HDFS-2488. Separate datatypes for InterDatanodeProtocol. Contributed by Suresh Srinivas.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1188487 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -78,6 +78,8 @@ Trunk (unreleased changes)
     HDFS-2489. Move Finalize and Register to separate file out of
     DatanodeCommand.java. (suresh)
 
+    HDFS-2488. Separate datatypes for InterDatanodeProtocol. (suresh)
+
   BUG FIXES
     HDFS-2287. TestParallelRead has a small off-by-one bug. (todd)
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolR23Compatible/BlockWritable.java

@@ -42,6 +42,7 @@ public class BlockWritable implements Writable {
        });
   }
 
+
   private long blockId;
   private long numBytes;
   private long generationStamp;
@@ -79,4 +80,16 @@ public class BlockWritable implements Writable {
   public Block convert() {
     return new Block(blockId, numBytes, generationStamp);
   }
+  
+  public long getBlockId() {
+    return blockId;
+  }
+
+  public long getNumBytes() {
+    return numBytes;
+  }
+
+  public long getGenerationStamp() {
+    return generationStamp;
+  }
 }

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

@@ -158,6 +158,9 @@ import org.apache.hadoop.hdfs.server.protocol.NamespaceInfo;
 import org.apache.hadoop.hdfs.server.protocol.ReceivedDeletedBlockInfo;
 import org.apache.hadoop.hdfs.server.protocol.ReplicaRecoveryInfo;
 import org.apache.hadoop.hdfs.server.protocol.UpgradeCommand;
+import org.apache.hadoop.hdfs.server.protocolR23Compatible.InterDatanodeProtocolServerSideTranslatorR23;
+import org.apache.hadoop.hdfs.server.protocolR23Compatible.InterDatanodeProtocolTranslatorR23;
+import org.apache.hadoop.hdfs.server.protocolR23Compatible.InterDatanodeWireProtocol;
 import org.apache.hadoop.hdfs.web.WebHdfsFileSystem;
 import org.apache.hadoop.hdfs.web.resources.Param;
 import org.apache.hadoop.http.HttpServer;
@@ -589,7 +592,11 @@ public class DataNode extends Configured
                               conf.getInt(DFS_DATANODE_HANDLER_COUNT_KEY, 
                                           DFS_DATANODE_HANDLER_COUNT_DEFAULT), 
                               false, conf, blockPoolTokenSecretManager);
-    ipcServer.addProtocol(InterDatanodeProtocol.class, this);
+    InterDatanodeProtocolServerSideTranslatorR23 
+        interDatanodeProtocolServerTranslator = 
+          new InterDatanodeProtocolServerSideTranslatorR23(this);
+    ipcServer.addProtocol(InterDatanodeWireProtocol.class, 
+        interDatanodeProtocolServerTranslator);
     
     // set service-level authorization security policy
     if (conf.getBoolean(
@@ -1641,15 +1648,13 @@ public class DataNode extends Configured
     if (InterDatanodeProtocol.LOG.isDebugEnabled()) {
       InterDatanodeProtocol.LOG.debug("InterDatanodeProtocol addr=" + addr);
     }
-    UserGroupInformation loginUgi = UserGroupInformation.getLoginUser();
+    final UserGroupInformation loginUgi = UserGroupInformation.getLoginUser();
     try {
       return loginUgi
           .doAs(new PrivilegedExceptionAction<InterDatanodeProtocol>() {
             public InterDatanodeProtocol run() throws IOException {
-              return (InterDatanodeProtocol) RPC.getProxy(
-                  InterDatanodeProtocol.class, InterDatanodeProtocol.versionID,
-                  addr, UserGroupInformation.getCurrentUser(), conf,
-                  NetUtils.getDefaultSocketFactory(conf), socketTimeout);
+              return new InterDatanodeProtocolTranslatorR23(addr, loginUgi,
+                  conf, NetUtils.getDefaultSocketFactory(conf), socketTimeout);
             }
           });
     } catch (InterruptedException ie) {

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

@@ -59,7 +59,6 @@ import org.apache.hadoop.hdfs.server.common.GenerationStamp;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.ReplicaState;
 import org.apache.hadoop.hdfs.server.datanode.metrics.FSDatasetMBean;
 import org.apache.hadoop.hdfs.server.protocol.BlockRecoveryCommand.RecoveringBlock;
-import org.apache.hadoop.hdfs.server.protocol.InterDatanodeProtocol;
 import org.apache.hadoop.hdfs.server.protocol.ReplicaRecoveryInfo;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.metrics2.util.MBeans;
@@ -1263,8 +1262,8 @@ public class FSDataset implements FSDatasetInterface {
       throws IOException {
     File f = validateBlockFile(bpid, b);
     if(f == null) {
-      if (InterDatanodeProtocol.LOG.isDebugEnabled()) {
-        InterDatanodeProtocol.LOG.debug("b=" + b + ", volumeMap=" + volumeMap);
+      if (DataNode.LOG.isDebugEnabled()) {
+        DataNode.LOG.debug("b=" + b + ", volumeMap=" + volumeMap);
       }
       throw new IOException("Block " + b + " is not valid.");
     }
@@ -2003,8 +2002,8 @@ public class FSDataset implements FSDatasetInterface {
       datanode.checkDiskError();
     }
     
-    if (InterDatanodeProtocol.LOG.isDebugEnabled()) {
-      InterDatanodeProtocol.LOG.debug("b=" + b + ", f=" + f);
+    if (DataNode.LOG.isDebugEnabled()) {
+      DataNode.LOG.debug("b=" + b + ", f=" + f);
     }
     return null;
   }

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

@@ -25,7 +25,9 @@ import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
+import org.apache.hadoop.hdfs.protocolR23Compatible.ClientNamenodeWireProtocol;
 import org.apache.hadoop.hdfs.server.protocol.BlockRecoveryCommand.RecoveringBlock;
+import org.apache.hadoop.hdfs.server.protocolR23Compatible.InterDatanodeWireProtocol;
 import org.apache.hadoop.ipc.VersionedProtocol;
 import org.apache.hadoop.security.KerberosInfo;
 
@@ -39,6 +41,23 @@ public interface InterDatanodeProtocol extends VersionedProtocol {
   public static final Log LOG = LogFactory.getLog(InterDatanodeProtocol.class);
 
   /**
+   * Until version 9, this class InterDatanodeProtocol served as both
+   * the interface to the DN AND the RPC protocol used to communicate with the 
+   * DN.
+   * 
+   * Post version 6L (release 23 of Hadoop), the protocol is implemented in
+   * {@literal ../protocolR23Compatible/InterDatanodeWireProtocol}
+   * 
+   * This class is used by both the DN to insulate from the protocol 
+   * serialization.
+   * 
+   * If you are adding/changing DN's interface then you need to 
+   * change both this class and ALSO
+   * {@link InterDatanodeWireProtocol}
+   * These changes need to be done in a compatible fashion as described in 
+   * {@link ClientNamenodeWireProtocol}
+   * 
+   * The log of historical changes can be retrieved from the svn).
    * 6: Add block pool ID to Block
    */
   public static final long versionID = 6L;

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/protocolR23Compatible/InterDatanodeProtocolServerSideTranslatorR23.java

@@ -0,0 +1,116 @@
+/**
+ * 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.hdfs.server.protocolR23Compatible;
+
+import java.io.IOException;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
+import org.apache.hadoop.hdfs.protocolR23Compatible.ExtendedBlockWritable;
+import org.apache.hadoop.hdfs.protocolR23Compatible.ProtocolSignatureWritable;
+import org.apache.hadoop.hdfs.server.protocol.InterDatanodeProtocol;
+import org.apache.hadoop.ipc.ProtocolSignature;
+import org.apache.hadoop.ipc.RPC;
+
+/**
+ * This class is used on the server side. Calls come across the wire for the
+ * protocol family of Release 23 onwards. This class translates the R23 data
+ * types to the internal data types used inside the DN as specified in the
+ * generic InterDatanodeProtocol.
+ */
+@InterfaceAudience.Private
+@InterfaceStability.Stable
+public class InterDatanodeProtocolServerSideTranslatorR23 implements
+    InterDatanodeWireProtocol {
+  final private InterDatanodeProtocol server;
+
+  /**
+   * 
+   * @param server - datanode server
+   * @throws IOException
+   */
+  public InterDatanodeProtocolServerSideTranslatorR23(
+      InterDatanodeProtocol server) throws IOException {
+    this.server = server;
+  }
+
+  /**
+   * the client side will redirect getProtocolSignature to
+   * getProtocolSignature2.
+   * 
+   * However the RPC layer below on the Server side will call getProtocolVersion
+   * and possibly in the future getProtocolSignature. Hence we still implement
+   * it even though the end client's call will never reach here.
+   */
+  @Override
+  public ProtocolSignature getProtocolSignature(String protocol,
+      long clientVersion, int clientMethodsHash) throws IOException {
+    /**
+     * Don't forward this to the server. The protocol version and signature is
+     * that of {@link InterDatanodeProtocol}
+     */
+    if (!protocol.equals(RPC.getProtocolName(InterDatanodeWireProtocol.class))) {
+      throw new IOException("Datanode Serverside implements "
+          + InterDatanodeWireProtocol.class
+          + ". The following requested protocol is unknown: " + protocol);
+    }
+
+    return ProtocolSignature.getProtocolSignature(clientMethodsHash,
+        InterDatanodeWireProtocol.versionID, InterDatanodeWireProtocol.class);
+  }
+
+  @Override
+  public ProtocolSignatureWritable getProtocolSignature2(String protocol,
+      long clientVersion, int clientMethodsHash) throws IOException {
+    /**
+     * Don't forward this to the server. The protocol version and signature is
+     * that of {@link ClientNamenodeProtocol}
+     */
+    return ProtocolSignatureWritable.convert(this.getProtocolSignature(
+        protocol, clientVersion, clientMethodsHash));
+
+  }
+
+  @Override
+  public long getProtocolVersion(String protocol, long clientVersion)
+      throws IOException {
+    if (protocol.equals(RPC.getProtocolName(InterDatanodeWireProtocol.class))) {
+      return InterDatanodeWireProtocol.versionID;
+    }
+    throw new IOException("Datanode Serverside implements "
+        + InterDatanodeWireProtocol.class
+        + ". The following requested protocol is unknown: " + protocol);
+  }
+
+  @Override
+  public ReplicaRecoveryInfoWritable initReplicaRecovery(
+      RecoveringBlockWritable rBlock) throws IOException {
+    return ReplicaRecoveryInfoWritable.convert(server
+        .initReplicaRecovery(rBlock.convert()));
+  }
+
+  @Override
+  public ExtendedBlockWritable updateReplicaUnderRecovery(
+      ExtendedBlockWritable oldBlock, long recoveryId, long newLength)
+      throws IOException {
+    ExtendedBlock b = ExtendedBlockWritable.convertExtendedBlock(oldBlock);
+    return ExtendedBlockWritable.convertExtendedBlock(server
+        .updateReplicaUnderRecovery(b, recoveryId, newLength));
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/protocolR23Compatible/InterDatanodeProtocolTranslatorR23.java

@@ -0,0 +1,96 @@
+/**
+ * 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.hdfs.server.protocolR23Compatible;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+
+import javax.net.SocketFactory;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
+import org.apache.hadoop.hdfs.protocolR23Compatible.ExtendedBlockWritable;
+import org.apache.hadoop.hdfs.protocolR23Compatible.ProtocolSignatureWritable;
+import org.apache.hadoop.hdfs.server.protocol.BlockRecoveryCommand.RecoveringBlock;
+import org.apache.hadoop.hdfs.server.protocol.InterDatanodeProtocol;
+import org.apache.hadoop.hdfs.server.protocol.ReplicaRecoveryInfo;
+import org.apache.hadoop.ipc.ProtocolSignature;
+import org.apache.hadoop.ipc.RPC;
+import org.apache.hadoop.security.UserGroupInformation;
+
+/**
+ * This class forwards InterDatanodeProtocol calls as RPC to the DN server while
+ * translating from the parameter types used in InterDatanodeProtocol to those
+ * used in protocolR23Compatile.*.
+ */
+@InterfaceAudience.Private
+@InterfaceStability.Stable
+public class InterDatanodeProtocolTranslatorR23 implements
+    InterDatanodeProtocol {
+
+  final private InterDatanodeWireProtocol rpcProxy;
+
+  /** used for testing */
+  public InterDatanodeProtocolTranslatorR23(InetSocketAddress addr,
+      UserGroupInformation ugi, Configuration conf, SocketFactory factory,
+      int socketTimeout)
+      throws IOException {
+    rpcProxy = createInterDatanodeProtocolProxy(addr, ugi, conf, factory,
+        socketTimeout);
+  }
+
+  static InterDatanodeWireProtocol createInterDatanodeProtocolProxy(
+      InetSocketAddress addr, UserGroupInformation ugi, Configuration conf,
+      SocketFactory factory, int socketTimeout) throws IOException {
+    return RPC.getProxy(InterDatanodeWireProtocol.class,
+        InterDatanodeWireProtocol.versionID, addr, ugi, conf, factory,
+        socketTimeout);
+  }
+
+  @Override
+  public ProtocolSignature getProtocolSignature(String protocolName,
+      long clientVersion, int clientMethodHash) throws IOException {
+    return ProtocolSignatureWritable.convert(rpcProxy.getProtocolSignature2(
+        protocolName, clientVersion, clientMethodHash));
+  }
+
+  @Override
+  public long getProtocolVersion(String protocolName, long clientVersion)
+      throws IOException {
+    return rpcProxy.getProtocolVersion(protocolName, clientVersion);
+  }
+
+  @Override
+  public ReplicaRecoveryInfo initReplicaRecovery(RecoveringBlock rBlock)
+      throws IOException {
+    return rpcProxy
+        .initReplicaRecovery(RecoveringBlockWritable.convert(rBlock)).convert();
+  }
+
+  @Override
+  public ExtendedBlock updateReplicaUnderRecovery(ExtendedBlock oldBlock,
+      long recoveryId, long newLength) throws IOException {
+    ExtendedBlockWritable eb = ExtendedBlockWritable
+        .convertExtendedBlock(oldBlock);
+    ExtendedBlockWritable b = rpcProxy.updateReplicaUnderRecovery(eb,
+        recoveryId, newLength);
+    return ExtendedBlockWritable.convertExtendedBlock(b);
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/protocolR23Compatible/InterDatanodeWireProtocol.java

@@ -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.
+ */
+
+package org.apache.hadoop.hdfs.server.protocolR23Compatible;
+
+import java.io.IOException;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.hdfs.DFSConfigKeys;
+import org.apache.hadoop.hdfs.protocolR23Compatible.ClientNamenodeWireProtocol;
+import org.apache.hadoop.hdfs.protocolR23Compatible.ExtendedBlockWritable;
+import org.apache.hadoop.hdfs.protocolR23Compatible.ProtocolSignatureWritable;
+import org.apache.hadoop.ipc.VersionedProtocol;
+import org.apache.hadoop.security.KerberosInfo;
+
+/** An inter-datanode protocol for updating generation stamp
+ */
+@KerberosInfo(
+    serverPrincipal = DFSConfigKeys.DFS_DATANODE_USER_NAME_KEY,
+    clientPrincipal = DFSConfigKeys.DFS_DATANODE_USER_NAME_KEY)
+@InterfaceAudience.Private
+public interface InterDatanodeWireProtocol extends VersionedProtocol {
+  public static final Log LOG = 
+      LogFactory.getLog(InterDatanodeWireProtocol.class);
+  /**
+   * The  rules for changing this protocol are the same as that for
+   * {@link ClientNamenodeWireProtocol} - see that java file for details.
+   * 6: Add block pool ID to Block
+   */
+  public static final long versionID = 6L;
+
+  /**
+   * Initialize a replica recovery.
+   * 
+   * @return actual state of the replica on this data-node or 
+   * null if data-node does not have the replica.
+   */
+  ReplicaRecoveryInfoWritable initReplicaRecovery(RecoveringBlockWritable rBlock)
+      throws IOException;
+
+  /**
+   * Update replica with the new generation stamp and length.  
+   */
+  ExtendedBlockWritable updateReplicaUnderRecovery(
+      ExtendedBlockWritable oldBlock, long recoveryId, long newLength)
+      throws IOException;
+  
+  /**
+   * This method is defined to get the protocol signature using 
+   * the R23 protocol - hence we have added the suffix of 2 to the method name
+   * to avoid conflict.
+   */
+  public ProtocolSignatureWritable getProtocolSignature2(
+      String protocol, long clientVersion, int clientMethodsHash)
+      throws IOException;
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/protocolR23Compatible/RecoveringBlockWritable.java

@@ -0,0 +1,104 @@
+/**
+ * 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.hdfs.server.protocolR23Compatible;
+
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.hdfs.protocolR23Compatible.DatanodeInfoWritable;
+import org.apache.hadoop.hdfs.protocolR23Compatible.ExtendedBlockWritable;
+import org.apache.hadoop.hdfs.protocolR23Compatible.LocatedBlockWritable;
+import org.apache.hadoop.hdfs.server.protocol.BlockRecoveryCommand.RecoveringBlock;
+import org.apache.hadoop.io.Writable;
+import org.apache.hadoop.io.WritableFactories;
+import org.apache.hadoop.io.WritableFactory;
+
+/**
+ * This is a block with locations from which it should be recovered and the new
+ * generation stamp, which the block will have after successful recovery.
+ * 
+ * The new generation stamp of the block, also plays role of the recovery id.
+ */
+@InterfaceAudience.Private
+@InterfaceStability.Evolving
+public class RecoveringBlockWritable implements Writable {
+  private long newGenerationStamp;
+  private LocatedBlockWritable locatedBlock;
+
+  /**
+   * Create empty RecoveringBlock.
+   */
+  public RecoveringBlockWritable() {
+    locatedBlock = new LocatedBlockWritable();
+    newGenerationStamp = -1L;
+  }
+
+  /**
+   * Create RecoveringBlock.
+   */
+  public RecoveringBlockWritable(ExtendedBlockWritable b,
+      DatanodeInfoWritable[] locs, long newGS) {
+    locatedBlock = new LocatedBlockWritable(b, locs, -1, false);
+    this.newGenerationStamp = newGS;
+  }
+
+  // /////////////////////////////////////////
+  // Writable
+  // /////////////////////////////////////////
+  static { // register a ctor
+    WritableFactories.setFactory(RecoveringBlockWritable.class,
+        new WritableFactory() {
+          public Writable newInstance() {
+            return new RecoveringBlockWritable();
+          }
+        });
+  }
+
+  public void write(DataOutput out) throws IOException {
+    locatedBlock.write(out);
+    out.writeLong(newGenerationStamp);
+  }
+
+  public void readFields(DataInput in) throws IOException {
+    locatedBlock = new LocatedBlockWritable();
+    locatedBlock.readFields(in);
+    newGenerationStamp = in.readLong();
+  }
+
+  public RecoveringBlock convert() {
+    ExtendedBlockWritable eb = locatedBlock.getBlock();
+    DatanodeInfoWritable[] dnInfo = locatedBlock.getLocations();
+    return new RecoveringBlock(ExtendedBlockWritable.convertExtendedBlock(eb),
+        DatanodeInfoWritable.convertDatanodeInfo(dnInfo), newGenerationStamp);
+  }
+
+  public static RecoveringBlockWritable convert(RecoveringBlock rBlock) {
+    if (rBlock == null) {
+      return null;
+    }
+    ExtendedBlockWritable eb = ExtendedBlockWritable
+        .convertExtendedBlock(rBlock.getBlock());
+    DatanodeInfoWritable[] dnInfo = DatanodeInfoWritable
+        .convertDatanodeInfo(rBlock.getLocations());
+    return new RecoveringBlockWritable(eb, dnInfo,
+        rBlock.getNewGenerationStamp());
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/protocolR23Compatible/ReplicaRecoveryInfoWritable.java

@@ -0,0 +1,87 @@
+/**
+ * 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.hdfs.server.protocolR23Compatible;
+
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.hdfs.protocolR23Compatible.BlockWritable;
+import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.ReplicaState;
+import org.apache.hadoop.hdfs.server.protocol.ReplicaRecoveryInfo;
+import org.apache.hadoop.io.Writable;
+import org.apache.hadoop.io.WritableFactories;
+import org.apache.hadoop.io.WritableFactory;
+
+/**
+ * Replica recovery information.
+ */
+@InterfaceAudience.Private
+@InterfaceStability.Evolving
+public class ReplicaRecoveryInfoWritable implements Writable {
+  private int originalState;
+  private BlockWritable block;
+
+  public ReplicaRecoveryInfoWritable() {
+  }
+
+  public ReplicaRecoveryInfoWritable(long blockId, long diskLen, long gs,
+      ReplicaState rState) {
+    block = new BlockWritable(blockId, diskLen, gs);
+    originalState = rState.getValue();
+  }
+
+  // /////////////////////////////////////////
+  // Writable
+  // /////////////////////////////////////////
+  static { // register a ctor
+    WritableFactories.setFactory(ReplicaRecoveryInfoWritable.class,
+        new WritableFactory() {
+          public Writable newInstance() {
+            return new ReplicaRecoveryInfoWritable();
+          }
+        });
+  }
+
+  @Override
+  public void readFields(DataInput in) throws IOException {
+    block = new BlockWritable();
+    block.readFields(in);
+    originalState = in.readInt();
+  }
+
+  @Override
+  public void write(DataOutput out) throws IOException {
+    block.write(out);
+    out.writeInt(originalState);
+  }
+
+  public static ReplicaRecoveryInfoWritable convert(ReplicaRecoveryInfo rrInfo) {
+    return new ReplicaRecoveryInfoWritable(rrInfo.getBlockId(),
+        rrInfo.getNumBytes(), rrInfo.getGenerationStamp(),
+        rrInfo.getOriginalReplicaState());
+  }
+
+  public ReplicaRecoveryInfo convert() {
+    return new ReplicaRecoveryInfo(block.getBlockId(), block.getNumBytes(),
+        block.getGenerationStamp(), ReplicaState.getState(originalState));
+  }
+}