HADOOP-11970. Replace uses of ThreadLocal<Random> with JDK7 ThreadLocalRandom (Sean Busbey via Colin P. McCabe)

(cherry picked from commit 470c87dbc6)

Conflicts:
	hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestReplicationPolicy.java
        hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/common/JspHelper.java

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

@@ -130,6 +130,9 @@ Release 2.8.0 - UNRELEASED
     HADOOP-11812. Implement listLocatedStatus for ViewFileSystem to speed up
     split calculation (gera)
 
+    HADOOP-11970. Replace uses of ThreadLocal<Random> with JDK7
+    ThreadLocalRandom.  (Sean Busbey via Colin P. McCabe)
+
   BUG FIXES
     HADOOP-11802: DomainSocketWatcher thread terminates sometimes after there
     is an I/O error during requestShortCircuitShm (cmccabe)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/retry/RetryPolicies.java

@@ -28,7 +28,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
-import java.util.Random;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.TimeUnit;
 
 import org.apache.commons.logging.Log;
@@ -47,13 +47,6 @@ public class RetryPolicies {
   
   public static final Log LOG = LogFactory.getLog(RetryPolicies.class);
   
-  private static ThreadLocal<Random> RANDOM = new ThreadLocal<Random>() {
-    @Override
-    protected Random initialValue() {
-      return new Random();
-    }
-  };
-  
   /**
    * <p>
    * Try once, and fail by re-throwing the exception.
@@ -321,7 +314,8 @@ public class RetryPolicies {
       }
 
       //calculate sleep time and return.
-      final double ratio = RANDOM.get().nextDouble() + 0.5;//0.5 <= ratio <=1.5
+      // ensure 0.5 <= ratio <=1.5
+      final double ratio = ThreadLocalRandom.current().nextDouble() + 0.5;
       final long sleepTime = Math.round(p.sleepMillis * ratio);
       return new RetryAction(RetryAction.RetryDecision.RETRY, sleepTime);
     }
@@ -610,7 +604,7 @@ public class RetryPolicies {
   private static long calculateExponentialTime(long time, int retries,
       long cap) {
     long baseTime = Math.min(time * (1L << retries), cap);
-    return (long) (baseTime * (RANDOM.get().nextDouble() + 0.5));
+    return (long) (baseTime * (ThreadLocalRandom.current().nextDouble() + 0.5));
   }
 
   private static long calculateExponentialTime(long time, int retries) {

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSClient.java

@@ -49,6 +49,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Random;
 import java.util.concurrent.SynchronousQueue;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -318,7 +319,8 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
     
     this.authority = nameNodeUri == null? "null": nameNodeUri.getAuthority();
     this.clientName = "DFSClient_" + dfsClientConf.getTaskId() + "_" + 
-        DFSUtil.getRandom().nextInt()  + "_" + Thread.currentThread().getId();
+        ThreadLocalRandom.current().nextInt()  + "_" +
+        Thread.currentThread().getId();
     int numResponseToDrop = conf.getInt(
         DFSConfigKeys.DFS_CLIENT_TEST_DROP_NAMENODE_RESPONSE_NUM_KEY,
         DFSConfigKeys.DFS_CLIENT_TEST_DROP_NAMENODE_RESPONSE_NUM_DEFAULT);

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSInputStream.java

@@ -40,6 +40,7 @@ import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorCompletionService;
 import java.util.concurrent.Future;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 
@@ -976,7 +977,9 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
           // expanded to 9000ms. 
           final int timeWindow = dfsClient.getConf().getTimeWindow();
           double waitTime = timeWindow * failures +       // grace period for the last round of attempt
-            timeWindow * (failures + 1) * DFSUtil.getRandom().nextDouble(); // expanding time window for each failure
+              // expanding time window for each failure
+              timeWindow * (failures + 1) *
+              ThreadLocalRandom.current().nextDouble();
           DFSClient.LOG.warn("DFS chooseDataNode: got # " + (failures + 1) + " IOException, will wait for " + waitTime + " msec.");
           Thread.sleep((long)waitTime);
         } catch (InterruptedException iex) {

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSUtil.java

@@ -50,8 +50,8 @@ import java.util.Date;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
-import java.util.Random;
 import java.util.Set;
+import java.util.concurrent.ThreadLocalRandom;
 
 import javax.net.SocketFactory;
 
@@ -105,12 +105,6 @@ public class DFSUtil {
   public static final Log LOG = LogFactory.getLog(DFSUtil.class.getName());
   
   private DFSUtil() { /* Hidden constructor */ }
-  private static final ThreadLocal<Random> RANDOM = new ThreadLocal<Random>() {
-    @Override
-    protected Random initialValue() {
-      return new Random();
-    }
-  };
   
   private static final ThreadLocal<SecureRandom> SECURE_RANDOM = new ThreadLocal<SecureRandom>() {
     @Override
@@ -119,11 +113,6 @@ public class DFSUtil {
     }
   };
 
-  /** @return a pseudo random number generator. */
-  public static Random getRandom() {
-    return RANDOM.get();
-  }
-  
   /** @return a pseudo secure random number generator. */
   public static SecureRandom getSecureRandom() {
     return SECURE_RANDOM.get();
@@ -132,9 +121,8 @@ public class DFSUtil {
   /** Shuffle the elements in the given array. */
   public static <T> T[] shuffle(final T[] array) {
     if (array != null && array.length > 0) {
-      final Random random = getRandom();
       for (int n = array.length; n > 1; ) {
-        final int randomIndex = random.nextInt(n);
+        final int randomIndex = ThreadLocalRandom.current().nextInt(n);
         n--;
         if (n != randomIndex) {
           final T tmp = array[randomIndex];

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java

@@ -35,6 +35,7 @@ import java.util.Queue;
 import java.util.Set;
 import java.util.TreeMap;
 import java.util.TreeSet;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.atomic.AtomicLong;
 
 import org.apache.hadoop.HadoopIllegalArgumentException;
@@ -1026,7 +1027,8 @@ public class BlockManager {
       return new BlocksWithLocations(new BlockWithLocations[0]);
     }
     Iterator<BlockInfoContiguous> iter = node.getBlockIterator();
-    int startBlock = DFSUtil.getRandom().nextInt(numBlocks); // starting from a random block
+    // starting from a random block
+    int startBlock = ThreadLocalRandom.current().nextInt(numBlocks);
     // skip blocks
     for(int i=0; i<startBlock; i++) {
       iter.next();
@@ -1671,7 +1673,7 @@ public class BlockManager {
       // switch to a different node randomly
       // this to prevent from deterministically selecting the same node even
       // if the node failed to replicate the block on previous iterations
-      if(DFSUtil.getRandom().nextBoolean())
+      if(ThreadLocalRandom.current().nextBoolean())
         srcNode = node;
     }
     if(numReplicas != null)
@@ -1927,7 +1929,7 @@ public class BlockManager {
           datanodeManager.getBlocksPerPostponedMisreplicatedBlocksRescan();
       long base = getPostponedMisreplicatedBlocksCount() - blocksPerRescan;
       if (base > 0) {
-        startIndex = DFSUtil.getRandom().nextLong() % (base+1);
+        startIndex = ThreadLocalRandom.current().nextLong() % (base+1);
         if (startIndex < 0) {
           startIndex += (base+1);
         }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeManager.java

@@ -51,6 +51,7 @@ import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.UnknownHostException;
 import java.util.*;
+import java.util.concurrent.ThreadLocalRandom;
 
 /**
  * Manage datanodes, include decommission and other activities.
@@ -457,7 +458,7 @@ public class DatanodeManager {
         // Try something rack local.
         if (node == null && !rackNodes.isEmpty()) {
           node = (DatanodeDescriptor) (rackNodes
-              .get(DFSUtil.getRandom().nextInt(rackNodes.size())));
+              .get(ThreadLocalRandom.current().nextInt(rackNodes.size())));
         }
       }
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/Host2NodesMap.java

@@ -20,12 +20,12 @@ package org.apache.hadoop.hdfs.server.blockmanagement;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.locks.ReadWriteLock;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
-import org.apache.hadoop.hdfs.DFSUtil;
 
 /** A map from host names to datanode descriptors. */
 @InterfaceAudience.Private
@@ -161,7 +161,7 @@ class Host2NodesMap {
         return nodes[0];
       }
       // more than one node
-      return nodes[DFSUtil.getRandom().nextInt(nodes.length)];
+      return nodes[ThreadLocalRandom.current().nextInt(nodes.length)];
     } finally {
       hostmapLock.readLock().unlock();
     }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/common/JspHelper.java

@@ -28,6 +28,7 @@ import java.net.InetSocketAddress;
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.HashMap;
+import java.util.concurrent.ThreadLocalRandom;
 
 import javax.servlet.ServletContext;
 import javax.servlet.http.HttpServletRequest;
@@ -150,7 +151,7 @@ public class JspHelper {
       throw new IOException("No active nodes contain this block");
     }
 
-    int index = doRandom ? DFSUtil.getRandom().nextInt(l) : 0;
+    int index = doRandom ? ThreadLocalRandom.current().nextInt(l) : 0;
     return nodes[index];
   }
 

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

@@ -28,13 +28,13 @@ import java.util.Collection;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.ThreadLocalRandom;
 
 import com.google.common.base.Joiner;
 import org.apache.commons.logging.Log;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.ha.HAServiceProtocol.HAServiceState;
 import org.apache.hadoop.hdfs.client.BlockReportOptions;
-import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.protocol.BlockListAsLongs;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
@@ -122,7 +122,7 @@ class BPServiceActor implements Runnable {
     this.dn = bpos.getDataNode();
     this.nnAddr = nnAddr;
     this.dnConf = dn.getDnConf();
-    prevBlockReportId = DFSUtil.getRandom().nextLong();
+    prevBlockReportId = ThreadLocalRandom.current().nextLong();
     scheduler = new Scheduler(dnConf.heartBeatInterval, dnConf.blockReportInterval);
   }
 
@@ -409,7 +409,7 @@ class BPServiceActor implements Runnable {
     // not send a 0 value ourselves.
     prevBlockReportId++;
     while (prevBlockReportId == 0) {
-      prevBlockReportId = DFSUtil.getRandom().nextLong();
+      prevBlockReportId = ThreadLocalRandom.current().nextLong();
     }
     return prevBlockReportId;
   }
@@ -1054,7 +1054,7 @@ class BPServiceActor implements Runnable {
       if (delay > 0) { // send BR after random delay
         // Numerical overflow is possible here and is okay.
         nextBlockReportTime =
-            monotonicNow() + DFSUtil.getRandom().nextInt((int) (delay));
+            monotonicNow() + ThreadLocalRandom.current().nextInt((int) (delay));
       } else { // send at next heartbeat
         nextBlockReportTime = monotonicNow();
       }
@@ -1073,7 +1073,7 @@ class BPServiceActor implements Runnable {
       // time before we start the periodic block reports.
       if (resetBlockReportTime) {
         nextBlockReportTime = monotonicNow() +
-            DFSUtil.getRandom().nextInt((int)(blockReportIntervalMs));
+            ThreadLocalRandom.current().nextInt((int)(blockReportIntervalMs));
         resetBlockReportTime = false;
       } else {
         /* say the last block report was at 8:20:14. The current report

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

@@ -31,6 +31,7 @@ import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledThreadPoolExecutor;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.TimeUnit;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -41,7 +42,6 @@ import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FileUtil;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
-import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsDatasetSpi;
@@ -327,7 +327,8 @@ public class DirectoryScanner implements Runnable {
 
   void start() {
     shouldRun = true;
-    long offset = DFSUtil.getRandom().nextInt((int) (scanPeriodMsecs/1000L)) * 1000L; //msec
+    long offset = ThreadLocalRandom.current().nextInt(
+        (int) (scanPeriodMsecs/1000L)) * 1000L; //msec
     long firstScanTime = Time.now() + offset;
     LOG.info("Periodic Directory Tree Verification scan starting at " 
         + firstScanTime + " with interval " + scanPeriodMsecs);

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

@@ -22,7 +22,6 @@ import static org.apache.hadoop.metrics2.impl.MsInfo.SessionId;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
-import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.metrics2.MetricsSystem;
 import org.apache.hadoop.metrics2.annotation.Metric;
 import org.apache.hadoop.metrics2.annotation.Metrics;
@@ -33,6 +32,8 @@ import org.apache.hadoop.metrics2.lib.MutableQuantiles;
 import org.apache.hadoop.metrics2.lib.MutableRate;
 import org.apache.hadoop.metrics2.source.JvmMetrics;
 
+import java.util.concurrent.ThreadLocalRandom;
+
 /**
  *
  * This class is for maintaining  the various DataNode statistics
@@ -177,7 +178,7 @@ public class DataNodeMetrics {
     MetricsSystem ms = DefaultMetricsSystem.instance();
     JvmMetrics jm = JvmMetrics.create("DataNode", sessionId, ms);
     String name = "DataNodeActivity-"+ (dnName.isEmpty()
-        ? "UndefinedDataNodeName"+ DFSUtil.getRandom().nextInt() 
+        ? "UndefinedDataNodeName"+ ThreadLocalRandom.current().nextInt()
             : dnName.replace(':', '-'));
 
     // Percentile measurement is off by default, by watching no intervals

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

@@ -32,6 +32,7 @@ import java.util.List;
 import java.util.Properties;
 import java.util.UUID;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.ThreadLocalRandom;
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
@@ -599,7 +600,7 @@ public class NNStorage extends Storage implements Closeable,
   private static int newNamespaceID() {
     int newID = 0;
     while(newID == 0)
-      newID = DFSUtil.getRandom().nextInt(0x7FFFFFFF);  // use 31 bits only
+      newID = ThreadLocalRandom.current().nextInt(0x7FFFFFFF);  // use 31 bits
     return newID;
   }
 

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

@@ -32,6 +32,7 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.TreeSet;
+import java.util.concurrent.ThreadLocalRandom;
 
 import org.apache.commons.io.IOUtils;
 import org.apache.commons.logging.Log;
@@ -44,7 +45,6 @@ import org.apache.hadoop.hdfs.BlockReader;
 import org.apache.hadoop.hdfs.BlockReaderFactory;
 import org.apache.hadoop.hdfs.DFSClient;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
-import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.RemotePeerFactory;
 import org.apache.hadoop.fs.StorageType;
 import org.apache.hadoop.hdfs.net.Peer;
@@ -909,7 +909,7 @@ public class NamenodeFsck implements DataEncryptionKeyFactory {
     }
     DatanodeInfo chosenNode;
     do {
-      chosenNode = nodes[DFSUtil.getRandom().nextInt(nodes.length)];
+      chosenNode = nodes[ThreadLocalRandom.current().nextInt(nodes.length)];
     } while (deadNodes.contains(chosenNode));
     return chosenNode;
   }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestAppendSnapshotTruncate.java

@@ -29,6 +29,7 @@ import java.util.HashMap;
 import java.util.Map;
 import java.util.Random;
 import java.util.concurrent.Callable;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
@@ -214,8 +215,7 @@ public class TestAppendSnapshotTruncate {
     
     @Override
     public String call() throws Exception {
-      final Random r = DFSUtil.getRandom();
+      final int op = ThreadLocalRandom.current().nextInt(6);
-      final int op = r.nextInt(6);
       if (op <= 1) {
         pauseAllFiles();
         try {
@@ -229,7 +229,8 @@ public class TestAppendSnapshotTruncate {
         if (keys.length == 0) {
           return "NO-OP";
         }
-        final String snapshot = keys[r.nextInt(keys.length)];
+        final String snapshot = keys[ThreadLocalRandom.current()
+            .nextInt(keys.length)];
         final String s = checkSnapshot(snapshot);
         
         if (op == 2) {
@@ -292,13 +293,13 @@ public class TestAppendSnapshotTruncate {
 
     @Override
     public String call() throws IOException {
-      final Random r = DFSUtil.getRandom();
+      final int op = ThreadLocalRandom.current().nextInt(9);
-      final int op = r.nextInt(9);
       if (op == 0) {
         return checkFullFile();
       } else {
-        final int nBlocks = r.nextInt(4) + 1;
+        final int nBlocks = ThreadLocalRandom.current().nextInt(4) + 1;
-        final int lastBlockSize = r.nextInt(BLOCK_SIZE) + 1;
+        final int lastBlockSize = ThreadLocalRandom.current()
+            .nextInt(BLOCK_SIZE) + 1;
         final int nBytes = nBlocks*BLOCK_SIZE + lastBlockSize;
 
         if (op <= 4) {
@@ -316,8 +317,8 @@ public class TestAppendSnapshotTruncate {
           .append(n).append(" bytes to ").append(file.getName());
 
       final byte[] bytes = new byte[n];
-      DFSUtil.getRandom().nextBytes(bytes);
+      ThreadLocalRandom.current().nextBytes(bytes);
-      
+
       { // write to local file
         final FileOutputStream out = new FileOutputStream(localFile, true);
         out.write(bytes, 0, bytes.length);
@@ -446,7 +447,6 @@ public class TestAppendSnapshotTruncate {
         final Thread t = new Thread(null, new Runnable() {
           @Override
           public void run() {
-            final Random r = DFSUtil.getRandom();
             for(State s; !(s = checkErrorState()).isTerminated;) {
               if (s == State.RUNNING) {
                 isCalling.set(true);
@@ -458,7 +458,7 @@ public class TestAppendSnapshotTruncate {
                 }
                 isCalling.set(false);
               }
-              sleep(r.nextInt(100) + 50);
+              sleep(ThreadLocalRandom.current().nextInt(100) + 50);
             }
           }
         }, name);

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestRollingUpgrade.java

@@ -19,6 +19,7 @@ package org.apache.hadoop.hdfs;
 
 import java.io.File;
 import java.io.IOException;
+import java.util.concurrent.ThreadLocalRandom;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -272,7 +273,7 @@ public class TestRollingUpgrade {
 
       final Path file = new Path(foo, "file");
       final byte[] data = new byte[1024];
-      DFSUtil.getRandom().nextBytes(data);
+      ThreadLocalRandom.current().nextBytes(data);
       final FSDataOutputStream out = cluster.getFileSystem().create(file);
       out.write(data, 0, data.length);
       out.close();
@@ -320,7 +321,8 @@ public class TestRollingUpgrade {
     Assert.assertTrue(dfs.exists(bar));
 
     //truncate a file
-    final int newLength = DFSUtil.getRandom().nextInt(data.length - 1) + 1;
+    final int newLength = ThreadLocalRandom.current().nextInt(data.length - 1)
+        + 1;
     dfs.truncate(file, newLength);
     TestFileTruncate.checkBlockRecovery(file, dfs);
     AppendTestUtil.checkFullFile(dfs, file, newLength, data);

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestReplicationPolicy.java

@@ -33,8 +33,8 @@ import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
-import java.util.Random;
 import java.util.Set;
+import java.util.concurrent.ThreadLocalRandom;
 
 import org.apache.commons.logging.impl.Log4JLogger;
 import org.apache.hadoop.conf.Configuration;
@@ -73,7 +73,6 @@ public class TestReplicationPolicy {
     ((Log4JLogger)BlockPlacementPolicy.LOG).getLogger().setLevel(Level.ALL);
   }
 
-  private final Random random = DFSUtil.getRandom();
   private static final int BLOCK_SIZE = 1024;
   private static final int NUM_OF_DATANODES = 6;
   private static NetworkTopology cluster;
@@ -848,14 +847,16 @@ public class TestReplicationPolicy {
           .getNamesystem().getBlockManager().neededReplications;
       for (int i = 0; i < 100; i++) {
         // Adding the blocks directly to normal priority
-        neededReplications.add(new Block(random.nextLong()), 2, 0, 3);
+        neededReplications.add(new Block(
+              ThreadLocalRandom.current().nextLong()), 2, 0, 3);
       }
       // Lets wait for the replication interval, to start process normal
       // priority blocks
       Thread.sleep(DFS_NAMENODE_REPLICATION_INTERVAL);
       
       // Adding the block directly to high priority list
-      neededReplications.add(new Block(random.nextLong()), 1, 0, 3);
+      neededReplications.add(new Block(
+              ThreadLocalRandom.current().nextLong()), 1, 0, 3);
       
       // Lets wait for the replication interval
       Thread.sleep(DFS_NAMENODE_REPLICATION_INTERVAL);
@@ -878,19 +879,24 @@ public class TestReplicationPolicy {
 
     for (int i = 0; i < 5; i++) {
       // Adding QUEUE_HIGHEST_PRIORITY block
-      underReplicatedBlocks.add(new Block(random.nextLong()), 1, 0, 3);
+      underReplicatedBlocks.add(new Block(ThreadLocalRandom.current().
+            nextLong()), 1, 0, 3);
 
       // Adding QUEUE_VERY_UNDER_REPLICATED block
-      underReplicatedBlocks.add(new Block(random.nextLong()), 2, 0, 7);
+      underReplicatedBlocks.add(new Block(ThreadLocalRandom.current().
+            nextLong()), 2, 0, 7);
 
       // Adding QUEUE_REPLICAS_BADLY_DISTRIBUTED block
-      underReplicatedBlocks.add(new Block(random.nextLong()), 6, 0, 6);
+      underReplicatedBlocks.add(new Block(ThreadLocalRandom.current().
+            nextLong()), 6, 0, 6);
 
       // Adding QUEUE_UNDER_REPLICATED block
-      underReplicatedBlocks.add(new Block(random.nextLong()), 5, 0, 6);
+      underReplicatedBlocks.add(new Block(ThreadLocalRandom.current().
+            nextLong()), 5, 0, 6);
 
       // Adding QUEUE_WITH_CORRUPT_BLOCKS block
-      underReplicatedBlocks.add(new Block(random.nextLong()), 0, 0, 3);
+      underReplicatedBlocks.add(new Block(ThreadLocalRandom.current().
+            nextLong()), 0, 0, 3);
     }
 
     // Choose 6 blocks from UnderReplicatedBlocks. Then it should pick 5 blocks
@@ -906,7 +912,8 @@ public class TestReplicationPolicy {
     assertTheChosenBlocks(chosenBlocks, 0, 4, 5, 1, 0);
 
     // Adding QUEUE_HIGHEST_PRIORITY
-    underReplicatedBlocks.add(new Block(random.nextLong()), 1, 0, 3);
+    underReplicatedBlocks.add(new Block(
+          ThreadLocalRandom.current().nextLong()), 1, 0, 3);
 
     // Choose 10 blocks from UnderReplicatedBlocks. Then it should pick 1 block from
     // QUEUE_HIGHEST_PRIORITY, 4 blocks from QUEUE_REPLICAS_BADLY_DISTRIBUTED

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestFileTruncate.java

@@ -31,6 +31,7 @@ import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
 import java.io.IOException;
+import java.util.concurrent.ThreadLocalRandom;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -46,7 +47,6 @@ import org.apache.hadoop.fs.permission.FsPermission;
 import org.apache.hadoop.hdfs.AppendTestUtil;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DFSTestUtil;
-import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.DistributedFileSystem;
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
@@ -164,11 +164,11 @@ public class TestFileTruncate {
     fs.mkdirs(dir);
     final Path p = new Path(dir, "file");
     final byte[] data = new byte[100 * BLOCK_SIZE];
-    DFSUtil.getRandom().nextBytes(data);
+    ThreadLocalRandom.current().nextBytes(data);
     writeContents(data, data.length, p);
 
     for(int n = data.length; n > 0; ) {
-      final int newLength = DFSUtil.getRandom().nextInt(n);
+      final int newLength = ThreadLocalRandom.current().nextInt(n);
       final boolean isReady = fs.truncate(p, newLength);
       LOG.info("newLength=" + newLength + ", isReady=" + isReady);
       assertEquals("File must be closed for truncating at the block boundary",
@@ -193,7 +193,7 @@ public class TestFileTruncate {
     fs.allowSnapshot(dir);
     final Path p = new Path(dir, "file");
     final byte[] data = new byte[BLOCK_SIZE];
-    DFSUtil.getRandom().nextBytes(data);
+    ThreadLocalRandom.current().nextBytes(data);
     writeContents(data, data.length, p);
     final String snapshot = "s0";
     fs.createSnapshot(dir, snapshot);
@@ -226,7 +226,7 @@ public class TestFileTruncate {
     final Path p = new Path(dir, "file");
     final byte[] data = new byte[2 * BLOCK_SIZE];
 
-    DFSUtil.getRandom().nextBytes(data);
+    ThreadLocalRandom.current().nextBytes(data);
     writeContents(data, data.length, p);
 
     final int newLength = data.length - 1;

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestDNFencing.java

@@ -24,6 +24,7 @@ import java.io.PrintWriter;
 import java.util.Collection;
 import java.util.List;
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ThreadLocalRandom;
 
 import com.google.common.base.Supplier;
 import com.google.common.collect.Lists;
@@ -37,7 +38,6 @@ import org.apache.hadoop.fs.StorageType;
 import org.apache.hadoop.hdfs.AppendTestUtil;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DFSTestUtil;
-import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.apache.hadoop.hdfs.MiniDFSNNTopology;
 import org.apache.hadoop.hdfs.protocol.Block;
@@ -640,7 +640,7 @@ public class TestDNFencing {
       Collection<DatanodeStorageInfo> chooseFrom = !first.isEmpty() ? first : second;
 
       List<DatanodeStorageInfo> l = Lists.newArrayList(chooseFrom);
-      return l.get(DFSUtil.getRandom().nextInt(l.size()));
+      return l.get(ThreadLocalRandom.current().nextInt(l.size()));
     }
   }
 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestHAAppend.java

@@ -20,6 +20,7 @@ package org.apache.hadoop.hdfs.server.namenode.ha;
 import static org.junit.Assert.assertEquals;
 
 import java.io.IOException;
+import java.util.concurrent.ThreadLocalRandom;
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FSDataOutputStream;
@@ -27,7 +28,6 @@ import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.AppendTestUtil;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
-import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.apache.hadoop.hdfs.MiniDFSNNTopology;
 import org.apache.hadoop.hdfs.server.namenode.TestFileTruncate;
@@ -73,7 +73,7 @@ public class TestHAAppend {
       Path fileToTruncate = new Path("/FileToTruncate");
       
       final byte[] data = new byte[1 << 16];
-      DFSUtil.getRandom().nextBytes(data);
+      ThreadLocalRandom.current().nextBytes(data);
       final int[] appendPos = AppendTestUtil.randomFilePartition(
           data.length, COUNT);
       final int[] truncatePos = AppendTestUtil.randomFilePartition(

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/util/TestByteArrayManager.java

@@ -27,6 +27,7 @@ import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -34,7 +35,6 @@ import java.util.concurrent.atomic.AtomicInteger;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.commons.logging.impl.Log4JLogger;
-import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys;
 import org.apache.hadoop.hdfs.util.ByteArrayManager.Counter;
 import org.apache.hadoop.hdfs.util.ByteArrayManager.CounterMap;
@@ -72,7 +72,7 @@ public class TestByteArrayManager {
     final long countResetTimePeriodMs = 200L;
     final Counter c = new Counter(countResetTimePeriodMs);
 
-    final int n = DFSUtil.getRandom().nextInt(512) + 512;
+    final int n = ThreadLocalRandom.current().nextInt(512) + 512;
     final List<Future<Integer>> futures = new ArrayList<Future<Integer>>(n);
     
     final ExecutorService pool = Executors.newFixedThreadPool(32);
@@ -334,7 +334,7 @@ public class TestByteArrayManager {
       public void run() {
         LOG.info("randomRecycler start");
         for(int i = 0; shouldRun(); i++) {
-          final int j = DFSUtil.getRandom().nextInt(runners.length);
+          final int j = ThreadLocalRandom.current().nextInt(runners.length);
           try {
             runners[j].recycle();
           } catch (Exception e) {
@@ -440,7 +440,7 @@ public class TestByteArrayManager {
         public byte[] call() throws Exception {
           final int lower = maxArrayLength == ByteArrayManager.MIN_ARRAY_LENGTH?
               0: maxArrayLength >> 1;
-          final int arrayLength = DFSUtil.getRandom().nextInt(
+          final int arrayLength = ThreadLocalRandom.current().nextInt(
               maxArrayLength - lower) + lower + 1;
           final byte[] array = bam.newByteArray(arrayLength);
           try {
@@ -496,7 +496,8 @@ public class TestByteArrayManager {
     @Override
     public void run() {
       for(int i = 0; i < n; i++) {
-        final boolean isAllocate = DFSUtil.getRandom().nextInt(NUM_RUNNERS) < p;
+        final boolean isAllocate = ThreadLocalRandom.current()
+            .nextInt(NUM_RUNNERS) < p;
         if (isAllocate) {
           submitAllocate();
         } else {
@@ -573,7 +574,6 @@ public class TestByteArrayManager {
         + ", nAllocations=" + nAllocations
         + ", maxArrays=" + maxArrays);
     
-    final Random ran = DFSUtil.getRandom();
     final ByteArrayManager[] impls = {
         new ByteArrayManager.NewByteArrayWithoutLimit(),
         new NewByteArrayWithLimit(maxArrays),
@@ -590,7 +590,7 @@ public class TestByteArrayManager {
       for(int j = 0; j < nTrials; j++) {
         final int[] sleepTime = new int[nAllocations];
         for(int k = 0; k < sleepTime.length; k++) {
-          sleepTime[k] = ran.nextInt(100);
+          sleepTime[k] = ThreadLocalRandom.current().nextInt(100);
         }
       
         final long elapsed = performanceTest(arrayLength, maxArrays, nThreads,

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/sharedcache/SharedCacheUploader.java

@@ -22,8 +22,8 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.lang.reflect.UndeclaredThrowableException;
 import java.net.URISyntaxException;
-import java.util.Random;
 import java.util.concurrent.Callable;
+import java.util.concurrent.ThreadLocalRandom;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -61,13 +61,6 @@ class SharedCacheUploader implements Callable<Boolean> {
       new FsPermission((short)00555);
 
   private static final Log LOG = LogFactory.getLog(SharedCacheUploader.class);
-  private static final ThreadLocal<Random> randomTl =
-      new ThreadLocal<Random>() {
-        @Override
-        protected Random initialValue() {
-          return new Random(System.nanoTime());
-        }
-      };
 
   private final LocalResource resource;
   private final Path localPath;
@@ -267,7 +260,7 @@ class SharedCacheUploader implements Callable<Boolean> {
   }
 
   private String getTemporaryFileName(Path path) {
-    return path.getName() + "-" + randomTl.get().nextLong();
+    return path.getName() + "-" + ThreadLocalRandom.current().nextLong();
   }
 
   @VisibleForTesting