HDFS-6956. Allow dynamically changing the tracing level in Hadoop servers (cmccabe)

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

@@ -296,6 +296,10 @@
       <!-- protobuf generated code -->
       <Class name="~org\.apache\.hadoop\.ipc\.proto\.GenericRefreshProtocolProtos.*"/>
     </Match>
+    <Match>
+      <!-- protobuf generated code -->
+      <Class name="~org\.apache\.hadoop\.tracing\.TraceAdminPB.*">
+    </Match>
 
     <!--
        Manually checked, misses child thread manually syncing on parent's intrinsic lock.

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

@@ -348,6 +348,7 @@
                   <include>ProtobufRpcEngine.proto</include>
                   <include>Security.proto</include>
                   <include>GetUserMappingsProtocol.proto</include>
+                  <include>TraceAdmin.proto</include>
                   <include>RefreshAuthorizationPolicyProtocol.proto</include>
                   <include>RefreshUserMappingsProtocol.proto</include>
                   <include>RefreshCallQueueProtocol.proto</include>

hadoop-common-project/hadoop-common/src/main/bin/hadoop

@@ -35,6 +35,7 @@ function hadoop_usage()
   echo "  jar <jar>            run a jar file"
   echo "  jnipath              prints the java.library.path"
   echo "  key                  manage keys via the KeyProvider"
+  echo "  trace                view and modify Hadoop tracing settings"
   echo "  version              print the version"
   echo " or"
   echo "  CLASSNAME            run the class named CLASSNAME"
@@ -159,6 +160,9 @@ case ${COMMAND} in
   key)
     CLASS=org.apache.hadoop.crypto.key.KeyShell
   ;;
+  trace)
+    CLASS=org.apache.hadoop.tracing.TraceAdmin
+  ;;
   version)
     CLASS=org.apache.hadoop.util.VersionInfo
   ;;

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

@@ -151,6 +151,9 @@ public class CommonConfigurationKeys extends CommonConfigurationKeysPublic {
   public static final String
   HADOOP_SECURITY_SERVICE_AUTHORIZATION_GENERIC_REFRESH =
       "security.refresh.generic.protocol.acl";
+  public static final String
+  HADOOP_SECURITY_SERVICE_AUTHORIZATION_TRACING =
+      "security.trace.protocol.acl";
   public static final String 
   SECURITY_HA_SERVICE_PROTOCOL_ACL = "security.ha.service.protocol.acl";
   public static final String 

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

@@ -18,17 +18,23 @@
 package org.apache.hadoop.tracing;
 
 import java.io.IOException;
-import java.util.Collection;
-import java.util.HashSet;
+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.ReflectionUtils;
 import org.apache.hadoop.util.ShutdownHookManager;
 import org.htrace.HTraceConfiguration;
 import org.htrace.SpanReceiver;
 import org.htrace.Trace;
+ 
 
 /**
  * This class provides functions for reading the names of SpanReceivers from
@@ -37,11 +43,15 @@
  * This class does nothing If no SpanReceiver is configured.
  */
 @InterfaceAudience.Private
-public class SpanReceiverHost {
-  public static final String SPAN_RECEIVERS_CONF_KEY = "hadoop.trace.spanreceiver.classes";
+public class SpanReceiverHost implements TraceAdminProtocol {
+  public static final String SPAN_RECEIVERS_CONF_KEY =
+    "hadoop.trace.spanreceiver.classes";
   private static final Log LOG = LogFactory.getLog(SpanReceiverHost.class);
-  private Collection<SpanReceiver> receivers = new HashSet<SpanReceiver>();
+  private final TreeMap<Long, SpanReceiver> receivers =
+      new TreeMap<Long, SpanReceiver>();
+  private Configuration config;
   private boolean closed = false;
+  private long highestId = 1;
 
   private static enum SingletonHolder {
     INSTANCE;
@@ -69,6 +79,8 @@ public void run() {
     }
   }
 
+  private static List<ConfigurationPair> EMPTY = Collections.emptyList();
+
   /**
    * Reads the names of classes specified in the
    * "hadoop.trace.spanreceiver.classes" property and instantiates and registers
@@ -79,58 +91,75 @@ public void run() {
    * called on them. This allows SpanReceivers to use values from the Hadoop
    * configuration.
    */
-  public void loadSpanReceivers(Configuration conf) {
-    Class<?> implClass = null;
-    String[] receiverNames = conf.getTrimmedStrings(SPAN_RECEIVERS_CONF_KEY);
+  public synchronized void loadSpanReceivers(Configuration conf) {
+    config = new Configuration(conf);
+    String[] receiverNames =
+        config.getTrimmedStrings(SPAN_RECEIVERS_CONF_KEY);
     if (receiverNames == null || receiverNames.length == 0) {
       return;
     }
     for (String className : receiverNames) {
       className = className.trim();
       try {
-        implClass = Class.forName(className);
-        receivers.add(loadInstance(implClass, conf));
+        SpanReceiver rcvr = loadInstance(className, EMPTY);
+        Trace.addReceiver(rcvr);
+        receivers.put(highestId++, rcvr);
         LOG.info("SpanReceiver " + className + " was loaded successfully.");
-      } catch (ClassNotFoundException e) {
-        LOG.warn("Class " + className + " cannot be found.", e);
       } catch (IOException e) {
-        LOG.warn("Load SpanReceiver " + className + " failed.", e);
+        LOG.error("Failed to load SpanReceiver", e);
       }
     }
-    for (SpanReceiver rcvr : receivers) {
-      Trace.addReceiver(rcvr);
-    }
   }
 
-  private SpanReceiver loadInstance(Class<?> implClass, Configuration conf)
-      throws IOException {
+  private synchronized SpanReceiver loadInstance(String className,
+      List<ConfigurationPair> extraConfig) throws IOException {
+    Class<?> implClass = null;
     SpanReceiver impl;
     try {
-      Object o = ReflectionUtils.newInstance(implClass, conf);
+      implClass = Class.forName(className);
+      Object o = ReflectionUtils.newInstance(implClass, config);
       impl = (SpanReceiver)o;
-      impl.configure(wrapHadoopConf(conf));
+      impl.configure(wrapHadoopConf(config, extraConfig));
+    } catch (ClassCastException e) {
+      throw new IOException("Class " + className +
+          " does not implement SpanReceiver.");
+    } catch (ClassNotFoundException e) {
+      throw new IOException("Class " + className + " cannot be found.");
     } catch (SecurityException e) {
-      throw new IOException(e);
+      throw new IOException("Got SecurityException while loading " +
+          "SpanReceiver " + className);
     } catch (IllegalArgumentException e) {
-      throw new IOException(e);
+      throw new IOException("Got IllegalArgumentException while loading " +
+          "SpanReceiver " + className, e);
     } catch (RuntimeException e) {
-      throw new IOException(e);
+      throw new IOException("Got RuntimeException while loading " +
+          "SpanReceiver " + className, e);
     }
-
     return impl;
   }
 
-  private static HTraceConfiguration wrapHadoopConf(final Configuration conf) {
+  private static HTraceConfiguration wrapHadoopConf(final Configuration conf,
+          List<ConfigurationPair> extraConfig) {
+    final HashMap<String, String> extraMap = new HashMap<String, String>();
+    for (ConfigurationPair pair : extraConfig) {
+      extraMap.put(pair.getKey(), pair.getValue());
+    }
     return new HTraceConfiguration() {
       public static final String HTRACE_CONF_PREFIX = "hadoop.";
 
       @Override
       public String get(String key) {
+        if (extraMap.containsKey(key)) {
+          return extraMap.get(key);
+        }
         return conf.get(HTRACE_CONF_PREFIX + key);
       }
 
       @Override
       public String get(String key, String defaultValue) {
+        if (extraMap.containsKey(key)) {
+          return extraMap.get(key);
+        }
         return conf.get(HTRACE_CONF_PREFIX + key, defaultValue);
       }
     };
@@ -142,12 +171,67 @@ public String get(String key, String defaultValue) {
   public synchronized void closeReceivers() {
     if (closed) return;
     closed = true;
-    for (SpanReceiver rcvr : receivers) {
+    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/SpanReceiverInfo.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.tracing;
+
+import java.util.LinkedList;
+import java.util.List;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+
+@InterfaceAudience.Public
+@InterfaceStability.Stable
+public class SpanReceiverInfo {
+  private final long id;
+  private final String className;
+  final List<ConfigurationPair> configPairs =
+      new LinkedList<ConfigurationPair>();
+
+  static class ConfigurationPair {
+    private final String key;
+    private final String value;
+
+    ConfigurationPair(String key, String value) {
+      this.key = key;
+      this.value = value;
+    }
+
+    public String getKey() {
+      return key;
+    }
+
+    public String getValue() {
+      return value;
+    }
+  }
+
+  SpanReceiverInfo(long id, String className) {
+    this.id = id;
+    this.className = className;
+  }
+
+  public long getId() {
+    return id;
+  }
+
+  public String getClassName() {
+    return className;
+  }
+}

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

@@ -0,0 +1,42 @@
+/**
+ * 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 org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.tracing.SpanReceiverInfo.ConfigurationPair;
+
+@InterfaceAudience.Public
+@InterfaceStability.Stable
+public class SpanReceiverInfoBuilder {
+  private SpanReceiverInfo info;
+
+  public SpanReceiverInfoBuilder(String className) {
+    info = new SpanReceiverInfo(0, className);
+  }
+
+  public void addConfigurationPair(String key, String value) {
+    info.configPairs.add(new ConfigurationPair(key, value));
+  }
+
+  public SpanReceiverInfo build() {
+    SpanReceiverInfo ret = info;
+    info = null;
+    return ret;
+  }
+}

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

@@ -0,0 +1,197 @@
+/**
+ * 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.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.PrintStream;
+import java.net.InetSocketAddress;
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.conf.Configured;
+import org.apache.hadoop.ipc.ProtobufRpcEngine;
+import org.apache.hadoop.ipc.RPC;
+import org.apache.hadoop.net.NetUtils;
+import org.apache.hadoop.security.UserGroupInformation;
+import org.apache.hadoop.tools.TableListing;
+import org.apache.hadoop.util.StringUtils;
+import org.apache.hadoop.util.Tool;
+
+/**
+ * A command-line tool for viewing and modifying tracing settings.
+ */
+@InterfaceAudience.Private
+public class TraceAdmin extends Configured implements Tool {
+  private TraceAdminProtocolPB proxy;
+  private TraceAdminProtocolTranslatorPB remote;
+
+  private void usage() {
+    PrintStream err = System.err;
+    err.print(
+        "Hadoop tracing configuration commands:\n" +
+            "  -add [-class classname] [-Ckey=value] [-Ckey2=value2] ...\n" +
+            "    Add a span receiver with the provided class name.  Configuration\n" +
+            "    keys for the span receiver can be specified with the -C options.\n" +
+            "    The span receiver will also inherit whatever configuration keys\n" +
+            "    exist in the daemon's configuration.\n" +
+            "  -help: Print this help message.\n" +
+            "  -host [hostname:port]\n" +
+            "    Specify the hostname and port of the daemon to examine.\n" +
+            "    Required for all commands.\n" +
+            "  -list: List the current span receivers.\n" +
+            "  -remove [id]\n" +
+            "    Remove the span receiver with the specified id.  Use -list to\n" +
+            "    find the id of each receiver.\n"
+    );
+  }
+
+  private int listSpanReceivers(List<String> args) throws IOException {
+    SpanReceiverInfo infos[] = remote.listSpanReceivers();
+    if (infos.length == 0) {
+      System.out.println("[no span receivers found]");
+      return 0;
+    }
+    TableListing listing = new TableListing.Builder().
+        addField("ID").
+        addField("CLASS").
+        showHeaders().
+        build();
+    for (SpanReceiverInfo info : infos) {
+      listing.addRow("" + info.getId(), info.getClassName());
+    }
+    System.out.println(listing.toString());
+    return 0;
+  }
+
+  private final static String CONFIG_PREFIX = "-C";
+
+  private int addSpanReceiver(List<String> args) throws IOException {
+    String className = StringUtils.popOptionWithArgument("-class", args);
+    if (className == null) {
+      System.err.println("You must specify the classname with -class.");
+      return 1;
+    }
+    ByteArrayOutputStream configStream = new ByteArrayOutputStream();
+    PrintStream configsOut = new PrintStream(configStream);
+    SpanReceiverInfoBuilder factory = new SpanReceiverInfoBuilder(className);
+    String prefix = "";
+    for (int i = 0; i < args.size(); ++i) {
+      String str = args.get(i);
+      if (!str.startsWith(CONFIG_PREFIX)) {
+        System.err.println("Can't understand argument: " + str);
+        return 1;
+      }
+      str = str.substring(CONFIG_PREFIX.length());
+      int equalsIndex = str.indexOf("=");
+      if (equalsIndex < 0) {
+        System.err.println("Can't parse configuration argument " + str);
+        System.err.println("Arguments must be in the form key=value");
+        return 1;
+      }
+      String key = str.substring(0, equalsIndex);
+      String value = str.substring(equalsIndex + 1);
+      factory.addConfigurationPair(key, value);
+      configsOut.print(prefix + key + " = " + value);
+      prefix = ", ";
+    }
+    try {
+      long id = remote.addSpanReceiver(factory.build());
+      System.out.println("Added trace span receiver " + id +
+          " with configuration " + configStream.toString());
+    } catch (IOException e) {
+      System.out.println("addSpanReceiver error with configuration " +
+          configStream.toString());
+      throw e;
+    }
+    return 0;
+  }
+
+  private int removeSpanReceiver(List<String> args) throws IOException {
+    String indexStr = StringUtils.popFirstNonOption(args);
+    long id = -1;
+    try {
+      id = Long.parseLong(indexStr);
+    } catch (NumberFormatException e) {
+      System.err.println("Failed to parse ID string " +
+          indexStr + ": " + e.getMessage());
+      return 1;
+    }
+    remote.removeSpanReceiver(id);
+    System.err.println("Removed trace span receiver " + id);
+    return 0;
+  }
+
+  @Override
+  public int run(String argv[]) throws Exception {
+    LinkedList<String> args = new LinkedList<String>();
+    for (String arg : argv) {
+      args.add(arg);
+    }
+    if (StringUtils.popOption("-h", args) ||
+        StringUtils.popOption("-help", args)) {
+      usage();
+      return 0;
+    } else if (args.size() == 0) {
+      usage();
+      return 0;
+    }
+    String hostPort = StringUtils.popOptionWithArgument("-host", args);
+    if (hostPort == null) {
+      System.err.println("You must specify a host with -host.");
+      return 1;
+    }
+    if (args.size() < 0) {
+      System.err.println("You must specify an operation.");
+      return 1;
+    }
+    RPC.setProtocolEngine(getConf(), TraceAdminProtocolPB.class,
+        ProtobufRpcEngine.class);
+    InetSocketAddress address = NetUtils.createSocketAddr(hostPort);
+    UserGroupInformation ugi = UserGroupInformation.getCurrentUser();
+    Class<?> xface = TraceAdminProtocolPB.class;
+    proxy = (TraceAdminProtocolPB)RPC.getProxy(xface,
+        RPC.getProtocolVersion(xface), address,
+        ugi, getConf(), NetUtils.getDefaultSocketFactory(getConf()), 0);
+    remote = new TraceAdminProtocolTranslatorPB(proxy);
+    try {
+      if (args.get(0).equals("-list")) {
+        return listSpanReceivers(args.subList(1, args.size()));
+      } else if (args.get(0).equals("-add")) {
+        return addSpanReceiver(args.subList(1, args.size()));
+      } else if (args.get(0).equals("-remove")) {
+        return removeSpanReceiver(args.subList(1, args.size()));
+      } else {
+        System.err.println("Unrecognized tracing command: " + args.get(0));
+        System.err.println("Use -help for help.");
+        return 1;
+      }
+    } finally {
+      remote.close();
+    }
+  }
+
+  public static void main(String[] argv) throws Exception {
+    TraceAdmin admin = new TraceAdmin();
+    admin.setConf(new Configuration());
+    System.exit(admin.run(argv));
+  }
+}

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

@@ -0,0 +1,69 @@
+/**
+ * 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.LinkedList;
+import java.util.List;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.fs.CommonConfigurationKeys;
+import org.apache.hadoop.io.retry.AtMostOnce;
+import org.apache.hadoop.io.retry.Idempotent;
+import org.apache.hadoop.ipc.ProtocolInfo;
+import org.apache.hadoop.security.KerberosInfo;
+
+/**
+ * Protocol interface that provides tracing.
+ */
+@KerberosInfo(
+    serverPrincipal=CommonConfigurationKeys.HADOOP_SECURITY_SERVICE_USER_NAME_KEY)
+@InterfaceAudience.Public
+@InterfaceStability.Evolving
+public interface TraceAdminProtocol {
+  public static final long versionID = 1L;
+
+  /**
+   * List the currently active trace span receivers.
+   * 
+   * @throws IOException        On error.
+   */
+  @Idempotent
+  public SpanReceiverInfo[] listSpanReceivers() throws IOException;
+
+  /**
+   * Add a new trace span receiver.
+   * 
+   * @param desc                The span receiver description.
+   * @return                    The ID of the new trace span receiver.
+   *
+   * @throws IOException        On error.
+   */
+  @AtMostOnce
+  public long addSpanReceiver(SpanReceiverInfo desc) throws IOException;
+
+  /**
+   * Remove a trace span receiver.
+   *
+   * @param spanReceiverId      The id of the span receiver to remove.
+   * @throws IOException        On error.
+   */
+  @AtMostOnce
+  public void removeSpanReceiver(long spanReceiverId) throws IOException;
+}

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

@@ -0,0 +1,38 @@
+/**
+ * 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 org.apache.hadoop.ipc.VersionedProtocol;
+import org.apache.hadoop.tracing.TraceAdminPB.TraceAdminService;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.fs.CommonConfigurationKeys;
+import org.apache.hadoop.ipc.ProtocolInfo;
+import org.apache.hadoop.security.KerberosInfo;
+
+@KerberosInfo(
+    serverPrincipal=CommonConfigurationKeys.HADOOP_SECURITY_SERVICE_USER_NAME_KEY)
+@ProtocolInfo(
+    protocolName = "org.apache.hadoop.tracing.TraceAdminPB.TraceAdminService",
+    protocolVersion = 1)
+@InterfaceAudience.Public
+@InterfaceStability.Evolving
+public interface TraceAdminProtocolPB extends
+    TraceAdminService.BlockingInterface, VersionedProtocol {
+}

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

@@ -0,0 +1,118 @@
+/**
+ * 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.Closeable;
+import java.io.IOException;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.io.retry.AtMostOnce;
+import org.apache.hadoop.ipc.ProtobufHelper;
+import org.apache.hadoop.ipc.ProtocolSignature;
+import org.apache.hadoop.ipc.RPC;
+import org.apache.hadoop.tracing.TraceAdminPB.AddSpanReceiverRequestProto;
+import org.apache.hadoop.tracing.TraceAdminPB.AddSpanReceiverResponseProto;
+import org.apache.hadoop.tracing.TraceAdminPB.ListSpanReceiversRequestProto;
+import org.apache.hadoop.tracing.TraceAdminPB.ListSpanReceiversResponseProto;
+import org.apache.hadoop.tracing.TraceAdminPB.ConfigPair;
+import org.apache.hadoop.tracing.TraceAdminPB.RemoveSpanReceiverRequestProto;
+import org.apache.hadoop.tracing.TraceAdminPB.RemoveSpanReceiverResponseProto;
+import com.google.protobuf.RpcController;
+import com.google.protobuf.ServiceException;
+
+@InterfaceAudience.Private
+public class TraceAdminProtocolServerSideTranslatorPB
+    implements TraceAdminProtocolPB, Closeable  {
+  private final TraceAdminProtocol server;
+
+  public TraceAdminProtocolServerSideTranslatorPB(TraceAdminProtocol server) {
+    this.server = server;
+  }
+
+  @Override
+  public void close() throws IOException {
+    RPC.stopProxy(server);
+  }
+
+  @Override
+  public ListSpanReceiversResponseProto listSpanReceivers(
+      RpcController controller, ListSpanReceiversRequestProto req)
+          throws ServiceException {
+    try {
+      SpanReceiverInfo[] descs = server.listSpanReceivers();
+      ListSpanReceiversResponseProto.Builder bld =
+          ListSpanReceiversResponseProto.newBuilder();
+      for (int i = 0; i < descs.length; ++i) {
+        bld.addDescriptions(TraceAdminPB.SpanReceiverListInfo.newBuilder().
+              setId(descs[i].getId()).
+              setClassName(descs[i].getClassName()).build());
+      }
+      return bld.build();
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
+  }
+
+  @Override
+  public AddSpanReceiverResponseProto addSpanReceiver(
+      RpcController controller, AddSpanReceiverRequestProto req)
+          throws ServiceException {
+    try {
+      SpanReceiverInfoBuilder factory =
+        new SpanReceiverInfoBuilder(req.getClassName());
+      for (ConfigPair config : req.getConfigList()) {
+        factory.addConfigurationPair(config.getKey(), config.getValue());
+      }
+      long id = server.addSpanReceiver(factory.build());
+      return AddSpanReceiverResponseProto.newBuilder().setId(id).build();
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
+  }
+
+  @Override
+  public RemoveSpanReceiverResponseProto removeSpanReceiver(
+      RpcController controller,  RemoveSpanReceiverRequestProto req)
+          throws ServiceException {
+    try {
+      server.removeSpanReceiver(req.getId());
+      return RemoveSpanReceiverResponseProto.getDefaultInstance();
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
+  }
+
+  @Override
+  public long getProtocolVersion(String protocol, long clientVersion)
+      throws IOException {
+    return TraceAdminProtocol.versionID;
+  }
+
+  @Override
+  public ProtocolSignature getProtocolSignature(String protocol,
+          long clientVersion, int clientMethodsHash) throws IOException {
+    if (!protocol.equals(RPC.getProtocolName(TraceAdminProtocolPB.class))) {
+      throw new IOException("Serverside implements " +
+          RPC.getProtocolName(TraceAdminProtocolPB.class) +
+          ". The following requested protocol is unknown: " + protocol);
+    }
+    return ProtocolSignature.getProtocolSignature(clientMethodsHash,
+        RPC.getProtocolVersion(TraceAdminProtocolPB.class),
+        TraceAdminProtocolPB.class);
+  }
+}

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

@@ -0,0 +1,105 @@
+/**
+ * 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.Closeable;
+import java.io.IOException;
+import java.util.ArrayList;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.ipc.ProtobufHelper;
+import org.apache.hadoop.ipc.ProtocolTranslator;
+import org.apache.hadoop.ipc.RPC;
+import org.apache.hadoop.tracing.TraceAdminPB.AddSpanReceiverRequestProto;
+import org.apache.hadoop.tracing.TraceAdminPB.AddSpanReceiverResponseProto;
+import org.apache.hadoop.tracing.TraceAdminPB.ListSpanReceiversRequestProto;
+import org.apache.hadoop.tracing.TraceAdminPB.ListSpanReceiversResponseProto;
+import org.apache.hadoop.tracing.TraceAdminPB.ConfigPair;
+import org.apache.hadoop.tracing.TraceAdminPB.RemoveSpanReceiverRequestProto;
+import org.apache.hadoop.tracing.TraceAdminPB.SpanReceiverListInfo;
+import org.apache.hadoop.tracing.SpanReceiverInfo.ConfigurationPair;
+import com.google.protobuf.ServiceException;
+
+@InterfaceAudience.Private
+public class TraceAdminProtocolTranslatorPB implements
+    TraceAdminProtocol, ProtocolTranslator, Closeable  {
+  private final TraceAdminProtocolPB rpcProxy;
+
+  public TraceAdminProtocolTranslatorPB(TraceAdminProtocolPB rpcProxy) {
+    this.rpcProxy = rpcProxy;
+  }
+
+  @Override
+  public void close() throws IOException {
+    RPC.stopProxy(rpcProxy);
+  }
+
+  @Override
+  public SpanReceiverInfo[] listSpanReceivers() throws IOException {
+    ArrayList<SpanReceiverInfo> infos = new ArrayList<SpanReceiverInfo>(1);
+    try {
+      ListSpanReceiversRequestProto req =
+          ListSpanReceiversRequestProto.newBuilder().build();
+      ListSpanReceiversResponseProto resp =
+          rpcProxy.listSpanReceivers(null, req);
+      for (SpanReceiverListInfo info : resp.getDescriptionsList()) {
+        infos.add(new SpanReceiverInfo(info.getId(), info.getClassName()));
+      }
+    } catch (ServiceException e) {
+      throw ProtobufHelper.getRemoteException(e);
+    }
+    return infos.toArray(new SpanReceiverInfo[infos.size()]);
+  }
+
+  @Override
+  public long addSpanReceiver(SpanReceiverInfo info) throws IOException {
+    try {
+      AddSpanReceiverRequestProto.Builder bld =
+          AddSpanReceiverRequestProto.newBuilder();
+      bld.setClassName(info.getClassName());
+      for (ConfigurationPair configPair : info.configPairs) {
+        ConfigPair tuple = ConfigPair.newBuilder().
+            setKey(configPair.getKey()).
+            setValue(configPair.getValue()).build();
+        bld.addConfig(tuple);
+      }
+      AddSpanReceiverResponseProto resp =
+          rpcProxy.addSpanReceiver(null, bld.build());
+      return resp.getId();
+    } catch (ServiceException e) {
+      throw ProtobufHelper.getRemoteException(e);
+    }
+  }
+
+  @Override
+  public void removeSpanReceiver(long spanReceiverId) throws IOException {
+    try {
+      RemoveSpanReceiverRequestProto req =
+          RemoveSpanReceiverRequestProto.newBuilder()
+            .setId(spanReceiverId).build();
+      rpcProxy.removeSpanReceiver(null, req);
+    } catch (ServiceException e) {
+      throw ProtobufHelper.getRemoteException(e);
+    }
+  }
+
+  @Override
+  public Object getUnderlyingProxyObject() {
+    return rpcProxy;
+  }
+}

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

@@ -0,0 +1,73 @@
+/**
+ * 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.
+ */
+
+/**
+ * These .proto interfaces are private and stable.
+ * Please see http://wiki.apache.org/hadoop/Compatibility
+ * for what changes are allowed for a *stable* .proto interface.
+ */
+
+option java_package = "org.apache.hadoop.tracing";
+option java_outer_classname = "TraceAdminPB";
+option java_generic_services = true;
+option java_generate_equals_and_hash = true;
+package hadoop.common;
+
+message ListSpanReceiversRequestProto {
+}
+
+message SpanReceiverListInfo {
+  required int64 id = 1;
+  required string className = 2;
+}
+
+message ListSpanReceiversResponseProto {
+  repeated SpanReceiverListInfo descriptions = 1;
+}
+
+message ConfigPair {
+  required string key = 1;
+  required string value = 2;
+}
+
+message AddSpanReceiverRequestProto {
+  required string className = 1;
+  repeated ConfigPair config = 2;
+}
+
+message AddSpanReceiverResponseProto {
+  required int64 id = 1;
+}
+
+message RemoveSpanReceiverRequestProto {
+  required int64 id = 1;
+}
+
+message RemoveSpanReceiverResponseProto {
+}
+
+service TraceAdminService {
+  rpc listSpanReceivers(ListSpanReceiversRequestProto)
+      returns(ListSpanReceiversResponseProto);
+
+  rpc addSpanReceiver(AddSpanReceiverRequestProto)
+      returns(AddSpanReceiverResponseProto);
+
+  rpc removeSpanReceiver(RemoveSpanReceiverRequestProto)
+      returns(RemoveSpanReceiverResponseProto);
+}

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

@@ -509,6 +509,9 @@ Release 2.6.0 - UNRELEASED
 
     HDFS-7077. Separate CipherSuite from crypto protocol version. (wang)
 
+    HDFS-6956. Allow dynamically changing the tracing level in Hadoop servers
+    (cmccabe)
+
   OPTIMIZATIONS
 
     HDFS-6690. Deduplicate xattr names in memory. (wang)

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

@@ -34,6 +34,7 @@
 import org.apache.hadoop.tools.GetUserMappingsProtocol;
 import org.apache.hadoop.ipc.RefreshCallQueueProtocol;
 import org.apache.hadoop.ipc.GenericRefreshProtocol;
+import org.apache.hadoop.tracing.TraceAdminProtocol;
 
 /**
  * {@link PolicyProvider} for HDFS protocols.
@@ -72,7 +73,10 @@ public class HDFSPolicyProvider extends PolicyProvider {
         RefreshCallQueueProtocol.class),
     new Service(
         CommonConfigurationKeys.HADOOP_SECURITY_SERVICE_AUTHORIZATION_GENERIC_REFRESH,
-        GenericRefreshProtocol.class)
+        GenericRefreshProtocol.class),
+    new Service(
+        CommonConfigurationKeys.HADOOP_SECURITY_SERVICE_AUTHORIZATION_TRACING,
+        TraceAdminProtocol.class)
   };
   
   @Override

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

@@ -179,6 +179,10 @@
 import org.apache.hadoop.security.authorize.AccessControlList;
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.security.token.TokenIdentifier;
+import org.apache.hadoop.tracing.TraceAdminPB;
+import org.apache.hadoop.tracing.TraceAdminPB.TraceAdminService;
+import org.apache.hadoop.tracing.TraceAdminProtocolPB;
+import org.apache.hadoop.tracing.TraceAdminProtocolServerSideTranslatorPB;
 import org.apache.hadoop.util.Daemon;
 import org.apache.hadoop.util.DiskChecker;
 import org.apache.hadoop.util.DiskChecker.DiskErrorException;
@@ -189,6 +193,8 @@
 import org.apache.hadoop.util.Time;
 import org.apache.hadoop.util.VersionInfo;
 import org.apache.hadoop.tracing.SpanReceiverHost;
+import org.apache.hadoop.tracing.SpanReceiverInfo;
+import org.apache.hadoop.tracing.TraceAdminProtocol;
 import org.mortbay.util.ajax.JSON;
 
 import com.google.common.annotations.VisibleForTesting;
@@ -230,7 +236,7 @@
 @InterfaceAudience.Private
 public class DataNode extends ReconfigurableBase
     implements InterDatanodeProtocol, ClientDatanodeProtocol,
-    DataNodeMXBean {
+        TraceAdminProtocol, DataNodeMXBean {
   public static final Log LOG = LogFactory.getLog(DataNode.class);
   
   static{
@@ -699,6 +705,14 @@ private void initIpcServer(Configuration conf) throws IOException {
         .newReflectiveBlockingService(interDatanodeProtocolXlator);
     DFSUtil.addPBProtocol(conf, InterDatanodeProtocolPB.class, service,
         ipcServer);
+
+    TraceAdminProtocolServerSideTranslatorPB traceAdminXlator =
+        new TraceAdminProtocolServerSideTranslatorPB(this);
+    BlockingService traceAdminService = TraceAdminService
+        .newReflectiveBlockingService(traceAdminXlator);
+    DFSUtil.addPBProtocol(conf, TraceAdminProtocolPB.class, traceAdminService,
+        ipcServer);
+
     LOG.info("Opened IPC server at " + ipcServer.getListenerAddress());
 
     // set service-level authorization security policy
@@ -3025,4 +3039,22 @@ public long getLastDiskErrorCheck() {
       return lastDiskErrorCheck;
     }
   }
+
+  @Override
+  public SpanReceiverInfo[] listSpanReceivers() throws IOException {
+    checkSuperuserPrivilege();
+    return spanReceiverHost.listSpanReceivers();
+  }
+
+  @Override
+  public long addSpanReceiver(SpanReceiverInfo info) throws IOException {
+    checkSuperuserPrivilege();
+    return spanReceiverHost.addSpanReceiver(info);
+  }
+
+  @Override
+  public void removeSpanReceiver(long id) throws IOException {
+    checkSuperuserPrivilege();
+    spanReceiverHost.removeSpanReceiver(id);
+  }
 }

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

@@ -61,6 +61,7 @@
 import org.apache.hadoop.ipc.RefreshCallQueueProtocol;
 import org.apache.hadoop.tools.GetUserMappingsProtocol;
 import org.apache.hadoop.tracing.SpanReceiverHost;
+import org.apache.hadoop.tracing.TraceAdminProtocol;
 import org.apache.hadoop.util.ExitUtil.ExitException;
 import org.apache.hadoop.util.GenericOptionsParser;
 import org.apache.hadoop.util.JvmPauseMonitor;
@@ -244,6 +245,8 @@ public long getProtocolVersion(String protocol,
       return RefreshCallQueueProtocol.versionID;
     } else if (protocol.equals(GetUserMappingsProtocol.class.getName())){
       return GetUserMappingsProtocol.versionID;
+    } else if (protocol.equals(TraceAdminProtocol.class.getName())){
+      return TraceAdminProtocol.versionID;
     } else {
       throw new IOException("Unknown protocol to name node: " + protocol);
     }
@@ -279,7 +282,7 @@ public long getProtocolVersion(String protocol,
 
   private JvmPauseMonitor pauseMonitor;
   private ObjectName nameNodeStatusBeanName;
-  private SpanReceiverHost spanReceiverHost;
+  SpanReceiverHost spanReceiverHost;
   /**
    * The namenode address that clients will use to access this namenode
    * or the name service. For HA configurations using logical URI, it

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

@@ -165,6 +165,11 @@
 import org.apache.hadoop.tools.proto.GetUserMappingsProtocolProtos.GetUserMappingsProtocolService;
 import org.apache.hadoop.tools.protocolPB.GetUserMappingsProtocolPB;
 import org.apache.hadoop.tools.protocolPB.GetUserMappingsProtocolServerSideTranslatorPB;
+import org.apache.hadoop.tracing.SpanReceiverInfo;
+import org.apache.hadoop.tracing.TraceAdminPB;
+import org.apache.hadoop.tracing.TraceAdminPB.TraceAdminService;
+import org.apache.hadoop.tracing.TraceAdminProtocolPB;
+import org.apache.hadoop.tracing.TraceAdminProtocolServerSideTranslatorPB;
 import org.apache.hadoop.util.VersionInfo;
 import org.apache.hadoop.util.VersionUtil;
 
@@ -256,6 +261,11 @@ public NameNodeRpcServer(Configuration conf, NameNode nn)
         new HAServiceProtocolServerSideTranslatorPB(this);
     BlockingService haPbService = HAServiceProtocolService
         .newReflectiveBlockingService(haServiceProtocolXlator);
+
+    TraceAdminProtocolServerSideTranslatorPB traceAdminXlator =
+        new TraceAdminProtocolServerSideTranslatorPB(this);
+    BlockingService traceAdminService = TraceAdminService
+        .newReflectiveBlockingService(traceAdminXlator);
     
     WritableRpcEngine.ensureInitialized();
 
@@ -300,7 +310,9 @@ public NameNodeRpcServer(Configuration conf, NameNode nn)
           genericRefreshService, serviceRpcServer);
       DFSUtil.addPBProtocol(conf, GetUserMappingsProtocolPB.class, 
           getUserMappingService, serviceRpcServer);
-  
+      DFSUtil.addPBProtocol(conf, TraceAdminProtocolPB.class,
+          traceAdminService, serviceRpcServer);
+
       // Update the address with the correct port
       InetSocketAddress listenAddr = serviceRpcServer.getListenerAddress();
       serviceRPCAddress = new InetSocketAddress(
@@ -346,6 +358,8 @@ public NameNodeRpcServer(Configuration conf, NameNode nn)
         genericRefreshService, clientRpcServer);
     DFSUtil.addPBProtocol(conf, GetUserMappingsProtocolPB.class, 
         getUserMappingService, clientRpcServer);
+    DFSUtil.addPBProtocol(conf, TraceAdminProtocolPB.class,
+        traceAdminService, clientRpcServer);
 
     // set service-level authorization security policy
     if (serviceAuthEnabled =
@@ -1597,5 +1611,22 @@ public EventsList getEditsFromTxid(long txid) throws IOException {
 
     return new EventsList(events, firstSeenTxid, maxSeenTxid, syncTxid);
   }
-}
 
+  @Override
+  public SpanReceiverInfo[] listSpanReceivers() throws IOException {
+    namesystem.checkSuperuserPrivilege();
+    return nn.spanReceiverHost.listSpanReceivers();
+  }
+
+  @Override
+  public long addSpanReceiver(SpanReceiverInfo info) throws IOException {
+    namesystem.checkSuperuserPrivilege();
+    return nn.spanReceiverHost.addSpanReceiver(info);
+  }
+
+  @Override
+  public void removeSpanReceiver(long id) throws IOException {
+    namesystem.checkSuperuserPrivilege();
+    nn.spanReceiverHost.removeSpanReceiver(id);
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/protocol/NamenodeProtocols.java

@@ -26,6 +26,7 @@
 import org.apache.hadoop.ipc.RefreshCallQueueProtocol;
 import org.apache.hadoop.ipc.GenericRefreshProtocol;
 import org.apache.hadoop.tools.GetUserMappingsProtocol;
+import org.apache.hadoop.tracing.TraceAdminProtocol;
 
 /** The full set of RPC methods implemented by the Namenode.  */
 @InterfaceAudience.Private
@@ -38,5 +39,6 @@ public interface NamenodeProtocols
           RefreshCallQueueProtocol,
           GenericRefreshProtocol,
           GetUserMappingsProtocol,
-          HAServiceProtocol {
+          HAServiceProtocol,
+          TraceAdminProtocol {
 }

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

@@ -0,0 +1,90 @@
+/**
+ * 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 org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.apache.hadoop.net.unix.TemporarySocketDirectory;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.PrintStream;
+
+public class TestTraceAdmin {
+
+  private String runTraceCommand(TraceAdmin trace, String... cmd)
+      throws Exception {
+    ByteArrayOutputStream baos = new ByteArrayOutputStream();
+    PrintStream ps = new PrintStream(baos);
+    PrintStream oldStdout = System.out;
+    PrintStream oldStderr = System.err;
+    System.setOut(ps);
+    System.setErr(ps);
+    int ret = -1;
+    try {
+      ret = trace.run(cmd);
+    } finally {
+      System.out.flush();
+      System.setOut(oldStdout);
+      System.setErr(oldStderr);
+    }
+    return "ret:" + ret + ", " + baos.toString();
+  }
+
+  private String getHostPortForNN(MiniDFSCluster cluster) {
+    return "127.0.0.1:" + cluster.getNameNodePort();
+  }
+
+  @Test
+  public void testCreateAndDestroySpanReceiver() throws Exception {
+    Configuration conf = new Configuration();
+    conf = new Configuration();
+    conf.set(SpanReceiverHost.SPAN_RECEIVERS_CONF_KEY, "");
+    MiniDFSCluster cluster =
+        new MiniDFSCluster.Builder(conf).numDataNodes(3).build();
+    cluster.waitActive();
+    TemporarySocketDirectory tempDir = new TemporarySocketDirectory();
+    String tracePath =
+        new File(tempDir.getDir(), "tracefile").getAbsolutePath();
+    try {
+      TraceAdmin trace = new TraceAdmin();
+      trace.setConf(conf);
+      Assert.assertEquals("ret:0, [no span receivers found]\n",
+          runTraceCommand(trace, "-list", "-host", getHostPortForNN(cluster)));
+      Assert.assertEquals("ret:0, Added trace span receiver 1 with " +
+          "configuration local-file-span-receiver.path = " + tracePath + "\n",
+          runTraceCommand(trace, "-add", "-host", getHostPortForNN(cluster),
+              "-class", "org.htrace.impl.LocalFileSpanReceiver",
+              "-Clocal-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.htrace.impl.LocalFileSpanReceiver"));
+      Assert.assertEquals("ret:0, Removed trace span receiver 1\n",
+          runTraceCommand(trace, "-remove", "1", "-host",
+              getHostPortForNN(cluster)));
+      Assert.assertEquals("ret:0, [no span receivers found]\n",
+          runTraceCommand(trace, "-list", "-host", getHostPortForNN(cluster)));
+    } finally {
+      cluster.shutdown();
+      tempDir.close();
+    }
+  }
+}