diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/RPC.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/RPC.java
index 069841b1c9b..eee364ccdee 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/RPC.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/RPC.java
@@ -580,6 +580,12 @@ public static <T> ProtocolProxy<T> getProtocolProxy(Class<T> protocol,
    * @param proxy the RPC proxy object to be stopped
    */
   public static void stopProxy(Object proxy) {
+    if (proxy instanceof ProtocolTranslator) {
+      RPC.stopProxy(((ProtocolTranslator)proxy)
+          .getUnderlyingProxyObject());
+      return;
+    }
+    
     InvocationHandler invocationHandler = null;
     try {
       invocationHandler = Proxy.getInvocationHandler(proxy);
diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-1623.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-1623.txt
index 18de5f63349..42bdcf8a860 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-1623.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-1623.txt
@@ -238,3 +238,5 @@ HDFS-3013. HA: NameNode format doesn't pick up dfs.namenode.name.dir.NameService
 HDFS-3019. Fix silent failure of TestEditLogJournalFailures (todd)
 
 HDFS-2958. Sweep for remaining proxy construction which doesn't go through failover path. (atm)
+
+HDFS-2920. fix remaining TODO items. (atm and todd)
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSClient.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSClient.java
index f0dc8ceff2a..83cd9a8a3ca 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSClient.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSClient.java
@@ -418,22 +418,9 @@ boolean renewLease() throws IOException {
   
   /**
    * Close connections the Namenode.
-   * The namenode variable is either a rpcProxy passed by a test or 
-   * created using the protocolTranslator which is closeable.
-   * If closeable then call close, else close using RPC.stopProxy().
    */
   void closeConnectionToNamenode() {
-    if (namenode instanceof Closeable) {
-      try {
-        ((Closeable) namenode).close();
-        return;
-      } catch (IOException e) {
-        // fall through - lets try the stopProxy
-        LOG.warn("Exception closing namenode, stopping the proxy");
-      }     
-    } else {
-      RPC.stopProxy(namenode);
-    }
+    RPC.stopProxy(namenode);
   }
   
   /** Abort and release resources held.  Ignore all errors. */
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/ClientProtocol.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/ClientProtocol.java
index 5ef00bfe9ca..641dfc11bb1 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/ClientProtocol.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/ClientProtocol.java
@@ -694,7 +694,6 @@ public boolean restoreFailedStorage(String arg)
    * 
    * @throws IOException
    */
-  //TODO(HA): Should this be @Idempotent?
   public void finalizeUpgrade() throws IOException;
 
   /**
@@ -704,7 +703,6 @@ public boolean restoreFailedStorage(String arg)
    * @return upgrade status information or null if no upgrades are in progress
    * @throws IOException
    */
-  //TODO(HA): Should this be @Idempotent?
   public UpgradeStatusReport distributedUpgradeProgress(UpgradeAction action) 
       throws IOException;
 
@@ -737,7 +735,7 @@ public CorruptFileBlocks listCorruptFileBlocks(String path, String cookie)
    * @param bandwidth Blanacer bandwidth in bytes per second for this datanode.
    * @throws IOException
    */
-  //TODO(HA): Should this be @Idempotent?
+  @Idempotent
   public void setBalancerBandwidth(long bandwidth) throws IOException;
   
   /**
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientDatanodeProtocolTranslatorPB.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientDatanodeProtocolTranslatorPB.java
index d03f27060b5..bc32ab00a56 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientDatanodeProtocolTranslatorPB.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientDatanodeProtocolTranslatorPB.java
@@ -45,6 +45,7 @@
 import org.apache.hadoop.ipc.ProtobufRpcEngine;
 import org.apache.hadoop.ipc.ProtocolMetaInterface;
 import org.apache.hadoop.ipc.ProtocolSignature;
+import org.apache.hadoop.ipc.ProtocolTranslator;
 import org.apache.hadoop.ipc.RPC;
 import org.apache.hadoop.ipc.RpcClientUtil;
 import org.apache.hadoop.ipc.RpcPayloadHeader.RpcKind;
@@ -63,7 +64,8 @@
 @InterfaceAudience.Private
 @InterfaceStability.Stable
 public class ClientDatanodeProtocolTranslatorPB implements
-    ProtocolMetaInterface, ClientDatanodeProtocol, Closeable {
+    ProtocolMetaInterface, ClientDatanodeProtocol,
+    ProtocolTranslator, Closeable {
   public static final Log LOG = LogFactory
       .getLog(ClientDatanodeProtocolTranslatorPB.class);
   
@@ -211,4 +213,9 @@ public boolean isMethodSupported(String methodName) throws IOException {
         ClientDatanodeProtocolPB.class, RpcKind.RPC_PROTOCOL_BUFFER,
         RPC.getProtocolVersion(ClientDatanodeProtocolPB.class), methodName);
   }
+
+  @Override
+  public Object getUnderlyingProxyObject() {
+    return rpcProxy;
+  }
 }
\ No newline at end of file
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java
index 9a76f1e43d7..cbae6f2246c 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java
@@ -19,7 +19,6 @@
 
 import java.io.IOException;
 import java.io.PrintWriter;
-import java.io.StringWriter;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPOfferService.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPOfferService.java
index c35b35f0647..aaba4fff2ad 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPOfferService.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPOfferService.java
@@ -383,7 +383,6 @@ synchronized void shutdownActor(BPServiceActor actor) {
 
     bpServices.remove(actor);
 
-    // TODO: synchronization should be a little better here
     if (bpServices.isEmpty()) {
       dn.shutdownBlockPool(this);
       
@@ -392,12 +391,6 @@ synchronized void shutdownActor(BPServiceActor actor) {
     }
   }
 
-  @Deprecated
-  synchronized InetSocketAddress getNNSocketAddress() {
-    // TODO(HA) this doesn't make sense anymore
-    return bpServiceToActive.getNNSocketAddress();
-  }
-
   /**
    * Called by the DN to report an error to the NNs.
    */
@@ -432,11 +425,9 @@ void reportRemoteBadBlock(DatanodeInfo dnInfo, ExtendedBlock block) {
   }
 
   /**
-   * TODO: this is still used in a few places where we need to sort out
-   * what to do in HA!
-   * @return a proxy to the active NN
+   * @return a proxy to the active NN, or null if the BPOS has not
+   * acknowledged any NN as active yet.
    */
-  @Deprecated
   synchronized DatanodeProtocolClientSideTranslatorPB getActiveNN() {
     if (bpServiceToActive != null) {
       return bpServiceToActive.bpNamenode;
@@ -596,6 +587,7 @@ private boolean processCommandFromActive(DatanodeCommand cmd,
       break;
     case DatanodeProtocol.DNA_SHUTDOWN:
       // TODO: DNA_SHUTDOWN appears to be unused - the NN never sends this command
+      // See HDFS-2987.
       throw new UnsupportedOperationException("Received unimplemented DNA_SHUTDOWN");
     case DatanodeProtocol.DNA_REGISTER:
       // namenode requested a registration - at start or if NN lost contact
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
index 982a5685033..75f32cbc04c 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
@@ -538,8 +538,8 @@ private void offerService() throws Exception {
         DatanodeCommand cmd = blockReport();
         processCommand(new DatanodeCommand[]{ cmd });
 
-        // Now safe to start scanning the block pool
-        // TODO(HA): this doesn't seem quite right
+        // Now safe to start scanning the block pool.
+        // If it has already been started, this is a no-op.
         if (dn.blockScanner != null) {
           dn.blockScanner.addBlockPool(bpos.getBlockPoolId());
         }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolManager.java
index 3176be20784..3355ee269a5 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolManager.java
@@ -86,16 +86,6 @@ synchronized BPOfferService get(String bpid) {
     return bpByBlockPoolId.get(bpid);
   }
   
-  // TODO(HA) would be good to kill this
-  synchronized BPOfferService get(InetSocketAddress addr) {
-    for (BPOfferService bpos : offerServices) {
-      if (bpos.containsNN(addr)) {
-        return bpos;
-      }
-    }
-    return null;
-  }
-
   synchronized void remove(BPOfferService t) {
     offerServices.remove(t);
     bpByBlockPoolId.remove(t.getBlockPoolId());
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
index acbcb032a8f..f13466a4abe 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
@@ -565,6 +565,23 @@ public void reportRemoteBadBlock(DatanodeInfo srcDataNode, ExtendedBlock block)
     bpos.reportRemoteBadBlock(srcDataNode, block);
   }
   
+  /**
+   * Try to send an error report to the NNs associated with the given
+   * block pool.
+   * @param bpid the block pool ID
+   * @param errCode error code to send
+   * @param errMsg textual message to send
+   */
+  void trySendErrorReport(String bpid, int errCode, String errMsg) {
+    BPOfferService bpos = blockPoolManager.get(bpid);
+    if (bpos == null) {
+      throw new IllegalArgumentException("Bad block pool: " + bpid);
+    }
+    bpos.trySendErrorReport(errCode, errMsg);
+  }
+
+
+  
   /**
    * Return the BPOfferService instance corresponding to the given block.
    * @param block
@@ -874,7 +891,7 @@ DatanodeRegistration getDNRegistrationByMachineName(String mName) {
     // TODO: all the BPs should have the same name as each other, they all come
     // from getName() here! and the use cases only are in tests where they just
     // call with getName(). So we could probably just make this method return
-    // the first BPOS's registration
+    // the first BPOS's registration. See HDFS-2609.
     BPOfferService [] bposArray = blockPoolManager.getAllNamenodeThreads();
     for (BPOfferService bpos : bposArray) {
       if(bpos.bpRegistration.getName().equals(mName))
@@ -920,22 +937,6 @@ public InterDatanodeProtocol run() throws IOException {
       throw new IOException(ie.getMessage());
     }
   }
-
-  /**
-   * get the name node address based on the block pool id
-   * @param bpid block pool ID
-   * @return namenode address corresponding to the bpid
-   */
-  public InetSocketAddress getNameNodeAddr(String bpid) {
-    // TODO(HA) this function doesn't make sense! used by upgrade code
-    // Should it return just the active one or simply return the BPService.
-    BPOfferService bp = blockPoolManager.get(bpid);
-    if (bp != null) {
-      return bp.getNNSocketAddress();
-    }
-    LOG.warn("No name node address found for block pool ID " + bpid);
-    return null;
-  }
   
   public InetSocketAddress getSelfAddr() {
     return selfAddr;
@@ -1869,7 +1870,7 @@ private void recoverBlock(RecoveringBlock rBlock) throws IOException {
    * @return Namenode corresponding to the bpid
    * @throws IOException
    */
-  public DatanodeProtocolClientSideTranslatorPB getBPNamenode(String bpid)
+  public DatanodeProtocolClientSideTranslatorPB getActiveNamenodeForBP(String bpid)
       throws IOException {
     BPOfferService bpos = blockPoolManager.get(bpid);
     if (bpos == null) {
@@ -1888,9 +1889,13 @@ public DatanodeProtocolClientSideTranslatorPB getBPNamenode(String bpid)
   void syncBlock(RecoveringBlock rBlock,
                          List<BlockRecord> syncList) throws IOException {
     ExtendedBlock block = rBlock.getBlock();
-    DatanodeProtocolClientSideTranslatorPB nn = getBPNamenode(block
-        .getBlockPoolId());
-    assert nn != null;
+    DatanodeProtocolClientSideTranslatorPB nn =
+      getActiveNamenodeForBP(block.getBlockPoolId());
+    if (nn == null) {
+      throw new IOException(
+          "Unable to synchronize block " + rBlock + ", since this DN "
+          + " has not acknowledged any NN as active.");
+    }
     
     long recoveryId = rBlock.getNewGenerationStamp();
     if (LOG.isDebugEnabled()) {
@@ -2111,14 +2116,19 @@ public int getInfoPort(){
 
   /**
    * Returned information is a JSON representation of a map with 
-   * name node host name as the key and block pool Id as the value
+   * name node host name as the key and block pool Id as the value.
+   * Note that, if there are multiple NNs in an NA nameservice,
+   * a given block pool may be represented twice.
    */
   @Override // DataNodeMXBean
   public String getNamenodeAddresses() {
     final Map<String, String> info = new HashMap<String, String>();
     for (BPOfferService bpos : blockPoolManager.getAllNamenodeThreads()) {
       if (bpos != null) {
-        info.put(bpos.getNNSocketAddress().getHostName(), bpos.getBlockPoolId());
+        for (BPServiceActor actor : bpos.getBPServiceActors()) {
+          info.put(actor.getNNSocketAddress().getHostName(),
+              bpos.getBlockPoolId());
+        }
       }
     }
     return JSON.toString(info);
@@ -2167,11 +2177,18 @@ public void deleteBlockPool(String blockPoolId, boolean force)
 
   /**
    * @param addr rpc address of the namenode
-   * @return true - if BPOfferService corresponding to the namenode is alive
+   * @return true if the datanode is connected to a NameNode at the
+   * given address
    */
-  public boolean isBPServiceAlive(InetSocketAddress addr) {
-    BPOfferService bp = blockPoolManager.get(addr);
-    return bp != null ? bp.isAlive() : false;
+  public boolean isConnectedToNN(InetSocketAddress addr) {
+    for (BPOfferService bpos : getAllBpOs()) {
+      for (BPServiceActor bpsa : bpos.getBPServiceActors()) {
+        if (addr.equals(bpsa.getNNSocketAddress())) {
+          return bpsa.isAlive();
+        }
+      }
+    }
+    return false;
   }
   
   /**
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/UpgradeManagerDatanode.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/UpgradeManagerDatanode.java
index 478fb5660d0..9ada40fd5f0 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/UpgradeManagerDatanode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/UpgradeManagerDatanode.java
@@ -92,7 +92,7 @@ public synchronized boolean startUpgrade() throws IOException {
           "UpgradeManagerDatanode.currentUpgrades is not null.";
         assert upgradeDaemon == null : 
           "UpgradeManagerDatanode.upgradeDaemon is not null.";
-        DatanodeProtocol nn = dataNode.getBPNamenode(bpid);
+        DatanodeProtocol nn = dataNode.getActiveNamenodeForBP(bpid);
         nn.processUpgradeCommand(broadcastCommand);
         return true;
       }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/UpgradeObjectDatanode.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/UpgradeObjectDatanode.java
index ddb1d6029f8..49d26212d09 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/UpgradeObjectDatanode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/UpgradeObjectDatanode.java
@@ -45,7 +45,7 @@ protected DataNode getDatanode() {
   }
   
   protected DatanodeProtocol getNamenode() throws IOException {
-    return dataNode.getBPNamenode(bpid);
+    return dataNode.getActiveNamenodeForBP(bpid);
   }
 
   void setDatanode(DataNode dataNode, String bpid) {
@@ -92,14 +92,7 @@ boolean preUpgradeAction(NamespaceInfo nsInfo) throws IOException {
             + " Name-node version = " + nsInfo.getLayoutVersion() + ".";
     DataNode.LOG.fatal( errorMsg );
     String bpid = nsInfo.getBlockPoolID();
-    DatanodeProtocol nn = dataNode.getBPNamenode(bpid);
-    try {
-      nn.errorReport(dataNode.getDNRegistrationForBP(bpid),
-                                    DatanodeProtocol.NOTIFY, errorMsg);
-    } catch(SocketTimeoutException e) {  // namenode is busy
-      DataNode.LOG.info("Problem connecting to server: " 
-                        + dataNode.getNameNodeAddr(nsInfo.getBlockPoolID()));
-    }
+    dataNode.trySendErrorReport(bpid, DatanodeProtocol.NOTIFY, errorMsg);
     throw new IOException(errorMsg);
   }
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java
index 9c1eb25807e..f922c11bc95 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java
@@ -282,18 +282,13 @@ INode unprotectedAddFile( String path,
       newNode = new INodeFile(permissions, 0, replication,
                               modificationTime, atime, preferredBlockSize);
     }
-    writeLock(); // TODO: this is silly, considering the assert above!
-    try {
-      try {
-        newNode = addNode(path, newNode, UNKNOWN_DISK_SPACE);
-      } catch (IOException e) {
-        return null;
-      }
-      return newNode;
-    } finally {
-      writeUnlock();
-    }
 
+    try {
+      newNode = addNode(path, newNode, UNKNOWN_DISK_SPACE);
+    } catch (IOException e) {
+      return null;
+    }
+    return newNode;
   }
 
   INodeDirectory addToParent(byte[] src, INodeDirectory parentINode,
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java
index bf1ec992c4c..84d4ace2833 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java
@@ -266,8 +266,8 @@ private void applyEditLogOp(FSEditLogOp op, FSDirectory fsDir,
 
       // Now close the file
       INodeFileUnderConstruction ucFile = (INodeFileUnderConstruction) oldFile;
-      // TODO: we could use removeLease(holder, path) here, but OP_CLOSE
-      // doesn't seem to serialize the holder... unclear why!
+      // One might expect that you could use removeLease(holder, path) here,
+      // but OP_CLOSE doesn't serialize the holder. So, remove by path.
       fsNamesys.leaseManager.removeLeaseWithPrefixPath(addCloseOp.path);
       INodeFile newFile = ucFile.convertToInodeFile();
       fsDir.replaceNode(addCloseOp.path, ucFile, newFile);
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImage.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImage.java
index adc3b46b7f5..7fb3d4bdfc5 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImage.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImage.java
@@ -226,7 +226,6 @@ boolean recoverTransitionRead(StartupOption startOpt, FSNamesystem target)
       }
     }
 
-    // TODO(HA): Have to figure out a story for the first 3 of these.
     // 3. Do transitions
     switch(startOpt) {
     case UPGRADE:
@@ -261,7 +260,6 @@ private boolean recoverStorageDirs(StartupOption startOpt,
       StorageState curState;
       try {
         curState = sd.analyzeStorage(startOpt, storage);
-        // TODO(HA): Fix this.
         String nameserviceId = DFSUtil.getNamenodeNameServiceId(conf);
         if (curState != StorageState.NORMAL && HAUtil.isHAEnabled(conf, nameserviceId)) {
           throw new IOException("Cannot start an HA namenode with name dirs " +
@@ -637,8 +635,6 @@ boolean loadFSImage(FSNamesystem target) throws IOException {
     
     // update the txid for the edit log
     editLog.setNextTxId(storage.getMostRecentCheckpointTxId() + numLoaded + 1);
-    // TODO(HA): This should probably always return false when HA is enabled and
-    // we're coming up in standby state.
     return needToSave;
   }
 
@@ -697,8 +693,6 @@ public long loadEdits(Iterable<EditLogInputStream> editStreams,
     } finally {
       FSEditLog.closeAllStreams(editStreams);
       // update the counts
-      // TODO(HA): this may be very slow -- we probably want to
-      // update them as we go for HA.
       target.dir.updateCountForINodeWithQuota();   
     }
     
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
index 4d54701bbb4..bc40864a4ed 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
@@ -533,7 +533,6 @@ void startActiveServices() throws IOException {
       
       if (!editLog.isOpenForWrite()) {
         // During startup, we're already open for write during initialization.
-        // TODO(HA): consider adding a startup state?
         editLog.initJournalsForWrite();
         // May need to recover
         editLog.recoverUnclosedStreams();
@@ -912,7 +911,6 @@ void close() {
     } finally {
       // using finally to ensure we also wait for lease daemon
       try {
-        // TODO: these lines spew lots of warnings about "already stopped" logs, etc
         stopActiveServices();
         stopStandbyServices();
         if (dir != null) {
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java
index 5dc62560232..d07ed860d22 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java
@@ -920,7 +920,7 @@ synchronized void monitorHealth()
     if (!haEnabled) {
       return; // no-op, if HA is not enabled
     }
-    // TODO:HA implement health check
+    // TODO(HA): implement health check
     return;
   }
   
@@ -963,7 +963,7 @@ synchronized boolean readyToBecomeActive()
   /**
    * Class used as expose {@link NameNode} as context to {@link HAState}
    * 
-   * TODO:HA
+   * TODO(HA):
    * When entering and exiting state, on failing to start services,
    * appropriate action is needed todo either shutdown the node or recover
    * from failure.
@@ -1005,7 +1005,6 @@ public void prepareToStopStandbyServices() throws ServiceFailedException {
     
     @Override
     public void stopStandbyServices() throws IOException {
-      // TODO(HA): Are we guaranteed to be the only active here?
       if (namesystem != null) {
         namesystem.stopStandbyServices();
       }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ha/StandbyCheckpointer.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ha/StandbyCheckpointer.java
index edfc53fb12c..036dd431ade 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ha/StandbyCheckpointer.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ha/StandbyCheckpointer.java
@@ -176,7 +176,7 @@ private void doCheckpoint() throws InterruptedException, IOException {
   public void cancelAndPreventCheckpoints() throws ServiceFailedException {
     try {
       thread.preventCheckpointsFor(PREVENT_AFTER_CANCEL_MS);
-      // TODO: there is a really narrow race here if we are just
+      // TODO(HA): there is a really narrow race here if we are just
       // about to start a checkpoint - this won't cancel it!
       namesystem.getFSImage().cancelSaveNamespace(
           "About to exit standby state");
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/MiniDFSCluster.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/MiniDFSCluster.java
index 770d0f1066a..658282a0e72 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/MiniDFSCluster.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/MiniDFSCluster.java
@@ -1696,9 +1696,9 @@ private synchronized boolean shouldWait(DatanodeInfo[] dnInfo,
     // If a datanode failed to start, then do not wait
     for (DataNodeProperties dn : dataNodes) {
       // the datanode thread communicating with the namenode should be alive
-      if (!dn.datanode.isBPServiceAlive(addr)) {
-        LOG.warn("BPOfferService failed to start in datanode " + dn.datanode
-            + " for namenode at " + addr);
+      if (!dn.datanode.isConnectedToNN(addr)) {
+        LOG.warn("BPOfferService in datanode " + dn.datanode
+            + " failed to connect to namenode at " + addr);
         return false;
       }
     }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBlockRecovery.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBlockRecovery.java
index 2a75998d798..59a61cf2ea9 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBlockRecovery.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBlockRecovery.java
@@ -461,7 +461,7 @@ public void testZeroLenReplicas() throws IOException, InterruptedException {
         initReplicaRecovery(any(RecoveringBlock.class));
     Daemon d = spyDN.recoverBlocks(initRecoveringBlocks());
     d.join();
-    DatanodeProtocol dnP = dn.getBPNamenode(POOL_ID);
+    DatanodeProtocol dnP = dn.getActiveNamenodeForBP(POOL_ID);
     verify(dnP).commitBlockSynchronization(
         block, RECOVERY_ID, 0, true, true, DatanodeID.EMPTY_ARRAY);
   }
@@ -518,7 +518,7 @@ public void testNoReplicaUnderRecovery() throws IOException {
     } catch (IOException e) {
       e.getMessage().startsWith("Cannot recover ");
     }
-    DatanodeProtocol namenode = dn.getBPNamenode(POOL_ID);
+    DatanodeProtocol namenode = dn.getActiveNamenodeForBP(POOL_ID);
     verify(namenode, never()).commitBlockSynchronization(
         any(ExtendedBlock.class), anyLong(), anyLong(), anyBoolean(),
         anyBoolean(), any(DatanodeID[].class));
@@ -547,7 +547,7 @@ public void testNotMatchedReplicaID() throws IOException {
       } catch (IOException e) {
         e.getMessage().startsWith("Cannot recover ");
       }
-      DatanodeProtocol namenode = dn.getBPNamenode(POOL_ID);
+      DatanodeProtocol namenode = dn.getActiveNamenodeForBP(POOL_ID);
       verify(namenode, never()).commitBlockSynchronization(
           any(ExtendedBlock.class), anyLong(), anyLong(), anyBoolean(),
           anyBoolean(), any(DatanodeID[].class));
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeMultipleRegistrations.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeMultipleRegistrations.java
index a3e8ceb90f0..20a16c31669 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeMultipleRegistrations.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeMultipleRegistrations.java
@@ -23,6 +23,8 @@
 import static org.junit.Assert.assertNotSame;
 
 import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.util.List;
 import java.util.Map;
 
 import org.apache.commons.logging.Log;
@@ -99,15 +101,15 @@ public void test2NNRegistration() throws IOException {
       BPOfferService bpos2 = dn.getAllBpOs()[1];
 
       // The order of bpos is not guaranteed, so fix the order
-      if (bpos1.getNNSocketAddress().equals(nn2.getNameNodeAddress())) {
+      if (getNNSocketAddress(bpos1).equals(nn2.getNameNodeAddress())) {
         BPOfferService tmp = bpos1;
         bpos1 = bpos2;
         bpos2 = tmp;
       }
 
-      assertEquals("wrong nn address", bpos1.getNNSocketAddress(),
+      assertEquals("wrong nn address", getNNSocketAddress(bpos1),
           nn1.getNameNodeAddress());
-      assertEquals("wrong nn address", bpos2.getNNSocketAddress(),
+      assertEquals("wrong nn address", getNNSocketAddress(bpos2),
           nn2.getNameNodeAddress());
       assertEquals("wrong bpid", bpos1.getBlockPoolId(), bpid1);
       assertEquals("wrong bpid", bpos2.getBlockPoolId(), bpid2);
@@ -121,6 +123,12 @@ public void test2NNRegistration() throws IOException {
       cluster.shutdown();
     }
   }
+  
+  private static InetSocketAddress getNNSocketAddress(BPOfferService bpos) {
+    List<BPServiceActor> actors = bpos.getBPServiceActors();
+    assertEquals(1, actors.size());
+    return actors.get(0).getNNSocketAddress();
+  }
 
   /**
    * starts single nn and single dn and verifies registration and handshake
@@ -154,14 +162,16 @@ public void testFedSingleNN() throws IOException {
 
       for (BPOfferService bpos : dn.getAllBpOs()) {
         LOG.info("reg: bpid=" + "; name=" + bpos.bpRegistration.name + "; sid="
-            + bpos.bpRegistration.storageID + "; nna=" + bpos.getNNSocketAddress());
+            + bpos.bpRegistration.storageID + "; nna=" +
+            getNNSocketAddress(bpos));
       }
 
       // try block report
       BPOfferService bpos1 = dn.getAllBpOs()[0];
       bpos1.triggerBlockReportForTests();
 
-      assertEquals("wrong nn address", bpos1.getNNSocketAddress(),
+      assertEquals("wrong nn address",
+          getNNSocketAddress(bpos1),
           nn1.getNameNodeAddress());
       assertEquals("wrong bpid", bpos1.getBlockPoolId(), bpid1);
       assertEquals("wrong cid", dn.getClusterId(), cid1);
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestRefreshNamenodes.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestRefreshNamenodes.java
index cfa1d64c903..2d6f2103796 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestRefreshNamenodes.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestRefreshNamenodes.java
@@ -22,15 +22,18 @@
 
 import java.io.IOException;
 import java.net.InetSocketAddress;
+import java.util.Set;
 
 import org.apache.hadoop.conf.Configuration;
-import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.apache.hadoop.hdfs.MiniDFSNNTopology;
 import org.apache.hadoop.hdfs.MiniDFSNNTopology.NNConf;
 import org.apache.hadoop.hdfs.MiniDFSNNTopology.NSConf;
 import org.junit.Test;
 
+import com.google.common.base.Joiner;
+import com.google.common.collect.Sets;
+
 /**
  * Tests datanode refresh namenode list functionality.
  */
@@ -65,21 +68,24 @@ public void testRefreshNamenodes() throws IOException {
 
       cluster.addNameNode(conf, nnPort4);
 
-      BPOfferService[] bpoList = dn.getAllBpOs();
       // Ensure a BPOfferService in the datanodes corresponds to
       // a namenode in the cluster
+      Set<InetSocketAddress> nnAddrsFromCluster = Sets.newHashSet();
       for (int i = 0; i < 4; i++) {
-        InetSocketAddress addr = cluster.getNameNode(i).getNameNodeAddress();
-        boolean found = false;
-        for (int j = 0; j < bpoList.length; j++) {
-          if (bpoList[j] != null && addr.equals(bpoList[j].getNNSocketAddress())) {
-            found = true;
-            bpoList[j] = null; // Erase the address that matched
-            break;
-          }
-        }
-        assertTrue("NameNode address " + addr + " is not found.", found);
+        assertTrue(nnAddrsFromCluster.add(
+            cluster.getNameNode(i).getNameNodeAddress()));
       }
+      
+      Set<InetSocketAddress> nnAddrsFromDN = Sets.newHashSet();
+      for (BPOfferService bpos : dn.getAllBpOs()) {
+        for (BPServiceActor bpsa : bpos.getBPServiceActors()) {
+          assertTrue(nnAddrsFromDN.add(bpsa.getNNSocketAddress()));
+        }
+      }
+      
+      assertEquals("",
+          Joiner.on(",").join(
+            Sets.symmetricDifference(nnAddrsFromCluster, nnAddrsFromDN)));
     } finally {
       if (cluster != null) {
         cluster.shutdown();
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestPipelinesFailover.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestPipelinesFailover.java
index 465987c6cb1..547ba72e493 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestPipelinesFailover.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestPipelinesFailover.java
@@ -179,7 +179,7 @@ public void testWriteOverFailoverWithDnFail() throws Exception {
 
       // write another block and a half
       AppendTestUtil.write(stm, BLOCK_AND_A_HALF, BLOCK_AND_A_HALF);
-      stm.hflush(); // TODO: see above
+      stm.hflush();
       
       LOG.info("Failing back to NN 0");
       cluster.transitionToStandby(0);
@@ -188,7 +188,7 @@ public void testWriteOverFailoverWithDnFail() throws Exception {
       cluster.stopDataNode(1);
       
       AppendTestUtil.write(stm, BLOCK_AND_A_HALF*2, BLOCK_AND_A_HALF);
-      stm.hflush(); // TODO: see above
+      stm.hflush();
       
       
       stm.close();
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestStandbyCheckpoints.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestStandbyCheckpoints.java
index a34d6bdfc21..5440c38cc22 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestStandbyCheckpoints.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestStandbyCheckpoints.java
@@ -127,9 +127,6 @@ public void testBothNodesInStandbyState() throws Exception {
     List<File> dirs = Lists.newArrayList();
     dirs.addAll(FSImageTestUtil.getNameNodeCurrentDirs(cluster, 0));
     dirs.addAll(FSImageTestUtil.getNameNodeCurrentDirs(cluster, 1));
-    // TODO: this failed once because it caught a ckpt file -- maybe
-    // this is possible if one of the NNs is really fast and the other is slow?
-    // need to loop this to suss out the race.
     FSImageTestUtil.assertParallelFilesAreIdentical(dirs, ImmutableSet.<String>of());
   }