HADOOP-9618. thread which detects GC pauses (Todd Lipcon via Colin Patrick McCabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1503810 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -36,6 +36,9 @@ Release 2.2.0 - UNRELEASED
     HADOOP-9703.  org.apache.hadoop.ipc.Client leaks threads on stop.
     (Tsuyoshi OZAWA vi Colin Patrick McCabe)
 
+    HADOOP-9618.  Add thread which detects GC pauses.
+    (Todd Lipcon via Colin Patrick McCabe)
+
   OPTIMIZATIONS
 
   BUG FIXES

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/JvmPauseMonitor.java

@@ -0,0 +1,196 @@
+/*
+ * 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.util;
+
+import java.lang.management.GarbageCollectorMXBean;
+import java.lang.management.ManagementFactory;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.conf.Configuration;
+
+import com.google.common.base.Joiner;
+import com.google.common.base.Preconditions;
+import com.google.common.base.Stopwatch;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
+import com.google.common.collect.Sets;
+
+/**
+ * Class which sets up a simple thread which runs in a loop sleeping
+ * for a short interval of time. If the sleep takes significantly longer
+ * than its target time, it implies that the JVM or host machine has
+ * paused processing, which may cause other problems. If such a pause is
+ * detected, the thread logs a message.
+ */
+@InterfaceAudience.Private
+public class JvmPauseMonitor {
+  private static final Log LOG = LogFactory.getLog(
+      JvmPauseMonitor.class);
+
+  /** The target sleep time */
+  private static final long SLEEP_INTERVAL_MS = 500;
+  
+  /** log WARN if we detect a pause longer than this threshold */
+  private final long warnThresholdMs;
+  private static final String WARN_THRESHOLD_KEY =
+      "jvm.pause.warn-threshold.ms";
+  private static final long WARN_THRESHOLD_DEFAULT = 10000;
+  
+  /** log INFO if we detect a pause longer than this threshold */
+  private final long infoThresholdMs;
+  private static final String INFO_THRESHOLD_KEY =
+      "jvm.pause.info-threshold.ms";
+  private static final long INFO_THRESHOLD_DEFAULT = 1000;
+
+  
+  private Thread monitorThread;
+  private volatile boolean shouldRun = true;
+  
+  public JvmPauseMonitor(Configuration conf) {
+    this.warnThresholdMs = conf.getLong(WARN_THRESHOLD_KEY, WARN_THRESHOLD_DEFAULT);
+    this.infoThresholdMs = conf.getLong(INFO_THRESHOLD_KEY, INFO_THRESHOLD_DEFAULT);
+  }
+  
+  public void start() {
+    Preconditions.checkState(monitorThread == null,
+        "Already started");
+    monitorThread = new Daemon(new Monitor());
+    monitorThread.start();
+  }
+  
+  public void stop() {
+    shouldRun = false;
+    monitorThread.interrupt();
+    try {
+      monitorThread.join();
+    } catch (InterruptedException e) {
+      Thread.currentThread().interrupt();
+    }
+  }
+  
+  private String formatMessage(long extraSleepTime,
+      Map<String, GcTimes> gcTimesAfterSleep,
+      Map<String, GcTimes> gcTimesBeforeSleep) {
+    
+    Set<String> gcBeanNames = Sets.intersection(
+        gcTimesAfterSleep.keySet(),
+        gcTimesBeforeSleep.keySet());
+    List<String> gcDiffs = Lists.newArrayList();
+    for (String name : gcBeanNames) {
+      GcTimes diff = gcTimesAfterSleep.get(name).subtract(
+          gcTimesBeforeSleep.get(name));
+      if (diff.gcCount != 0) {
+        gcDiffs.add("GC pool '" + name + "' had collection(s): " +
+            diff.toString());
+      }
+    }
+    
+    String ret = "Detected pause in JVM or host machine (eg GC): " +
+        "pause of approximately " + extraSleepTime + "ms\n";
+    if (gcDiffs.isEmpty()) {
+      ret += "No GCs detected";
+    } else {
+      ret += Joiner.on("\n").join(gcDiffs);
+    }
+    return ret;
+  }
+  
+  private Map<String, GcTimes> getGcTimes() {
+    Map<String, GcTimes> map = Maps.newHashMap();
+    List<GarbageCollectorMXBean> gcBeans =
+        ManagementFactory.getGarbageCollectorMXBeans();
+    for (GarbageCollectorMXBean gcBean : gcBeans) {
+      map.put(gcBean.getName(), new GcTimes(gcBean));
+    }
+    return map;
+  }
+  
+  private static class GcTimes {
+    private GcTimes(GarbageCollectorMXBean gcBean) {
+      gcCount = gcBean.getCollectionCount();
+      gcTimeMillis = gcBean.getCollectionTime();
+    }
+    
+    private GcTimes(long count, long time) {
+      this.gcCount = count;
+      this.gcTimeMillis = time;
+    }
+
+    private GcTimes subtract(GcTimes other) {
+      return new GcTimes(this.gcCount - other.gcCount,
+          this.gcTimeMillis - other.gcTimeMillis);
+    }
+    
+    @Override
+    public String toString() {
+      return "count=" + gcCount + " time=" + gcTimeMillis + "ms";
+    }
+    
+    private long gcCount;
+    private long gcTimeMillis;
+  }
+
+  private class Monitor implements Runnable {
+    @Override
+    public void run() {
+      Stopwatch sw = new Stopwatch();
+      Map<String, GcTimes> gcTimesBeforeSleep = getGcTimes();
+      while (shouldRun) {
+        sw.reset().start();
+        try {
+          Thread.sleep(SLEEP_INTERVAL_MS);
+        } catch (InterruptedException ie) {
+          return;
+        }
+        long extraSleepTime = sw.elapsedMillis() - SLEEP_INTERVAL_MS;
+        Map<String, GcTimes> gcTimesAfterSleep = getGcTimes();
+
+        if (extraSleepTime > warnThresholdMs) {
+          LOG.warn(formatMessage(
+              extraSleepTime, gcTimesAfterSleep, gcTimesBeforeSleep));
+        } else if (extraSleepTime > infoThresholdMs) {
+          LOG.info(formatMessage(
+              extraSleepTime, gcTimesAfterSleep, gcTimesBeforeSleep));
+        }
+        
+        gcTimesBeforeSleep = gcTimesAfterSleep;
+      }
+    }
+  }
+  
+  /**
+   * Simple 'main' to facilitate manual testing of the pause monitor.
+   * 
+   * This main function just leaks memory into a list. Running this class
+   * with a 1GB heap will very quickly go into "GC hell" and result in
+   * log messages about the GC pauses.
+   */
+  public static void main(String []args) throws Exception {
+    new JvmPauseMonitor(new Configuration()).start();
+    List<String> list = Lists.newArrayList();
+    int i = 0;
+    while (true) {
+      list.add(String.valueOf(i++));
+    }
+  }
+}

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

@@ -171,6 +171,7 @@ import org.apache.hadoop.util.DiskChecker;
 import org.apache.hadoop.util.DiskChecker.DiskErrorException;
 import org.apache.hadoop.util.DiskChecker.DiskOutOfSpaceException;
 import org.apache.hadoop.util.GenericOptionsParser;
+import org.apache.hadoop.util.JvmPauseMonitor;
 import org.apache.hadoop.util.ServicePlugin;
 import org.apache.hadoop.util.StringUtils;
 import org.apache.hadoop.util.Time;
@@ -284,6 +285,8 @@ public class DataNode extends Configured
   // For InterDataNodeProtocol
   public RPC.Server ipcServer;
 
+  private JvmPauseMonitor pauseMonitor;
+
   private SecureResources secureResources = null;
   private AbstractList<File> dataDirs;
   private Configuration conf;
@@ -739,6 +742,8 @@ public class DataNode extends Configured
     registerMXBean();
     initDataXceiver(conf);
     startInfoServer(conf);
+    pauseMonitor = new JvmPauseMonitor(conf);
+    pauseMonitor.start();
   
     // BlockPoolTokenSecretManager is required to create ipc server.
     this.blockPoolTokenSecretManager = new BlockPoolTokenSecretManager();
@@ -1221,6 +1226,9 @@ public class DataNode extends Configured
     if (ipcServer != null) {
       ipcServer.stop();
     }
+    if (pauseMonitor != null) {
+      pauseMonitor.stop();
+    }
     
     if (dataXceiverServer != null) {
       ((DataXceiverServer) this.dataXceiverServer.getRunnable()).kill();

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java

@@ -78,6 +78,7 @@ import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.security.authorize.RefreshAuthorizationPolicyProtocol;
 import org.apache.hadoop.tools.GetUserMappingsProtocol;
 import org.apache.hadoop.util.ExitUtil.ExitException;
+import org.apache.hadoop.util.JvmPauseMonitor;
 import org.apache.hadoop.util.ServicePlugin;
 import org.apache.hadoop.util.StringUtils;
 
@@ -256,6 +257,8 @@ public class NameNode {
   private List<ServicePlugin> plugins;
   
   private NameNodeRpcServer rpcServer;
+
+  private JvmPauseMonitor pauseMonitor;
   
   /** Format a new filesystem.  Destroys any filesystem that may already
    * exist at this location.  **/
@@ -463,6 +466,9 @@ public class NameNode {
     } else {
       validateConfigurationSettingsOrAbort(conf);
     }
+    
+    pauseMonitor = new JvmPauseMonitor(conf);
+    pauseMonitor.start();
 
     startCommonServices(conf);
   }
@@ -543,6 +549,7 @@ public class NameNode {
   private void stopCommonServices() {
     if(namesystem != null) namesystem.close();
     if(rpcServer != null) rpcServer.stop();
+    if (pauseMonitor != null) pauseMonitor.stop();
     if (plugins != null) {
       for (ServicePlugin p : plugins) {
         try {