HDFS-9080. Update htrace version to 4.0.1 (cmccabe)

(cherry picked from commit 892ade689f)

Conflicts:
	hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSClient.java
        hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/BlockStorageLocationUtil.java
	hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java

hadoop-common-project/hadoop-common/pom.xml

@@ -246,7 +246,7 @@
 
     <dependency>
       <groupId>org.apache.htrace</groupId>
-      <artifactId>htrace-core</artifactId>
+      <artifactId>htrace-core4</artifactId>
     </dependency>
     <dependency>
       <groupId>org.apache.zookeeper</groupId>

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeys.java

@@ -295,4 +295,7 @@ public class CommonConfigurationKeys extends CommonConfigurationKeysPublic {
   public static final String NFS_EXPORTS_ALLOWED_HOSTS_SEPARATOR = ";";
   public static final String NFS_EXPORTS_ALLOWED_HOSTS_KEY = "nfs.exports.allowed.hosts";
   public static final String NFS_EXPORTS_ALLOWED_HOSTS_KEY_DEFAULT = "* rw";
+
+  // HDFS client HTrace configuration.
+  public static final String  FS_CLIENT_HTRACE_PREFIX = "fs.client.htrace.";
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FSOutputSummer.java

@@ -21,8 +21,8 @@ package org.apache.hadoop.fs;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.util.DataChecksum;
-import org.apache.htrace.NullScope;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.TraceScope;
+import org.apache.htrace.core.Tracer;
 
 import java.io.IOException;
 import java.io.OutputStream;
@@ -43,6 +43,8 @@ abstract public class FSOutputSummer extends OutputStream {
   private byte checksum[];
   // The number of valid bytes in the buffer.
   private int count;
+  // The HTrace tracer to use
+  private Tracer tracer;
   
   // We want this value to be a multiple of 3 because the native code checksums
   // 3 chunks simultaneously. The chosen value of 9 strikes a balance between
@@ -197,7 +199,7 @@ abstract public class FSOutputSummer extends OutputStream {
   }
 
   protected TraceScope createWriteTraceScope() {
-    return NullScope.INSTANCE;
+    return null;
   }
 
   /** Generate checksums for the given data chunks and output chunks & checksums
@@ -215,7 +217,9 @@ abstract public class FSOutputSummer extends OutputStream {
             getChecksumSize());
       }
     } finally {
-      scope.close();
+      if (scope != null) {
+        scope.close();
+      }
     }
   }
 

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileContext.java

@@ -61,6 +61,7 @@ import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.util.ShutdownHookManager;
 
 import com.google.common.base.Preconditions;
+import org.apache.htrace.core.Tracer;
 
 /**
  * The FileContext class provides an interface to the application writer for
@@ -232,12 +233,14 @@ public class FileContext {
   private final Configuration conf;
   private final UserGroupInformation ugi;
   final boolean resolveSymlinks;
+  private final Tracer tracer;
 
   private FileContext(final AbstractFileSystem defFs,
     final FsPermission theUmask, final Configuration aConf) {
     defaultFS = defFs;
     umask = FsPermission.getUMask(aConf);
     conf = aConf;
+    tracer = FsTracer.get(aConf);
     try {
       ugi = UserGroupInformation.getCurrentUser();
     } catch (IOException e) {
@@ -2731,4 +2734,8 @@ public class FileContext {
       throws IOException {
     return defaultFS.getAllStoragePolicies();
   }
+
+  Tracer getTracer() {
+    return tracer;
+  }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileSystem.java

@@ -67,9 +67,8 @@ import org.apache.hadoop.util.Progressable;
 import org.apache.hadoop.util.ReflectionUtils;
 import org.apache.hadoop.util.ShutdownHookManager;
 import org.apache.hadoop.util.StringUtils;
-import org.apache.htrace.Span;
+import org.apache.htrace.core.Tracer;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.TraceScope;
 
 import com.google.common.annotations.VisibleForTesting;
 
@@ -129,6 +128,13 @@ public abstract class FileSystem extends Configured implements Closeable {
   private Set<Path> deleteOnExit = new TreeSet<Path>();
   
   boolean resolveSymlinks;
+
+  private Tracer tracer;
+
+  protected final Tracer getTracer() {
+    return tracer;
+  }
+
   /**
    * This method adds a file system for testing so that we can find it later. It
    * is only for testing.
@@ -2692,14 +2698,13 @@ public abstract class FileSystem extends Configured implements Closeable {
 
   private static FileSystem createFileSystem(URI uri, Configuration conf
       ) throws IOException {
-    TraceScope scope = Trace.startSpan("FileSystem#createFileSystem");
+    Tracer tracer = FsTracer.get(conf);
-    Span span = scope.getSpan();
+    TraceScope scope = tracer.newScope("FileSystem#createFileSystem");
-    if (span != null) {
+    scope.addKVAnnotation("scheme", uri.getScheme());
-      span.addKVAnnotation("scheme", uri.getScheme());
-    }
     try {
       Class<?> clazz = getFileSystemClass(uri.getScheme(), conf);
       FileSystem fs = (FileSystem)ReflectionUtils.newInstance(clazz, conf);
+      fs.tracer = tracer;
       fs.initialize(uri, conf);
       return fs;
     } finally {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FsShell.java

@@ -32,16 +32,13 @@ import org.apache.hadoop.conf.Configured;
 import org.apache.hadoop.fs.shell.Command;
 import org.apache.hadoop.fs.shell.CommandFactory;
 import org.apache.hadoop.fs.shell.FsCommand;
-import org.apache.hadoop.tracing.SpanReceiverHost;
 import org.apache.hadoop.tools.TableListing;
 import org.apache.hadoop.tracing.TraceUtils;
 import org.apache.hadoop.util.StringUtils;
 import org.apache.hadoop.util.Tool;
 import org.apache.hadoop.util.ToolRunner;
-import org.apache.htrace.Sampler;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.SamplerBuilder;
+import org.apache.htrace.core.Tracer;
-import org.apache.htrace.Trace;
-import org.apache.htrace.TraceScope;
 
 /** Provide command line access to a FileSystem. */
 @InterfaceAudience.Private
@@ -54,13 +51,12 @@ public class FsShell extends Configured implements Tool {
   private FileSystem fs;
   private Trash trash;
   protected CommandFactory commandFactory;
-  private Sampler traceSampler;
 
   private final String usagePrefix =
     "Usage: hadoop fs [generic options]";
 
-  private SpanReceiverHost spanReceiverHost;
+  private Tracer tracer;
-  static final String SEHLL_HTRACE_PREFIX = "dfs.shell.htrace.";
+  static final String SHELL_HTRACE_PREFIX = "fs.shell.htrace.";
 
   /**
    * Default ctor with no configuration.  Be sure to invoke
@@ -102,8 +98,9 @@ public class FsShell extends Configured implements Tool {
       commandFactory.addObject(new Usage(), "-usage");
       registerCommands(commandFactory);
     }
-    this.spanReceiverHost =
+    this.tracer = new Tracer.Builder("FsShell").
-        SpanReceiverHost.get(getConf(), SEHLL_HTRACE_PREFIX);
+        conf(TraceUtils.wrapHadoopConf(SHELL_HTRACE_PREFIX, getConf())).
+        build();
   }
 
   protected void registerCommands(CommandFactory factory) {
@@ -285,8 +282,6 @@ public class FsShell extends Configured implements Tool {
   public int run(String argv[]) throws Exception {
     // initialize FsShell
     init();
-    traceSampler = new SamplerBuilder(TraceUtils.
-        wrapHadoopConf(SEHLL_HTRACE_PREFIX, getConf())).build();
     int exitCode = -1;
     if (argv.length < 1) {
       printUsage(System.err);
@@ -298,7 +293,7 @@ public class FsShell extends Configured implements Tool {
         if (instance == null) {
           throw new UnknownCommandException();
         }
-        TraceScope scope = Trace.startSpan(instance.getCommandName(), traceSampler);
+        TraceScope scope = tracer.newScope(instance.getCommandName());
         if (scope.getSpan() != null) {
           String args = StringUtils.join(" ", argv);
           if (args.length() > 2048) {
@@ -324,6 +319,7 @@ public class FsShell extends Configured implements Tool {
         e.printStackTrace(System.err);
       }
     }
+    tracer.close();
     return exitCode;
   }
   
@@ -350,9 +346,6 @@ public class FsShell extends Configured implements Tool {
       fs.close();
       fs = null;
     }
-    if (this.spanReceiverHost != null) {
-      this.spanReceiverHost.closeReceivers();
-    }
   }
 
   /**

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FsTracer.java

@@ -0,0 +1,64 @@
+/**
+ * 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.fs;
+
+import com.google.common.annotations.VisibleForTesting;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.tracing.TraceUtils;
+import org.apache.htrace.core.Tracer;
+
+/**
+ * Holds the HTrace Tracer used for FileSystem operations.
+ *
+ * Ideally, this would be owned by the DFSClient, rather than global.  However,
+ * the FileContext API may create a new DFSClient for each operation in some
+ * cases.  Because of this, we cannot store this Tracer inside DFSClient.  See
+ * HADOOP-6356 for details.
+ */
+@InterfaceAudience.Private
+@InterfaceStability.Unstable
+public final class FsTracer {
+  private static Tracer instance;
+
+  public static synchronized Tracer get(Configuration conf) {
+    if (instance == null) {
+      instance = new Tracer.Builder("FSClient").
+          conf(TraceUtils.wrapHadoopConf(CommonConfigurationKeys.
+              FS_CLIENT_HTRACE_PREFIX, conf)).
+          build();
+    }
+    return instance;
+  }
+
+  @VisibleForTesting
+  public static synchronized void clear() {
+    if (instance == null) {
+      return;
+    }
+    try {
+      instance.close();
+    } finally {
+      instance = null;
+    }
+  }
+
+  private FsTracer() {
+  }
+}

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/Globber.java

@@ -28,9 +28,8 @@ import org.apache.commons.logging.Log;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 
-import org.apache.htrace.Span;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.Tracer;
-import org.apache.htrace.TraceScope;
 
 @InterfaceAudience.Private
 @InterfaceStability.Unstable
@@ -41,12 +40,14 @@ class Globber {
   private final FileContext fc;
   private final Path pathPattern;
   private final PathFilter filter;
+  private final Tracer tracer;
   
   public Globber(FileSystem fs, Path pathPattern, PathFilter filter) {
     this.fs = fs;
     this.fc = null;
     this.pathPattern = pathPattern;
     this.filter = filter;
+    this.tracer = fs.getTracer();
   }
 
   public Globber(FileContext fc, Path pathPattern, PathFilter filter) {
@@ -54,6 +55,7 @@ class Globber {
     this.fc = fc;
     this.pathPattern = pathPattern;
     this.filter = filter;
+    this.tracer = fc.getTracer();
   }
 
   private FileStatus getFileStatus(Path path) throws IOException {
@@ -140,11 +142,8 @@ class Globber {
   }
 
   public FileStatus[] glob() throws IOException {
-    TraceScope scope = Trace.startSpan("Globber#glob");
+    TraceScope scope = tracer.newScope("Globber#glob");
-    Span span = scope.getSpan();
+    scope.addKVAnnotation("pattern", pathPattern.toUri().getPath());
-    if (span != null) {
-      span.addKVAnnotation("pattern", pathPattern.toUri().getPath());
-    }
     try {
       return doGlob();
     } finally {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java

@@ -92,7 +92,8 @@ import org.apache.hadoop.util.ProtoUtil;
 import org.apache.hadoop.util.ReflectionUtils;
 import org.apache.hadoop.util.StringUtils;
 import org.apache.hadoop.util.Time;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.Span;
+import org.apache.htrace.core.Tracer;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
@@ -722,8 +723,9 @@ public class Client {
         if (LOG.isDebugEnabled()) {
           LOG.debug("Connecting to "+server);
         }
-        if (Trace.isTracing()) {
+        Span span = Tracer.getCurrentSpan();
-          Trace.addTimelineAnnotation("IPC client connecting to " + server);
+        if (span != null) {
+          span.addTimelineAnnotation("IPC client connecting to " + server);
         }
         short numRetries = 0;
         Random rand = null;
@@ -796,8 +798,9 @@ public class Client {
           // update last activity time
           touch();
 
-          if (Trace.isTracing()) {
+          span = Tracer.getCurrentSpan();
-            Trace.addTimelineAnnotation("IPC client connected to " + server);
+          if (span != null) {
+            span.addTimelineAnnotation("IPC client connected to " + server);
           }
 
           // start the receiver thread after the socket connection has been set

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/ProtobufRpcEngine.java

@@ -49,8 +49,8 @@ import org.apache.hadoop.security.token.SecretManager;
 import org.apache.hadoop.security.token.TokenIdentifier;
 import org.apache.hadoop.util.ProtoUtil;
 import org.apache.hadoop.util.Time;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.TraceScope;
+import org.apache.htrace.core.Tracer;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.protobuf.BlockingService;
@@ -206,12 +206,13 @@ public class ProtobufRpcEngine implements RpcEngine {
             + method.getName() + "]");
       }
 
-      TraceScope traceScope = null;
       // if Tracing is on then start a new span for this rpc.
       // guard it in the if statement to make sure there isn't
       // any extra string manipulation.
-      if (Trace.isTracing()) {
+      Tracer tracer = Tracer.curThreadTracer();
-        traceScope = Trace.startSpan(RpcClientUtil.methodToTraceString(method));
+      TraceScope traceScope = null;
+      if (tracer != null) {
+        traceScope = tracer.newScope(RpcClientUtil.methodToTraceString(method));
       }
 
       RequestHeaderProto rpcRequestHeader = constructRpcRequestHeader(method);
@@ -236,9 +237,9 @@ public class ProtobufRpcEngine implements RpcEngine {
               remoteId + ": " + method.getName() +
                 " {" + e + "}");
         }
-        if (Trace.isTracing()) {
+        if (traceScope != null) {
-          traceScope.getSpan().addTimelineAnnotation(
+          traceScope.addTimelineAnnotation("Call got exception: " +
-              "Call got exception: " + e.toString());
+              e.toString());
         }
         throw new ServiceException(e);
       } finally {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Server.java

@@ -116,10 +116,9 @@ import org.apache.hadoop.util.ProtoUtil;
 import org.apache.hadoop.util.ReflectionUtils;
 import org.apache.hadoop.util.StringUtils;
 import org.apache.hadoop.util.Time;
-import org.apache.htrace.Span;
+import org.apache.htrace.core.SpanId;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.TraceInfo;
+import org.apache.htrace.core.Tracer;
-import org.apache.htrace.TraceScope;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.protobuf.ByteString;
@@ -138,6 +137,7 @@ public abstract class Server {
   private List<AuthMethod> enabledAuthMethods;
   private RpcSaslProto negotiateResponse;
   private ExceptionsHandler exceptionsHandler = new ExceptionsHandler();
+  private Tracer tracer;
   
   public void addTerseExceptions(Class<?>... exceptionClass) {
     exceptionsHandler.addTerseExceptions(exceptionClass);
@@ -578,7 +578,7 @@ public abstract class Server {
     private ByteBuffer rpcResponse;       // the response for this call
     private final RPC.RpcKind rpcKind;
     private final byte[] clientId;
-    private final Span traceSpan; // the tracing span on the server side
+    private final TraceScope traceScope; // the HTrace scope on the server side
 
     public Call(int id, int retryCount, Writable param, 
         Connection connection) {
@@ -592,7 +592,7 @@ public abstract class Server {
     }
 
     public Call(int id, int retryCount, Writable param, Connection connection,
-        RPC.RpcKind kind, byte[] clientId, Span span) {
+        RPC.RpcKind kind, byte[] clientId, TraceScope traceScope) {
       this.callId = id;
       this.retryCount = retryCount;
       this.rpcRequest = param;
@@ -601,7 +601,7 @@ public abstract class Server {
       this.rpcResponse = null;
       this.rpcKind = kind;
       this.clientId = clientId;
-      this.traceSpan = span;
+      this.traceScope = traceScope;
     }
     
     @Override
@@ -1929,19 +1929,24 @@ public abstract class Server {
             RpcErrorCodeProto.FATAL_DESERIALIZING_REQUEST, err);
       }
         
-      Span traceSpan = null;
+      TraceScope traceScope = null;
       if (header.hasTraceInfo()) {
-        // If the incoming RPC included tracing info, always continue the trace
+        if (tracer != null) {
-        TraceInfo parentSpan = new TraceInfo(header.getTraceInfo().getTraceId(),
+          // If the incoming RPC included tracing info, always continue the
-                                             header.getTraceInfo().getParentId());
+          // trace
-        traceSpan = Trace.startSpan(
+          SpanId parentSpanId = new SpanId(
-            RpcClientUtil.toTraceName(rpcRequest.toString()),
+              header.getTraceInfo().getTraceId(),
-            parentSpan).detach();
+              header.getTraceInfo().getParentId());
+          traceScope = tracer.newScope(
+              RpcClientUtil.toTraceName(rpcRequest.toString()),
+              parentSpanId);
+          traceScope.detach();
+        }
       }
 
       Call call = new Call(header.getCallId(), header.getRetryCount(),
           rpcRequest, this, ProtoUtil.convert(header.getRpcKind()),
-          header.getClientId().toByteArray(), traceSpan);
+          header.getClientId().toByteArray(), traceScope);
 
       if (callQueue.isClientBackoffEnabled()) {
         // if RPC queue is full, we will ask the RPC client to back off by
@@ -2123,8 +2128,9 @@ public abstract class Server {
           Writable value = null;
 
           CurCall.set(call);
-          if (call.traceSpan != null) {
+          if (call.traceScope != null) {
-            traceScope = Trace.continueSpan(call.traceSpan);
+            call.traceScope.reattach();
+            traceScope = call.traceScope;
             traceScope.getSpan().addTimelineAnnotation("called");
           }
 
@@ -2201,21 +2207,18 @@ public abstract class Server {
         } catch (InterruptedException e) {
           if (running) {                          // unexpected -- log it
             LOG.info(Thread.currentThread().getName() + " unexpectedly interrupted", e);
-            if (Trace.isTracing()) {
+            if (traceScope != null) {
               traceScope.getSpan().addTimelineAnnotation("unexpectedly interrupted: " +
                   StringUtils.stringifyException(e));
             }
           }
         } catch (Exception e) {
           LOG.info(Thread.currentThread().getName() + " caught an exception", e);
-          if (Trace.isTracing()) {
+          if (traceScope != null) {
             traceScope.getSpan().addTimelineAnnotation("Exception: " +
                 StringUtils.stringifyException(e));
           }
         } finally {
-          if (traceScope != null) {
-            traceScope.close();
-          }
           IOUtils.cleanup(LOG, traceScope);
         }
       }
@@ -2529,6 +2532,10 @@ public abstract class Server {
   /** Sets the socket buffer size used for responding to RPCs */
   public void setSocketSendBufSize(int size) { this.socketSendBufferSize = size; }
 
+  public void setTracer(Tracer t) {
+    this.tracer = t;
+  }
+
   /** Starts the service.  Must be called before any calls will be handled. */
   public synchronized void start() {
     responder.start();

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/WritableRpcEngine.java

@@ -42,8 +42,8 @@ import org.apache.hadoop.util.Time;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.conf.*;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.TraceScope;
+import org.apache.htrace.core.Tracer;
 
 /** An RpcEngine implementation for Writable data. */
 @InterfaceStability.Evolving
@@ -233,9 +233,14 @@ public class WritableRpcEngine implements RpcEngine {
       if (LOG.isDebugEnabled()) {
         startTime = Time.now();
       }
+
+      // if Tracing is on then start a new span for this rpc.
+      // guard it in the if statement to make sure there isn't
+      // any extra string manipulation.
+      Tracer tracer = Tracer.curThreadTracer();
       TraceScope traceScope = null;
-      if (Trace.isTracing()) {
+      if (tracer != null) {
-        traceScope = Trace.startSpan(RpcClientUtil.methodToTraceString(method));
+        traceScope = tracer.newScope(RpcClientUtil.methodToTraceString(method));
       }
       ObjectWritable value;
       try {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/tracing/SpanReceiverHost.java

@@ -1,208 +0,0 @@
-/**
- * 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.tracing;
-
-import java.io.IOException;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.TreeMap;
-
-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 org.apache.hadoop.tracing.SpanReceiverInfo.ConfigurationPair;
-import org.apache.hadoop.util.ShutdownHookManager;
-import org.apache.htrace.SpanReceiver;
-import org.apache.htrace.SpanReceiverBuilder;
-import org.apache.htrace.Trace;
-import org.apache.htrace.impl.LocalFileSpanReceiver;
-
-/**
- * This class provides functions for reading the names of SpanReceivers from
- * the Hadoop configuration, adding those SpanReceivers to the Tracer,
- * and closing those SpanReceivers when appropriate.
- * This class does nothing If no SpanReceiver is configured.
- */
-@InterfaceAudience.Private
-public class SpanReceiverHost implements TraceAdminProtocol {
-  public static final String SPAN_RECEIVERS_CONF_SUFFIX =
-      "spanreceiver.classes";
-  private static final Log LOG = LogFactory.getLog(SpanReceiverHost.class);
-  private static final HashMap<String, SpanReceiverHost> hosts =
-      new HashMap<String, SpanReceiverHost>(1);
-  private final TreeMap<Long, SpanReceiver> receivers =
-      new TreeMap<Long, SpanReceiver>();
-  private final String confPrefix;
-  private Configuration config;
-  private boolean closed = false;
-  private long highestId = 1;
-
-  private final static String LOCAL_FILE_SPAN_RECEIVER_PATH_SUFFIX =
-      "local-file-span-receiver.path";
-
-  public static SpanReceiverHost get(Configuration conf, String confPrefix) {
-    synchronized (SpanReceiverHost.class) {
-      SpanReceiverHost host = hosts.get(confPrefix);
-      if (host != null) {
-        return host;
-      }
-      final SpanReceiverHost newHost = new SpanReceiverHost(confPrefix);
-      newHost.loadSpanReceivers(conf);
-      ShutdownHookManager.get().addShutdownHook(new Runnable() {
-          public void run() {
-            newHost.closeReceivers();
-          }
-        }, 0);
-      hosts.put(confPrefix, newHost);
-      return newHost;
-    }
-  }
-
-  private static List<ConfigurationPair> EMPTY = Collections.emptyList();
-
-  private SpanReceiverHost(String confPrefix) {
-    this.confPrefix = confPrefix;
-  }
-
-  /**
-   * Reads the names of classes specified in the
-   * "hadoop.htrace.spanreceiver.classes" property and instantiates and registers
-   * them with the Tracer as SpanReceiver's.
-   *
-   * The nullary constructor is called during construction, but if the classes
-   * specified implement the Configurable interface, setConfiguration() will be
-   * called on them. This allows SpanReceivers to use values from the Hadoop
-   * configuration.
-   */
-  public synchronized void loadSpanReceivers(Configuration conf) {
-    config = new Configuration(conf);
-    String receiverKey = confPrefix + SPAN_RECEIVERS_CONF_SUFFIX;
-    String[] receiverNames = config.getTrimmedStrings(receiverKey);
-    if (receiverNames == null || receiverNames.length == 0) {
-      if (LOG.isTraceEnabled()) {
-        LOG.trace("No span receiver names found in " + receiverKey + ".");
-      }
-      return;
-    }
-    // It's convenient to have each daemon log to a random trace file when
-    // testing.
-    String pathKey = confPrefix + LOCAL_FILE_SPAN_RECEIVER_PATH_SUFFIX;
-    if (config.get(pathKey) == null) {
-      String uniqueFile = LocalFileSpanReceiver.getUniqueLocalTraceFileName();
-      config.set(pathKey, uniqueFile);
-      if (LOG.isTraceEnabled()) {
-        LOG.trace("Set " + pathKey + " to " + uniqueFile);
-      }
-    }
-    for (String className : receiverNames) {
-      try {
-        SpanReceiver rcvr = loadInstance(className, EMPTY);
-        Trace.addReceiver(rcvr);
-        receivers.put(highestId++, rcvr);
-        LOG.info("Loaded SpanReceiver " + className + " successfully.");
-      } catch (IOException e) {
-        LOG.error("Failed to load SpanReceiver", e);
-      }
-    }
-  }
-
-  private synchronized SpanReceiver loadInstance(String className,
-      List<ConfigurationPair> extraConfig) throws IOException {
-    SpanReceiverBuilder builder =
-        new SpanReceiverBuilder(TraceUtils.
-            wrapHadoopConf(confPrefix, config, extraConfig));
-    SpanReceiver rcvr = builder.spanReceiverClass(className.trim()).build();
-    if (rcvr == null) {
-      throw new IOException("Failed to load SpanReceiver " + className);
-    }
-    return rcvr;
-  }
-
-  /**
-   * Calls close() on all SpanReceivers created by this SpanReceiverHost.
-   */
-  public synchronized void closeReceivers() {
-    if (closed) return;
-    closed = true;
-    for (SpanReceiver rcvr : receivers.values()) {
-      try {
-        rcvr.close();
-      } catch (IOException e) {
-        LOG.warn("Unable to close SpanReceiver correctly: " + e.getMessage(), e);
-      }
-    }
-    receivers.clear();
-  }
-
-  public synchronized SpanReceiverInfo[] listSpanReceivers()
-      throws IOException {
-    SpanReceiverInfo[] info = new SpanReceiverInfo[receivers.size()];
-    int i = 0;
-
-    for(Map.Entry<Long, SpanReceiver> entry : receivers.entrySet()) {
-      info[i] = new SpanReceiverInfo(entry.getKey(),
-          entry.getValue().getClass().getName());
-      i++;
-    }
-    return info;
-  }
-
-  public synchronized long addSpanReceiver(SpanReceiverInfo info)
-      throws IOException {
-    StringBuilder configStringBuilder = new StringBuilder();
-    String prefix = "";
-    for (ConfigurationPair pair : info.configPairs) {
-      configStringBuilder.append(prefix).append(pair.getKey()).
-          append(" = ").append(pair.getValue());
-      prefix = ", ";
-    }
-    SpanReceiver rcvr = null;
-    try {
-      rcvr = loadInstance(info.getClassName(), info.configPairs);
-    } catch (IOException e) {
-      LOG.info("Failed to add SpanReceiver " + info.getClassName() +
-          " with configuration " + configStringBuilder.toString(), e);
-      throw e;
-    } catch (RuntimeException e) {
-      LOG.info("Failed to add SpanReceiver " + info.getClassName() +
-          " with configuration " + configStringBuilder.toString(), e);
-      throw e;
-    }
-    Trace.addReceiver(rcvr);
-    long newId = highestId++;
-    receivers.put(newId, rcvr);
-    LOG.info("Successfully added SpanReceiver " + info.getClassName() +
-        " with configuration " + configStringBuilder.toString());
-    return newId;
-  }
-
-  public synchronized void removeSpanReceiver(long spanReceiverId)
-      throws IOException {
-    SpanReceiver rcvr = receivers.remove(spanReceiverId);
-    if (rcvr == null) {
-      throw new IOException("There is no span receiver with id " + spanReceiverId);
-    }
-    Trace.removeReceiver(rcvr);
-    rcvr.close();
-    LOG.info("Successfully removed SpanReceiver " + spanReceiverId +
-        " with class " + rcvr.getClass().getName());
-  }
-}

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/tracing/TraceUtils.java

@@ -24,7 +24,7 @@ import java.util.List;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.tracing.SpanReceiverInfo.ConfigurationPair;
-import org.apache.htrace.HTraceConfiguration;
+import org.apache.htrace.core.HTraceConfiguration;
 
 /**
  * This class provides utility functions for tracing.
@@ -32,6 +32,7 @@ import org.apache.htrace.HTraceConfiguration;
 @InterfaceAudience.Private
 public class TraceUtils {
   private static List<ConfigurationPair> EMPTY = Collections.emptyList();
+  static final String DEFAULT_HADOOP_PREFIX = "hadoop.htrace.";
 
   public static HTraceConfiguration wrapHadoopConf(final String prefix,
         final Configuration conf) {
@@ -47,16 +48,27 @@ public class TraceUtils {
     return new HTraceConfiguration() {
       @Override
       public String get(String key) {
-        return get(key, "");
+        String ret = getInternal(prefix + key);
+        if (ret != null) {
+          return ret;
+        }
+        return getInternal(DEFAULT_HADOOP_PREFIX  + key);
       }
 
       @Override
       public String get(String key, String defaultValue) {
-        String prefixedKey = prefix + key;
+        String ret = get(key);
-        if (extraMap.containsKey(prefixedKey)) {
+        if (ret != null) {
-          return extraMap.get(prefixedKey);
+          return ret;
         }
-        return conf.get(prefixedKey, defaultValue);
+        return defaultValue;
+      }
+
+      private String getInternal(String key) {
+        if (extraMap.containsKey(key)) {
+          return extraMap.get(key);
+        }
+        return conf.get(key);
       }
     };
   }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/tracing/TracerConfigurationManager.java

@@ -0,0 +1,100 @@
+/**
+ * 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.tracing;
+
+import java.io.IOException;
+
+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 org.apache.hadoop.tracing.SpanReceiverInfo.ConfigurationPair;
+import org.apache.htrace.core.SpanReceiver;
+import org.apache.htrace.core.TracerPool;
+
+/**
+ * This class provides functions for managing the tracer configuration at
+ * runtime via an RPC protocol.
+ */
+@InterfaceAudience.Private
+public class TracerConfigurationManager implements TraceAdminProtocol {
+  private static final Log LOG =
+      LogFactory.getLog(TracerConfigurationManager.class);
+
+  private final String confPrefix;
+  private final Configuration conf;
+
+  public TracerConfigurationManager(String confPrefix, Configuration conf) {
+    this.confPrefix = confPrefix;
+    this.conf = conf;
+  }
+
+  public synchronized SpanReceiverInfo[] listSpanReceivers()
+      throws IOException {
+    TracerPool pool = TracerPool.getGlobalTracerPool();
+    SpanReceiver[] receivers = pool.getReceivers();
+    SpanReceiverInfo[] info = new SpanReceiverInfo[receivers.length];
+    for (int i = 0; i < receivers.length; i++) {
+      SpanReceiver receiver = receivers[i];
+      info[i] = new SpanReceiverInfo(receiver.getId(),
+          receiver.getClass().getName());
+    }
+    return info;
+  }
+
+  public synchronized long addSpanReceiver(SpanReceiverInfo info)
+      throws IOException {
+    StringBuilder configStringBuilder = new StringBuilder();
+    String prefix = "";
+    for (ConfigurationPair pair : info.configPairs) {
+      configStringBuilder.append(prefix).append(pair.getKey()).
+          append(" = ").append(pair.getValue());
+      prefix = ", ";
+    }
+    SpanReceiver rcvr = null;
+    try {
+      rcvr = new SpanReceiver.Builder(TraceUtils.wrapHadoopConf(
+              confPrefix, conf, info.configPairs)).
+          className(info.getClassName().trim()).
+          build();
+    } catch (RuntimeException e) {
+      LOG.info("Failed to add SpanReceiver " + info.getClassName() +
+          " with configuration " + configStringBuilder.toString(), e);
+      throw e;
+    }
+    TracerPool.getGlobalTracerPool().addReceiver(rcvr);
+    LOG.info("Successfully added SpanReceiver " + info.getClassName() +
+        " with configuration " + configStringBuilder.toString());
+    return rcvr.getId();
+  }
+
+  public synchronized void removeSpanReceiver(long spanReceiverId)
+      throws IOException {
+    SpanReceiver[] receivers =
+        TracerPool.getGlobalTracerPool().getReceivers();
+    for (SpanReceiver receiver : receivers) {
+      if (receiver.getId() == spanReceiverId) {
+        TracerPool.getGlobalTracerPool().removeAndCloseReceiver(receiver);
+        LOG.info("Successfully removed SpanReceiver " + spanReceiverId +
+            " with class " + receiver.getClass().getName());
+        return;
+      }
+    }
+    throw new IOException("There is no span receiver with id " + spanReceiverId);
+  }
+}

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

@@ -27,8 +27,8 @@ import org.apache.hadoop.ipc.protobuf.IpcConnectionContextProtos.UserInformation
 import org.apache.hadoop.ipc.protobuf.RpcHeaderProtos.*;
 import org.apache.hadoop.security.SaslRpcServer.AuthMethod;
 import org.apache.hadoop.security.UserGroupInformation;
-import org.apache.htrace.Span;
+import org.apache.htrace.core.Span;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.Tracer;
 
 import com.google.protobuf.ByteString;
 
@@ -169,11 +169,12 @@ public abstract class ProtoUtil {
         .setRetryCount(retryCount).setClientId(ByteString.copyFrom(uuid));
 
     // Add tracing info if we are currently tracing.
-    if (Trace.isTracing()) {
+    Span span = Tracer.getCurrentSpan();
-      Span s = Trace.currentSpan();
+    if (span != null) {
       result.setTraceInfo(RPCTraceInfoProto.newBuilder()
-          .setParentId(s.getSpanId())
+          .setTraceId(span.getSpanId().getHigh())
-          .setTraceId(s.getTraceId()).build());
+          .setParentId(span.getSpanId().getLow())
+            .build());
     }
 
     return result.build();

hadoop-common-project/hadoop-common/src/main/proto/RpcHeader.proto

@@ -61,8 +61,9 @@ enum RpcKindProto {
  * what span caused the new span we will create when this message is received.
  */
 message RPCTraceInfoProto {
-  optional int64 traceId = 1;
+    optional int64 traceId = 1; // parentIdHigh
-  optional int64 parentId = 2;
+    optional int64 parentId = 2; // parentIdLow
+
 }
 
 message RpcRequestHeaderProto { // the header for the RpcRequest

hadoop-common-project/hadoop-common/src/main/resources/core-default.xml

@@ -2000,4 +2000,19 @@ for ldap providers in the same way as above does.
       the limit is 0 or the -safely is not specified in -rm command.
     </description>
   </property>
+
+  <property>
+    <name>fs.client.htrace.sampler.classes</name>
+    <value></value>
+    <description>The class names of the HTrace Samplers to use for Hadoop
+      filesystem clients.
+    </description>
+  </property>
+
+  <property>
+    <name>hadoop.htrace.span.receiver.classes</name>
+    <value></value>
+    <description>The class names of the Span Receivers to use for Hadoop.
+    </description>
+  </property>
 </configuration>

hadoop-common-project/hadoop-common/src/site/markdown/Tracing.md

@@ -49,37 +49,14 @@ interface bundled with HTrace or implementing it by yourself.
 * HTracedRESTReceiver
 * ZipkinSpanReceiver
 
-In order to set up SpanReceivers for HDFS servers,
+See core-default.xml for a description of HTrace configuration keys.  In some
-configure what SpanReceivers you'd like to use
+cases, you will also need to add the jar containing the SpanReceiver that you
-by putting a comma separated list of the fully-qualified class name of classes implementing SpanReceiver
+are using to the classpath of Hadoop on each node. (In the example above,
-in `hdfs-site.xml` property: `dfs.htrace.spanreceiver.classes`.
+LocalFileSpanReceiver is included in the htrace-core4 jar which is bundled
-
+with Hadoop.)
-```xml
-      <property>
-        <name>dfs.htrace.spanreceiver.classes</name>
-        <value>org.apache.htrace.impl.LocalFileSpanReceiver</value>
-      </property>
-      <property>
-        <name>dfs.htrace.local-file-span-receiver.path</name>
-        <value>/var/log/hadoop/htrace.out</value>
-      </property>
-```
-
-You can omit package name prefix if you use span receiver bundled with HTrace.
-
-```xml
-      <property>
-        <name>dfs.htrace.spanreceiver.classes</name>
-        <value>LocalFileSpanReceiver</value>
-      </property>
-```
-
-You also need to add the jar bundling SpanReceiver to the classpath of Hadoop
-on each node. (LocalFileSpanReceiver in the example above is included in the
-jar of htrace-core which is bundled with Hadoop.)
 
 ```
-    $ cp htrace-htraced/target/htrace-htraced-3.2.0-incubating.jar $HADOOP_HOME/share/hadoop/common/lib/
+    $ cp htrace-htraced/target/htrace-htraced-4.0.1-incubating.jar $HADOOP_HOME/share/hadoop/common/lib/
 ```
 
 ### Dynamic update of tracing configuration
@@ -92,11 +69,11 @@ You need to run the command against all servers if you want to update the config
 
       $ hadoop trace -list -host 192.168.56.2:9000
       ID  CLASS
-      1   org.apache.htrace.impl.LocalFileSpanReceiver
+      1   org.apache.htrace.core.LocalFileSpanReceiver
 
       $ hadoop trace -list -host 192.168.56.2:50020
       ID  CLASS
-      1   org.apache.htrace.impl.LocalFileSpanReceiver
+      1   org.apache.htrace.core.LocalFileSpanReceiver
 
 `hadoop trace -remove` removes span receiver from server.
 `-remove` options takes id of span receiver as argument.
@@ -113,7 +90,7 @@ You can specify the configuration associated with span receiver by `-Ckey=value`
 
       $ hadoop trace -list -host 192.168.56.2:9000
       ID  CLASS
-      2   org.apache.htrace.impl.LocalFileSpanReceiver
+      2   org.apache.htrace.core.LocalFileSpanReceiver
 
 ### Starting tracing spans by HTrace API
 
@@ -121,26 +98,21 @@ In order to trace, you will need to wrap the traced logic with **tracing span**
 When there is running tracing spans,
 the tracing information is propagated to servers along with RPC requests.
 
-In addition, you need to initialize `SpanReceiverHost` once per process.
-
 ```java
     import org.apache.hadoop.hdfs.HdfsConfiguration;
-    import org.apache.hadoop.tracing.SpanReceiverHost;
+    import org.apache.htrace.core.Tracer;
-    import org.apache.htrace.Sampler;
+    import org.apache.htrace.core.TraceScope;
-    import org.apache.htrace.Trace;
-    import org.apache.htrace.TraceScope;
 
     ...
 
-        SpanReceiverHost.getInstance(new HdfsConfiguration());
 
     ...
 
-        TraceScope ts = Trace.startSpan("Gets", Sampler.ALWAYS);
+        TraceScope ts = tracer.newScope("Gets");
         try {
           ... // traced logic
         } finally {
-          if (ts != null) ts.close();
+          ts.close();
         }
 ```
 
@@ -154,11 +126,10 @@ which start tracing span before invoking HDFS shell command.
     import org.apache.hadoop.fs.FsShell;
     import org.apache.hadoop.hdfs.DFSConfigKeys;
     import org.apache.hadoop.hdfs.HdfsConfiguration;
-    import org.apache.hadoop.tracing.SpanReceiverHost;
+    import org.apache.hadoop.tracing.TraceUtils;
     import org.apache.hadoop.util.ToolRunner;
-    import org.apache.htrace.Sampler;
+    import org.apache.htrace.core.Trace;
-    import org.apache.htrace.Trace;
+    import org.apache.htrace.core.TraceScope;
-    import org.apache.htrace.TraceScope;
 
     public class TracingFsShell {
       public static void main(String argv[]) throws Exception {
@@ -166,13 +137,19 @@ which start tracing span before invoking HDFS shell command.
         FsShell shell = new FsShell();
         conf.setQuietMode(false);
         shell.setConf(conf);
-        SpanReceiverHost.get(conf, DFSConfigKeys.DFS_SERVER_HTRACE_PREFIX);
+        Tracer tracer = new Tracer.Builder().
+            name("TracingFsShell).
+            conf(TraceUtils.wrapHadoopConf("tracing.fs.shell.htrace.", conf)).
+            build();
         int res = 0;
-        try (TraceScope ts = Trace.startSpan("FsShell", Sampler.ALWAYS)) {
+        TraceScope scope = tracer.newScope("FsShell");
+        try {
           res = ToolRunner.run(shell, argv);
         } finally {
+          scope.close();
           shell.close();
         }
+        tracer.close();
         System.exit(res);
       }
     }
@@ -189,16 +166,15 @@ The DFSClient can enable tracing internally. This allows you to use HTrace with
 your client without modifying the client source code.
 
 Configure the span receivers and samplers in `hdfs-site.xml`
-by properties `dfs.client.htrace.sampler` and `dfs.client.htrace.sampler`.
+by properties `fs.client.htrace.sampler.classes` and
-The value of `dfs.client.htrace.sampler` can be NeverSampler, AlwaysSampler or ProbabilitySampler.
+`fs.client.htrace.spanreceiver.classes`.  The value of
+`fs.client.htrace.sampler.classes` can be NeverSampler, AlwaysSampler or
+ProbabilitySampler.
 
 * NeverSampler: HTrace is OFF for all requests to namenodes and datanodes;
 * AlwaysSampler: HTrace is ON for all requests to namenodes and datanodes;
 * ProbabilitySampler: HTrace is ON for some percentage% of  requests to namenodes and datanodes
 
-You do not need to enable this if your client program has been modified
-to use HTrace.
-
 ```xml
       <property>
         <name>dfs.client.htrace.spanreceiver.classes</name>

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestFsShell.java

@@ -24,10 +24,9 @@ import junit.framework.AssertionFailedError;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.tracing.SetSpanReceiver;
-import org.apache.hadoop.tracing.SpanReceiverHost;
 import org.apache.hadoop.util.ToolRunner;
-import org.apache.htrace.SamplerBuilder;
+import org.apache.htrace.core.AlwaysSampler;
-import org.apache.htrace.impl.AlwaysSampler;
+import org.apache.htrace.core.Tracer;
 import org.junit.Assert;
 import org.junit.Test;
 
@@ -53,10 +52,10 @@ public class TestFsShell {
   @Test
   public void testTracing() throws Throwable {
     Configuration conf = new Configuration();
-    String prefix = FsShell.SEHLL_HTRACE_PREFIX;
+    String prefix = "fs.shell.htrace.";
-    conf.set(prefix + SpanReceiverHost.SPAN_RECEIVERS_CONF_SUFFIX,
+    conf.set(prefix + Tracer.SPAN_RECEIVER_CLASSES_KEY,
         SetSpanReceiver.class.getName());
-    conf.set(prefix + SamplerBuilder.SAMPLER_CONF_KEY,
+    conf.set(prefix + Tracer.SAMPLER_CLASSES_KEY,
         AlwaysSampler.class.getName());
     conf.setQuietMode(false);
     FsShell shell = new FsShell(conf);

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/tracing/SetSpanReceiver.java

@@ -19,9 +19,10 @@ package org.apache.hadoop.tracing;
 
 import com.google.common.base.Supplier;
 import org.apache.hadoop.test.GenericTestUtils;
-import org.apache.htrace.Span;
+import org.apache.htrace.core.Span;
-import org.apache.htrace.SpanReceiver;
+import org.apache.htrace.core.SpanId;
-import org.apache.htrace.HTraceConfiguration;
+import org.apache.htrace.core.SpanReceiver;
+import org.apache.htrace.core.HTraceConfiguration;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.LinkedList;
@@ -39,7 +40,7 @@ import org.junit.Assert;
  * push all the metrics to a static place, and would make testing
  * SpanReceiverHost harder.
  */
-public class SetSpanReceiver implements SpanReceiver {
+public class SetSpanReceiver extends SpanReceiver {
 
   public SetSpanReceiver(HTraceConfiguration conf) {
   }
@@ -68,8 +69,8 @@ public class SetSpanReceiver implements SpanReceiver {
   }
 
   public static class SetHolder {
-    public static ConcurrentHashMap<Long, Span> spans =
+    public static ConcurrentHashMap<SpanId, Span> spans =
-        new ConcurrentHashMap<Long, Span>();
+        new ConcurrentHashMap<SpanId, Span>();
 
     public static Map<String, List<Span>> getMap() {
       Map<String, List<Span>> map = new HashMap<String, List<Span>>();

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/tracing/TestTraceUtils.java

@@ -21,7 +21,7 @@ import static org.junit.Assert.assertEquals;
 import java.util.LinkedList;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.tracing.SpanReceiverInfo.ConfigurationPair;
-import org.apache.htrace.HTraceConfiguration;
+import org.apache.htrace.core.HTraceConfiguration;
 import org.junit.Test;
 
 public class TestTraceUtils {

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/BlockReaderFactory.java

@@ -66,6 +66,7 @@ import org.apache.hadoop.util.Time;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
+import org.apache.htrace.core.Tracer;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -178,6 +179,11 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
    */
   private Configuration configuration;
 
+  /**
+   * The HTrace tracer to use.
+   */
+  private Tracer tracer;
+
   /**
    * Information about the domain socket path we should use to connect to the
    * local peer-- or null if we haven't examined the local domain socket.
@@ -282,6 +288,11 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
     return this;
   }
 
+  public BlockReaderFactory setTracer(Tracer tracer) {
+    this.tracer = tracer;
+    return this;
+  }
+
   @VisibleForTesting
   public static void setFailureInjectorForTesting(FailureInjector injector) {
     failureInjector = injector;
@@ -435,7 +446,7 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
     try {
       return BlockReaderLocalLegacy.newBlockReader(conf,
           userGroupInformation, configuration, fileName, block, token,
-          datanode, startOffset, length, storageType);
+          datanode, startOffset, length, storageType, tracer);
     } catch (RemoteException remoteException) {
       ioe = remoteException.unwrapRemoteException(
                 InvalidToken.class, AccessControlException.class);
@@ -496,6 +507,7 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
         setVerifyChecksum(verifyChecksum).
         setCachingStrategy(cachingStrategy).
         setStorageType(storageType).
+        setTracer(tracer).
         build();
   }
 
@@ -865,12 +877,12 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
       return RemoteBlockReader.newBlockReader(fileName,
           block, token, startOffset, length, conf.getIoBufferSize(),
           verifyChecksum, clientName, peer, datanode,
-          clientContext.getPeerCache(), cachingStrategy);
+          clientContext.getPeerCache(), cachingStrategy, tracer);
     } else {
       return RemoteBlockReader2.newBlockReader(
           fileName, block, token, startOffset, length,
           verifyChecksum, clientName, peer, datanode,
-          clientContext.getPeerCache(), cachingStrategy);
+          clientContext.getPeerCache(), cachingStrategy, tracer);
     }
   }
 

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/BlockReaderLocal.java

@@ -34,9 +34,8 @@ import org.apache.hadoop.hdfs.shortcircuit.ClientMmap;
 import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitReplica;
 import org.apache.hadoop.util.DataChecksum;
 import org.apache.hadoop.util.DirectBufferPool;
-import org.apache.htrace.Sampler;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.Tracer;
-import org.apache.htrace.TraceScope;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
@@ -75,6 +74,7 @@ class BlockReaderLocal implements BlockReader {
     private long dataPos;
     private ExtendedBlock block;
     private StorageType storageType;
+    private Tracer tracer;
 
     public Builder(ShortCircuitConf conf) {
       this.maxReadahead = Integer.MAX_VALUE;
@@ -120,6 +120,11 @@ class BlockReaderLocal implements BlockReader {
       return this;
     }
 
+    public Builder setTracer(Tracer tracer) {
+      this.tracer = tracer;
+      return this;
+    }
+
     public BlockReaderLocal build() {
       Preconditions.checkNotNull(replica);
       return new BlockReaderLocal(this);
@@ -228,6 +233,11 @@ class BlockReaderLocal implements BlockReader {
    */
   private StorageType storageType;
 
+  /**
+   * The Tracer to use.
+   */
+  private final Tracer tracer;
+
   private BlockReaderLocal(Builder builder) {
     this.replica = builder.replica;
     this.dataIn = replica.getDataStream().getChannel();
@@ -257,6 +267,7 @@ class BlockReaderLocal implements BlockReader {
     }
     this.maxReadaheadLength = maxReadaheadChunks * bytesPerChecksum;
     this.storageType = builder.storageType;
+    this.tracer = builder.tracer;
   }
 
   private synchronized void createDataBufIfNeeded() {
@@ -324,8 +335,8 @@ class BlockReaderLocal implements BlockReader {
    */
   private synchronized int fillBuffer(ByteBuffer buf, boolean canSkipChecksum)
       throws IOException {
-    TraceScope scope = Trace.startSpan("BlockReaderLocal#fillBuffer(" +
+    TraceScope scope = tracer.newScope(
-        block.getBlockId() + ")", Sampler.NEVER);
+        "BlockReaderLocal#fillBuffer(" + block.getBlockId() + ")");
     try {
       int total = 0;
       long startDataPos = dataPos;

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/BlockReaderLocalLegacy.java

@@ -50,10 +50,8 @@ import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.util.DataChecksum;
 import org.apache.hadoop.util.DirectBufferPool;
-import org.apache.htrace.Sampler;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.Tracer;
-import org.apache.htrace.TraceScope;
-
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -182,7 +180,8 @@ class BlockReaderLocalLegacy implements BlockReader {
   private long startOffset;
   private final String filename;
   private long blockId;
-  
+  private final Tracer tracer;
+
   /**
    * The only way this object can be instantiated.
    */
@@ -190,8 +189,8 @@ class BlockReaderLocalLegacy implements BlockReader {
       UserGroupInformation userGroupInformation,
       Configuration configuration, String file, ExtendedBlock blk,
       Token<BlockTokenIdentifier> token, DatanodeInfo node, 
-      long startOffset, long length, StorageType storageType)
+      long startOffset, long length, StorageType storageType,
-      throws IOException {
+      Tracer tracer) throws IOException {
     final ShortCircuitConf scConf = conf.getShortCircuitConf();
     LocalDatanodeInfo localDatanodeInfo = getLocalDatanodeInfo(node
         .getIpcPort());
@@ -239,10 +238,10 @@ class BlockReaderLocalLegacy implements BlockReader {
             - (startOffset % checksum.getBytesPerChecksum());
         localBlockReader = new BlockReaderLocalLegacy(scConf, file, blk, token,
             startOffset, length, pathinfo, checksum, true, dataIn,
-            firstChunkOffset, checksumIn);
+            firstChunkOffset, checksumIn, tracer);
       } else {
         localBlockReader = new BlockReaderLocalLegacy(scConf, file, blk, token,
-            startOffset, length, pathinfo, dataIn);
+            startOffset, length, pathinfo, dataIn, tracer);
       }
     } catch (IOException e) {
       // remove from cache
@@ -321,18 +320,18 @@ class BlockReaderLocalLegacy implements BlockReader {
 
   private BlockReaderLocalLegacy(ShortCircuitConf conf, String hdfsfile,
       ExtendedBlock block, Token<BlockTokenIdentifier> token, long startOffset,
-      long length, BlockLocalPathInfo pathinfo, FileInputStream dataIn)
+      long length, BlockLocalPathInfo pathinfo, FileInputStream dataIn,
-      throws IOException {
+      Tracer tracer) throws IOException {
     this(conf, hdfsfile, block, token, startOffset, length, pathinfo,
         DataChecksum.newDataChecksum(DataChecksum.Type.NULL, 4), false,
-        dataIn, startOffset, null);
+        dataIn, startOffset, null, tracer);
   }
 
   private BlockReaderLocalLegacy(ShortCircuitConf conf, String hdfsfile,
       ExtendedBlock block, Token<BlockTokenIdentifier> token, long startOffset,
       long length, BlockLocalPathInfo pathinfo, DataChecksum checksum,
       boolean verifyChecksum, FileInputStream dataIn, long firstChunkOffset,
-      FileInputStream checksumIn) throws IOException {
+      FileInputStream checksumIn, Tracer tracer) throws IOException {
     this.filename = hdfsfile;
     this.checksum = checksum;
     this.verifyChecksum = verifyChecksum;
@@ -368,6 +367,7 @@ class BlockReaderLocalLegacy implements BlockReader {
         bufferPool.returnBuffer(checksumBuff);
       }
     }
+    this.tracer = tracer;
   }
 
   /**
@@ -375,8 +375,8 @@ class BlockReaderLocalLegacy implements BlockReader {
    */
   private int fillBuffer(FileInputStream stream, ByteBuffer buf)
       throws IOException {
-    TraceScope scope = Trace.startSpan("BlockReaderLocalLegacy#fillBuffer(" +
+    TraceScope scope = tracer.
-        blockId + ")", Sampler.NEVER);
+        newScope("BlockReaderLocalLegacy#fillBuffer(" + blockId + ")");
     try {
       int bytesRead = stream.getChannel().read(buf);
       if (bytesRead < 0) {

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/BlockStorageLocationUtil.java

@@ -46,9 +46,9 @@ import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier;
 import org.apache.hadoop.hdfs.security.token.block.InvalidBlockTokenException;
 import org.apache.hadoop.ipc.RPC;
 import org.apache.hadoop.security.token.Token;
-import org.apache.htrace.Span;
+import org.apache.htrace.core.SpanId;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.TraceScope;
+import org.apache.htrace.core.Tracer;
 
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
@@ -74,7 +74,8 @@ class BlockStorageLocationUtil {
    */
   private static List<VolumeBlockLocationCallable> createVolumeBlockLocationCallables(
       Configuration conf, Map<DatanodeInfo, List<LocatedBlock>> datanodeBlocks,
-      int timeout, boolean connectToDnViaHostname, Span parent) {
+      int timeout, boolean connectToDnViaHostname,
+      Tracer tracer, SpanId parentSpanId) {
     
     if (datanodeBlocks.isEmpty()) {
       return Lists.newArrayList();
@@ -114,7 +115,7 @@ class BlockStorageLocationUtil {
       }
       VolumeBlockLocationCallable callable = new VolumeBlockLocationCallable(
           conf, datanode, poolId, blockIds, dnTokens, timeout, 
-          connectToDnViaHostname, parent);
+          connectToDnViaHostname, tracer, parentSpanId);
       callables.add(callable);
     }
     return callables;
@@ -133,12 +134,12 @@ class BlockStorageLocationUtil {
    */
   static Map<DatanodeInfo, HdfsBlocksMetadata> queryDatanodesForHdfsBlocksMetadata(
       Configuration conf, Map<DatanodeInfo, List<LocatedBlock>> datanodeBlocks,
-      int poolsize, int timeoutMs, boolean connectToDnViaHostname)
+      int poolsize, int timeoutMs, boolean connectToDnViaHostname,
-        throws InvalidBlockTokenException {
+      Tracer tracer, SpanId parentSpanId) throws InvalidBlockTokenException {
 
     List<VolumeBlockLocationCallable> callables = 
         createVolumeBlockLocationCallables(conf, datanodeBlocks, timeoutMs, 
-            connectToDnViaHostname, Trace.currentSpan());
+            connectToDnViaHostname, tracer, parentSpanId);
     
     // Use a thread pool to execute the Callables in parallel
     List<Future<HdfsBlocksMetadata>> futures = 
@@ -322,12 +323,14 @@ class BlockStorageLocationUtil {
     private final long[] blockIds;
     private final List<Token<BlockTokenIdentifier>> dnTokens;
     private final boolean connectToDnViaHostname;
-    private final Span parentSpan;
+    private final Tracer tracer;
+    private final SpanId parentSpanId;
     
     VolumeBlockLocationCallable(Configuration configuration,
         DatanodeInfo datanode, String poolId, long []blockIds,
         List<Token<BlockTokenIdentifier>> dnTokens, int timeout, 
-        boolean connectToDnViaHostname, Span parentSpan) {
+        boolean connectToDnViaHostname,
+        Tracer tracer, SpanId parentSpanId) {
       this.configuration = configuration;
       this.timeout = timeout;
       this.datanode = datanode;
@@ -335,7 +338,8 @@ class BlockStorageLocationUtil {
       this.blockIds = blockIds;
       this.dnTokens = dnTokens;
       this.connectToDnViaHostname = connectToDnViaHostname;
-      this.parentSpan = parentSpan;
+      this.tracer = tracer;
+      this.parentSpanId = parentSpanId;
     }
     
     public DatanodeInfo getDatanodeInfo() {
@@ -348,7 +352,7 @@ class BlockStorageLocationUtil {
       // Create the RPC proxy and make the RPC
       ClientDatanodeProtocol cdp = null;
       TraceScope scope =
-          Trace.startSpan("getHdfsBlocksMetadata", parentSpan);
+          tracer.newScope("getHdfsBlocksMetadata", parentSpanId);
       try {
         cdp = DFSUtilClient.createClientDatanodeProtocolProxy(
             datanode, configuration,

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

@@ -77,6 +77,7 @@ import org.apache.hadoop.fs.FileEncryptionInfo;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.FsServerDefaults;
 import org.apache.hadoop.fs.FsStatus;
+import org.apache.hadoop.fs.FsTracer;
 import org.apache.hadoop.fs.HdfsBlockLocation;
 import org.apache.hadoop.fs.InvalidPathException;
 import org.apache.hadoop.fs.MD5MD5CRC32CastagnoliFileChecksum;
@@ -172,24 +173,19 @@ import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.security.token.SecretManager.InvalidToken;
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.security.token.TokenRenewer;
-import org.apache.hadoop.tracing.SpanReceiverHost;
-import org.apache.hadoop.tracing.TraceUtils;
 import org.apache.hadoop.util.Daemon;
 import org.apache.hadoop.util.DataChecksum;
 import org.apache.hadoop.util.DataChecksum.Type;
 import org.apache.hadoop.util.Progressable;
 import org.apache.hadoop.util.Time;
-import org.apache.htrace.Sampler;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.SamplerBuilder;
-import org.apache.htrace.Span;
-import org.apache.htrace.Trace;
-import org.apache.htrace.TraceScope;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Joiner;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.Lists;
 import com.google.common.net.InetAddresses;
+import org.apache.htrace.core.Tracer;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -212,6 +208,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public static final long SERVER_DEFAULTS_VALIDITY_PERIOD = 60 * 60 * 1000L; // 1 hour
 
   private final Configuration conf;
+  private final Tracer tracer;
   private final DfsClientConf dfsClientConf;
   final ClientProtocol namenode;
   /* The service used for delegation tokens */
@@ -238,7 +235,6 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   private static final DFSHedgedReadMetrics HEDGED_READ_METRIC =
       new DFSHedgedReadMetrics();
   private static ThreadPoolExecutor HEDGED_READ_THREAD_POOL;
-  private final Sampler<?> traceSampler;
   private final int smallBufferSize;
 
   public DfsClientConf getConf() {
@@ -302,11 +298,8 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public DFSClient(URI nameNodeUri, ClientProtocol rpcNamenode,
       Configuration conf, FileSystem.Statistics stats)
     throws IOException {
-    SpanReceiverHost.get(conf, HdfsClientConfigKeys.DFS_CLIENT_HTRACE_PREFIX);
-    traceSampler = new SamplerBuilder(TraceUtils.
-        wrapHadoopConf(HdfsClientConfigKeys.DFS_CLIENT_HTRACE_PREFIX, conf))
-        .build();
     // Copy only the required DFSClient configuration
+    this.tracer = FsTracer.get(conf);
     this.dfsClientConf = new DfsClientConf(conf);
     this.conf = conf;
     this.stats = stats;
@@ -628,7 +621,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    * @see ClientProtocol#getPreferredBlockSize(String)
    */
   public long getBlockSize(String f) throws IOException {
-    TraceScope scope = getPathTraceScope("getBlockSize", f);
+    TraceScope scope = newPathTraceScope("getBlockSize", f);
     try {
       return namenode.getPreferredBlockSize(f);
     } catch (IOException ie) {
@@ -670,7 +663,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public Token<DelegationTokenIdentifier> getDelegationToken(Text renewer)
       throws IOException {
     assert dtService != null;
-    TraceScope scope = Trace.startSpan("getDelegationToken", traceSampler);
+    TraceScope scope = tracer.newScope("getDelegationToken");
     try {
       Token<DelegationTokenIdentifier> token =
         namenode.getDelegationToken(renewer);
@@ -826,7 +819,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   @VisibleForTesting
   public LocatedBlocks getLocatedBlocks(String src, long start, long length)
       throws IOException {
-    TraceScope scope = getPathTraceScope("getBlockLocations", src);
+    TraceScope scope = newPathTraceScope("getBlockLocations", src);
     try {
       return callGetBlockLocations(namenode, src, start, length);
     } finally {
@@ -858,7 +851,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   boolean recoverLease(String src) throws IOException {
     checkOpen();
 
-    TraceScope scope = getPathTraceScope("recoverLease", src);
+    TraceScope scope = newPathTraceScope("recoverLease", src);
     try {
       return namenode.recoverLease(src, clientName);
     } catch (RemoteException re) {
@@ -884,7 +877,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   public BlockLocation[] getBlockLocations(String src, long start, 
         long length) throws IOException, UnresolvedLinkException {
-    TraceScope scope = getPathTraceScope("getBlockLocations", src);
+    TraceScope scope = newPathTraceScope("getBlockLocations", src);
     try {
       LocatedBlocks blocks = getLocatedBlocks(src, start, length);
       BlockLocation[] locations =  DFSUtilClient.locatedBlocks2Locations(blocks);
@@ -950,14 +943,14 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
         
     // Make RPCs to the datanodes to get volume locations for its replicas
     TraceScope scope =
-      Trace.startSpan("getBlockStorageLocations", traceSampler);
+      tracer.newScope("getBlockStorageLocations");
     Map<DatanodeInfo, HdfsBlocksMetadata> metadatas;
     try {
       metadatas = BlockStorageLocationUtil.
           queryDatanodesForHdfsBlocksMetadata(conf, datanodeBlocks,
               getConf().getFileBlockStorageLocationsNumThreads(),
               getConf().getFileBlockStorageLocationsTimeoutMs(),
-              getConf().isConnectToDnViaHostname());
+              getConf().isConnectToDnViaHostname(), tracer, scope.getSpanId());
       if (LOG.isTraceEnabled()) {
         LOG.trace("metadata returned: "
             + Joiner.on("\n").withKeyValueSeparator("=").join(metadatas));
@@ -983,7 +976,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   private KeyVersion decryptEncryptedDataEncryptionKey(FileEncryptionInfo
       feInfo) throws IOException {
-    TraceScope scope = Trace.startSpan("decryptEDEK", traceSampler);
+    TraceScope scope = tracer.newScope("decryptEDEK");
     try {
       KeyProvider provider = getKeyProvider();
       if (provider == null) {
@@ -1139,7 +1132,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
       throws IOException, UnresolvedLinkException {
     checkOpen();
     //    Get block info from namenode
-    TraceScope scope = getPathTraceScope("newDFSInputStream", src);
+    TraceScope scope = newPathTraceScope("newDFSInputStream", src);
     try {
       return new DFSInputStream(this, src, verifyChecksum, null);
     } finally {
@@ -1384,7 +1377,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   public void createSymlink(String target, String link, boolean createParent)
       throws IOException {
-    TraceScope scope = getPathTraceScope("createSymlink", target);
+    TraceScope scope = newPathTraceScope("createSymlink", target);
     try {
       final FsPermission dirPerm = applyUMask(null);
       namenode.createSymlink(target, link, dirPerm, createParent);
@@ -1410,7 +1403,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   public String getLinkTarget(String path) throws IOException { 
     checkOpen();
-    TraceScope scope = getPathTraceScope("getLinkTarget", path);
+    TraceScope scope = newPathTraceScope("getLinkTarget", path);
     try {
       return namenode.getLinkTarget(path);
     } catch (RemoteException re) {
@@ -1506,7 +1499,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   public boolean setReplication(String src, short replication)
       throws IOException {
-    TraceScope scope = getPathTraceScope("setReplication", src);
+    TraceScope scope = newPathTraceScope("setReplication", src);
     try {
       return namenode.setReplication(src, replication);
     } catch(RemoteException re) {
@@ -1529,7 +1522,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   public void setStoragePolicy(String src, String policyName)
       throws IOException {
-    TraceScope scope = getPathTraceScope("setStoragePolicy", src);
+    TraceScope scope = newPathTraceScope("setStoragePolicy", src);
     try {
       namenode.setStoragePolicy(src, policyName);
     } catch (RemoteException e) {
@@ -1550,7 +1543,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   public BlockStoragePolicy getStoragePolicy(String path) throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("getStoragePolicy", path);
+    TraceScope scope = newPathTraceScope("getStoragePolicy", path);
     try {
       return namenode.getStoragePolicy(path);
     } catch (RemoteException e) {
@@ -1567,7 +1560,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    * @return All the existing storage policies
    */
   public BlockStoragePolicy[] getStoragePolicies() throws IOException {
-    TraceScope scope = Trace.startSpan("getStoragePolicies", traceSampler);
+    TraceScope scope = tracer.newScope("getStoragePolicies");
     try {
       return namenode.getStoragePolicies();
     } finally {
@@ -1583,7 +1576,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   @Deprecated
   public boolean rename(String src, String dst) throws IOException {
     checkOpen();
-    TraceScope scope = getSrcDstTraceScope("rename", src, dst);
+    TraceScope scope = newSrcDstTraceScope("rename", src, dst);
     try {
       return namenode.rename(src, dst);
     } catch(RemoteException re) {
@@ -1604,7 +1597,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   public void concat(String trg, String [] srcs) throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("concat", traceSampler);
+    TraceScope scope = tracer.newScope("concat");
     try {
       namenode.concat(trg, srcs);
     } catch(RemoteException re) {
@@ -1622,7 +1615,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public void rename(String src, String dst, Options.Rename... options)
       throws IOException {
     checkOpen();
-    TraceScope scope = getSrcDstTraceScope("rename2", src, dst);
+    TraceScope scope = newSrcDstTraceScope("rename2", src, dst);
     try {
       namenode.rename2(src, dst, options);
     } catch(RemoteException re) {
@@ -1651,11 +1644,14 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
       throw new HadoopIllegalArgumentException(
           "Cannot truncate to a negative file size: " + newLength + ".");
     }
+    TraceScope scope = newPathTraceScope("truncate", src);
     try {
       return namenode.truncate(src, newLength, clientName);
     } catch (RemoteException re) {
       throw re.unwrapRemoteException(AccessControlException.class,
           UnresolvedPathException.class);
+    } finally {
+      scope.close();
     }
   }
 
@@ -1678,7 +1674,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   public boolean delete(String src, boolean recursive) throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("delete", src);
+    TraceScope scope = newPathTraceScope("delete", src);
     try {
       return namenode.delete(src, recursive);
     } catch(RemoteException re) {
@@ -1720,7 +1716,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public DirectoryListing listPaths(String src,  byte[] startAfter,
       boolean needLocation) throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("listPaths", src);
+    TraceScope scope = newPathTraceScope("listPaths", src);
     try {
       return namenode.getListing(src, startAfter, needLocation);
     } catch(RemoteException re) {
@@ -1742,7 +1738,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   public HdfsFileStatus getFileInfo(String src) throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("getFileInfo", src);
+    TraceScope scope = newPathTraceScope("getFileInfo", src);
     try {
       return namenode.getFileInfo(src);
     } catch(RemoteException re) {
@@ -1760,7 +1756,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   public boolean isFileClosed(String src) throws IOException{
     checkOpen();
-    TraceScope scope = getPathTraceScope("isFileClosed", src);
+    TraceScope scope = newPathTraceScope("isFileClosed", src);
     try {
       return namenode.isFileClosed(src);
     } catch(RemoteException re) {
@@ -1782,7 +1778,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   public HdfsFileStatus getFileLinkInfo(String src) throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("getFileLinkInfo", src);
+    TraceScope scope = newPathTraceScope("getFileLinkInfo", src);
     try {
       return namenode.getFileLinkInfo(src);
     } catch(RemoteException re) {
@@ -2085,7 +2081,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public void setPermission(String src, FsPermission permission)
       throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("setPermission", src);
+    TraceScope scope = newPathTraceScope("setPermission", src);
     try {
       namenode.setPermission(src, permission);
     } catch(RemoteException re) {
@@ -2110,7 +2106,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public void setOwner(String src, String username, String groupname)
       throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("setOwner", src);
+    TraceScope scope = newPathTraceScope("setOwner", src);
     try {
       namenode.setOwner(src, username, groupname);
     } catch(RemoteException re) {
@@ -2126,7 +2122,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
 
   private long[] callGetStats() throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("getStats", traceSampler);
+    TraceScope scope = tracer.newScope("getStats");
     try {
       return namenode.getStats();
     } finally {
@@ -2185,7 +2181,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
                                                  String cookie)
         throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("listCorruptFileBlocks", path);
+    TraceScope scope = newPathTraceScope("listCorruptFileBlocks", path);
     try {
       return namenode.listCorruptFileBlocks(path, cookie);
     } finally {
@@ -2196,7 +2192,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public DatanodeInfo[] datanodeReport(DatanodeReportType type)
       throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("datanodeReport", traceSampler);
+    TraceScope scope = tracer.newScope("datanodeReport");
     try {
       return namenode.getDatanodeReport(type);
     } finally {
@@ -2208,7 +2204,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
       DatanodeReportType type) throws IOException {
     checkOpen();
     TraceScope scope =
-        Trace.startSpan("datanodeStorageReport", traceSampler);
+        tracer.newScope("datanodeStorageReport");
     try {
       return namenode.getDatanodeStorageReport(type);
     } finally {
@@ -2238,7 +2234,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   public boolean setSafeMode(SafeModeAction action, boolean isChecked) throws IOException{
     TraceScope scope =
-        Trace.startSpan("setSafeMode", traceSampler);
+        tracer.newScope("setSafeMode");
     try {
       return namenode.setSafeMode(action, isChecked);
     } finally {
@@ -2257,7 +2253,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public String createSnapshot(String snapshotRoot, String snapshotName)
       throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("createSnapshot", traceSampler);
+    TraceScope scope = tracer.newScope("createSnapshot");
     try {
       return namenode.createSnapshot(snapshotRoot, snapshotName);
     } catch(RemoteException re) {
@@ -2279,7 +2275,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public void deleteSnapshot(String snapshotRoot, String snapshotName)
       throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("deleteSnapshot", traceSampler);
+    TraceScope scope = tracer.newScope("deleteSnapshot");
     try {
       namenode.deleteSnapshot(snapshotRoot, snapshotName);
     } catch(RemoteException re) {
@@ -2300,7 +2296,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public void renameSnapshot(String snapshotDir, String snapshotOldName,
       String snapshotNewName) throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("renameSnapshot", traceSampler);
+    TraceScope scope = tracer.newScope("renameSnapshot");
     try {
       namenode.renameSnapshot(snapshotDir, snapshotOldName, snapshotNewName);
     } catch(RemoteException re) {
@@ -2319,8 +2315,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public SnapshottableDirectoryStatus[] getSnapshottableDirListing()
       throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("getSnapshottableDirListing",
+    TraceScope scope = tracer.newScope("getSnapshottableDirListing");
-        traceSampler);
     try {
       return namenode.getSnapshottableDirListing();
     } catch(RemoteException re) {
@@ -2337,7 +2332,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   public void allowSnapshot(String snapshotRoot) throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("allowSnapshot", traceSampler);
+    TraceScope scope = tracer.newScope("allowSnapshot");
     try {
       namenode.allowSnapshot(snapshotRoot);
     } catch (RemoteException re) {
@@ -2354,7 +2349,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   public void disallowSnapshot(String snapshotRoot) throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("disallowSnapshot", traceSampler);
+    TraceScope scope = tracer.newScope("disallowSnapshot");
     try {
       namenode.disallowSnapshot(snapshotRoot);
     } catch (RemoteException re) {
@@ -2372,7 +2367,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public SnapshotDiffReport getSnapshotDiffReport(String snapshotDir,
       String fromSnapshot, String toSnapshot) throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("getSnapshotDiffReport", traceSampler);
+    TraceScope scope = tracer.newScope("getSnapshotDiffReport");
     try {
       return namenode.getSnapshotDiffReport(snapshotDir,
           fromSnapshot, toSnapshot);
@@ -2386,7 +2381,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public long addCacheDirective(
       CacheDirectiveInfo info, EnumSet<CacheFlag> flags) throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("addCacheDirective", traceSampler);
+    TraceScope scope = tracer.newScope("addCacheDirective");
     try {
       return namenode.addCacheDirective(info, flags);
     } catch (RemoteException re) {
@@ -2399,7 +2394,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public void modifyCacheDirective(
       CacheDirectiveInfo info, EnumSet<CacheFlag> flags) throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("modifyCacheDirective", traceSampler);
+    TraceScope scope = tracer.newScope("modifyCacheDirective");
     try {
       namenode.modifyCacheDirective(info, flags);
     } catch (RemoteException re) {
@@ -2412,7 +2407,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public void removeCacheDirective(long id)
       throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("removeCacheDirective", traceSampler);
+    TraceScope scope = tracer.newScope("removeCacheDirective");
     try {
       namenode.removeCacheDirective(id);
     } catch (RemoteException re) {
@@ -2424,12 +2419,12 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   
   public RemoteIterator<CacheDirectiveEntry> listCacheDirectives(
       CacheDirectiveInfo filter) throws IOException {
-    return new CacheDirectiveIterator(namenode, filter, traceSampler);
+    return new CacheDirectiveIterator(namenode, filter, tracer);
   }
 
   public void addCachePool(CachePoolInfo info) throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("addCachePool", traceSampler);
+    TraceScope scope = tracer.newScope("addCachePool");
     try {
       namenode.addCachePool(info);
     } catch (RemoteException re) {
@@ -2441,7 +2436,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
 
   public void modifyCachePool(CachePoolInfo info) throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("modifyCachePool", traceSampler);
+    TraceScope scope = tracer.newScope("modifyCachePool");
     try {
       namenode.modifyCachePool(info);
     } catch (RemoteException re) {
@@ -2453,7 +2448,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
 
   public void removeCachePool(String poolName) throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("removeCachePool", traceSampler);
+    TraceScope scope = tracer.newScope("removeCachePool");
     try {
       namenode.removeCachePool(poolName);
     } catch (RemoteException re) {
@@ -2464,7 +2459,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   }
 
   public RemoteIterator<CachePoolEntry> listCachePools() throws IOException {
-    return new CachePoolIterator(namenode, traceSampler);
+    return new CachePoolIterator(namenode, tracer);
   }
 
   /**
@@ -2473,7 +2468,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    * @see ClientProtocol#saveNamespace()
    */
   void saveNamespace() throws AccessControlException, IOException {
-    TraceScope scope = Trace.startSpan("saveNamespace", traceSampler);
+    TraceScope scope = tracer.newScope("saveNamespace");
     try {
       namenode.saveNamespace();
     } catch(RemoteException re) {
@@ -2490,7 +2485,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    * @see ClientProtocol#rollEdits()
    */
   long rollEdits() throws AccessControlException, IOException {
-    TraceScope scope = Trace.startSpan("rollEdits", traceSampler);
+    TraceScope scope = tracer.newScope("rollEdits");
     try {
       return namenode.rollEdits();
     } catch(RemoteException re) {
@@ -2512,7 +2507,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   boolean restoreFailedStorage(String arg)
       throws AccessControlException, IOException{
-    TraceScope scope = Trace.startSpan("restoreFailedStorage", traceSampler);
+    TraceScope scope = tracer.newScope("restoreFailedStorage");
     try {
       return namenode.restoreFailedStorage(arg);
     } finally {
@@ -2528,7 +2523,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    * @see ClientProtocol#refreshNodes()
    */
   public void refreshNodes() throws IOException {
-    TraceScope scope = Trace.startSpan("refreshNodes", traceSampler);
+    TraceScope scope = tracer.newScope("refreshNodes");
     try {
       namenode.refreshNodes();
     } finally {
@@ -2542,7 +2537,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    * @see ClientProtocol#metaSave(String)
    */
   public void metaSave(String pathname) throws IOException {
-    TraceScope scope = Trace.startSpan("metaSave", traceSampler);
+    TraceScope scope = tracer.newScope("metaSave");
     try {
       namenode.metaSave(pathname);
     } finally {
@@ -2559,7 +2554,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    * @see ClientProtocol#setBalancerBandwidth(long)
    */
   public void setBalancerBandwidth(long bandwidth) throws IOException {
-    TraceScope scope = Trace.startSpan("setBalancerBandwidth", traceSampler);
+    TraceScope scope = tracer.newScope("setBalancerBandwidth");
     try {
       namenode.setBalancerBandwidth(bandwidth);
     } finally {
@@ -2571,7 +2566,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    * @see ClientProtocol#finalizeUpgrade()
    */
   public void finalizeUpgrade() throws IOException {
-    TraceScope scope = Trace.startSpan("finalizeUpgrade", traceSampler);
+    TraceScope scope = tracer.newScope("finalizeUpgrade");
     try {
       namenode.finalizeUpgrade();
     } finally {
@@ -2580,7 +2575,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   }
 
   RollingUpgradeInfo rollingUpgrade(RollingUpgradeAction action) throws IOException {
-    TraceScope scope = Trace.startSpan("rollingUpgrade", traceSampler);
+    TraceScope scope = tracer.newScope("rollingUpgrade");
     try {
       return namenode.rollingUpgrade(action);
     } finally {
@@ -2638,7 +2633,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
     if(LOG.isDebugEnabled()) {
       LOG.debug(src + ": masked=" + absPermission);
     }
-    TraceScope scope = Trace.startSpan("mkdir", traceSampler);
+    TraceScope scope = tracer.newScope("mkdir");
     try {
       return namenode.mkdirs(src, absPermission, createParent);
     } catch(RemoteException re) {
@@ -2665,7 +2660,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    * @see ClientProtocol#getContentSummary(String)
    */
   ContentSummary getContentSummary(String src) throws IOException {
-    TraceScope scope = getPathTraceScope("getContentSummary", src);
+    TraceScope scope = newPathTraceScope("getContentSummary", src);
     try {
       return namenode.getContentSummary(src);
     } catch(RemoteException re) {
@@ -2693,7 +2688,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
                                          storagespaceQuota);
                                          
     }
-    TraceScope scope = getPathTraceScope("setQuota", src);
+    TraceScope scope = newPathTraceScope("setQuota", src);
     try {
       // Pass null as storage type for traditional namespace/storagespace quota.
       namenode.setQuota(src, namespaceQuota, storagespaceQuota, null);
@@ -2728,7 +2723,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
       throw new IllegalArgumentException("Don't support Quota for storage type : "
         + type.toString());
     }
-    TraceScope scope = getPathTraceScope("setQuotaByStorageType", src);
+    TraceScope scope = newPathTraceScope("setQuotaByStorageType", src);
     try {
       namenode.setQuota(src, HdfsConstants.QUOTA_DONT_SET, quota, type);
     } catch (RemoteException re) {
@@ -2748,7 +2743,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
    */
   public void setTimes(String src, long mtime, long atime) throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("setTimes", src);
+    TraceScope scope = newPathTraceScope("setTimes", src);
     try {
       namenode.setTimes(src, mtime, atime);
     } catch(RemoteException re) {
@@ -2809,7 +2804,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public void modifyAclEntries(String src, List<AclEntry> aclSpec)
       throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("modifyAclEntries", src);
+    TraceScope scope = newPathTraceScope("modifyAclEntries", src);
     try {
       namenode.modifyAclEntries(src, aclSpec);
     } catch(RemoteException re) {
@@ -2828,7 +2823,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public void removeAclEntries(String src, List<AclEntry> aclSpec)
       throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("removeAclEntries", traceSampler);
+    TraceScope scope = tracer.newScope("removeAclEntries");
     try {
       namenode.removeAclEntries(src, aclSpec);
     } catch(RemoteException re) {
@@ -2846,7 +2841,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
 
   public void removeDefaultAcl(String src) throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("removeDefaultAcl", traceSampler);
+    TraceScope scope = tracer.newScope("removeDefaultAcl");
     try {
       namenode.removeDefaultAcl(src);
     } catch(RemoteException re) {
@@ -2864,7 +2859,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
 
   public void removeAcl(String src) throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("removeAcl", traceSampler);
+    TraceScope scope = tracer.newScope("removeAcl");
     try {
       namenode.removeAcl(src);
     } catch(RemoteException re) {
@@ -2882,7 +2877,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
 
   public void setAcl(String src, List<AclEntry> aclSpec) throws IOException {
     checkOpen();
-    TraceScope scope = Trace.startSpan("setAcl", traceSampler);
+    TraceScope scope = tracer.newScope("setAcl");
     try {
       namenode.setAcl(src, aclSpec);
     } catch(RemoteException re) {
@@ -2900,7 +2895,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
 
   public AclStatus getAclStatus(String src) throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("getAclStatus", src);
+    TraceScope scope = newPathTraceScope("getAclStatus", src);
     try {
       return namenode.getAclStatus(src);
     } catch(RemoteException re) {
@@ -2916,7 +2911,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public void createEncryptionZone(String src, String keyName)
     throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("createEncryptionZone", src);
+    TraceScope scope = newPathTraceScope("createEncryptionZone", src);
     try {
       namenode.createEncryptionZone(src, keyName);
     } catch (RemoteException re) {
@@ -2931,7 +2926,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public EncryptionZone getEZForPath(String src)
           throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("getEZForPath", src);
+    TraceScope scope = newPathTraceScope("getEZForPath", src);
     try {
       return namenode.getEZForPath(src);
     } catch (RemoteException re) {
@@ -2945,13 +2940,13 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public RemoteIterator<EncryptionZone> listEncryptionZones()
       throws IOException {
     checkOpen();
-    return new EncryptionZoneIterator(namenode, traceSampler);
+    return new EncryptionZoneIterator(namenode, tracer);
   }
 
   public void setXAttr(String src, String name, byte[] value, 
       EnumSet<XAttrSetFlag> flag) throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("setXAttr", src);
+    TraceScope scope = newPathTraceScope("setXAttr", src);
     try {
       namenode.setXAttr(src, XAttrHelper.buildXAttr(name, value), flag);
     } catch (RemoteException re) {
@@ -2968,7 +2963,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   
   public byte[] getXAttr(String src, String name) throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("getXAttr", src);
+    TraceScope scope = newPathTraceScope("getXAttr", src);
     try {
       final List<XAttr> xAttrs = XAttrHelper.buildXAttrAsList(name);
       final List<XAttr> result = namenode.getXAttrs(src, xAttrs);
@@ -2984,7 +2979,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   
   public Map<String, byte[]> getXAttrs(String src) throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("getXAttrs", src);
+    TraceScope scope = newPathTraceScope("getXAttrs", src);
     try {
       return XAttrHelper.buildXAttrMap(namenode.getXAttrs(src, null));
     } catch(RemoteException re) {
@@ -2999,7 +2994,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public Map<String, byte[]> getXAttrs(String src, List<String> names) 
       throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("getXAttrs", src);
+    TraceScope scope = newPathTraceScope("getXAttrs", src);
     try {
       return XAttrHelper.buildXAttrMap(namenode.getXAttrs(
           src, XAttrHelper.buildXAttrs(names)));
@@ -3015,7 +3010,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   public List<String> listXAttrs(String src)
           throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("listXAttrs", src);
+    TraceScope scope = newPathTraceScope("listXAttrs", src);
     try {
       final Map<String, byte[]> xattrs =
         XAttrHelper.buildXAttrMap(namenode.listXAttrs(src));
@@ -3031,7 +3026,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
 
   public void removeXAttr(String src, String name) throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("removeXAttr", src);
+    TraceScope scope = newPathTraceScope("removeXAttr", src);
     try {
       namenode.removeXAttr(src, XAttrHelper.buildXAttr(name));
     } catch(RemoteException re) {
@@ -3048,7 +3043,7 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
 
   public void checkAccess(String src, FsAction mode) throws IOException {
     checkOpen();
-    TraceScope scope = getPathTraceScope("checkAccess", src);
+    TraceScope scope = newPathTraceScope("checkAccess", src);
     try {
       namenode.checkAccess(src, mode);
     } catch (RemoteException re) {
@@ -3061,12 +3056,13 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   }
 
   public DFSInotifyEventInputStream getInotifyEventStream() throws IOException {
-    return new DFSInotifyEventInputStream(traceSampler, namenode);
+    return new DFSInotifyEventInputStream(namenode, tracer);
   }
 
   public DFSInotifyEventInputStream getInotifyEventStream(long lastReadTxid)
       throws IOException {
-    return new DFSInotifyEventInputStream(traceSampler, namenode, lastReadTxid);
+    return new DFSInotifyEventInputStream(namenode, tracer,
+          lastReadTxid);
   }
 
   @Override // RemotePeerFactory
@@ -3176,28 +3172,26 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
     return saslClient;
   }
 
-  TraceScope getPathTraceScope(String description, String path) {
+  TraceScope newPathTraceScope(String description, String path) {
-    TraceScope scope = Trace.startSpan(description, traceSampler);
+    TraceScope scope = tracer.newScope(description);
-    Span span = scope.getSpan();
+    if (path != null) {
-    if (span != null) {
+      scope.addKVAnnotation("path", path);
-      if (path != null) {
-        span.addKVAnnotation("path", path);
-      }
     }
     return scope;
   }
 
-  TraceScope getSrcDstTraceScope(String description, String src, String dst) {
+  TraceScope newSrcDstTraceScope(String description, String src, String dst) {
-    TraceScope scope = Trace.startSpan(description, traceSampler);
+    TraceScope scope = tracer.newScope(description);
-    Span span = scope.getSpan();
+    if (src != null) {
-    if (span != null) {
+      scope.addKVAnnotation("src", src);
-      if (src != null) {
+    }
-        span.addKVAnnotation("src", src);
+    if (dst != null) {
-      }
+      scope.addKVAnnotation("dst", dst);
-      if (dst != null) {
-        span.addKVAnnotation("dst", dst);
-      }
     }
     return scope;
   }
+
+  Tracer getTracer() {
+    return tracer;
+  }
 }

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSInotifyEventInputStream.java

@@ -26,9 +26,8 @@ import org.apache.hadoop.hdfs.inotify.EventBatchList;
 import org.apache.hadoop.hdfs.inotify.MissingEventsException;
 import org.apache.hadoop.hdfs.protocol.ClientProtocol;
 import org.apache.hadoop.util.Time;
-import org.apache.htrace.Sampler;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.Tracer;
-import org.apache.htrace.TraceScope;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -47,11 +46,6 @@ public class DFSInotifyEventInputStream {
   public static final Logger LOG = LoggerFactory.getLogger(
       DFSInotifyEventInputStream.class);
 
-  /**
-   * The trace sampler to use when making RPCs to the NameNode.
-   */
-  private final Sampler<?> traceSampler;
-
   private final ClientProtocol namenode;
   private Iterator<EventBatch> it;
   private long lastReadTxid;
@@ -65,20 +59,22 @@ public class DFSInotifyEventInputStream {
    */
   private Random rng = new Random();
 
+  private final Tracer tracer;
+
   private static final int INITIAL_WAIT_MS = 10;
 
-  DFSInotifyEventInputStream(Sampler<?> traceSampler, ClientProtocol namenode)
+  DFSInotifyEventInputStream(ClientProtocol namenode, Tracer tracer)
         throws IOException {
     // Only consider new transaction IDs.
-    this(traceSampler, namenode, namenode.getCurrentEditLogTxid());
+    this(namenode, tracer, namenode.getCurrentEditLogTxid());
   }
 
-  DFSInotifyEventInputStream(Sampler traceSampler, ClientProtocol namenode,
+  DFSInotifyEventInputStream(ClientProtocol namenode,
-        long lastReadTxid) throws IOException {
+        Tracer tracer, long lastReadTxid) throws IOException {
-    this.traceSampler = traceSampler;
     this.namenode = namenode;
     this.it = Iterators.emptyIterator();
     this.lastReadTxid = lastReadTxid;
+    this.tracer = tracer;
   }
 
   /**
@@ -98,8 +94,7 @@ public class DFSInotifyEventInputStream {
    * The next available batch of events will be returned.
    */
   public EventBatch poll() throws IOException, MissingEventsException {
-    TraceScope scope =
+    TraceScope scope = tracer.newScope("inotifyPoll");
-        Trace.startSpan("inotifyPoll", traceSampler);
     try {
       // need to keep retrying until the NN sends us the latest committed txid
       if (lastReadTxid == -1) {
@@ -180,7 +175,7 @@ public class DFSInotifyEventInputStream {
    */
   public EventBatch poll(long time, TimeUnit tu) throws IOException,
       InterruptedException, MissingEventsException {
-    TraceScope scope = Trace.startSpan("inotifyPollWithTimeout", traceSampler);
+    TraceScope scope = tracer.newScope("inotifyPollWithTimeout");
     EventBatch next = null;
     try {
       long initialTime = Time.monotonicNow();
@@ -217,7 +212,7 @@ public class DFSInotifyEventInputStream {
    */
   public EventBatch take() throws IOException, InterruptedException,
       MissingEventsException {
-    TraceScope scope = Trace.startSpan("inotifyTake", traceSampler);
+    TraceScope scope = tracer.newScope("inotifyTake");
     EventBatch next = null;
     try {
       int nextWaitMin = INITIAL_WAIT_MS;

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

@@ -55,6 +55,7 @@ import org.apache.hadoop.fs.CanUnbuffer;
 import org.apache.hadoop.fs.ChecksumException;
 import org.apache.hadoop.fs.FSInputStream;
 import org.apache.hadoop.fs.FileEncryptionInfo;
+import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.HasEnhancedByteBufferAccess;
 import org.apache.hadoop.fs.ReadOption;
 import org.apache.hadoop.fs.StorageType;
@@ -78,9 +79,9 @@ import org.apache.hadoop.net.NetUtils;
 import org.apache.hadoop.security.token.SecretManager.InvalidToken;
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.util.IdentityHashStore;
-import org.apache.htrace.Span;
+import org.apache.htrace.core.SpanId;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.TraceScope;
+import org.apache.htrace.core.Tracer;
 
 import com.google.common.annotations.VisibleForTesting;
 
@@ -678,6 +679,7 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
         setClientCacheContext(dfsClient.getClientContext()).
         setUserGroupInformation(dfsClient.ugi).
         setConfiguration(dfsClient.getConfiguration()).
+        setTracer(dfsClient.getTracer()).
         build();
   }
 
@@ -941,7 +943,7 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
   public synchronized int read(final byte buf[], int off, int len) throws IOException {
     ReaderStrategy byteArrayReader = new ByteArrayStrategy(buf);
     TraceScope scope =
-        dfsClient.getPathTraceScope("DFSInputStream#byteArrayRead", src);
+        dfsClient.newPathTraceScope("DFSInputStream#byteArrayRead", src);
     try {
       return readWithStrategy(byteArrayReader, off, len);
     } finally {
@@ -953,7 +955,7 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
   public synchronized int read(final ByteBuffer buf) throws IOException {
     ReaderStrategy byteBufferReader = new ByteBufferStrategy(buf);
     TraceScope scope =
-        dfsClient.getPathTraceScope("DFSInputStream#byteBufferRead", src);
+        dfsClient.newPathTraceScope("DFSInputStream#byteBufferRead", src);
     try {
       return readWithStrategy(byteBufferReader, 0, buf.remaining());
     } finally {
@@ -1120,14 +1122,14 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
       final ByteBuffer bb,
       final Map<ExtendedBlock, Set<DatanodeInfo>> corruptedBlockMap,
       final int hedgedReadId) {
-    final Span parentSpan = Trace.currentSpan();
+    final SpanId parentSpanId = Tracer.getCurrentSpanId();
     return new Callable<ByteBuffer>() {
       @Override
       public ByteBuffer call() throws Exception {
         byte[] buf = bb.array();
         int offset = bb.position();
-        TraceScope scope =
+        TraceScope scope = dfsClient.getTracer().
-            Trace.startSpan("hedgedRead" + hedgedReadId, parentSpan);
+            newScope("hedgedRead" + hedgedReadId, parentSpanId);
         try {
           actualGetFromOneDataNode(datanode, block, start, end, buf,
               offset, corruptedBlockMap);
@@ -1449,8 +1451,8 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
   @Override
   public int read(long position, byte[] buffer, int offset, int length)
       throws IOException {
-    TraceScope scope =
+    TraceScope scope = dfsClient.
-        dfsClient.getPathTraceScope("DFSInputStream#byteArrayPread", src);
+        newPathTraceScope("DFSInputStream#byteArrayPread", src);
     try {
       return pread(position, buffer, offset, length);
     } finally {

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSOutputStream.java

@@ -32,6 +32,7 @@ import org.apache.hadoop.fs.CreateFlag;
 import org.apache.hadoop.fs.FSOutputSummer;
 import org.apache.hadoop.fs.FileAlreadyExistsException;
 import org.apache.hadoop.fs.FileEncryptionInfo;
+import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.ParentNotDirectoryException;
 import org.apache.hadoop.fs.Syncable;
 import org.apache.hadoop.fs.permission.FsPermission;
@@ -62,9 +63,7 @@ import org.apache.hadoop.util.DataChecksum;
 import org.apache.hadoop.util.DataChecksum.Type;
 import org.apache.hadoop.util.Progressable;
 import org.apache.hadoop.util.Time;
-import org.apache.htrace.Sampler;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.Trace;
-import org.apache.htrace.TraceScope;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -227,7 +226,7 @@ public class DFSOutputStream extends FSOutputSummer
       short replication, long blockSize, Progressable progress, int buffersize,
       DataChecksum checksum, String[] favoredNodes) throws IOException {
     TraceScope scope =
-        dfsClient.getPathTraceScope("newStreamForCreate", src);
+        dfsClient.newPathTraceScope("newStreamForCreate", src);
     try {
       HdfsFileStatus stat = null;
 
@@ -350,7 +349,7 @@ public class DFSOutputStream extends FSOutputSummer
       LocatedBlock lastBlock, HdfsFileStatus stat, DataChecksum checksum,
       String[] favoredNodes) throws IOException {
     TraceScope scope =
-        dfsClient.getPathTraceScope("newStreamForAppend", src);
+        dfsClient.newPathTraceScope("newStreamForAppend", src);
     try {
       final DFSOutputStream out = new DFSOutputStream(dfsClient, src, flags,
           progress, lastBlock, stat, checksum, favoredNodes);
@@ -375,7 +374,7 @@ public class DFSOutputStream extends FSOutputSummer
   }
 
   protected TraceScope createWriteTraceScope() {
-    return dfsClient.getPathTraceScope("DFSOutputStream#write", src);
+    return dfsClient.newPathTraceScope("DFSOutputStream#write", src);
   }
 
   // @see FSOutputSummer#writeChunk()
@@ -495,7 +494,7 @@ public class DFSOutputStream extends FSOutputSummer
   @Override
   public void hflush() throws IOException {
     TraceScope scope =
-        dfsClient.getPathTraceScope("hflush", src);
+        dfsClient.newPathTraceScope("hflush", src);
     try {
       flushOrSync(false, EnumSet.noneOf(SyncFlag.class));
     } finally {
@@ -506,7 +505,7 @@ public class DFSOutputStream extends FSOutputSummer
   @Override
   public void hsync() throws IOException {
     TraceScope scope =
-        dfsClient.getPathTraceScope("hsync", src);
+        dfsClient.newPathTraceScope("hsync", src);
     try {
       flushOrSync(true, EnumSet.noneOf(SyncFlag.class));
     } finally {
@@ -529,7 +528,7 @@ public class DFSOutputStream extends FSOutputSummer
    */
   public void hsync(EnumSet<SyncFlag> syncFlags) throws IOException {
     TraceScope scope =
-        dfsClient.getPathTraceScope("hsync", src);
+        dfsClient.newPathTraceScope("hsync", src);
     try {
       flushOrSync(true, syncFlags);
     } finally {
@@ -770,7 +769,7 @@ public class DFSOutputStream extends FSOutputSummer
   @Override
   public synchronized void close() throws IOException {
     TraceScope scope =
-        dfsClient.getPathTraceScope("DFSOutputStream#close", src);
+        dfsClient.newPathTraceScope("DFSOutputStream#close", src);
     try {
       closeImpl();
     } finally {
@@ -799,7 +798,7 @@ public class DFSOutputStream extends FSOutputSummer
       // get last block before destroying the streamer
       ExtendedBlock lastBlock = getStreamer().getBlock();
       closeThreads(false);
-      TraceScope scope = Trace.startSpan("completeFile", Sampler.NEVER);
+      TraceScope scope = dfsClient.getTracer().newScope("completeFile");
       try {
         completeFile(lastBlock);
       } finally {

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSPacket.java

@@ -27,7 +27,9 @@ import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.protocol.datatransfer.PacketHeader;
 import org.apache.hadoop.hdfs.util.ByteArrayManager;
-import org.apache.htrace.Span;
+import org.apache.htrace.core.Span;
+import org.apache.htrace.core.SpanId;
+import org.apache.htrace.core.TraceScope;
 
 /****************************************************************
  * DFSPacket is used by DataStreamer and DFSOutputStream.
@@ -38,7 +40,7 @@ import org.apache.htrace.Span;
 @InterfaceAudience.Private
 class DFSPacket {
   public static final long HEART_BEAT_SEQNO = -1L;
-  private static long[] EMPTY = new long[0];
+  private static SpanId[] EMPTY = new SpanId[0];
   private final long seqno; // sequence number of buffer in block
   private final long offsetInBlock; // offset in block
   private boolean syncBlock; // this packet forces the current block to disk
@@ -65,9 +67,9 @@ class DFSPacket {
   private int checksumPos;
   private final int dataStart;
   private int dataPos;
-  private long[] traceParents = EMPTY;
+  private SpanId[] traceParents = EMPTY;
   private int traceParentsUsed;
-  private Span span;
+  private TraceScope scope;
 
   /**
    * Create a new packet.
@@ -293,7 +295,10 @@ class DFSPacket {
     addTraceParent(span.getSpanId());
   }
 
-  public void addTraceParent(long id) {
+  public void addTraceParent(SpanId id) {
+    if (!id.isValid()) {
+      return;
+    }
     if (traceParentsUsed == traceParents.length) {
       int newLength = (traceParents.length == 0) ? 8 :
           traceParents.length * 2;
@@ -310,18 +315,18 @@ class DFSPacket {
    *
    * Protected by the DFSOutputStream dataQueue lock.
    */
-  public long[] getTraceParents() {
+  public SpanId[] getTraceParents() {
     // Remove duplicates from the array.
     int len = traceParentsUsed;
     Arrays.sort(traceParents, 0, len);
     int i = 0, j = 0;
-    long prevVal = 0; // 0 is not a valid span id
+    SpanId prevVal = SpanId.INVALID;
     while (true) {
       if (i == len) {
         break;
       }
-      long val = traceParents[i];
+      SpanId val = traceParents[i];
-      if (val != prevVal) {
+      if (!val.equals(prevVal)) {
         traceParents[j] = val;
         j++;
         prevVal = val;
@@ -335,11 +340,11 @@ class DFSPacket {
     return traceParents;
   }
 
-  public void setTraceSpan(Span span) {
+  public void setTraceScope(TraceScope scope) {
-    this.span = span;
+    this.scope = scope;
   }
 
-  public Span getTraceSpan() {
+  public TraceScope getTraceScope() {
-    return span;
+    return scope;
   }
 }

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DataStreamer.java

@@ -41,6 +41,7 @@ import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 
 import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.StorageType;
 import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys.BlockWrite;
 import org.apache.hadoop.hdfs.client.impl.DfsClientConf;
@@ -79,12 +80,11 @@ import org.apache.hadoop.util.Daemon;
 import org.apache.hadoop.util.DataChecksum;
 import org.apache.hadoop.util.Progressable;
 import org.apache.hadoop.util.Time;
-import org.apache.htrace.NullScope;
+import org.apache.htrace.core.Sampler;
-import org.apache.htrace.Sampler;
+import org.apache.htrace.core.Span;
-import org.apache.htrace.Span;
+import org.apache.htrace.core.SpanId;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.TraceInfo;
+import org.apache.htrace.core.Tracer;
-import org.apache.htrace.TraceScope;
 
 import com.google.common.cache.CacheBuilder;
 import com.google.common.cache.CacheLoader;
@@ -505,7 +505,7 @@ class DataStreamer extends Daemon {
   @Override
   public void run() {
     long lastPacket = Time.monotonicNow();
-    TraceScope scope = NullScope.INSTANCE;
+    TraceScope scope = null;
     while (!streamerClosed && dfsClient.clientRunning) {
       // if the Responder encountered an error, shutdown Responder
       if (errorState.hasError() && response != null) {
@@ -556,12 +556,11 @@ class DataStreamer extends Daemon {
               LOG.warn("Caught exception", e);
             }
             one = dataQueue.getFirst(); // regular data packet
-            long parents[] = one.getTraceParents();
+            SpanId[] parents = one.getTraceParents();
             if (parents.length > 0) {
-              scope = Trace.startSpan("dataStreamer", new TraceInfo(0, parents[0]));
+              scope = dfsClient.getTracer().
-              // TODO: use setParents API once it's available from HTrace 3.2
+                  newScope("dataStreamer", parents[0]);
-              // scope = Trace.startSpan("dataStreamer", Sampler.ALWAYS);
+              scope.getSpan().setParents(parents);
-              // scope.getSpan().setParents(parents);
             }
           }
         }
@@ -612,12 +611,16 @@ class DataStreamer extends Daemon {
         }
 
         // send the packet
-        Span span = null;
+        SpanId spanId = SpanId.INVALID;
         synchronized (dataQueue) {
           // move packet from dataQueue to ackQueue
           if (!one.isHeartbeatPacket()) {
-            span = scope.detach();
+            if (scope != null) {
-            one.setTraceSpan(span);
+              spanId = scope.getSpanId();
+              scope.detach();
+              one.setTraceScope(scope);
+            }
+            scope = null;
             dataQueue.removeFirst();
             ackQueue.addLast(one);
             dataQueue.notifyAll();
@@ -630,7 +633,8 @@ class DataStreamer extends Daemon {
         }
 
         // write out data to remote datanode
-        TraceScope writeScope = Trace.startSpan("writeTo", span);
+        TraceScope writeScope = dfsClient.getTracer().
+            newScope("DataStreamer#writeTo", spanId);
         try {
           one.writeTo(blockStream);
           blockStream.flush();
@@ -697,7 +701,10 @@ class DataStreamer extends Daemon {
           streamerClosed = true;
         }
       } finally {
-        scope.close();
+        if (scope != null) {
+          scope.close();
+          scope = null;
+        }
       }
     }
     closeInternal();
@@ -731,7 +738,8 @@ class DataStreamer extends Daemon {
    * @throws IOException
    */
   void waitForAckedSeqno(long seqno) throws IOException {
-    TraceScope scope = Trace.startSpan("waitForAckedSeqno", Sampler.NEVER);
+    TraceScope scope = dfsClient.getTracer().
+        newScope("waitForAckedSeqno");
     try {
       if (LOG.isDebugEnabled()) {
         LOG.debug("Waiting for ack for: " + seqno);
@@ -781,7 +789,7 @@ class DataStreamer extends Daemon {
           while (!streamerClosed && dataQueue.size() + ackQueue.size() >
               dfsClient.getConf().getWriteMaxPackets()) {
             if (firstWait) {
-              Span span = Trace.currentSpan();
+              Span span = Tracer.getCurrentSpan();
               if (span != null) {
                 span.addTimelineAnnotation("dataQueue.wait");
               }
@@ -802,7 +810,7 @@ class DataStreamer extends Daemon {
             }
           }
         } finally {
-          Span span = Trace.currentSpan();
+          Span span = Tracer.getCurrentSpan();
           if ((span != null) && (!firstWait)) {
             span.addTimelineAnnotation("end.wait");
           }
@@ -934,7 +942,7 @@ class DataStreamer extends Daemon {
       setName("ResponseProcessor for block " + block);
       PipelineAck ack = new PipelineAck();
 
-      TraceScope scope = NullScope.INSTANCE;
+      TraceScope scope = null;
       while (!responderClosed && dfsClient.clientRunning && !isLastPacketInBlock) {
         // process responses from datanodes.
         try {
@@ -1021,8 +1029,11 @@ class DataStreamer extends Daemon {
           block.setNumBytes(one.getLastByteOffsetBlock());
 
           synchronized (dataQueue) {
-            scope = Trace.continueSpan(one.getTraceSpan());
+            scope = one.getTraceScope();
-            one.setTraceSpan(null);
+            if (scope != null) {
+              scope.reattach();
+              one.setTraceScope(null);
+            }
             lastAckedSeqno = seqno;
             ackQueue.removeFirst();
             dataQueue.notifyAll();
@@ -1043,7 +1054,10 @@ class DataStreamer extends Daemon {
             responderClosed = true;
           }
         } finally {
+          if (scope != null) {
             scope.close();
+          }
+          scope = null;
         }
       }
     }
@@ -1109,11 +1123,12 @@ class DataStreamer extends Daemon {
         // a client waiting on close() will be aware that the flush finished.
         synchronized (dataQueue) {
           DFSPacket endOfBlockPacket = dataQueue.remove();  // remove the end of block packet
-          Span span = endOfBlockPacket.getTraceSpan();
+          // Close any trace span associated with this Packet
-          if (span != null) {
+          TraceScope scope = endOfBlockPacket.getTraceScope();
-            // Close any trace span associated with this Packet
+          if (scope != null) {
-            TraceScope scope = Trace.continueSpan(span);
+            scope.reattach();
             scope.close();
+            endOfBlockPacket.setTraceScope(null);
           }
           assert endOfBlockPacket.isLastPacketInBlock();
           assert lastAckedSeqno == endOfBlockPacket.getSeqno() - 1;
@@ -1741,7 +1756,7 @@ class DataStreamer extends Daemon {
   void queuePacket(DFSPacket packet) {
     synchronized (dataQueue) {
       if (packet == null) return;
-      packet.addTraceParent(Trace.currentSpan());
+      packet.addTraceParent(Tracer.getCurrentSpanId());
       dataQueue.addLast(packet);
       lastQueuedSeqno = packet.getSeqno();
       if (LOG.isDebugEnabled()) {

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/RemoteBlockReader.java

@@ -47,9 +47,8 @@ import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.net.NetUtils;
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.util.DataChecksum;
-import org.apache.htrace.Sampler;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.Tracer;
-import org.apache.htrace.TraceScope;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -106,6 +105,8 @@ public class RemoteBlockReader extends FSInputChecker implements BlockReader {
   int dataLeft = 0;
   
   private final PeerCache peerCache;
+
+  private final Tracer tracer;
   
   /* FSInputChecker interface */
   
@@ -210,9 +211,8 @@ public class RemoteBlockReader extends FSInputChecker implements BlockReader {
   protected synchronized int readChunk(long pos, byte[] buf, int offset, 
                                        int len, byte[] checksumBuf) 
                                        throws IOException {
-    TraceScope scope =
+    TraceScope scope = tracer.
-        Trace.startSpan("RemoteBlockReader#readChunk(" + blockId + ")",
+        newScope("RemoteBlockReader#readChunk(" + blockId + ")");
-            Sampler.NEVER);
     try {
       return readChunkImpl(pos, buf, offset, len, checksumBuf);
     } finally {
@@ -346,7 +346,7 @@ public class RemoteBlockReader extends FSInputChecker implements BlockReader {
   private RemoteBlockReader(String file, String bpid, long blockId,
       DataInputStream in, DataChecksum checksum, boolean verifyChecksum,
       long startOffset, long firstChunkOffset, long bytesToRead, Peer peer,
-      DatanodeID datanodeID, PeerCache peerCache) {
+      DatanodeID datanodeID, PeerCache peerCache, Tracer tracer) {
     // Path is used only for printing block and file information in debug
     super(new Path("/" + Block.BLOCK_FILE_PREFIX + blockId +
                     ":" + bpid + ":of:"+ file)/*too non path-like?*/,
@@ -378,6 +378,7 @@ public class RemoteBlockReader extends FSInputChecker implements BlockReader {
     bytesPerChecksum = this.checksum.getBytesPerChecksum();
     checksumSize = this.checksum.getChecksumSize();
     this.peerCache = peerCache;
+    this.tracer = tracer;
   }
 
   /**
@@ -402,7 +403,8 @@ public class RemoteBlockReader extends FSInputChecker implements BlockReader {
                                      String clientName, Peer peer,
                                      DatanodeID datanodeID,
                                      PeerCache peerCache,
-                                     CachingStrategy cachingStrategy)
+                                     CachingStrategy cachingStrategy,
+                                     Tracer tracer)
                                        throws IOException {
     // in and out will be closed when sock is closed (by the caller)
     final DataOutputStream out =
@@ -438,7 +440,7 @@ public class RemoteBlockReader extends FSInputChecker implements BlockReader {
 
     return new RemoteBlockReader(file, block.getBlockPoolId(), block.getBlockId(),
         in, checksum, verifyChecksum, startOffset, firstChunkOffset, len,
-        peer, datanodeID, peerCache);
+        peer, datanodeID, peerCache, tracer);
   }
 
   @Override

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/RemoteBlockReader2.java

@@ -48,12 +48,11 @@ import org.apache.hadoop.hdfs.shortcircuit.ClientMmap;
 import org.apache.hadoop.net.NetUtils;
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.util.DataChecksum;
-import org.apache.htrace.Sampler;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.Trace;
-import org.apache.htrace.TraceScope;
 
 import com.google.common.annotations.VisibleForTesting;
 
+import org.apache.htrace.core.Tracer;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -126,6 +125,8 @@ public class RemoteBlockReader2  implements BlockReader {
 
   private boolean sentStatusCode = false;
 
+  private final Tracer tracer;
+
   @VisibleForTesting
   public Peer getPeer() {
     return peer;
@@ -144,8 +145,8 @@ public class RemoteBlockReader2  implements BlockReader {
     }
 
     if (curDataSlice == null || curDataSlice.remaining() == 0 && bytesNeededToFinish > 0) {
-      TraceScope scope = Trace.startSpan(
+      TraceScope scope = tracer.newScope(
-          "RemoteBlockReader2#readNextPacket(" + blockId + ")", Sampler.NEVER);
+          "RemoteBlockReader2#readNextPacket(" + blockId + ")");
       try {
         readNextPacket();
       } finally {
@@ -172,8 +173,8 @@ public class RemoteBlockReader2  implements BlockReader {
   @Override
   public synchronized int read(ByteBuffer buf) throws IOException {
     if (curDataSlice == null || curDataSlice.remaining() == 0 && bytesNeededToFinish > 0) {
-      TraceScope scope = Trace.startSpan(
+      TraceScope scope = tracer.newScope(
-          "RemoteBlockReader2#readNextPacket(" + blockId + ")", Sampler.NEVER);
+          "RemoteBlockReader2#readNextPacket(" + blockId + ")");
       try {
         readNextPacket();
       } finally {
@@ -292,7 +293,7 @@ public class RemoteBlockReader2  implements BlockReader {
   protected RemoteBlockReader2(String file, String bpid, long blockId,
       DataChecksum checksum, boolean verifyChecksum,
       long startOffset, long firstChunkOffset, long bytesToRead, Peer peer,
-      DatanodeID datanodeID, PeerCache peerCache) {
+      DatanodeID datanodeID, PeerCache peerCache, Tracer tracer) {
     this.isLocal = DFSUtilClient.isLocalAddress(NetUtils.
         createSocketAddr(datanodeID.getXferAddr()));
     // Path is used only for printing block and file information in debug
@@ -313,6 +314,7 @@ public class RemoteBlockReader2  implements BlockReader {
     this.bytesNeededToFinish = bytesToRead + (startOffset - firstChunkOffset);
     bytesPerChecksum = this.checksum.getBytesPerChecksum();
     checksumSize = this.checksum.getChecksumSize();
+    this.tracer = tracer;
   }
 
 
@@ -407,7 +409,8 @@ public class RemoteBlockReader2  implements BlockReader {
                                      String clientName,
                                      Peer peer, DatanodeID datanodeID,
                                      PeerCache peerCache,
-                                     CachingStrategy cachingStrategy) throws IOException {
+                                     CachingStrategy cachingStrategy,
+                                     Tracer tracer) throws IOException {
     // in and out will be closed when sock is closed (by the caller)
     final DataOutputStream out = new DataOutputStream(new BufferedOutputStream(
           peer.getOutputStream()));
@@ -440,7 +443,7 @@ public class RemoteBlockReader2  implements BlockReader {
 
     return new RemoteBlockReader2(file, block.getBlockPoolId(), block.getBlockId(),
         checksum, verifyChecksum, startOffset, firstChunkOffset, len, peer,
-        datanodeID, peerCache);
+        datanodeID, peerCache, tracer);
   }
 
   static void checkSuccess(

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocol/CacheDirectiveIterator.java

@@ -25,11 +25,10 @@ import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.fs.BatchedRemoteIterator;
 import org.apache.hadoop.fs.InvalidRequestException;
 import org.apache.hadoop.ipc.RemoteException;
-import org.apache.htrace.Sampler;
-import org.apache.htrace.Trace;
-import org.apache.htrace.TraceScope;
 
 import com.google.common.base.Preconditions;
+import org.apache.htrace.core.TraceScope;
+import org.apache.htrace.core.Tracer;
 
 /**
  * CacheDirectiveIterator is a remote iterator that iterates cache directives.
@@ -42,14 +41,14 @@ public class CacheDirectiveIterator
 
   private CacheDirectiveInfo filter;
   private final ClientProtocol namenode;
-  private final Sampler<?> traceSampler;
+  private final Tracer tracer;
 
   public CacheDirectiveIterator(ClientProtocol namenode,
-      CacheDirectiveInfo filter, Sampler<?> traceSampler) {
+      CacheDirectiveInfo filter, Tracer tracer) {
     super(0L);
     this.namenode = namenode;
     this.filter = filter;
-    this.traceSampler = traceSampler;
+    this.tracer = tracer;
   }
 
   private static CacheDirectiveInfo removeIdFromFilter(CacheDirectiveInfo filter) {
@@ -94,7 +93,7 @@ public class CacheDirectiveIterator
   public BatchedEntries<CacheDirectiveEntry> makeRequest(Long prevKey)
       throws IOException {
     BatchedEntries<CacheDirectiveEntry> entries = null;
-    TraceScope scope = Trace.startSpan("listCacheDirectives", traceSampler);
+    TraceScope scope = tracer.newScope("listCacheDirectives");
     try {
       entries = namenode.listCacheDirectives(prevKey, filter);
     } catch (IOException e) {

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocol/CachePoolIterator.java

@@ -23,9 +23,8 @@ import java.io.IOException;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.fs.BatchedRemoteIterator;
-import org.apache.htrace.Sampler;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.Tracer;
-import org.apache.htrace.TraceScope;
 
 /**
  * CachePoolIterator is a remote iterator that iterates cache pools.
@@ -37,18 +36,18 @@ public class CachePoolIterator
     extends BatchedRemoteIterator<String, CachePoolEntry> {
 
   private final ClientProtocol namenode;
-  private final Sampler traceSampler;
+  private final Tracer tracer;
 
-  public CachePoolIterator(ClientProtocol namenode, Sampler traceSampler) {
+  public CachePoolIterator(ClientProtocol namenode, Tracer tracer) {
     super("");
     this.namenode = namenode;
-    this.traceSampler = traceSampler;
+    this.tracer = tracer;
   }
 
   @Override
   public BatchedEntries<CachePoolEntry> makeRequest(String prevKey)
       throws IOException {
-    TraceScope scope = Trace.startSpan("listCachePools", traceSampler);
+    TraceScope scope = tracer.newScope("listCachePools");
     try {
       return namenode.listCachePools(prevKey);
     } finally {

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocol/EncryptionZoneIterator.java

@@ -23,9 +23,8 @@ import java.io.IOException;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.fs.BatchedRemoteIterator;
-import org.apache.htrace.Sampler;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.Tracer;
-import org.apache.htrace.TraceScope;
 
 /**
  * EncryptionZoneIterator is a remote iterator that iterates over encryption
@@ -37,19 +36,18 @@ public class EncryptionZoneIterator
     extends BatchedRemoteIterator<Long, EncryptionZone> {
 
   private final ClientProtocol namenode;
-  private final Sampler<?> traceSampler;
+  private final Tracer tracer;
 
-  public EncryptionZoneIterator(ClientProtocol namenode,
+  public EncryptionZoneIterator(ClientProtocol namenode, Tracer tracer) {
-                                Sampler<?> traceSampler) {
     super(Long.valueOf(0));
     this.namenode = namenode;
-    this.traceSampler = traceSampler;
+    this.tracer = tracer;
   }
 
   @Override
   public BatchedEntries<EncryptionZone> makeRequest(Long prevId)
       throws IOException {
-    TraceScope scope = Trace.startSpan("listEncryptionZones", traceSampler);
+    TraceScope scope = tracer.newScope("listEncryptionZones");
     try {
       return namenode.listEncryptionZones(prevId);
     } finally {

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocol/datatransfer/DataTransferProtoUtil.java

@@ -35,10 +35,8 @@ import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier;
 import org.apache.hadoop.hdfs.security.token.block.InvalidBlockTokenException;
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.util.DataChecksum;
-import org.apache.htrace.Span;
+import org.apache.htrace.core.SpanId;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.Tracer;
-import org.apache.htrace.TraceInfo;
-import org.apache.htrace.TraceScope;
 
 /**
  * Static utilities for dealing with the protocol buffers used by the
@@ -89,39 +87,21 @@ public abstract class DataTransferProtoUtil {
     BaseHeaderProto.Builder builder =  BaseHeaderProto.newBuilder()
       .setBlock(PBHelperClient.convert(blk))
       .setToken(PBHelperClient.convert(blockToken));
-    if (Trace.isTracing()) {
+    SpanId spanId = Tracer.getCurrentSpanId();
-      Span s = Trace.currentSpan();
+    if (spanId.isValid()) {
       builder.setTraceInfo(DataTransferTraceInfoProto.newBuilder()
-          .setTraceId(s.getTraceId())
+          .setTraceId(spanId.getHigh())
-          .setParentId(s.getSpanId()));
+          .setParentId(spanId.getLow()));
     }
     return builder.build();
   }
 
-  public static TraceInfo fromProto(DataTransferTraceInfoProto proto) {
+  public static SpanId fromProto(DataTransferTraceInfoProto proto) {
-    if (proto == null) return null;
+    if ((proto != null) && proto.hasTraceId() &&
-    if (!proto.hasTraceId()) return null;
+          proto.hasParentId()) {
-    return new TraceInfo(proto.getTraceId(), proto.getParentId());
+      return new SpanId(proto.getTraceId(), proto.getParentId());
-  }
-
-  public static TraceScope continueTraceSpan(ClientOperationHeaderProto header,
-      String description) {
-    return continueTraceSpan(header.getBaseHeader(), description);
-  }
-
-  public static TraceScope continueTraceSpan(BaseHeaderProto header,
-      String description) {
-    return continueTraceSpan(header.getTraceInfo(), description);
-  }
-
-  public static TraceScope continueTraceSpan(DataTransferTraceInfoProto proto,
-      String description) {
-    TraceScope scope = null;
-    TraceInfo info = fromProto(proto);
-    if (info != null) {
-      scope = Trace.startSpan(description, info);
     }
-    return scope;
+    return null;
   }
 
   public static void checkBlockOpStatus(

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocol/datatransfer/Sender.java

@@ -48,8 +48,8 @@ import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitShm.SlotId;
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.util.DataChecksum;
 
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.SpanId;
-import org.apache.htrace.Span;
+import org.apache.htrace.core.Tracer;
 
 import com.google.protobuf.Message;
 
@@ -200,10 +200,11 @@ public class Sender implements DataTransferProtocol {
     ReleaseShortCircuitAccessRequestProto.Builder builder =
         ReleaseShortCircuitAccessRequestProto.newBuilder().
         setSlotId(PBHelperClient.convert(slotId));
-    if (Trace.isTracing()) {
+    SpanId spanId = Tracer.getCurrentSpanId();
-      Span s = Trace.currentSpan();
+    if (spanId.isValid()) {
-      builder.setTraceInfo(DataTransferTraceInfoProto.newBuilder()
+      builder.setTraceInfo(DataTransferTraceInfoProto.newBuilder().
-          .setTraceId(s.getTraceId()).setParentId(s.getSpanId()));
+          setTraceId(spanId.getHigh()).
+          setParentId(spanId.getLow()));
     }
     ReleaseShortCircuitAccessRequestProto proto = builder.build();
     send(out, Op.RELEASE_SHORT_CIRCUIT_FDS, proto);
@@ -214,10 +215,11 @@ public class Sender implements DataTransferProtocol {
     ShortCircuitShmRequestProto.Builder builder =
         ShortCircuitShmRequestProto.newBuilder().
         setClientName(clientName);
-    if (Trace.isTracing()) {
+    SpanId spanId = Tracer.getCurrentSpanId();
-      Span s = Trace.currentSpan();
+    if (spanId.isValid()) {
-      builder.setTraceInfo(DataTransferTraceInfoProto.newBuilder()
+      builder.setTraceInfo(DataTransferTraceInfoProto.newBuilder().
-          .setTraceId(s.getTraceId()).setParentId(s.getSpanId()));
+          setTraceId(spanId.getHigh()).
+          setParentId(spanId.getLow()));
     }
     ShortCircuitShmRequestProto proto = builder.build();
     send(out, Op.REQUEST_SHORT_CIRCUIT_SHM, proto);

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -638,6 +638,8 @@ Release 2.8.0 - UNRELEASED
     HDFS-8740. Move DistributedFileSystem to hadoop-hdfs-client. (Mingliang Liu
     via wheat9)
 
+    HDFS-9080. Update htrace version to 4.0.1 (cmccabe)
+
   OPTIMIZATIONS
 
     HDFS-8026. Trace FSOutputSummer#writeChecksumChunks rather than

hadoop-hdfs-project/hadoop-hdfs/pom.xml

@@ -192,7 +192,7 @@ http://maven.apache.org/xsd/maven-4.0.0.xsd">
     </dependency>
     <dependency>
       <groupId>org.apache.htrace</groupId>
-      <artifactId>htrace-core</artifactId>
+      <artifactId>htrace-core4</artifactId>
     </dependency>
     <dependency>
       <groupId>org.apache.hadoop</groupId>

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

@@ -64,12 +64,8 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
   public static final String DFS_WEBHDFS_ACL_PERMISSION_PATTERN_DEFAULT =
       HdfsClientConfigKeys.DFS_WEBHDFS_ACL_PERMISSION_PATTERN_DEFAULT;
 
-  // HDFS HTrace configuration is controlled by dfs.htrace.spanreceiver.classes,
+  public static final String DFS_CLIENT_HTRACE_SAMPLER_CLASSES =
-  // etc.
+      "dfs.client.htrace.sampler.classes";
-  public static final String  DFS_SERVER_HTRACE_PREFIX = "dfs.htrace.";
-  @Deprecated
-  public static final String  DFS_CLIENT_HTRACE_PREFIX =
-      HdfsClientConfigKeys.DFS_CLIENT_HTRACE_PREFIX;
 
   // HA related configuration
   public static final String  DFS_DATANODE_RESTART_REPLICA_EXPIRY_KEY = "dfs.datanode.restart.replica.expiration";

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/datatransfer/Receiver.java

@@ -18,7 +18,6 @@
 package org.apache.hadoop.hdfs.protocol.datatransfer;
 
 import static org.apache.hadoop.hdfs.protocol.datatransfer.DataTransferProtoUtil.fromProto;
-import static org.apache.hadoop.hdfs.protocol.datatransfer.DataTransferProtoUtil.continueTraceSpan;
 import static org.apache.hadoop.hdfs.protocolPB.PBHelperClient.vintPrefixed;
 
 import java.io.DataInputStream;
@@ -27,7 +26,10 @@ import java.io.IOException;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
+import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.BaseHeaderProto;
 import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.CachingStrategyProto;
+import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.ClientOperationHeaderProto;
+import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.DataTransferTraceInfoProto;
 import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.OpBlockChecksumProto;
 import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.OpCopyBlockProto;
 import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.OpReadBlockProto;
@@ -40,14 +42,21 @@ import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.ShortCircuitShmR
 import org.apache.hadoop.hdfs.protocolPB.PBHelperClient;
 import org.apache.hadoop.hdfs.server.datanode.CachingStrategy;
 import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitShm.SlotId;
-import org.apache.htrace.TraceScope;
+import org.apache.htrace.core.SpanId;
+import org.apache.htrace.core.TraceScope;
+import org.apache.htrace.core.Tracer;
 
 /** Receiver */
 @InterfaceAudience.Private
 @InterfaceStability.Evolving
 public abstract class Receiver implements DataTransferProtocol {
+  private final Tracer tracer;
   protected DataInputStream in;
-  
+
+  protected Receiver(Tracer tracer) {
+    this.tracer = tracer;
+  }
+
   /** Initialize a receiver for DataTransferProtocol with a socket. */
   protected void initialize(final DataInputStream in) {
     this.in = in;
@@ -64,6 +73,26 @@ public abstract class Receiver implements DataTransferProtocol {
     return Op.read(in);
   }
 
+  private TraceScope continueTraceSpan(DataTransferTraceInfoProto proto,
+                                       String description) {
+    TraceScope scope = null;
+    SpanId spanId = fromProto(proto);
+    if (spanId != null) {
+      scope = tracer.newScope(description, spanId);
+    }
+    return scope;
+  }
+
+  private TraceScope continueTraceSpan(ClientOperationHeaderProto header,
+                                             String description) {
+    return continueTraceSpan(header.getBaseHeader(), description);
+  }
+
+  private TraceScope continueTraceSpan(BaseHeaderProto header,
+                                             String description) {
+    return continueTraceSpan(header.getTraceInfo(), description);
+  }
+
   /** Process op by the corresponding method. */
   protected final void processOp(Op op) throws IOException {
     switch(op) {

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/qjournal/server/JournalNode.java

@@ -43,10 +43,12 @@ import org.apache.hadoop.metrics2.lib.DefaultMetricsSystem;
 import org.apache.hadoop.metrics2.source.JvmMetrics;
 import org.apache.hadoop.metrics2.util.MBeans;
 import org.apache.hadoop.security.SecurityUtil;
+import org.apache.hadoop.tracing.TraceUtils;
 import org.apache.hadoop.util.DiskChecker;
 import org.apache.hadoop.util.StringUtils;
 import org.apache.hadoop.util.Tool;
 import org.apache.hadoop.util.ToolRunner;
+import org.apache.htrace.core.Tracer;
 import org.mortbay.util.ajax.JSON;
 
 import com.google.common.base.Preconditions;
@@ -69,6 +71,7 @@ public class JournalNode implements Tool, Configurable, JournalNodeMXBean {
   private ObjectName journalNodeInfoBeanName;
   private String httpServerURI;
   private File localDir;
+  Tracer tracer;
 
   static {
     HdfsConfiguration.init();
@@ -105,6 +108,11 @@ public class JournalNode implements Tool, Configurable, JournalNodeMXBean {
     this.localDir = new File(
         conf.get(DFSConfigKeys.DFS_JOURNALNODE_EDITS_DIR_KEY,
         DFSConfigKeys.DFS_JOURNALNODE_EDITS_DIR_DEFAULT).trim());
+    if (this.tracer == null) {
+      this.tracer = new Tracer.Builder("JournalNode").
+          conf(TraceUtils.wrapHadoopConf("journalnode.htrace", conf)).
+          build();
+    }
   }
 
   private static void validateAndCreateJournalDir(File dir) throws IOException {
@@ -203,6 +211,10 @@ public class JournalNode implements Tool, Configurable, JournalNodeMXBean {
       MBeans.unregister(journalNodeInfoBeanName);
       journalNodeInfoBeanName = null;
     }
+    if (tracer != null) {
+      tracer.close();
+      tracer = null;
+    }
   }
 
   /**
@@ -326,5 +338,4 @@ public class JournalNode implements Tool, Configurable, JournalNodeMXBean {
   public Long getJournalCTime(String journalId) throws IOException {
     return getOrCreateJournal(journalId).getJournalCTime();
   }
-
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/qjournal/server/JournalNodeRpcServer.java

@@ -85,6 +85,7 @@ class JournalNodeRpcServer implements QJournalProtocol {
       CommonConfigurationKeys.HADOOP_SECURITY_AUTHORIZATION, false)) {
           server.refreshServiceAcl(confCopy, new HDFSPolicyProvider());
     }
+    this.server.setTracer(jn.tracer);
   }
 
   void start() {

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

@@ -47,9 +47,8 @@ import org.apache.hadoop.io.ReadaheadPool.ReadaheadRequest;
 import org.apache.hadoop.io.nativeio.NativeIO;
 import org.apache.hadoop.net.SocketOutputStream;
 import org.apache.hadoop.util.DataChecksum;
-import org.apache.htrace.Sampler;
+import org.apache.htrace.core.Sampler;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.TraceScope;
 
 import static org.apache.hadoop.io.nativeio.NativeIO.POSIX.POSIX_FADV_DONTNEED;
 import static org.apache.hadoop.io.nativeio.NativeIO.POSIX.POSIX_FADV_SEQUENTIAL;
@@ -708,8 +707,8 @@ class BlockSender implements java.io.Closeable {
    */
   long sendBlock(DataOutputStream out, OutputStream baseStream, 
                  DataTransferThrottler throttler) throws IOException {
-    TraceScope scope =
+    TraceScope scope = datanode.tracer.
-        Trace.startSpan("sendBlock_" + block.getBlockId(), Sampler.NEVER);
+        newScope("sendBlock_" + block.getBlockId());
     try {
       return doSendBlock(out, baseStream, throttler);
     } finally {

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

@@ -189,12 +189,13 @@ import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.security.UserGroupInformation.AuthenticationMethod;
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.security.token.TokenIdentifier;
-import org.apache.hadoop.tracing.SpanReceiverHost;
 import org.apache.hadoop.tracing.SpanReceiverInfo;
 import org.apache.hadoop.tracing.TraceAdminPB.TraceAdminService;
 import org.apache.hadoop.tracing.TraceAdminProtocol;
 import org.apache.hadoop.tracing.TraceAdminProtocolPB;
 import org.apache.hadoop.tracing.TraceAdminProtocolServerSideTranslatorPB;
+import org.apache.hadoop.tracing.TraceUtils;
+import org.apache.hadoop.tracing.TracerConfigurationManager;
 import org.apache.hadoop.util.Daemon;
 import org.apache.hadoop.util.DiskChecker;
 import org.apache.hadoop.util.DiskChecker.DiskErrorException;
@@ -204,6 +205,7 @@ import org.apache.hadoop.util.ServicePlugin;
 import org.apache.hadoop.util.StringUtils;
 import org.apache.hadoop.util.Time;
 import org.apache.hadoop.util.VersionInfo;
+import org.apache.htrace.core.Tracer;
 import org.mortbay.util.ajax.JSON;
 
 import com.google.common.annotations.VisibleForTesting;
@@ -288,6 +290,8 @@ public class DataNode extends ReconfigurableBase
 
   public static final Log METRICS_LOG = LogFactory.getLog("DataNodeMetricsLog");
 
+  private static final String DATANODE_HTRACE_PREFIX = "datanode.htrace.";
+
   /**
    * Use {@link NetUtils#createSocketAddr(String)} instead.
    */
@@ -368,11 +372,18 @@ public class DataNode extends ReconfigurableBase
   private boolean isPermissionEnabled;
   private String dnUserName = null;
 
-  private SpanReceiverHost spanReceiverHost;
+  final Tracer tracer;
+  private final TracerConfigurationManager tracerConfigurationManager;
   private static final int NUM_CORES = Runtime.getRuntime()
       .availableProcessors();
   private static final double CONGESTION_RATIO = 1.5;
 
+  private static Tracer createTracer(Configuration conf) {
+    return new Tracer.Builder("DataNode").
+        conf(TraceUtils.wrapHadoopConf(DATANODE_HTRACE_PREFIX , conf)).
+        build();
+  }
+
   private long[] oobTimeouts; /** timeout value of each OOB type */
 
   private ScheduledThreadPoolExecutor metricsLoggerTimer;
@@ -385,6 +396,9 @@ public class DataNode extends ReconfigurableBase
   DataNode(final Configuration conf) {
     super(conf);
     this.blockScanner = new BlockScanner(this, conf);
+    this.tracer = createTracer(conf);
+    this.tracerConfigurationManager =
+        new TracerConfigurationManager(DATANODE_HTRACE_PREFIX, conf);
     this.fileDescriptorPassingDisabledReason = null;
     this.maxNumberOfBlocksToLog = 0;
     this.confVersion = null;
@@ -405,6 +419,9 @@ public class DataNode extends ReconfigurableBase
            final List<StorageLocation> dataDirs,
            final SecureResources resources) throws IOException {
     super(conf);
+    this.tracer = createTracer(conf);
+    this.tracerConfigurationManager =
+        new TracerConfigurationManager(DATANODE_HTRACE_PREFIX, conf);
     this.blockScanner = new BlockScanner(this, conf);
     this.lastDiskErrorCheck = 0;
     this.maxNumberOfBlocksToLog = conf.getLong(DFS_MAX_NUM_BLOCKS_TO_LOG_KEY,
@@ -1144,9 +1161,6 @@ public class DataNode extends ReconfigurableBase
     this.dnConf = new DNConf(conf);
     checkSecureConfig(dnConf, conf, resources);
 
-    this.spanReceiverHost =
-      SpanReceiverHost.get(conf, DFSConfigKeys.DFS_SERVER_HTRACE_PREFIX);
-
     if (dnConf.maxLockedMemory > 0) {
       if (!NativeIO.POSIX.getCacheManipulator().verifyCanMlock()) {
         throw new RuntimeException(String.format(
@@ -1851,9 +1865,6 @@ public class DataNode extends ReconfigurableBase
       MBeans.unregister(dataNodeInfoBeanName);
       dataNodeInfoBeanName = null;
     }
-    if (this.spanReceiverHost != null) {
-      this.spanReceiverHost.closeReceivers();
-    }
     if (shortCircuitRegistry != null) shortCircuitRegistry.shutdown();
     LOG.info("Shutdown complete.");
     synchronized(this) {
@@ -1862,6 +1873,7 @@ public class DataNode extends ReconfigurableBase
       // Notify the main thread.
       notifyAll();
     }
+    tracer.close();
   }
   
   
@@ -2294,6 +2306,7 @@ public class DataNode extends ReconfigurableBase
     if (localDataXceiverServer != null) {
       localDataXceiverServer.start();
     }
+    ipcServer.setTracer(tracer);
     ipcServer.start();
     startPlugins(conf);
   }
@@ -3283,19 +3296,19 @@ public class DataNode extends ReconfigurableBase
   @Override
   public SpanReceiverInfo[] listSpanReceivers() throws IOException {
     checkSuperuserPrivilege();
-    return spanReceiverHost.listSpanReceivers();
+    return tracerConfigurationManager.listSpanReceivers();
   }
 
   @Override
   public long addSpanReceiver(SpanReceiverInfo info) throws IOException {
     checkSuperuserPrivilege();
-    return spanReceiverHost.addSpanReceiver(info);
+    return tracerConfigurationManager.addSpanReceiver(info);
   }
 
   @Override
   public void removeSpanReceiver(long id) throws IOException {
     checkSuperuserPrivilege();
-    spanReceiverHost.removeSpanReceiver(id);
+    tracerConfigurationManager.removeSpanReceiver(id);
   }
 
   /**

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

@@ -126,7 +126,7 @@ class DataXceiver extends Receiver implements Runnable {
   
   private DataXceiver(Peer peer, DataNode datanode,
       DataXceiverServer dataXceiverServer) throws IOException {
-
+    super(datanode.tracer);
     this.peer = peer;
     this.dnConf = datanode.getDnConf();
     this.socketIn = peer.getInputStream();

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

@@ -71,12 +71,14 @@ import org.apache.hadoop.security.SecurityUtil;
 import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.security.authorize.RefreshAuthorizationPolicyProtocol;
 import org.apache.hadoop.tools.GetUserMappingsProtocol;
-import org.apache.hadoop.tracing.SpanReceiverHost;
 import org.apache.hadoop.tracing.TraceAdminProtocol;
+import org.apache.hadoop.tracing.TraceUtils;
+import org.apache.hadoop.tracing.TracerConfigurationManager;
 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;
+import org.apache.htrace.core.Tracer;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -318,6 +320,8 @@ public class NameNode implements NameNodeStatusMXBean {
   public static final HAState ACTIVE_STATE = new ActiveState();
   public static final HAState STANDBY_STATE = new StandbyState();
 
+  private static final String NAMENODE_HTRACE_PREFIX = "namenode.htrace.";
+
   public static final Log MetricsLog =
       LogFactory.getLog("NameNodeMetricsLog");
 
@@ -345,7 +349,8 @@ public class NameNode implements NameNodeStatusMXBean {
 
   private JvmPauseMonitor pauseMonitor;
   private ObjectName nameNodeStatusBeanName;
-  SpanReceiverHost spanReceiverHost;
+  protected final Tracer tracer;
+  protected final TracerConfigurationManager tracerConfigurationManager;
   ScheduledThreadPoolExecutor metricsLoggerTimer;
 
   /**
@@ -620,9 +625,6 @@ public class NameNode implements NameNodeStatusMXBean {
       startHttpServer(conf);
     }
 
-    this.spanReceiverHost =
-      SpanReceiverHost.get(conf, DFSConfigKeys.DFS_SERVER_HTRACE_PREFIX);
-
     loadNamesystem(conf);
 
     rpcServer = createRpcServer(conf);
@@ -812,8 +814,13 @@ public class NameNode implements NameNodeStatusMXBean {
     this(conf, NamenodeRole.NAMENODE);
   }
 
-  protected NameNode(Configuration conf, NamenodeRole role) 
+  protected NameNode(Configuration conf, NamenodeRole role)
-      throws IOException { 
+      throws IOException {
+    this.tracer = new Tracer.Builder("NameNode").
+        conf(TraceUtils.wrapHadoopConf(NAMENODE_HTRACE_PREFIX, conf)).
+        build();
+    this.tracerConfigurationManager =
+        new TracerConfigurationManager(NAMENODE_HTRACE_PREFIX, conf);
     this.conf = conf;
     this.role = role;
     setClientNamenodeAddress(conf);
@@ -896,10 +903,8 @@ public class NameNode implements NameNodeStatusMXBean {
         MBeans.unregister(nameNodeStatusBeanName);
         nameNodeStatusBeanName = null;
       }
-      if (this.spanReceiverHost != null) {
-        this.spanReceiverHost.closeReceivers();
-      }
     }
+    tracer.close();
   }
 
   synchronized boolean isStopRequested() {

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

@@ -412,6 +412,10 @@ class NameNodeRpcServer implements NamenodeProtocols {
         FSLimitException.PathComponentTooLongException.class,
         FSLimitException.MaxDirectoryItemsExceededException.class,
         UnresolvedPathException.class);
+    clientRpcServer.setTracer(nn.tracer);
+    if (serviceRpcServer != null) {
+      clientRpcServer.setTracer(nn.tracer);
+    }
  }
 
   /** Allow access to the client RPC server for testing */
@@ -2019,20 +2023,20 @@ class NameNodeRpcServer implements NamenodeProtocols {
   public SpanReceiverInfo[] listSpanReceivers() throws IOException {
     checkNNStartup();
     namesystem.checkSuperuserPrivilege();
-    return nn.spanReceiverHost.listSpanReceivers();
+    return nn.tracerConfigurationManager.listSpanReceivers();
   }
 
   @Override // TraceAdminProtocol
   public long addSpanReceiver(SpanReceiverInfo info) throws IOException {
     checkNNStartup();
     namesystem.checkSuperuserPrivilege();
-    return nn.spanReceiverHost.addSpanReceiver(info);
+    return nn.tracerConfigurationManager.addSpanReceiver(info);
   }
 
   @Override // TraceAdminProtocol
   public void removeSpanReceiver(long id) throws IOException {
     checkNNStartup();
     namesystem.checkSuperuserPrivilege();
-    nn.spanReceiverHost.removeSpanReceiver(id);
+    nn.tracerConfigurationManager.removeSpanReceiver(id);
   }
 }

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

@@ -81,6 +81,7 @@ import org.apache.hadoop.security.AccessControlException;
 import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.util.Time;
+import org.apache.htrace.core.Tracer;
 
 import com.google.common.annotations.VisibleForTesting;
 
@@ -136,6 +137,8 @@ public class NamenodeFsck implements DataEncryptionKeyFactory {
 
   private boolean showReplicaDetails = false;
   private long staleInterval;
+  private Tracer tracer;
+
   /**
    * True if we encountered an internal error during FSCK, such as not being
    * able to delete a corrupt file.
@@ -198,6 +201,7 @@ public class NamenodeFsck implements DataEncryptionKeyFactory {
     this.staleInterval =
         conf.getLong(DFSConfigKeys.DFS_NAMENODE_STALE_DATANODE_INTERVAL_KEY,
           DFSConfigKeys.DFS_NAMENODE_STALE_DATANODE_INTERVAL_DEFAULT);
+    this.tracer = new Tracer.Builder("NamenodeFsck").build();
 
     for (Iterator<String> it = pmap.keySet().iterator(); it.hasNext();) {
       String key = it.next();
@@ -850,6 +854,7 @@ public class NamenodeFsck implements DataEncryptionKeyFactory {
             setCachingStrategy(CachingStrategy.newDropBehind()).
             setClientCacheContext(dfs.getClientContext()).
             setConfiguration(namenode.conf).
+            setTracer(tracer).
             setRemotePeerFactory(new RemotePeerFactory() {
               @Override
               public Peer newConnectedPeer(InetSocketAddress addr,

hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml

@@ -2440,19 +2440,10 @@
 </property>
 
 <property>
-  <name>dfs.htrace.spanreceiver.classes</name>
+  <name>dfs.client.htrace.sampler.classes</name>
   <value></value>
   <description>
-    The class name of the HTrace SpanReceiver for the NameNode and DataNode.
+    The class names of the HTrace Samplers to use for the HDFS client.
-  </description>
-</property>
-
-<property>
-  <name>dfs.client.htrace.spanreceiver.classes</name>
-  <value></value>
-  <description>
-    The class name of the HTrace SpanReceiver for the HDFS client. You do not
-    need to enable this if your client program has been modified to use HTrace.
   </description>
 </property>
 

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

@@ -30,6 +30,7 @@ import java.util.Random;
 
 import org.apache.commons.io.IOUtils;
 import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.FsTracer;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.net.Peer;
 import org.apache.hadoop.hdfs.protocol.DatanodeID;
@@ -192,6 +193,7 @@ public class BlockReaderTestUtil {
       setCachingStrategy(CachingStrategy.newDefaultStrategy()).
       setConfiguration(fs.getConf()).
       setAllowShortCircuitLocalReads(true).
+      setTracer(FsTracer.get(fs.getConf())).
       setRemotePeerFactory(new RemotePeerFactory() {
         @Override
         public Peer newConnectedPeer(InetSocketAddress addr,

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

@@ -41,6 +41,7 @@ import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitCache;
 import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitReplica;
 import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitShm;
 import org.apache.hadoop.hdfs.shortcircuit.ShortCircuitShm.ShmId;
+import org.apache.hadoop.fs.FsTracer;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.net.unix.DomainSocket;
 import org.apache.hadoop.net.unix.TemporarySocketDirectory;
@@ -195,6 +196,7 @@ public class TestBlockReaderLocal {
           setShortCircuitReplica(replica).
           setCachingStrategy(new CachingStrategy(false, readahead)).
           setVerifyChecksum(checksum).
+          setTracer(FsTracer.get(conf)).
           build();
       dataIn = null;
       metaIn = null;

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

@@ -27,6 +27,7 @@ import java.util.concurrent.atomic.AtomicReference;
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FSDataOutputStream;
+import org.apache.hadoop.fs.FsTracer;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.DataStreamer.LastExceptionInStreamer;
 import org.apache.hadoop.hdfs.client.impl.DfsClientConf;
@@ -34,6 +35,7 @@ import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
 import org.apache.hadoop.hdfs.protocol.datatransfer.BlockConstructionStage;
+import org.apache.htrace.core.SpanId;
 import org.junit.AfterClass;
 import org.junit.Assert;
 import org.junit.BeforeClass;
@@ -119,6 +121,7 @@ public class TestDFSOutputStream {
     DfsClientConf dfsClientConf = mock(DfsClientConf.class);
     DFSClient client = mock(DFSClient.class);
     when(client.getConf()).thenReturn(dfsClientConf);
+    when(client.getTracer()).thenReturn(FsTracer.get(new Configuration()));
     client.clientRunning = true;
     DataStreamer stream = new DataStreamer(
         mock(HdfsFileStatus.class),
@@ -139,7 +142,7 @@ public class TestDFSOutputStream {
         Whitebox.getInternalState(stream, "congestedNodes");
     congestedNodes.add(mock(DatanodeInfo.class));
     DFSPacket packet = mock(DFSPacket.class);
-    when(packet.getTraceParents()).thenReturn(new long[] {});
+    when(packet.getTraceParents()).thenReturn(new SpanId[] {});
     dataQueue.add(packet);
     stream.run();
     Assert.assertTrue(congestedNodes.isEmpty());

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

@@ -20,6 +20,7 @@ package org.apache.hadoop.hdfs;
 import java.util.Random;
 import org.apache.hadoop.hdfs.protocol.datatransfer.PacketHeader;
 import org.apache.hadoop.io.DataOutputBuffer;
+import org.apache.htrace.core.SpanId;
 import org.junit.Assert;
 import org.junit.Test;
 
@@ -70,24 +71,24 @@ public class TestDFSPacket {
   public void testAddParentsGetParents() throws Exception {
     DFSPacket p = new DFSPacket(null, maxChunksPerPacket,
                                 0, 0, checksumSize, false);
-    long parents[] = p.getTraceParents();
+    SpanId parents[] = p.getTraceParents();
     Assert.assertEquals(0, parents.length);
-    p.addTraceParent(123);
+    p.addTraceParent(new SpanId(0, 123));
-    p.addTraceParent(123);
+    p.addTraceParent(new SpanId(0, 123));
     parents = p.getTraceParents();
     Assert.assertEquals(1, parents.length);
-    Assert.assertEquals(123, parents[0]);
+    Assert.assertEquals(new SpanId(0, 123), parents[0]);
     parents = p.getTraceParents(); // test calling 'get' again.
     Assert.assertEquals(1, parents.length);
-    Assert.assertEquals(123, parents[0]);
+    Assert.assertEquals(new SpanId(0, 123), parents[0]);
-    p.addTraceParent(1);
+    p.addTraceParent(new SpanId(0, 1));
-    p.addTraceParent(456);
+    p.addTraceParent(new SpanId(0, 456));
-    p.addTraceParent(789);
+    p.addTraceParent(new SpanId(0, 789));
     parents = p.getTraceParents();
     Assert.assertEquals(4, parents.length);
-    Assert.assertEquals(1, parents[0]);
+    Assert.assertEquals(new SpanId(0, 1), parents[0]);
-    Assert.assertEquals(123, parents[1]);
+    Assert.assertEquals(new SpanId(0, 123), parents[1]);
-    Assert.assertEquals(456, parents[2]);
+    Assert.assertEquals(new SpanId(0, 456), parents[2]);
-    Assert.assertEquals(789, parents[3]);
+    Assert.assertEquals(new SpanId(0, 789), parents[3]);
   }
 }

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

@@ -50,6 +50,7 @@ import org.apache.hadoop.fs.CacheFlag;
 import org.apache.hadoop.fs.FileStatus;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.FileSystemTestHelper;
+import org.apache.hadoop.fs.FsTracer;
 import org.apache.hadoop.fs.InvalidRequestException;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.fs.RemoteIterator;
@@ -89,7 +90,6 @@ import org.apache.hadoop.util.GSet;
 import org.apache.log4j.Level;
 import org.apache.log4j.LogManager;
 import org.apache.log4j.Logger;
-import org.apache.htrace.Sampler;
 import org.junit.After;
 import org.junit.Assert;
 import org.junit.Before;
@@ -910,7 +910,7 @@ public class TestCacheDirectives {
 
     // Uncache and check each path in sequence
     RemoteIterator<CacheDirectiveEntry> entries =
-      new CacheDirectiveIterator(nnRpc, null, Sampler.NEVER);
+      new CacheDirectiveIterator(nnRpc, null, FsTracer.get(conf));
     for (int i=0; i<numFiles; i++) {
       CacheDirectiveEntry entry = entries.next();
       nnRpc.removeCacheDirective(entry.getInfo().getId());

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

@@ -387,6 +387,7 @@ public class TestFsck {
 
       // Copy the non-corrupt blocks of corruptFileName to lost+found.
       outStr = runFsck(conf, 1, false, "/", "-move");
+      FSImage.LOG.info("WATERMELON: outStr = " + outStr);
       assertTrue(outStr.contains(NamenodeFsck.CORRUPT_STATUS));
 
       // Make sure that we properly copied the block files from the DataNodes

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/tools/TestHdfsConfigFields.java

@@ -77,8 +77,8 @@ public class TestHdfsConfigFields extends TestConfigurationFieldsBase {
     // Some properties have moved to HdfsClientConfigKeys
     xmlPropsToSkipCompare.add("dfs.client.short.circuit.replica.stale.threshold.ms");
 
-    // Ignore SpanReceiveHost properties
+    // Ignore HTrace properties
-    xmlPropsToSkipCompare.add("dfs.htrace.spanreceiver.classes");
+    xmlPropsToSkipCompare.add("fs.client.htrace");
-    xmlPropsToSkipCompare.add("dfs.client.htrace.spanreceiver.classes");
+    xmlPropsToSkipCompare.add("hadoop.htrace");
   }
 }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/tracing/TestTraceAdmin.java

@@ -21,6 +21,7 @@ import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.apache.hadoop.net.unix.TemporarySocketDirectory;
+import org.apache.htrace.core.Tracer;
 import org.junit.Assert;
 import org.junit.Test;
 
@@ -58,8 +59,8 @@ public class TestTraceAdmin {
   public void testCreateAndDestroySpanReceiver() throws Exception {
     Configuration conf = new Configuration();
     conf = new Configuration();
-    conf.set(DFSConfigKeys.DFS_SERVER_HTRACE_PREFIX  +
+    conf.set(TraceUtils.DEFAULT_HADOOP_PREFIX +
-        SpanReceiverHost.SPAN_RECEIVERS_CONF_SUFFIX, "");
+        Tracer.SPAN_RECEIVER_CLASSES_KEY, "");
     MiniDFSCluster cluster =
         new MiniDFSCluster.Builder(conf).numDataNodes(3).build();
     cluster.waitActive();
@@ -74,12 +75,12 @@ public class TestTraceAdmin {
       Assert.assertEquals("ret:0, Added trace span receiver 1 with " +
           "configuration dfs.htrace.local-file-span-receiver.path = " + tracePath + NEWLINE,
           runTraceCommand(trace, "-add", "-host", getHostPortForNN(cluster),
-              "-class", "org.apache.htrace.impl.LocalFileSpanReceiver",
+              "-class", "org.apache.htrace.core.LocalFileSpanReceiver",
               "-Cdfs.htrace.local-file-span-receiver.path=" + tracePath));
       String list =
           runTraceCommand(trace, "-list", "-host", getHostPortForNN(cluster));
       Assert.assertTrue(list.startsWith("ret:0"));
-      Assert.assertTrue(list.contains("1   org.apache.htrace.impl.LocalFileSpanReceiver"));
+      Assert.assertTrue(list.contains("1   org.apache.htrace.core.LocalFileSpanReceiver"));
       Assert.assertEquals("ret:0, Removed trace span receiver 1" + NEWLINE,
           runTraceCommand(trace, "-remove", "1", "-host",
               getHostPortForNN(cluster)));

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/tracing/TestTracing.java

@@ -17,50 +17,72 @@
  */
 package org.apache.hadoop.tracing;
 
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.List;
+import java.util.Map;
 import org.apache.commons.lang.RandomStringUtils;
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.CommonConfigurationKeys;
 import org.apache.hadoop.fs.FSDataInputStream;
 import org.apache.hadoop.fs.FSDataOutputStream;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.FsTracer;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.DistributedFileSystem;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys;
-import org.apache.htrace.Sampler;
+import org.apache.htrace.core.Sampler;
-import org.apache.htrace.Span;
+import org.apache.htrace.core.Span;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.TraceScope;
+import org.apache.htrace.core.Tracer;
 import org.junit.After;
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.BeforeClass;
 import org.junit.Test;
-import java.io.IOException;
-import java.nio.ByteBuffer;
-import java.util.List;
-import java.util.Map;
 
 public class TestTracing {
-
-  private static Configuration conf;
   private static MiniDFSCluster cluster;
   private static DistributedFileSystem dfs;
 
+  private Tracer prevTracer;
+
+  private final static Configuration TRACING_CONF;
+  private final static Configuration NO_TRACING_CONF;
+
+  static {
+    NO_TRACING_CONF = new Configuration();
+    NO_TRACING_CONF.setLong("dfs.blocksize", 100 * 1024);
+
+    TRACING_CONF = new Configuration(NO_TRACING_CONF);
+    TRACING_CONF.set(CommonConfigurationKeys.FS_CLIENT_HTRACE_PREFIX +
+        Tracer.SPAN_RECEIVER_CLASSES_KEY,
+        SetSpanReceiver.class.getName());
+    TRACING_CONF.set(CommonConfigurationKeys.FS_CLIENT_HTRACE_PREFIX +
+        Tracer.SAMPLER_CLASSES_KEY, "AlwaysSampler");
+  }
+
   @Test
   public void testTracing() throws Exception {
     // write and read without tracing started
     String fileName = "testTracingDisabled.dat";
     writeTestFile(fileName);
-    Assert.assertTrue(SetSpanReceiver.size() == 0);
+    Assert.assertEquals(0, SetSpanReceiver.size());
     readTestFile(fileName);
-    Assert.assertTrue(SetSpanReceiver.size() == 0);
+    Assert.assertEquals(0, SetSpanReceiver.size());
 
-    writeWithTracing();
+    writeTestFile("testReadTraceHooks.dat");
-    readWithTracing();
+
+    FsTracer.clear();
+    Tracer tracer = FsTracer.get(TRACING_CONF);
+    writeWithTracing(tracer);
+    readWithTracing(tracer);
   }
 
-  public void writeWithTracing() throws Exception {
+  private void writeWithTracing(Tracer tracer) throws Exception {
     long startTime = System.currentTimeMillis();
-    TraceScope ts = Trace.startSpan("testWriteTraceHooks", Sampler.ALWAYS);
+    TraceScope ts = tracer.newScope("testWriteTraceHooks");
     writeTestFile("testWriteTraceHooks.dat");
     long endTime = System.currentTimeMillis();
     ts.close();
@@ -107,7 +129,8 @@ public class TestTracing {
     };
     for (String desc : spansInTopTrace) {
       for (Span span : map.get(desc)) {
-        Assert.assertEquals(ts.getSpan().getTraceId(), span.getTraceId());
+        Assert.assertEquals(ts.getSpan().getSpanId().getHigh(),
+                            span.getSpanId().getHigh());
       }
     }
 
@@ -120,12 +143,10 @@ public class TestTracing {
     SetSpanReceiver.clear();
   }
 
-  public void readWithTracing() throws Exception {
+  private void readWithTracing(Tracer tracer) throws Exception {
-    String fileName = "testReadTraceHooks.dat";
-    writeTestFile(fileName);
     long startTime = System.currentTimeMillis();
-    TraceScope ts = Trace.startSpan("testReadTraceHooks", Sampler.ALWAYS);
+    TraceScope ts = tracer.newScope("testReadTraceHooks");
-    readTestFile(fileName);
+    readTestFile("testReadTraceHooks.dat");
     ts.close();
     long endTime = System.currentTimeMillis();
 
@@ -150,7 +171,11 @@ public class TestTracing {
     // There should only be one trace id as it should all be homed in the
     // top trace.
     for (Span span : SetSpanReceiver.getSpans()) {
-      Assert.assertEquals(ts.getSpan().getTraceId(), span.getTraceId());
+      System.out.println(span.toJson());
+    }
+    for (Span span : SetSpanReceiver.getSpans()) {
+      Assert.assertEquals(ts.getSpan().getSpanId().getHigh(),
+                          span.getSpanId().getHigh());
     }
     SetSpanReceiver.clear();
   }
@@ -185,18 +210,9 @@ public class TestTracing {
     }
   }
 
-  @BeforeClass
-  public static void setup() throws IOException {
-    conf = new Configuration();
-    conf.setLong("dfs.blocksize", 100 * 1024);
-    conf.set(HdfsClientConfigKeys.DFS_CLIENT_HTRACE_PREFIX +
-        SpanReceiverHost.SPAN_RECEIVERS_CONF_SUFFIX,
-        SetSpanReceiver.class.getName());
-  }
-
   @Before
   public void startCluster() throws IOException {
-    cluster = new MiniDFSCluster.Builder(conf)
+    cluster = new MiniDFSCluster.Builder(NO_TRACING_CONF)
         .numDataNodes(3)
         .build();
     cluster.waitActive();
@@ -207,6 +223,6 @@ public class TestTracing {
   @After
   public void shutDown() throws IOException {
     cluster.shutdown();
+    FsTracer.clear();
   }
-
 }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/tracing/TestTracingShortCircuitLocalRead.java

@@ -23,6 +23,8 @@ import java.io.IOException;
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FSDataInputStream;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.FsTracer;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DFSTestUtil;
@@ -33,9 +35,8 @@ import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.net.unix.DomainSocket;
 import org.apache.hadoop.net.unix.TemporarySocketDirectory;
 import org.apache.hadoop.util.NativeCodeLoader;
-import org.apache.htrace.Sampler;
+import org.apache.htrace.core.TraceScope;
-import org.apache.htrace.Trace;
+import org.apache.htrace.core.Tracer;
-import org.apache.htrace.TraceScope;
 import org.junit.AfterClass;
 import org.junit.BeforeClass;
 import org.junit.Test;
@@ -44,7 +45,6 @@ public class TestTracingShortCircuitLocalRead {
   private static Configuration conf;
   private static MiniDFSCluster cluster;
   private static DistributedFileSystem dfs;
-  private static SpanReceiverHost spanReceiverHost;
   private static TemporarySocketDirectory sockDir;
   static final Path TEST_PATH = new Path("testShortCircuitTraceHooks");
   static final int TEST_LENGTH = 1234;
@@ -64,9 +64,12 @@ public class TestTracingShortCircuitLocalRead {
   public void testShortCircuitTraceHooks() throws IOException {
     assumeTrue(NativeCodeLoader.isNativeCodeLoaded() && !Path.WINDOWS);
     conf = new Configuration();
-    conf.set(HdfsClientConfigKeys.DFS_CLIENT_HTRACE_PREFIX +
+    conf.set(TraceUtils.DEFAULT_HADOOP_PREFIX +
-        SpanReceiverHost.SPAN_RECEIVERS_CONF_SUFFIX,
+            Tracer.SPAN_RECEIVER_CLASSES_KEY,
         SetSpanReceiver.class.getName());
+    conf.set(TraceUtils.DEFAULT_HADOOP_PREFIX +
+            Tracer.SAMPLER_CLASSES_KEY,
+        "AlwaysSampler");
     conf.setLong("dfs.blocksize", 100 * 1024);
     conf.setBoolean(HdfsClientConfigKeys.Read.ShortCircuit.KEY, true);
     conf.setBoolean(HdfsClientConfigKeys.Read.ShortCircuit.SKIP_CHECKSUM_KEY, false);
@@ -81,7 +84,8 @@ public class TestTracingShortCircuitLocalRead {
     try {
       DFSTestUtil.createFile(dfs, TEST_PATH, TEST_LENGTH, (short)1, 5678L);
 
-      TraceScope ts = Trace.startSpan("testShortCircuitTraceHooks", Sampler.ALWAYS);
+      TraceScope ts = FsTracer.get(conf).
+          newScope("testShortCircuitTraceHooks");
       FSDataInputStream stream = dfs.open(TEST_PATH);
       byte buf[] = new byte[TEST_LENGTH];
       IOUtils.readFully(stream, buf, 0, TEST_LENGTH);

hadoop-project/pom.xml

@@ -806,8 +806,8 @@
       </dependency>
       <dependency>
         <groupId>org.apache.htrace</groupId>
-        <artifactId>htrace-core</artifactId>
+        <artifactId>htrace-core4</artifactId>
-        <version>3.2.0-incubating</version>
+        <version>4.0.1-incubating</version>
       </dependency>
       <dependency>
         <groupId>org.jdom</groupId>