorConstructor.newInstance(conf, context);
+
+          return result;
+        } catch (InstantiationException ex) {
+          LOG.error("Can't make a speculator -- check "
+              + MRJobConfig.MR_AM_JOB_SPECULATOR, ex);
+          throw new YarnRuntimeException(ex);
+        } catch (IllegalAccessException ex) {
+          LOG.error("Can't make a speculator -- check "
+              + MRJobConfig.MR_AM_JOB_SPECULATOR, ex);
+          throw new YarnRuntimeException(ex);
+        } catch (InvocationTargetException ex) {
+          LOG.error("Can't make a speculator -- check "
+              + MRJobConfig.MR_AM_JOB_SPECULATOR, ex);
+          throw new YarnRuntimeException(ex);
+        } catch (NoSuchMethodException ex) {
+          LOG.error("Can't make a speculator -- check "
+              + MRJobConfig.MR_AM_JOB_SPECULATOR, ex);
+          throw new YarnRuntimeException(ex);
+        }
+      }
+    });
   }
 
   protected TaskAttemptListener createTaskAttemptListener(AppContext context,
@@ -712,7 +728,7 @@ public class MRAppMaster extends CompositeService {
   protected EventHandler<CommitterEvent> createCommitterEventHandler(
       AppContext context, OutputCommitter committer) {
     return new CommitterEventHandler(context, committer,
-        getRMHeartbeatHandler());
+        getRMHeartbeatHandler(), jobClassLoader);
   }
 
   protected ContainerAllocator createContainerAllocator(
@@ -1083,8 +1099,8 @@ public class MRAppMaster extends CompositeService {
     //start all the components
     super.serviceStart();
 
-    // set job classloader if configured
-    MRApps.setJobClassLoader(getConfig());
+    // finally set the job classloader
+    MRApps.setClassLoader(jobClassLoader, getConfig());
 
     if (initFailed) {
       JobEvent initFailedEvent = new JobEvent(job.getID(), JobEventType.JOB_INIT_FAILED);
@@ -1101,19 +1117,24 @@ public class MRAppMaster extends CompositeService {
     TaskLog.syncLogsShutdown(logSyncer);
   }
 
-  private boolean isRecoverySupported(OutputCommitter committer2)
-      throws IOException {
+  private boolean isRecoverySupported() throws IOException {
     boolean isSupported = false;
-    JobContext _jobContext;
+    Configuration conf = getConfig();
     if (committer != null) {
+      final JobContext _jobContext;
       if (newApiCommitter) {
          _jobContext = new JobContextImpl(
-            getConfig(), TypeConverter.fromYarn(getJobId()));
+            conf, TypeConverter.fromYarn(getJobId()));
       } else {
           _jobContext = new org.apache.hadoop.mapred.JobContextImpl(
-                new JobConf(getConfig()), TypeConverter.fromYarn(getJobId()));
+                new JobConf(conf), TypeConverter.fromYarn(getJobId()));
       }
-      isSupported = committer.isRecoverySupported(_jobContext);
+      isSupported = callWithJobClassLoader(conf,
+          new ExceptionAction<Boolean>() {
+            public Boolean call(Configuration conf) throws IOException {
+              return committer.isRecoverySupported(_jobContext);
+            }
+      });
     }
     return isSupported;
   }
@@ -1127,7 +1148,7 @@ public class MRAppMaster extends CompositeService {
         MRJobConfig.MR_AM_JOB_RECOVERY_ENABLE,
         MRJobConfig.MR_AM_JOB_RECOVERY_ENABLE_DEFAULT);
 
-    boolean recoverySupportedByCommitter = isRecoverySupported(committer);
+    boolean recoverySupportedByCommitter = isRecoverySupported();
 
     // If a shuffle secret was not provided by the job client then this app
     // attempt will generate one.  However that disables recovery if there
@@ -1312,7 +1333,7 @@ public class MRAppMaster extends CompositeService {
       this.conf = config;
     }
     @Override
-    public void handle(SpeculatorEvent event) {
+    public void handle(final SpeculatorEvent event) {
       if (disabled) {
         return;
       }
@@ -1339,7 +1360,12 @@ public class MRAppMaster extends CompositeService {
       if ( (shouldMapSpec && (tType == null || tType == TaskType.MAP))
         || (shouldReduceSpec && (tType == null || tType == TaskType.REDUCE))) {
         // Speculator IS enabled, direct the event to there.
-        speculator.handle(event);
+        callWithJobClassLoader(conf, new Action<Void>() {
+          public Void call(Configuration conf) {
+            speculator.handle(event);
+            return null;
+          }
+        });
       }
     }
 
@@ -1499,6 +1525,102 @@ public class MRAppMaster extends CompositeService {
     });
   }
 
+  /**
+   * Creates a job classloader based on the configuration if the job classloader
+   * is enabled. It is a no-op if the job classloader is not enabled.
+   */
+  private void createJobClassLoader(Configuration conf) throws IOException {
+    jobClassLoader = MRApps.createJobClassLoader(conf);
+  }
+
+  /**
+   * Executes the given action with the job classloader set as the configuration
+   * classloader as well as the thread context class loader if the job
+   * classloader is enabled. After the call, the original classloader is
+   * restored.
+   *
+   * If the job classloader is enabled and the code needs to load user-supplied
+   * classes via configuration or thread context classloader, this method should
+   * be used in order to load them.
+   *
+   * @param conf the configuration on which the classloader will be set
+   * @param action the callable action to be executed
+   */
+  <T> T callWithJobClassLoader(Configuration conf, Action<T> action) {
+    // if the job classloader is enabled, we may need it to load the (custom)
+    // classes; we make the job classloader available and unset it once it is
+    // done
+    ClassLoader currentClassLoader = conf.getClassLoader();
+    boolean setJobClassLoader =
+        jobClassLoader != null && currentClassLoader != jobClassLoader;
+    if (setJobClassLoader) {
+      MRApps.setClassLoader(jobClassLoader, conf);
+    }
+    try {
+      return action.call(conf);
+    } finally {
+      if (setJobClassLoader) {
+        // restore the original classloader
+        MRApps.setClassLoader(currentClassLoader, conf);
+      }
+    }
+  }
+
+  /**
+   * Executes the given action that can throw a checked exception with the job
+   * classloader set as the configuration classloader as well as the thread
+   * context class loader if the job classloader is enabled. After the call, the
+   * original classloader is restored.
+   *
+   * If the job classloader is enabled and the code needs to load user-supplied
+   * classes via configuration or thread context classloader, this method should
+   * be used in order to load them.
+   *
+   * @param conf the configuration on which the classloader will be set
+   * @param action the callable action to be executed
+   * @throws IOException if the underlying action throws an IOException
+   * @throws YarnRuntimeException if the underlying action throws an exception
+   * other than an IOException
+   */
+  <T> T callWithJobClassLoader(Configuration conf, ExceptionAction<T> action)
+      throws IOException {
+    // if the job classloader is enabled, we may need it to load the (custom)
+    // classes; we make the job classloader available and unset it once it is
+    // done
+    ClassLoader currentClassLoader = conf.getClassLoader();
+    boolean setJobClassLoader =
+        jobClassLoader != null && currentClassLoader != jobClassLoader;
+    if (setJobClassLoader) {
+      MRApps.setClassLoader(jobClassLoader, conf);
+    }
+    try {
+      return action.call(conf);
+    } catch (IOException e) {
+      throw e;
+    } catch (YarnRuntimeException e) {
+      throw e;
+    } catch (Exception e) {
+      // wrap it with a YarnRuntimeException
+      throw new YarnRuntimeException(e);
+    } finally {
+      if (setJobClassLoader) {
+        // restore the original classloader
+        MRApps.setClassLoader(currentClassLoader, conf);
+      }
+    }
+  }
+
+  /**
+   * Action to be wrapped with setting and unsetting the job classloader
+   */
+  private static interface Action<T> {
+    T call(Configuration conf);
+  }
+
+  private static interface ExceptionAction<T> {
+    T call(Configuration conf) throws Exception;
+  }
+
   @Override
   protected void serviceStop() throws Exception {
     super.serviceStop();

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/commit/CommitterEventHandler.java

@@ -68,6 +68,7 @@ public class CommitterEventHandler extends AbstractService
   private BlockingQueue<CommitterEvent> eventQueue =
       new LinkedBlockingQueue<CommitterEvent>();
   private final AtomicBoolean stopped;
+  private final ClassLoader jobClassLoader;
   private Thread jobCommitThread = null;
   private int commitThreadCancelTimeoutMs;
   private long commitWindowMs;
@@ -79,11 +80,17 @@ public class CommitterEventHandler extends AbstractService
 
   public CommitterEventHandler(AppContext context, OutputCommitter committer,
       RMHeartbeatHandler rmHeartbeatHandler) {
+    this(context, committer, rmHeartbeatHandler, null);
+  }
+  
+  public CommitterEventHandler(AppContext context, OutputCommitter committer,
+      RMHeartbeatHandler rmHeartbeatHandler, ClassLoader jobClassLoader) {
     super("CommitterEventHandler");
     this.context = context;
     this.committer = committer;
     this.rmHeartbeatHandler = rmHeartbeatHandler;
     this.stopped = new AtomicBoolean(false);
+    this.jobClassLoader = jobClassLoader;
   }
 
   @Override
@@ -109,9 +116,23 @@ public class CommitterEventHandler extends AbstractService
 
   @Override
   protected void serviceStart() throws Exception {
-    ThreadFactory tf = new ThreadFactoryBuilder()
-      .setNameFormat("CommitterEvent Processor #%d")
-      .build();
+    ThreadFactoryBuilder tfBuilder = new ThreadFactoryBuilder()
+        .setNameFormat("CommitterEvent Processor #%d");
+    if (jobClassLoader != null) {
+      // if the job classloader is enabled, we need to use the job classloader
+      // as the thread context classloader (TCCL) of these threads in case the
+      // committer needs to load another class via TCCL
+      ThreadFactory backingTf = new ThreadFactory() {
+        @Override
+        public Thread newThread(Runnable r) {
+          Thread thread = new Thread(r);
+          thread.setContextClassLoader(jobClassLoader);
+          return thread;
+        }
+      };
+      tfBuilder.setThreadFactory(backingTf);
+    }
+    ThreadFactory tf = tfBuilder.build();
     launcherPool = new ThreadPoolExecutor(5, 5, 1,
         TimeUnit.HOURS, new LinkedBlockingQueue<Runnable>(), tf);
     eventHandlingThread = new Thread(new Runnable() {

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-common/src/main/java/org/apache/hadoop/mapreduce/v2/util/MRApps.java

@@ -327,8 +327,8 @@ public class MRApps extends Apps {
   }
 
   /**
-   * Sets a {@link ApplicationClassLoader} on the given configuration and as
-   * the context classloader, if
+   * Creates and sets a {@link ApplicationClassLoader} on the given
+   * configuration and as the thread context classloader, if
    * {@link MRJobConfig#MAPREDUCE_JOB_CLASSLOADER} is set to true, and
    * the APP_CLASSPATH environment variable is set.
    * @param conf
@@ -336,24 +336,52 @@ public class MRApps extends Apps {
    */
   public static void setJobClassLoader(Configuration conf)
       throws IOException {
+    setClassLoader(createJobClassLoader(conf), conf);
+  }
+
+  /**
+   * Creates a {@link ApplicationClassLoader} if
+   * {@link MRJobConfig#MAPREDUCE_JOB_CLASSLOADER} is set to true, and
+   * the APP_CLASSPATH environment variable is set.
+   * @param conf
+   * @returns the created job classloader, or null if the job classloader is not
+   * enabled or the APP_CLASSPATH environment variable is not set
+   * @throws IOException
+   */
+  public static ClassLoader createJobClassLoader(Configuration conf)
+      throws IOException {
+    ClassLoader jobClassLoader = null;
     if (conf.getBoolean(MRJobConfig.MAPREDUCE_JOB_CLASSLOADER, false)) {
       String appClasspath = System.getenv(Environment.APP_CLASSPATH.key());
       if (appClasspath == null) {
-        LOG.warn("Not using job classloader since APP_CLASSPATH is not set.");
+        LOG.warn("Not creating job classloader since APP_CLASSPATH is not set.");
       } else {
-        LOG.info("Using job classloader");
+        LOG.info("Creating job classloader");
         if (LOG.isDebugEnabled()) {
           LOG.debug("APP_CLASSPATH=" + appClasspath);
         }
         String[] systemClasses = getSystemClasses(conf);
-        ClassLoader jobClassLoader = createJobClassLoader(appClasspath,
+        jobClassLoader = createJobClassLoader(appClasspath,
             systemClasses);
-        if (jobClassLoader != null) {
-          conf.setClassLoader(jobClassLoader);
-          Thread.currentThread().setContextClassLoader(jobClassLoader);
-        }
       }
     }
+    return jobClassLoader;
+  }
+
+  /**
+   * Sets the provided classloader on the given configuration and as the thread
+   * context classloader if the classloader is not null.
+   * @param classLoader
+   * @param conf
+   */
+  public static void setClassLoader(ClassLoader classLoader,
+      Configuration conf) {
+    if (classLoader != null) {
+      LOG.info("Setting classloader " + classLoader.getClass().getName() +
+          " on the configuration and as the thread context classloader");
+      conf.setClassLoader(classLoader);
+      Thread.currentThread().setContextClassLoader(classLoader);
+    }
   }
 
   @VisibleForTesting

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-jobclient/src/test/java/org/apache/hadoop/mapreduce/v2/TestMRJobs.java

@@ -33,8 +33,8 @@ import java.util.HashMap;
 import java.util.Map;
 import java.util.jar.JarOutputStream;
 import java.util.zip.ZipEntry;
-import org.apache.commons.io.FileUtils;
 
+import org.apache.commons.io.FileUtils;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.FailingMapper;
@@ -77,6 +77,10 @@ import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
 import org.apache.hadoop.mapreduce.lib.output.NullOutputFormat;
 import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
 import org.apache.hadoop.mapreduce.v2.api.records.JobId;
+import org.apache.hadoop.mapreduce.v2.app.AppContext;
+import org.apache.hadoop.mapreduce.v2.app.MRAppMaster;
+import org.apache.hadoop.mapreduce.v2.app.speculate.DefaultSpeculator;
+import org.apache.hadoop.mapreduce.v2.app.speculate.Speculator;
 import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.security.token.TokenIdentifier;
@@ -86,6 +90,7 @@ import org.apache.hadoop.yarn.api.records.ApplicationId;
 import org.apache.hadoop.yarn.api.records.ContainerId;
 import org.apache.hadoop.yarn.conf.YarnConfiguration;
 import org.apache.hadoop.yarn.server.resourcemanager.rmapp.RMAppState;
+import org.apache.hadoop.yarn.util.ApplicationClassLoader;
 import org.apache.hadoop.yarn.util.ConverterUtils;
 import org.apache.log4j.Level;
 import org.junit.AfterClass;
@@ -210,7 +215,19 @@ public class TestMRJobs {
   @Test(timeout = 300000)
   public void testJobClassloader() throws IOException, InterruptedException,
       ClassNotFoundException {
-    LOG.info("\n\n\nStarting testJobClassloader().");
+    testJobClassloader(false);
+  }
+
+  @Test(timeout = 300000)
+  public void testJobClassloaderWithCustomClasses() throws IOException,
+      InterruptedException, ClassNotFoundException {
+    testJobClassloader(true);
+  }
+
+  private void testJobClassloader(boolean useCustomClasses) throws IOException,
+      InterruptedException, ClassNotFoundException {
+    LOG.info("\n\n\nStarting testJobClassloader()"
+        + " useCustomClasses=" + useCustomClasses);
 
     if (!(new File(MiniMRYarnCluster.APPJAR)).exists()) {
       LOG.info("MRAppJar " + MiniMRYarnCluster.APPJAR
@@ -221,6 +238,19 @@ public class TestMRJobs {
     // set master address to local to test that local mode applied iff framework == local
     sleepConf.set(MRConfig.MASTER_ADDRESS, "local");
     sleepConf.setBoolean(MRJobConfig.MAPREDUCE_JOB_CLASSLOADER, true);
+    if (useCustomClasses) {
+      // to test AM loading user classes such as output format class, we want
+      // to blacklist them from the system classes (they need to be prepended
+      // as the first match wins)
+      String systemClasses =
+          sleepConf.get(MRJobConfig.MAPREDUCE_JOB_CLASSLOADER_SYSTEM_CLASSES);
+      // exclude the custom classes from system classes
+      systemClasses = "-" + CustomOutputFormat.class.getName() + ",-" +
+          CustomSpeculator.class.getName() + "," +
+          systemClasses;
+      sleepConf.set(MRJobConfig.MAPREDUCE_JOB_CLASSLOADER_SYSTEM_CLASSES,
+          systemClasses);
+    }
     sleepConf.set(MRJobConfig.IO_SORT_MB, TEST_IO_SORT_MB);
     sleepConf.set(MRJobConfig.MR_AM_LOG_LEVEL, Level.ALL.toString());
     sleepConf.set(MRJobConfig.MAP_LOG_LEVEL, Level.ALL.toString());
@@ -233,12 +263,66 @@ public class TestMRJobs {
     job.addFileToClassPath(APP_JAR); // The AppMaster jar itself.
     job.setJarByClass(SleepJob.class);
     job.setMaxMapAttempts(1); // speed up failures
+    if (useCustomClasses) {
+      // set custom output format class and speculator class
+      job.setOutputFormatClass(CustomOutputFormat.class);
+      final Configuration jobConf = job.getConfiguration();
+      jobConf.setClass(MRJobConfig.MR_AM_JOB_SPECULATOR, CustomSpeculator.class,
+          Speculator.class);
+      // speculation needs to be enabled for the speculator to be loaded
+      jobConf.setBoolean(MRJobConfig.MAP_SPECULATIVE, true);
+    }
     job.submit();
     boolean succeeded = job.waitForCompletion(true);
     Assert.assertTrue("Job status: " + job.getStatus().getFailureInfo(),
         succeeded);
   }
 
+  public static class CustomOutputFormat<K,V> extends NullOutputFormat<K,V> {
+    public CustomOutputFormat() {
+      verifyClassLoader(getClass());
+    }
+
+    /**
+     * Verifies that the class was loaded by the job classloader if it is in the
+     * context of the MRAppMaster, and if not throws an exception to fail the
+     * job.
+     */
+    private void verifyClassLoader(Class<?> cls) {
+      // to detect that it is instantiated in the context of the MRAppMaster, we
+      // inspect the stack trace and determine a caller is MRAppMaster
+      for (StackTraceElement e: new Throwable().getStackTrace()) {
+        if (e.getClassName().equals(MRAppMaster.class.getName()) &&
+            !(cls.getClassLoader() instanceof ApplicationClassLoader)) {
+          throw new ExceptionInInitializerError("incorrect classloader used");
+        }
+      }
+    }
+  }
+
+  public static class CustomSpeculator extends DefaultSpeculator {
+    public CustomSpeculator(Configuration conf, AppContext context) {
+      super(conf, context);
+      verifyClassLoader(getClass());
+    }
+
+    /**
+     * Verifies that the class was loaded by the job classloader if it is in the
+     * context of the MRAppMaster, and if not throws an exception to fail the
+     * job.
+     */
+    private void verifyClassLoader(Class<?> cls) {
+      // to detect that it is instantiated in the context of the MRAppMaster, we
+      // inspect the stack trace and determine a caller is MRAppMaster
+      for (StackTraceElement e: new Throwable().getStackTrace()) {
+        if (e.getClassName().equals(MRAppMaster.class.getName()) &&
+            !(cls.getClassLoader() instanceof ApplicationClassLoader)) {
+          throw new ExceptionInInitializerError("incorrect classloader used");
+        }
+      }
+    }
+  }
+
   protected void verifySleepJobCounters(Job job) throws InterruptedException,
       IOException {
     Counters counters = job.getCounters();