HDFS-11511. Support Timeout when checking single disk. Contributed by Hanisha Koneru.

LICENSE.txt

@@ -2660,3 +2660,23 @@ available under the Creative Commons By Attribution 3.0 License.
         this trademark restriction does not form part of this License.
 
         Creative Commons may be contacted at https://creativecommons.org/.
+--------------------------------------------------------------------------------
+
+For: hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs
+/server/datanode/checker/AbstractFuture.java and
+hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs
+/server/datanode/checker/TimeoutFuture.java
+
+Copyright (C) 2007 The Guava Authors
+
+Licensed 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.

hadoop-hdfs-project/hadoop-hdfs/dev-support/findbugsExcludeFile.xml

@@ -240,4 +240,16 @@
         <Method name="getBlockLayoutRedundancy" />
         <Bug pattern="BIT_IOR_OF_SIGNED_BYTE" />
     </Match>
+    <Match>
+        <Class name="org.apache.hadoop.hdfs.server.datanode.checker.AbstractFuture" />
+        <Bug pattern="DLS_DEAD_STORE_OF_CLASS_LITERAL" />
+    </Match>
+    <Match>
+        <Class name="org.apache.hadoop.hdfs.server.datanode.checker.AbstractFuture" />
+        <Bug pattern="DLS_DEAD_LOCAL_STORE" />
+    </Match>
+    <Match>
+        <Class name="org.apache.hadoop.hdfs.server.datanode.checker.AbstractFuture" />
+        <Bug pattern="NS_DANGEROUS_NON_SHORT_CIRCUIT" />
+    </Match>
  </FindBugsFilter>

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/checker/DatasetVolumeChecker.java

@@ -91,6 +91,7 @@ public class DatasetVolumeChecker {
    * Minimum time between two successive disk checks of a volume.
    */
   private final long minDiskCheckGapMs;
+  private final long diskCheckTimeout;
 
   /**
    * Timestamp of the last check of all volumes.
@@ -136,6 +137,17 @@ public class DatasetVolumeChecker {
           + minDiskCheckGapMs + " (should be >= 0)");
     }
 
+    diskCheckTimeout = conf.getTimeDuration(
+        DFSConfigKeys.DFS_DATANODE_DISK_CHECK_TIMEOUT_KEY,
+        DFSConfigKeys.DFS_DATANODE_DISK_CHECK_TIMEOUT_DEFAULT,
+        TimeUnit.MILLISECONDS);
+
+    if (diskCheckTimeout < 0) {
+      throw new DiskErrorException("Invalid value configured for "
+          + DFS_DATANODE_DISK_CHECK_TIMEOUT_KEY + " - "
+          + diskCheckTimeout + " (should be >= 0)");
+    }
+
     lastAllVolumesCheck = timer.monotonicNow() - minDiskCheckGapMs;
 
     if (maxVolumeFailuresTolerated < 0) {
@@ -145,7 +157,8 @@ public class DatasetVolumeChecker {
     }
 
     delegateChecker = new ThrottledAsyncChecker<>(
-        timer, minDiskCheckGapMs, Executors.newCachedThreadPool(
+        timer, minDiskCheckGapMs, diskCheckTimeout,
+        Executors.newCachedThreadPool(
             new ThreadFactoryBuilder()
                 .setNameFormat("DataNode DiskChecker thread %d")
                 .setDaemon(true)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/checker/StorageLocationChecker.java

@@ -119,6 +119,7 @@ public class StorageLocationChecker {
             DFSConfigKeys.DFS_DATANODE_DISK_CHECK_MIN_GAP_KEY,
             DFSConfigKeys.DFS_DATANODE_DISK_CHECK_MIN_GAP_DEFAULT,
             TimeUnit.MILLISECONDS),
+        0,
         Executors.newCachedThreadPool(
             new ThreadFactoryBuilder()
                 .setNameFormat("StorageLocationChecker thread %d")

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/checker/ThrottledAsyncChecker.java

@@ -38,6 +38,8 @@ import java.util.Map;
 import java.util.WeakHashMap;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutorService;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 
 /**
@@ -64,12 +66,14 @@ public class ThrottledAsyncChecker<K, V> implements AsyncChecker<K, V> {
    * The ExecutorService used to schedule asynchronous checks.
    */
   private final ListeningExecutorService executorService;
+  private final ScheduledExecutorService scheduledExecutorService;
 
   /**
    * The minimum gap in milliseconds between two successive checks
    * of the same object. This is the throttle.
    */
   private final long minMsBetweenChecks;
+  private final long diskCheckTimeout;
 
   /**
    * Map of checks that are currently in progress. Protected by the object
@@ -86,12 +90,23 @@ public class ThrottledAsyncChecker<K, V> implements AsyncChecker<K, V> {
 
   ThrottledAsyncChecker(final Timer timer,
                         final long minMsBetweenChecks,
+                        final long diskCheckTimeout,
                         final ExecutorService executorService) {
     this.timer = timer;
     this.minMsBetweenChecks = minMsBetweenChecks;
+    this.diskCheckTimeout = diskCheckTimeout;
     this.executorService = MoreExecutors.listeningDecorator(executorService);
     this.checksInProgress = new HashMap<>();
     this.completedChecks = new WeakHashMap<>();
+
+    if (this.diskCheckTimeout > 0) {
+      ScheduledThreadPoolExecutor scheduledThreadPoolExecutor = new
+          ScheduledThreadPoolExecutor(1);
+      this.scheduledExecutorService = MoreExecutors
+          .getExitingScheduledExecutorService(scheduledThreadPoolExecutor);
+    } else {
+      this.scheduledExecutorService = null;
+    }
   }
 
   /**
@@ -120,13 +135,23 @@ public class ThrottledAsyncChecker<K, V> implements AsyncChecker<K, V> {
       }
     }
 
-    final ListenableFuture<V> lf = executorService.submit(
+    final ListenableFuture<V> lfWithoutTimeout = executorService.submit(
         new Callable<V>() {
           @Override
           public V call() throws Exception {
             return target.check(context);
           }
         });
+    final ListenableFuture<V> lf;
+
+    if (diskCheckTimeout > 0) {
+      lf = TimeoutFuture
+          .create(lfWithoutTimeout, diskCheckTimeout, TimeUnit.MILLISECONDS,
+              scheduledExecutorService);
+    } else {
+      lf = lfWithoutTimeout;
+    }
+
     checksInProgress.put(target, lf);
     addResultCachingCallback(target, lf);
     return Optional.of(lf);
@@ -174,6 +199,16 @@ public class ThrottledAsyncChecker<K, V> implements AsyncChecker<K, V> {
       executorService.shutdownNow();
       executorService.awaitTermination(timeout, timeUnit);
     }
+    if (scheduledExecutorService != null) {
+      // Try orderly shutdown
+      scheduledExecutorService.shutdown();
+
+      if (!scheduledExecutorService.awaitTermination(timeout, timeUnit)) {
+        // Interrupt executing tasks and wait again.
+        scheduledExecutorService.shutdownNow();
+        scheduledExecutorService.awaitTermination(timeout, timeUnit);
+      }
+    }
   }
 
   /**

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/checker/TimeoutFuture.java

@@ -0,0 +1,162 @@
+/*
+ * Copyright (C) 2007 The Guava Authors
+ *
+ * Licensed 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.
+ */
+
+/**
+ * Some portions of this class have been modified to make it functional in this
+ * package.
+ */
+package org.apache.hadoop.hdfs.server.datanode.checker;
+
+import com.google.common.base.Preconditions;
+import com.google.common.util.concurrent.ListenableFuture;
+import org.apache.hadoop.hdfs.server.datanode.checker.AbstractFuture;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.annotation.Nullable;
+import java.util.concurrent.Future;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+/**
+ * Implementation of {@code Futures#withTimeout}.
+ * <p>
+ * <p>Future that delegates to another but will finish early (via a
+ * {@link TimeoutException} wrapped in an {@link ExecutionException}) if the
+ * specified duration expires. The delegate future is interrupted and
+ * cancelled if it times out.
+ */
+final class TimeoutFuture<V> extends AbstractFuture.TrustedFuture<V> {
+  public static final Logger LOG = LoggerFactory.getLogger(
+      TimeoutFuture.class);
+
+  static <V> ListenableFuture<V> create(
+      ListenableFuture<V> delegate,
+      long time,
+      TimeUnit unit,
+      ScheduledExecutorService scheduledExecutor) {
+    TimeoutFuture<V> result = new TimeoutFuture<V>(delegate);
+    TimeoutFuture.Fire<V> fire = new TimeoutFuture.Fire<V>(result);
+    result.timer = scheduledExecutor.schedule(fire, time, unit);
+    delegate.addListener(fire, directExecutor());
+    return result;
+  }
+
+  /*
+   * Memory visibility of these fields. There are two cases to consider.
+   *
+   * 1. visibility of the writes to these fields to Fire.run:
+   *
+   * The initial write to delegateRef is made definitely visible via the
+   * semantics of addListener/SES.schedule. The later racy write in cancel()
+   * is not guaranteed to be observed, however that is fine since the
+   * correctness is based on the atomic state in our base class. The initial
+   * write to timer is never definitely visible to Fire.run since it is
+   * assigned after SES.schedule is called. Therefore Fire.run has to check
+   * for null. However, it should be visible if Fire.run is called by
+   * delegate.addListener since addListener is called after the assignment
+   * to timer, and importantly this is the main situation in which we need to
+   * be able to see the write.
+   *
+   * 2. visibility of the writes to an afterDone() call triggered by cancel():
+   *
+   * Since these fields are non-final that means that TimeoutFuture is not
+   * being 'safely published', thus a motivated caller may be able to expose
+   * the reference to another thread that would then call cancel() and be
+   * unable to cancel the delegate. There are a number of ways to solve this,
+   * none of which are very pretty, and it is currently believed to be a
+   * purely theoretical problem (since the other actions should supply
+   * sufficient write-barriers).
+   */
+
+  @Nullable private ListenableFuture<V> delegateRef;
+  @Nullable private Future<?> timer;
+
+  private TimeoutFuture(ListenableFuture<V> delegate) {
+    this.delegateRef = Preconditions.checkNotNull(delegate);
+  }
+
+  /**
+   * A runnable that is called when the delegate or the timer completes.
+   */
+  private static final class Fire<V> implements Runnable {
+    @Nullable
+    TimeoutFuture<V> timeoutFutureRef;
+
+    Fire(
+        TimeoutFuture<V> timeoutFuture) {
+      this.timeoutFutureRef = timeoutFuture;
+    }
+
+    @Override
+    public void run() {
+      // If either of these reads return null then we must be after a
+      // successful cancel or another call to this method.
+      TimeoutFuture<V> timeoutFuture = timeoutFutureRef;
+      if (timeoutFuture == null) {
+        return;
+      }
+      ListenableFuture<V> delegate = timeoutFuture.delegateRef;
+      if (delegate == null) {
+        return;
+      }
+
+      /*
+       * If we're about to complete the TimeoutFuture, we want to release our
+       * reference to it. Otherwise, we'll pin it (and its result) in memory
+       * until the timeout task is GCed. (The need to clear our reference to
+       * the TimeoutFuture is the reason we use a *static* nested class with
+       * a manual reference back to the "containing" class.)
+       *
+       * This has the nice-ish side effect of limiting reentrancy: run() calls
+       * timeoutFuture.setException() calls run(). That reentrancy would
+       * already be harmless, since timeoutFuture can be set (and delegate
+       * cancelled) only once. (And "set only once" is important for other
+       * reasons: run() can still be invoked concurrently in different threads,
+       * even with the above null checks.)
+       */
+      timeoutFutureRef = null;
+      if (delegate.isDone()) {
+        timeoutFuture.setFuture(delegate);
+      } else {
+        try {
+          timeoutFuture.setException(
+              new TimeoutException("Future timed out: " + delegate));
+        } finally {
+          delegate.cancel(true);
+        }
+      }
+    }
+  }
+
+  @Override
+  protected void afterDone() {
+    maybePropagateCancellation(delegateRef);
+
+    Future<?> localTimer = timer;
+    // Try to cancel the timer as an optimization.
+    // timer may be null if this call to run was by the timer task since there
+    // is no happens-before edge between the assignment to timer and an
+    // execution of the timer task.
+    if (localTimer != null) {
+      localTimer.cancel(false);
+    }
+
+    delegateRef = null;
+    timer = null;
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/checker/TestDatasetVolumeCheckerTimeout.java

@@ -0,0 +1,134 @@
+/**
+ * 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.hdfs.server.datanode.checker;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hdfs.DFSConfigKeys;
+import org.apache.hadoop.hdfs.HdfsConfiguration;
+import org.apache.hadoop.hdfs.LogVerificationAppender;
+import org.apache.hadoop.hdfs.server.datanode.StorageLocation;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeReference;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
+import org.apache.hadoop.util.FakeTimer;
+import org.apache.log4j.Level;
+import org.apache.log4j.Logger;
+import org.apache.log4j.spi.LoggingEvent;
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TestName;
+import static org.mockito.Matchers.anyObject;
+import static org.mockito.Mockito.*;
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.stubbing.Answer;
+import org.slf4j.LoggerFactory;
+
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * Test that timeout is triggered during Disk Volume Checker.
+ */
+public class TestDatasetVolumeCheckerTimeout {
+  public static final org.slf4j.Logger LOG =
+      LoggerFactory.getLogger(TestDatasetVolumeCheckerTimeout.class);
+
+  @Rule
+  public TestName testName = new TestName();
+
+  static Configuration conf;
+  private static final long DISK_CHECK_TIMEOUT = 10;
+  private static final long DISK_CHECK_TIME = 100;
+  static ReentrantLock lock = new ReentrantLock();
+
+  static {
+    conf = new HdfsConfiguration();
+    conf.setTimeDuration(
+        DFSConfigKeys.DFS_DATANODE_DISK_CHECK_TIMEOUT_KEY,
+        DISK_CHECK_TIMEOUT, TimeUnit.MILLISECONDS);
+  }
+
+  static FsVolumeSpi makeSlowVolume() throws Exception {
+    final FsVolumeSpi volume = mock(FsVolumeSpi.class);
+    final FsVolumeReference reference = mock(FsVolumeReference.class);
+    final StorageLocation location = mock(StorageLocation.class);
+
+    when(reference.getVolume()).thenReturn(volume);
+    when(volume.obtainReference()).thenReturn(reference);
+    when(volume.getStorageLocation()).thenReturn(location);
+
+    when(volume.check(anyObject())).thenAnswer(new Answer<VolumeCheckResult>() {
+      @Override
+      public VolumeCheckResult answer(
+          InvocationOnMock invocationOnMock) throws Throwable {
+        // Wait for the disk check to timeout and then release lock.
+        lock.lock();
+        lock.unlock();
+        return VolumeCheckResult.HEALTHY;
+      }
+    });
+
+    return volume;
+  }
+
+  @Test (timeout = 1000)
+  public void testDiskCheckTimeout() throws Exception {
+    LOG.info("Executing {}", testName.getMethodName());
+    final FsVolumeSpi volume = makeSlowVolume();
+
+    final DatasetVolumeChecker checker =
+        new DatasetVolumeChecker(conf, new FakeTimer());
+    final AtomicLong numCallbackInvocations = new AtomicLong(0);
+
+    lock.lock();
+    /**
+     * Request a check and ensure it triggered {@link FsVolumeSpi#check}.
+     */
+    boolean result =
+        checker.checkVolume(volume, new DatasetVolumeChecker.Callback() {
+          @Override
+          public void call(Set<FsVolumeSpi> healthyVolumes,
+              Set<FsVolumeSpi> failedVolumes) {
+            numCallbackInvocations.incrementAndGet();
+
+            // Assert that the disk check registers a failed volume due to
+            // timeout
+            assertThat(healthyVolumes.size(), is(0));
+            assertThat(failedVolumes.size(), is(1));
+          }
+        });
+
+    // Wait for the callback
+    Thread.sleep(DISK_CHECK_TIME);
+
+    // Release lock
+    lock.unlock();
+
+    // Ensure that the check was invoked only once.
+    verify(volume, times(1)).check(anyObject());
+    assertThat(numCallbackInvocations.get(), is(1L));
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/checker/TestThrottledAsyncChecker.java

@@ -59,7 +59,7 @@ public class TestThrottledAsyncChecker {
     final NoOpCheckable target2 = new NoOpCheckable();
     final FakeTimer timer = new FakeTimer();
     ThrottledAsyncChecker<Boolean, Boolean> checker =
-        new ThrottledAsyncChecker<>(timer, MIN_ERROR_CHECK_GAP,
+        new ThrottledAsyncChecker<>(timer, MIN_ERROR_CHECK_GAP, 0,
                                     getExecutorService());
 
     // check target1 and ensure we get back the expected result.
@@ -99,7 +99,7 @@ public class TestThrottledAsyncChecker {
     final FakeTimer timer = new FakeTimer();
     final LatchedCallback callback = new LatchedCallback(target);
     ThrottledAsyncChecker<Boolean, Boolean> checker =
-        new ThrottledAsyncChecker<>(timer, MIN_ERROR_CHECK_GAP,
+        new ThrottledAsyncChecker<>(timer, MIN_ERROR_CHECK_GAP, 0,
             getExecutorService());
 
     Optional<ListenableFuture<Boolean>> olf =
@@ -124,7 +124,7 @@ public class TestThrottledAsyncChecker {
     LatchedCheckable target = new LatchedCheckable();
     final FakeTimer timer = new FakeTimer();
     ThrottledAsyncChecker<Boolean, Boolean> checker =
-        new ThrottledAsyncChecker<>(timer, MIN_ERROR_CHECK_GAP,
+        new ThrottledAsyncChecker<>(timer, MIN_ERROR_CHECK_GAP, 0,
             getExecutorService());
     final Optional<ListenableFuture<Boolean>> olf1 =
         checker.schedule(target, true);
@@ -167,7 +167,7 @@ public class TestThrottledAsyncChecker {
     final NoOpCheckable target1 = new NoOpCheckable();
     final FakeTimer timer = new FakeTimer();
     ThrottledAsyncChecker<Boolean, Boolean> checker =
-        new ThrottledAsyncChecker<>(timer, MIN_ERROR_CHECK_GAP,
+        new ThrottledAsyncChecker<>(timer, MIN_ERROR_CHECK_GAP, 0,
             getExecutorService());
 
     assertTrue(checker.schedule(target1, true).isPresent());
@@ -203,7 +203,7 @@ public class TestThrottledAsyncChecker {
     final ThrowingCheckable target1 = new ThrowingCheckable();
     final FakeTimer timer = new FakeTimer();
     ThrottledAsyncChecker<Boolean, Boolean> checker =
-        new ThrottledAsyncChecker<>(timer, MIN_ERROR_CHECK_GAP,
+        new ThrottledAsyncChecker<>(timer, MIN_ERROR_CHECK_GAP, 0,
             getExecutorService());
 
     assertTrue(checker.schedule(target1, true).isPresent());

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/checker/TestThrottledAsyncCheckerTimeout.java

@@ -0,0 +1,223 @@
+/**
+ * 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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.hdfs.server.datanode.checker;
+
+import com.google.common.base.Optional;
+import com.google.common.util.concurrent.FutureCallback;
+import com.google.common.util.concurrent.Futures;
+import com.google.common.util.concurrent.ListenableFuture;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hdfs.DFSConfigKeys;
+import org.apache.hadoop.hdfs.HdfsConfiguration;
+import org.apache.hadoop.hdfs.LogVerificationAppender;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
+import org.apache.hadoop.util.FakeTimer;
+import org.apache.log4j.Logger;
+import org.apache.log4j.spi.LoggingEvent;
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.*;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TestName;
+import static org.mockito.Matchers.any;
+import static org.mockito.Matchers.anyObject;
+import static org.mockito.Matchers.anySet;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import org.slf4j.LoggerFactory;
+
+import java.util.Set;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.ScheduledThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.locks.ReentrantLock;
+
+public class TestThrottledAsyncCheckerTimeout {
+  public static final org.slf4j.Logger LOG =
+      LoggerFactory.getLogger(TestThrottledAsyncCheckerTimeout.class);
+
+  @Rule
+  public TestName testName = new TestName();
+
+  Configuration conf;
+  private static final long DISK_CHECK_TIMEOUT = 10;
+  private static final long DISK_CHECK_TIME = 100;
+  private ReentrantLock lock;
+
+  private ExecutorService getExecutorService() {
+    return new ScheduledThreadPoolExecutor(1);
+  }
+
+  @Before
+  public void initializeLock() {
+    lock = new ReentrantLock();
+  }
+
+  @Test	(timeout = 1000)
+  public void testDiskCheckTimeout() throws Exception {
+    LOG.info("Executing {}", testName.getMethodName());
+
+    final DummyCheckable target = new DummyCheckable();
+    final FakeTimer timer = new FakeTimer();
+    ThrottledAsyncChecker<Boolean, Boolean> checker =
+        new ThrottledAsyncChecker<>(timer, 0, DISK_CHECK_TIMEOUT,
+            getExecutorService());
+
+    // Acquire lock to halt checker. Release after timeout occurs.
+    lock.lock();
+
+    final Optional<ListenableFuture<Boolean>> olf = checker
+        .schedule(target, true);
+
+    final AtomicLong numCallbackInvocationsSuccess = new AtomicLong(0);
+    final AtomicLong numCallbackInvocationsFailure = new AtomicLong(0);
+
+    AtomicBoolean callbackResult = new AtomicBoolean(false);
+    final Throwable[] throwable = new Throwable[1];
+
+    assertTrue(olf.isPresent());
+    Futures.addCallback(olf.get(), new FutureCallback<Boolean>() {
+      @Override
+      public void onSuccess(Boolean result) {
+        numCallbackInvocationsSuccess.incrementAndGet();
+        callbackResult.set(true);
+      }
+
+      @Override
+      public void onFailure(Throwable t) {
+        throwable[0] = t;
+        numCallbackInvocationsFailure.incrementAndGet();
+        callbackResult.set(true);
+      }
+    });
+
+    while (!callbackResult.get()) {
+      // Wait for the callback
+      Thread.sleep(DISK_CHECK_TIMEOUT);
+    }
+
+    lock.unlock();
+
+    assertThat(numCallbackInvocationsFailure.get(), is(1L));
+    assertThat(numCallbackInvocationsSuccess.get(), is(0L));
+    assertTrue(throwable[0] instanceof TimeoutException);
+  }
+
+  @Test (timeout = 2000)
+  public void testDiskCheckTimeoutInvokesOneCallbackOnly() throws Exception {
+    LOG.info("Executing {}", testName.getMethodName());
+
+    final DummyCheckable target = new DummyCheckable();
+    final FakeTimer timer = new FakeTimer();
+    ThrottledAsyncChecker<Boolean, Boolean> checker =
+        new ThrottledAsyncChecker<>(timer, 0, DISK_CHECK_TIMEOUT,
+            getExecutorService());
+    FutureCallback<Boolean> futureCallback = mock(FutureCallback.class);
+
+    // Acquire lock to halt disk checker. Release after timeout occurs.
+    lock.lock();
+
+    final Optional<ListenableFuture<Boolean>> olf1 = checker
+        .schedule(target, true);
+
+    assertTrue(olf1.isPresent());
+    Futures.addCallback(olf1.get(), futureCallback);
+
+    // Wait for the callback
+    Thread.sleep(DISK_CHECK_TIMEOUT);
+
+    // Verify that timeout results in only 1 onFailure call and 0 onSuccess
+    // calls.
+    verify(futureCallback, times(1)).onFailure(any());
+    verify(futureCallback, times(0)).onSuccess(any());
+
+    // Release lock so that target can acquire it.
+    lock.unlock();
+
+    final Optional<ListenableFuture<Boolean>> olf2 = checker
+        .schedule(target, true);
+
+    assertTrue(olf2.isPresent());
+    Futures.addCallback(olf2.get(), futureCallback);
+
+    // Wait for the callback
+    Thread.sleep(DISK_CHECK_TIME);
+
+    // Verify that normal check (dummy) results in only 1 onSuccess call.
+    // Number of times onFailure is invoked should remain the same - 1.
+    verify(futureCallback, times(1)).onFailure(any());
+    verify(futureCallback, times(1)).onSuccess(any());
+  }
+
+  @Test (timeout = 1000)
+  public void testTimeoutExceptionIsNotThrownForGoodDisk() throws Exception {
+    LOG.info("Executing {}", testName.getMethodName());
+
+    final DummyCheckable target = new DummyCheckable();
+    final FakeTimer timer = new FakeTimer();
+    ThrottledAsyncChecker<Boolean, Boolean> checker =
+        new ThrottledAsyncChecker<>(timer, 0, DISK_CHECK_TIMEOUT,
+            getExecutorService());
+
+    final Optional<ListenableFuture<Boolean>> olf = checker
+        .schedule(target, true);
+
+    AtomicBoolean callbackResult = new AtomicBoolean(false);
+    final Throwable[] throwable = new Throwable[1];
+
+    assertTrue(olf.isPresent());
+    Futures.addCallback(olf.get(), new FutureCallback<Boolean>() {
+      @Override
+      public void onSuccess(Boolean result) {
+        callbackResult.set(true);
+      }
+
+      @Override
+      public void onFailure(Throwable t) {
+        throwable[0] = t;
+        callbackResult.set(true);
+      }
+    });
+
+    while (!callbackResult.get()) {
+      // Wait for the callback
+      Thread.sleep(DISK_CHECK_TIMEOUT);
+    }
+
+    assertTrue(throwable[0] == null);
+  }
+
+  /**
+   * A dummy Checkable that just returns true after acquiring lock.
+   */
+  protected class DummyCheckable implements Checkable<Boolean,Boolean> {
+
+    @Override
+    public Boolean check(Boolean context) throws Exception {
+      // Wait to acquire lock
+      lock.lock();
+      lock.unlock();
+      return true;
+    }
+  }
+}