HDFS-2301. Start/stop appropriate namenode services when transition to active and standby states. Contributed by Suresh Srinivas.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-1623@1182080 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-1623.txt

@@ -11,3 +11,5 @@ HDFS-1974. Introduce active and standy states to the namenode. (suresh)
 HDFS-2407. getServerDefaults and getStats don't check operation category (atm)
 
 HDFS-1973. HA: HDFS clients must handle namenode failover and switch over to the new active namenode. (atm)
+
+HDFS-2301. Start/stop appropriate namenode services when transition to active and standby states. (suresh)

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

@@ -81,13 +81,13 @@ public class BackupNode extends NameNode {
   // Common NameNode methods implementation for backup node.
   /////////////////////////////////////////////////////
   @Override // NameNode
-  protected InetSocketAddress getRpcServerAddress(Configuration conf) throws IOException {
+  protected InetSocketAddress getRpcServerAddress(Configuration conf) {
     String addr = conf.get(BN_ADDRESS_NAME_KEY, BN_ADDRESS_DEFAULT);
     return NetUtils.createSocketAddr(addr);
   }
   
   @Override
-  protected InetSocketAddress getServiceRpcServerAddress(Configuration conf) throws IOException {
+  protected InetSocketAddress getServiceRpcServerAddress(Configuration conf) {
     String addr = conf.get(BN_SERVICE_RPC_ADDRESS_KEY);
     if (addr == null || addr.isEmpty()) {
       return null;
@@ -135,11 +135,6 @@ protected void initialize(Configuration conf) throws IOException {
                  CommonConfigurationKeys.FS_TRASH_INTERVAL_DEFAULT);
     NamespaceInfo nsInfo = handshake(conf);
     super.initialize(conf);
-    // Backup node should never do lease recovery,
-    // therefore lease hard limit should never expire.
-    namesystem.leaseManager.setLeasePeriod(
-        HdfsConstants.LEASE_SOFTLIMIT_PERIOD, Long.MAX_VALUE);
-    
     clusterId = nsInfo.getClusterID();
     blockPoolId = nsInfo.getBlockPoolID();
 

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

@@ -130,7 +130,6 @@
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.security.token.delegation.DelegationKey;
 import org.apache.hadoop.util.Daemon;
-import org.apache.hadoop.util.StringUtils;
 import org.apache.hadoop.util.VersionInfo;
 import org.mortbay.util.ajax.JSON;
 
@@ -347,28 +346,30 @@ void loadFSImage(StartupOption startOpt, FSImage fsImage)
     dir.imageLoadComplete();
   }
 
-  void activateSecretManager() throws IOException {
+  void startSecretManager() throws IOException {
     if (dtSecretManager != null) {
       dtSecretManager.startThreads();
     }
   }
   
-  /**
+  void stopSecretManager() {
-   * Activate FSNamesystem daemons.
+    if (dtSecretManager != null) {
+      dtSecretManager.stopThreads();
+    }
+  }
+  
+  /** 
+   * Start services common to both active and standby states
+   * @throws IOException
    */
-  void activate(Configuration conf) throws IOException {
+  void startCommonServices(Configuration conf) throws IOException {
     this.registerMBean(); // register the MBean for the FSNamesystemState
-
     writeLock();
     try {
       nnResourceChecker = new NameNodeResourceChecker(conf);
       checkAvailableResources();
-
       setBlockTotal();
       blockManager.activate(conf);
-
-      this.lmthread = new Daemon(leaseManager.new Monitor());
-      lmthread.start();
       this.nnrmthread = new Daemon(new NameNodeResourceMonitor());
       nnrmthread.start();
     } finally {
@@ -378,7 +379,70 @@ void activate(Configuration conf) throws IOException {
     registerMXBean();
     DefaultMetricsSystem.instance().register(this);
   }
+  
+  /** 
+   * Stop services common to both active and standby states
+   * @throws IOException
+   */
+  void stopCommonServices() {
+    writeLock();
+    try {
+      if (blockManager != null) blockManager.close();
+      if (nnrmthread != null) nnrmthread.interrupt();
+    } finally {
+      writeUnlock();
+    }
+  }
+  
+  /**
+   * Start services required in active state
+   * @throws IOException
+   */
+  void startActiveServices() throws IOException {
+    LOG.info("Starting services required for active state");
+    writeLock();
+    try {
+      startSecretManager();
+      lmthread = new Daemon(leaseManager.new Monitor());
+      lmthread.start();
+    } finally {
+      writeUnlock();
+    }
+  }
+  
+  /** 
+   * Start services required in active state 
+   * @throws InterruptedException
+   */
+  void stopActiveServices() {
+    LOG.info("Stopping services started for active state");
+    writeLock();
+    try {
+      stopSecretManager();
+      if (lmthread != null) {
+        try {
+          lmthread.interrupt();
+          lmthread.join(3000);
+        } catch (InterruptedException ie) {
+          LOG.warn("Encountered exception ", ie);
+        }
+        lmthread = null;
+      }
+    } finally {
+      writeUnlock();
+    }
+  }
+  
+  /** Start services required in standby state */
+  void startStandbyServices() {
+    LOG.info("Starting services required for standby state");
+  }
 
+  /** Stop services required in standby state */
+  void stopStandbyServices() {
+    LOG.info("Stopping services started for standby state");
+  }
+  
   public static Collection<URI> getNamespaceDirs(Configuration conf) {
     return getStorageDirs(conf, DFS_NAMENODE_NAME_DIR_KEY);
   }
@@ -502,7 +566,7 @@ NamespaceInfo getNamespaceInfo() {
   }
 
   /**
-   * Version of {@see #getNamespaceInfo()} that is not protected by a lock.
+   * Version of @see #getNamespaceInfo() that is not protected by a lock.
    */
   NamespaceInfo unprotectedGetNamespaceInfo() {
     return new NamespaceInfo(dir.fsImage.getStorage().getNamespaceID(),
@@ -519,23 +583,16 @@ NamespaceInfo unprotectedGetNamespaceInfo() {
   void close() {
     fsRunning = false;
     try {
-      if (blockManager != null) blockManager.close();
+      stopCommonServices();
       if (smmthread != null) smmthread.interrupt();
-      if (dtSecretManager != null) dtSecretManager.stopThreads();
-      if (nnrmthread != null) nnrmthread.interrupt();
-    } catch (Exception e) {
-      LOG.warn("Exception shutting down FSNamesystem", e);
     } finally {
       // using finally to ensure we also wait for lease daemon
       try {
-        if (lmthread != null) {
+        stopActiveServices();
-          lmthread.interrupt();
+        stopStandbyServices();
-          lmthread.join(3000);
-        }
         if (dir != null) {
           dir.close();
         }
-      } catch (InterruptedException ie) {
       } catch (IOException ie) {
         LOG.error("Error closing FSDirectory", ie);
         IOUtils.cleanup(LOG, dir);
@@ -1386,7 +1443,7 @@ LocatedBlock appendFile(String src, String holder, String clientMachine)
     try {
       lb = startFileInternal(src, null, holder, clientMachine, 
                         EnumSet.of(CreateFlag.APPEND), 
-                        false, blockManager.maxReplication, (long)0);
+                        false, blockManager.maxReplication, 0);
     } finally {
       writeUnlock();
     }
@@ -1469,7 +1526,7 @@ LocatedBlock getAdditionalBlock(String src,
       fileLength = pendingFile.computeContentSummary().getLength();
       blockSize = pendingFile.getPreferredBlockSize();
       clientNode = pendingFile.getClientNode();
-      replication = (int)pendingFile.getReplication();
+      replication = pendingFile.getReplication();
     } finally {
       writeUnlock();
     }
@@ -2264,7 +2321,7 @@ private Lease reassignLease(Lease lease, String src, String newHolder,
   }
   
   Lease reassignLeaseInternal(Lease lease, String src, String newHolder,
-      INodeFileUnderConstruction pendingFile) throws IOException {
+      INodeFileUnderConstruction pendingFile) {
     assert hasWriteLock();
     pendingFile.setClientName(newHolder);
     return leaseManager.reassignLease(lease, src, newHolder);
@@ -2869,13 +2926,9 @@ private SafeModeInfo(boolean resourcesLow) {
      * @return true if in safe mode
      */
     private synchronized boolean isOn() {
-      try {
+      assert isConsistent() : " SafeMode: Inconsistent filesystem state: "
-        assert isConsistent() : " SafeMode: Inconsistent filesystem state: "
+        + "Total num of blocks, active blocks, or "
-          + "Total num of blocks, active blocks, or "
+        + "total safe blocks don't match.";
-          + "total safe blocks don't match.";
-      } catch(IOException e) {
-        System.err.print(StringUtils.stringifyException(e));
-      }
       return this.reached >= 0;
     }
       
@@ -3029,7 +3082,7 @@ private synchronized void setBlockTotal(int total) {
       this.blockTotal = total;
       this.blockThreshold = (int) (blockTotal * threshold);
       this.blockReplQueueThreshold = 
-        (int) (((double) blockTotal) * replQueueThreshold);
+        (int) (blockTotal * replQueueThreshold);
       checkMode();
     }
       
@@ -3039,7 +3092,7 @@ private synchronized void setBlockTotal(int total) {
      * @param replication current replication 
      */
     private synchronized void incrementSafeBlockCount(short replication) {
-      if ((int)replication == safeReplication)
+      if (replication == safeReplication)
         this.blockSafe++;
       checkMode();
     }
@@ -3172,7 +3225,7 @@ public String toString() {
      * Checks consistency of the class state.
      * This is costly and currently called only in assert.
      */
-    private boolean isConsistent() throws IOException {
+    private boolean isConsistent() {
       if (blockTotal == -1 && blockSafe == -1) {
         return true; // manual safe mode
       }

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

@@ -38,15 +38,13 @@
 import org.apache.hadoop.fs.Trash;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.*;
 import org.apache.hadoop.hdfs.DFSUtil;
-import org.apache.hadoop.hdfs.HDFSPolicyProvider;
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.protocol.ClientProtocol;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
-import org.apache.hadoop.hdfs.protocol.UnregisteredNodeException;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.NamenodeRole;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.StartupOption;
-import org.apache.hadoop.hdfs.server.common.IncorrectVersionException;
 import org.apache.hadoop.hdfs.server.namenode.ha.ActiveState;
+import org.apache.hadoop.hdfs.server.namenode.ha.HAContext;
 import org.apache.hadoop.hdfs.server.namenode.ha.HAState;
 import org.apache.hadoop.hdfs.server.namenode.ha.StandbyState;
 import org.apache.hadoop.hdfs.server.namenode.metrics.NameNodeMetrics;
@@ -55,9 +53,6 @@
 import org.apache.hadoop.hdfs.server.protocol.NamenodeProtocol;
 import org.apache.hadoop.hdfs.server.protocol.NamenodeProtocols;
 import org.apache.hadoop.hdfs.server.protocol.NamenodeRegistration;
-import org.apache.hadoop.hdfs.server.protocol.NodeRegistration;
-import org.apache.hadoop.ipc.RPC;
-import org.apache.hadoop.ipc.Server;
 import org.apache.hadoop.metrics2.lib.DefaultMetricsSystem;
 import org.apache.hadoop.net.NetUtils;
 import org.apache.hadoop.security.RefreshUserMappingsProtocol;
@@ -172,19 +167,18 @@ public long getProtocolVersion(String protocol,
     }
   }
     
-
-
   public static final int DEFAULT_PORT = 8020;
-
   public static final Log LOG = LogFactory.getLog(NameNode.class.getName());
   public static final Log stateChangeLog = LogFactory.getLog("org.apache.hadoop.hdfs.StateChange");
   public static final HAState ACTIVE_STATE = new ActiveState();
   public static final HAState STANDBY_STATE = new StandbyState();
   
   protected FSNamesystem namesystem; 
+  protected final Configuration conf;
   protected NamenodeRole role;
   private HAState state;
   private final boolean haEnabled;
+  private final HAContext haContext;
 
   
   /** httpServer */
@@ -313,12 +307,11 @@ boolean isRole(NamenodeRole that) {
    * Given a configuration get the address of the service rpc server
    * If the service rpc is not configured returns null
    */
-  protected InetSocketAddress getServiceRpcServerAddress(Configuration conf)
+  protected InetSocketAddress getServiceRpcServerAddress(Configuration conf) {
-    throws IOException {
     return NameNode.getServiceAddress(conf, false);
   }
 
-  protected InetSocketAddress getRpcServerAddress(Configuration conf) throws IOException {
+  protected InetSocketAddress getRpcServerAddress(Configuration conf) {
     return getAddress(conf);
   }
   
@@ -396,7 +389,7 @@ protected void initialize(Configuration conf) throws IOException {
       throw e;
     }
 
-    activate(conf);
+    startCommonServices(conf);
   }
   
   /**
@@ -430,19 +423,11 @@ protected void validateConfigurationSettings(final Configuration conf)
     } 
   }
 
-  /**
+  /** Start the services common to active and standby states */
-   * Activate name-node servers and threads.
+  private void startCommonServices(Configuration conf) throws IOException {
-   */
+    namesystem.startCommonServices(conf);
-  void activate(Configuration conf) throws IOException {
-    if ((isRole(NamenodeRole.NAMENODE))
-        && (UserGroupInformation.isSecurityEnabled())) {
-      namesystem.activateSecretManager();
-    }
-    namesystem.activate(conf);
     startHttpServer(conf);
     rpcServer.start();
-    startTrashEmptier(conf);
-    
     plugins = conf.getInstances(DFS_NAMENODE_PLUGINS_KEY,
         ServicePlugin.class);
     for (ServicePlugin p: plugins) {
@@ -452,13 +437,28 @@ void activate(Configuration conf) throws IOException {
         LOG.warn("ServicePlugin " + p + " could not be started", t);
       }
     }
-    
     LOG.info(getRole() + " up at: " + rpcServer.getRpcAddress());
     if (rpcServer.getServiceRpcAddress() != null) {
-      LOG.info(getRole() + " service server is up at: " + rpcServer.getServiceRpcAddress()); 
+      LOG.info(getRole() + " service server is up at: "
+          + rpcServer.getServiceRpcAddress());
     }
   }
-
+  
+  private void stopCommonServices() {
+    if(namesystem != null) namesystem.close();
+    if(rpcServer != null) rpcServer.stop();
+    if (plugins != null) {
+      for (ServicePlugin p : plugins) {
+        try {
+          p.stop();
+        } catch (Throwable t) {
+          LOG.warn("ServicePlugin " + p + " could not be stopped", t);
+        }
+      }
+    }   
+    stopHttpServer();
+  }
+  
   private void startTrashEmptier(Configuration conf) throws IOException {
     long trashInterval 
       = conf.getLong(CommonConfigurationKeys.FS_TRASH_INTERVAL_KEY, 
@@ -470,11 +470,26 @@ private void startTrashEmptier(Configuration conf) throws IOException {
     this.emptier.start();
   }
   
+  private void stopTrashEmptier() {
+    if (this.emptier != null) {
+      emptier.interrupt();
+      emptier = null;
+    }
+  }
+  
   private void startHttpServer(final Configuration conf) throws IOException {
     httpServer = new NameNodeHttpServer(conf, this, getHttpServerAddress(conf));
     httpServer.start();
     setHttpServerAddress(conf);
   }
+  
+  private void stopHttpServer() {
+    try {
+      if (httpServer != null) httpServer.stop();
+    } catch (Exception e) {
+      LOG.error("Exception while stopping httpserver", e);
+    }
+  }
 
   /**
    * Start NameNode.
@@ -509,18 +524,28 @@ public NameNode(Configuration conf) throws IOException {
 
   protected NameNode(Configuration conf, NamenodeRole role) 
       throws IOException { 
+    this.conf = conf;
     this.role = role;
     this.haEnabled = DFSUtil.isHAEnabled(conf);
-    this.state = !haEnabled ? ACTIVE_STATE : STANDBY_STATE;
+    this.haContext = new NameNodeHAContext();
     try {
       initializeGenericKeys(conf, getNameServiceId(conf));
       initialize(conf);
+      if (!haEnabled) {
+        state = ACTIVE_STATE;
+      } else {
+        state = STANDBY_STATE;;
+      }
+      state.enterState(haContext);
     } catch (IOException e) {
       this.stop();
       throw e;
     } catch (HadoopIllegalArgumentException e) {
       this.stop();
       throw e;
+    } catch (ServiceFailedException e) {
+      this.stop();
+      throw new IOException("Service failed to start", e);
     }
   }
 
@@ -532,6 +557,7 @@ public void join() {
     try {
       this.rpcServer.join();
     } catch (InterruptedException ie) {
+      LOG.info("Caught interrupted exception ", ie);
     }
   }
 
@@ -544,23 +570,12 @@ public void stop() {
         return;
       stopRequested = true;
     }
-    if (plugins != null) {
-      for (ServicePlugin p : plugins) {
-        try {
-          p.stop();
-        } catch (Throwable t) {
-          LOG.warn("ServicePlugin " + p + " could not be stopped", t);
-        }
-      }
-    }
     try {
-      if (httpServer != null) httpServer.stop();
+      state.exitState(haContext);
-    } catch (Exception e) {
+    } catch (ServiceFailedException e) {
-      LOG.error("Exception while stopping httpserver", e);
+      LOG.warn("Encountered exception while exiting state ", e);
     }
-    if(namesystem != null) namesystem.close();
+    stopCommonServices();
-    if(emptier != null) emptier.interrupt();
-    if(rpcServer != null) rpcServer.stop();
     if (metrics != null) {
       metrics.shutdown();
     }
@@ -876,27 +891,61 @@ synchronized void transitionToActive() throws ServiceFailedException {
     if (!haEnabled) {
       throw new ServiceFailedException("HA for namenode is not enabled");
     }
-    state.setState(this, ACTIVE_STATE);
+    state.setState(haContext, ACTIVE_STATE);
   }
   
   synchronized void transitionToStandby() throws ServiceFailedException {
     if (!haEnabled) {
       throw new ServiceFailedException("HA for namenode is not enabled");
     }
-    state.setState(this, STANDBY_STATE);
+    state.setState(haContext, STANDBY_STATE);
   }
   
   /** Check if an operation of given category is allowed */
   protected synchronized void checkOperation(final OperationCategory op)
       throws UnsupportedActionException {
-    state.checkOperation(this, op);
+    state.checkOperation(haContext, op);
   }
   
-  public synchronized HAState getState() {
+  /**
-    return state;
+   * Class used as expose {@link NameNode} as context to {@link HAState}
-  }
+   * 
-  
+   * TODO:HA
-  public synchronized void setState(final HAState s) {
+   * When entering and exiting state, on failing to start services,
-    state = s;
+   * appropriate action is needed todo either shutdown the node or recover
+   * from failure.
+   */
+  private class NameNodeHAContext implements HAContext {
+    @Override
+    public void setState(HAState s) {
+      state = s;
+    }
+
+    @Override
+    public HAState getState() {
+      return state;
+    }
+
+    @Override
+    public void startActiveServices() throws IOException {
+      namesystem.startActiveServices();
+      startTrashEmptier(conf);
+    }
+
+    @Override
+    public void stopActiveServices() throws IOException {
+      namesystem.stopActiveServices();
+      stopTrashEmptier();
+    }
+
+    @Override
+    public void startStandbyServices() throws IOException {
+      // TODO:HA Start reading editlog from active
+    }
+
+    @Override
+    public void stopStandbyServices() throws IOException {
+      // TODO:HA Stop reading editlog from active
+    }
   }
 }

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

@@ -17,6 +17,9 @@
  */
 package org.apache.hadoop.hdfs.server.namenode.ha;
 
+import java.io.IOException;
+
+import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.ha.ServiceFailedException;
 import org.apache.hadoop.hdfs.server.namenode.NameNode;
 import org.apache.hadoop.hdfs.server.namenode.NameNode.OperationCategory;
@@ -27,33 +30,42 @@
  * service and handles operations of type {@link OperationCategory#WRITE} and
  * {@link OperationCategory#READ}.
  */
+@InterfaceAudience.Private
 public class ActiveState extends HAState {
   public ActiveState() {
     super("active");
   }
 
   @Override
-  public void checkOperation(NameNode nn, OperationCategory op)
+  public void checkOperation(HAContext context, OperationCategory op)
       throws UnsupportedActionException {
     return; // Other than journal all operations are allowed in active state
   }
   
   @Override
-  public void setState(NameNode nn, HAState s) throws ServiceFailedException {
+  public void setState(HAContext context, HAState s) throws ServiceFailedException {
     if (s == NameNode.STANDBY_STATE) {
-      setStateInternal(nn, s);
+      setStateInternal(context, s);
       return;
     }
-    super.setState(nn, s);
+    super.setState(context, s);
   }
 
   @Override
-  protected void enterState(NameNode nn) throws ServiceFailedException {
+  public void enterState(HAContext context) throws ServiceFailedException {
-    // TODO:HA
+    try {
+      context.startActiveServices();
+    } catch (IOException e) {
+      throw new ServiceFailedException("Failed to start active services", e);
+    }
   }
 
   @Override
-  protected void exitState(NameNode nn) throws ServiceFailedException {
+  public void exitState(HAContext context) throws ServiceFailedException {
-    // TODO:HA
+    try {
+      context.stopActiveServices();
+    } catch (IOException e) {
+      throw new ServiceFailedException("Failed to stop active services", e);
+    }
   }
 }

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

@@ -0,0 +1,30 @@
+package org.apache.hadoop.hdfs.server.namenode.ha;
+
+import java.io.IOException;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+
+/**
+ * Context that is to be used by {@link HAState} for getting/setting the
+ * current state and performing required operations.
+ */
+@InterfaceAudience.Private
+public interface HAContext {
+  /** Set the state of the context to given {@code state} */
+  public void setState(HAState state);
+  
+  /** Get the state from the context */
+  public HAState getState();
+  
+  /** Start the services required in active state */
+  public void startActiveServices() throws IOException;
+  
+  /** Stop the services when exiting active state */
+  public void stopActiveServices() throws IOException;
+  
+  /** Start the services required in standby state */
+  public void startStandbyServices() throws IOException;
+  
+  /** Stop the services when exiting standby state */
+  public void stopStandbyServices() throws IOException;
+}

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

@@ -19,7 +19,6 @@
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.ha.ServiceFailedException;
-import org.apache.hadoop.hdfs.server.namenode.NameNode;
 import org.apache.hadoop.hdfs.server.namenode.NameNode.OperationCategory;
 import org.apache.hadoop.hdfs.server.namenode.UnsupportedActionException;
 
@@ -44,38 +43,38 @@ public HAState(String name) {
    * @param s new state
    * @throws ServiceFailedException on failure to transition to new state.
    */
-  protected final void setStateInternal(final NameNode nn, final HAState s)
+  protected final void setStateInternal(final HAContext context, final HAState s)
       throws ServiceFailedException {
-    exitState(nn);
+    exitState(context);
-    nn.setState(s);
+    context.setState(s);
-    s.enterState(nn);
+    s.enterState(context);
   }
 
   /**
    * Method to be overridden by subclasses to perform steps necessary for
    * entering a state.
-   * @param nn Namenode
+   * @param context HA context
    * @throws ServiceFailedException on failure to enter the state.
    */
-  protected abstract void enterState(final NameNode nn)
+  public abstract void enterState(final HAContext context)
       throws ServiceFailedException;
 
   /**
    * Method to be overridden by subclasses to perform steps necessary for
    * exiting a state.
-   * @param nn Namenode
+   * @param context HA context
    * @throws ServiceFailedException on failure to enter the state.
    */
-  protected abstract void exitState(final NameNode nn)
+  public abstract void exitState(final HAContext context)
       throws ServiceFailedException;
 
   /**
    * Move from the existing state to a new state
-   * @param nn Namenode
+   * @param context HA context
    * @param s new state
    * @throws ServiceFailedException on failure to transition to new state.
    */
-  public void setState(NameNode nn, HAState s) throws ServiceFailedException {
+  public void setState(HAContext context, HAState s) throws ServiceFailedException {
     if (this == s) { // Aleady in the new state
       return;
     }
@@ -85,15 +84,15 @@ public void setState(NameNode nn, HAState s) throws ServiceFailedException {
   
   /**
    * Check if an operation is supported in a given state.
-   * @param nn Namenode
+   * @param context HA context
    * @param op Type of the operation.
    * @throws UnsupportedActionException if a given type of operation is not
    *           supported in this state.
    */
-  public void checkOperation(final NameNode nn, final OperationCategory op)
+  public void checkOperation(final HAContext context, final OperationCategory op)
       throws UnsupportedActionException {
     String msg = "Operation category " + op + " is not supported in state "
-        + nn.getState();
+        + context.getState();
     throw new UnsupportedActionException(msg);
   }
   

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

@@ -17,6 +17,9 @@
  */
 package org.apache.hadoop.hdfs.server.namenode.ha;
 
+import java.io.IOException;
+
+import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.ha.ServiceFailedException;
 import org.apache.hadoop.hdfs.server.namenode.NameNode;
 
@@ -31,28 +34,37 @@
  * 
  * It does not handle read/write/checkpoint operations.
  */
+@InterfaceAudience.Private
 public class StandbyState extends HAState {
   public StandbyState() {
     super("standby");
   }
 
   @Override
-  public void setState(NameNode nn, HAState s) throws ServiceFailedException {
+  public void setState(HAContext context, HAState s) throws ServiceFailedException {
     if (s == NameNode.ACTIVE_STATE) {
-      setStateInternal(nn, s);
+      setStateInternal(context, s);
       return;
     }
-    super.setState(nn, s);
+    super.setState(context, s);
   }
 
   @Override
-  protected void enterState(NameNode nn) throws ServiceFailedException {
+  public void enterState(HAContext context) throws ServiceFailedException {
-    // TODO:HA
+    try {
+      context.startStandbyServices();
+    } catch (IOException e) {
+      throw new ServiceFailedException("Failed to start standby services", e);
+    }
   }
 
   @Override
-  protected void exitState(NameNode nn) throws ServiceFailedException {
+  public void exitState(HAContext context) throws ServiceFailedException {
-    // TODO:HA
+    try {
+      context.stopStandbyServices();
+    } catch (IOException e) {
+      throw new ServiceFailedException("Failed to stop standby services", e);
+    }
   }
 }