HDFS-4393. Make empty request and responses in protocol translators can be static final members. Contributed by Brandon Li.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1434844 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -491,6 +491,9 @@ Release 2.0.3-alpha - Unreleased
     HDFS-4392. Use NetUtils#getFreeSocketPort in MiniDFSCluster.
     (Andrew Purtell via suresh)
 
+    HDFS-4393. Make empty request and responses in protocol translators can be
+    static final members. (Brandon Li via suresh)
+
   OPTIMIZATIONS
 
     HDFS-3429. DataNode reads checksums even if client does not need them (todd)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientDatanodeProtocolTranslatorPB.java

@@ -77,7 +77,7 @@ public class ClientDatanodeProtocolTranslatorPB implements
   /** RpcController is not used and hence is set to null */
   private final static RpcController NULL_CONTROLLER = null;
   private final ClientDatanodeProtocolPB rpcProxy;
-  private final static RefreshNamenodesRequestProto REFRESH_NAMENODES = 
+  private final static RefreshNamenodesRequestProto VOID_REFRESH_NAMENODES = 
       RefreshNamenodesRequestProto.newBuilder().build();
 
   public ClientDatanodeProtocolTranslatorPB(DatanodeID datanodeid,
@@ -170,7 +170,7 @@ public class ClientDatanodeProtocolTranslatorPB implements
   @Override
   public void refreshNamenodes() throws IOException {
     try {
-      rpcProxy.refreshNamenodes(NULL_CONTROLLER, REFRESH_NAMENODES);
+      rpcProxy.refreshNamenodes(NULL_CONTROLLER, VOID_REFRESH_NAMENODES);
     } catch (ServiceException e) {
       throw ProtobufHelper.getRemoteException(e);
     }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolServerSideTranslatorPB.java

@@ -148,6 +148,78 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     ClientNamenodeProtocolPB {
   final private ClientProtocol server;
 
+  private static final CreateResponseProto VOID_CREATE_RESPONSE = 
+  CreateResponseProto.newBuilder().build();
+
+  private static final AppendResponseProto VOID_APPEND_RESPONSE = 
+  AppendResponseProto.newBuilder().build();
+
+  private static final SetPermissionResponseProto VOID_SET_PERM_RESPONSE = 
+  SetPermissionResponseProto.newBuilder().build();
+
+  private static final SetOwnerResponseProto VOID_SET_OWNER_RESPONSE = 
+  SetOwnerResponseProto.newBuilder().build();
+
+  private static final AbandonBlockResponseProto VOID_ADD_BLOCK_RESPONSE = 
+  AbandonBlockResponseProto.newBuilder().build();
+
+  private static final ReportBadBlocksResponseProto VOID_REP_BAD_BLOCK_RESPONSE = 
+  ReportBadBlocksResponseProto.newBuilder().build();
+
+  private static final ConcatResponseProto VOID_CONCAT_RESPONSE = 
+  ConcatResponseProto.newBuilder().build();
+
+  private static final Rename2ResponseProto VOID_RENAME2_RESPONSE = 
+  Rename2ResponseProto.newBuilder().build();
+
+  private static final GetListingResponseProto VOID_GETLISTING_RESPONSE = 
+  GetListingResponseProto.newBuilder().build();
+
+  private static final RenewLeaseResponseProto VOID_RENEWLEASE_RESPONSE = 
+  RenewLeaseResponseProto.newBuilder().build();
+
+  private static final SaveNamespaceResponseProto VOID_SAVENAMESPACE_RESPONSE = 
+  SaveNamespaceResponseProto.newBuilder().build();
+
+  private static final RefreshNodesResponseProto VOID_REFRESHNODES_RESPONSE = 
+  RefreshNodesResponseProto.newBuilder().build();
+
+  private static final FinalizeUpgradeResponseProto VOID_FINALIZEUPGRADE_RESPONSE = 
+  FinalizeUpgradeResponseProto.newBuilder().build();
+
+  private static final MetaSaveResponseProto VOID_METASAVE_RESPONSE = 
+  MetaSaveResponseProto.newBuilder().build();
+
+  private static final GetFileInfoResponseProto VOID_GETFILEINFO_RESPONSE = 
+  GetFileInfoResponseProto.newBuilder().build();
+
+  private static final GetFileLinkInfoResponseProto VOID_GETFILELINKINFO_RESPONSE = 
+  GetFileLinkInfoResponseProto.newBuilder().build();
+
+  private static final SetQuotaResponseProto VOID_SETQUOTA_RESPONSE = 
+  SetQuotaResponseProto.newBuilder().build();
+
+  private static final FsyncResponseProto VOID_FSYNC_RESPONSE = 
+  FsyncResponseProto.newBuilder().build();
+
+  private static final SetTimesResponseProto VOID_SETTIMES_RESPONSE = 
+  SetTimesResponseProto.newBuilder().build();
+
+  private static final CreateSymlinkResponseProto VOID_CREATESYMLINK_RESPONSE = 
+  CreateSymlinkResponseProto.newBuilder().build();
+
+  private static final UpdatePipelineResponseProto
+    VOID_UPDATEPIPELINE_RESPONSE = 
+  UpdatePipelineResponseProto.newBuilder().build();
+
+  private static final CancelDelegationTokenResponseProto 
+      VOID_CANCELDELEGATIONTOKEN_RESPONSE = 
+          CancelDelegationTokenResponseProto.newBuilder().build();
+
+  private static final SetBalancerBandwidthResponseProto 
+      VOID_SETBALANCERBANDWIDTH_RESPONSE = 
+        SetBalancerBandwidthResponseProto.newBuilder().build();
+
   /**
    * Constructor
    * 
@@ -192,9 +264,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
   }
 
   
-  static final CreateResponseProto VOID_CREATE_RESPONSE = 
-      CreateResponseProto.newBuilder().build();
-  
   @Override
   public CreateResponseProto create(RpcController controller,
       CreateRequestProto req) throws ServiceException {
@@ -209,9 +278,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     return VOID_CREATE_RESPONSE;
   }
   
-  static final AppendResponseProto NULL_APPEND_RESPONSE = 
-      AppendResponseProto.newBuilder().build();
-  
   @Override
   public AppendResponseProto append(RpcController controller,
       AppendRequestProto req) throws ServiceException {
@@ -221,7 +287,7 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
         return AppendResponseProto.newBuilder()
             .setBlock(PBHelper.convert(result)).build();
       }
-      return NULL_APPEND_RESPONSE;
+      return VOID_APPEND_RESPONSE;
     } catch (IOException e) {
       throw new ServiceException(e);
     }
@@ -240,9 +306,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
   }
 
 
-  static final SetPermissionResponseProto VOID_SET_PERM_RESPONSE = 
-      SetPermissionResponseProto.newBuilder().build();
-
   @Override
   public SetPermissionResponseProto setPermission(RpcController controller,
       SetPermissionRequestProto req) throws ServiceException {
@@ -254,9 +317,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     return VOID_SET_PERM_RESPONSE;
   }
 
-  static final SetOwnerResponseProto VOID_SET_OWNER_RESPONSE = 
-      SetOwnerResponseProto.newBuilder().build();
-
   @Override
   public SetOwnerResponseProto setOwner(RpcController controller,
       SetOwnerRequestProto req) throws ServiceException {
@@ -270,9 +330,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     return VOID_SET_OWNER_RESPONSE;
   }
 
-  static final AbandonBlockResponseProto VOID_ADD_BLOCK_RESPONSE = 
-      AbandonBlockResponseProto.newBuilder().build();
-
   @Override
   public AbandonBlockResponseProto abandonBlock(RpcController controller,
       AbandonBlockRequestProto req) throws ServiceException {
@@ -338,9 +395,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     }
   }
   
-  static final ReportBadBlocksResponseProto VOID_REP_BAD_BLOCK_RESPONSE = 
-      ReportBadBlocksResponseProto.newBuilder().build();
-  
   @Override
   public ReportBadBlocksResponseProto reportBadBlocks(RpcController controller,
       ReportBadBlocksRequestProto req) throws ServiceException {
@@ -354,9 +408,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     return VOID_REP_BAD_BLOCK_RESPONSE;
   }
 
-  static final ConcatResponseProto VOID_CONCAT_RESPONSE = 
-      ConcatResponseProto.newBuilder().build();
-  
   @Override
   public ConcatResponseProto concat(RpcController controller,
       ConcatRequestProto req) throws ServiceException {
@@ -380,9 +431,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     }
   }
 
-  static final Rename2ResponseProto VOID_RENAME2_RESPONSE = 
-      Rename2ResponseProto.newBuilder().build();
-  
   @Override
   public Rename2ResponseProto rename2(RpcController controller,
       Rename2RequestProto req) throws ServiceException {
@@ -419,8 +467,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     }
   }
 
-  static final GetListingResponseProto NULL_GETLISTING_RESPONSE = 
-      GetListingResponseProto.newBuilder().build();
   @Override
   public GetListingResponseProto getListing(RpcController controller,
       GetListingRequestProto req) throws ServiceException {
@@ -432,16 +478,13 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
         return GetListingResponseProto.newBuilder().setDirList(
           PBHelper.convert(result)).build();
       } else {
-        return NULL_GETLISTING_RESPONSE;
+        return VOID_GETLISTING_RESPONSE;
       }
     } catch (IOException e) {
       throw new ServiceException(e);
     }
   }
   
-  static final RenewLeaseResponseProto VOID_RENEWLEASE_RESPONSE = 
-      RenewLeaseResponseProto.newBuilder().build();
-  
   @Override
   public RenewLeaseResponseProto renewLease(RpcController controller,
       RenewLeaseRequestProto req) throws ServiceException {
@@ -526,9 +569,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     }
   }
   
-  static final SaveNamespaceResponseProto VOID_SAVENAMESPACE_RESPONSE = 
-      SaveNamespaceResponseProto.newBuilder().build();
-
   @Override
   public SaveNamespaceResponseProto saveNamespace(RpcController controller,
       SaveNamespaceRequestProto req) throws ServiceException {
@@ -555,9 +595,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
   }
 
 
-  static final RefreshNodesResponseProto VOID_REFRESHNODES_RESPONSE = 
-      RefreshNodesResponseProto.newBuilder().build();
-
   @Override
   public RefreshNodesResponseProto refreshNodes(RpcController controller,
       RefreshNodesRequestProto req) throws ServiceException {
@@ -570,9 +607,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
 
   }
 
-  static final FinalizeUpgradeResponseProto VOID_FINALIZEUPGRADE_RESPONSE = 
-      FinalizeUpgradeResponseProto.newBuilder().build();
-
   @Override
   public FinalizeUpgradeResponseProto finalizeUpgrade(RpcController controller,
       FinalizeUpgradeRequestProto req) throws ServiceException {
@@ -599,9 +633,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     }
   }
 
-  static final MetaSaveResponseProto VOID_METASAVE_RESPONSE = 
-      MetaSaveResponseProto.newBuilder().build();
-  
   @Override
   public MetaSaveResponseProto metaSave(RpcController controller,
       MetaSaveRequestProto req) throws ServiceException {
@@ -614,8 +645,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
 
   }
 
-  static final GetFileInfoResponseProto NULL_GETFILEINFO_RESPONSE = 
-      GetFileInfoResponseProto.newBuilder().build();
   @Override
   public GetFileInfoResponseProto getFileInfo(RpcController controller,
       GetFileInfoRequestProto req) throws ServiceException {
@@ -626,14 +655,12 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
         return GetFileInfoResponseProto.newBuilder().setFs(
             PBHelper.convert(result)).build();
       }
-      return NULL_GETFILEINFO_RESPONSE;      
+      return VOID_GETFILEINFO_RESPONSE;      
     } catch (IOException e) {
       throw new ServiceException(e);
     }
   }
 
-  static final GetFileLinkInfoResponseProto NULL_GETFILELINKINFO_RESPONSE = 
-      GetFileLinkInfoResponseProto.newBuilder().build();
   @Override
   public GetFileLinkInfoResponseProto getFileLinkInfo(RpcController controller,
       GetFileLinkInfoRequestProto req) throws ServiceException {
@@ -645,7 +672,7 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
             PBHelper.convert(result)).build();
       } else {
         System.out.println("got  null result for getFileLinkInfo for " + req.getSrc());
-        return NULL_GETFILELINKINFO_RESPONSE;      
+        return VOID_GETFILELINKINFO_RESPONSE;      
       }
 
     } catch (IOException e) {
@@ -666,9 +693,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     }
   }
   
-  static final SetQuotaResponseProto VOID_SETQUOTA_RESPONSE = 
-      SetQuotaResponseProto.newBuilder().build();
-  
   @Override
   public SetQuotaResponseProto setQuota(RpcController controller,
       SetQuotaRequestProto req) throws ServiceException {
@@ -681,9 +705,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     }
   }
   
-  static final FsyncResponseProto VOID_FSYNC_RESPONSE = 
-      FsyncResponseProto.newBuilder().build();
-
   @Override
   public FsyncResponseProto fsync(RpcController controller,
       FsyncRequestProto req) throws ServiceException {
@@ -695,9 +716,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     }
   }
 
-  static final SetTimesResponseProto VOID_SETTIMES_RESPONSE = 
-      SetTimesResponseProto.newBuilder().build();
-
   @Override
   public SetTimesResponseProto setTimes(RpcController controller,
       SetTimesRequestProto req) throws ServiceException {
@@ -709,9 +727,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     }
   }
 
-  static final CreateSymlinkResponseProto VOID_CREATESYMLINK_RESPONSE = 
-      CreateSymlinkResponseProto.newBuilder().build();
-
   @Override
   public CreateSymlinkResponseProto createSymlink(RpcController controller,
       CreateSymlinkRequestProto req) throws ServiceException {
@@ -755,9 +770,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     }
   }
 
-  static final UpdatePipelineResponseProto VOID_UPDATEPIPELINE_RESPONSE = 
-      UpdatePipelineResponseProto.newBuilder().build();
-
   @Override
   public UpdatePipelineResponseProto updatePipeline(RpcController controller,
       UpdatePipelineRequestProto req) throws ServiceException {
@@ -805,10 +817,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     }
   }
 
-  static final CancelDelegationTokenResponseProto 
-      VOID_CANCELDELEGATIONTOKEN_RESPONSE = 
-      CancelDelegationTokenResponseProto.newBuilder().build();
-  
   @Override
   public CancelDelegationTokenResponseProto cancelDelegationToken(
       RpcController controller, CancelDelegationTokenRequestProto req)
@@ -822,10 +830,6 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     }
   }
 
-  static final SetBalancerBandwidthResponseProto 
-    VOID_SETBALANCERBANDWIDTH_RESPONSE = 
-      SetBalancerBandwidthResponseProto.newBuilder().build();
-
   @Override
   public SetBalancerBandwidthResponseProto setBalancerBandwidth(
       RpcController controller, SetBalancerBandwidthRequestProto req)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolTranslatorPB.java

@@ -129,6 +129,29 @@ public class ClientNamenodeProtocolTranslatorPB implements
     ProtocolMetaInterface, ClientProtocol, Closeable, ProtocolTranslator {
   final private ClientNamenodeProtocolPB rpcProxy;
 
+  static final GetServerDefaultsRequestProto VOID_GET_SERVER_DEFAULT_REQUEST = 
+  GetServerDefaultsRequestProto.newBuilder().build();
+
+  private final static GetFsStatusRequestProto VOID_GET_FSSTATUS_REQUEST =
+  GetFsStatusRequestProto.newBuilder().build();
+
+  private final static SaveNamespaceRequestProto VOID_SAVE_NAMESPACE_REQUEST =
+  SaveNamespaceRequestProto.newBuilder().build();
+
+  private final static RollEditsRequestProto VOID_ROLLEDITS_REQUEST = 
+  RollEditsRequestProto.getDefaultInstance();
+
+  private final static RefreshNodesRequestProto VOID_REFRESH_NODES_REQUEST =
+  RefreshNodesRequestProto.newBuilder().build();
+
+  private final static FinalizeUpgradeRequestProto
+  VOID_FINALIZE_UPGRADE_REQUEST =
+      FinalizeUpgradeRequestProto.newBuilder().build();
+
+  private final static GetDataEncryptionKeyRequestProto
+  VOID_GET_DATA_ENCRYPTIONKEY_REQUEST =
+      GetDataEncryptionKeyRequestProto.newBuilder().build();
+
   public ClientNamenodeProtocolTranslatorPB(ClientNamenodeProtocolPB proxy) {
     rpcProxy = proxy;
   }
@@ -160,7 +183,7 @@ public class ClientNamenodeProtocolTranslatorPB implements
 
   @Override
   public FsServerDefaults getServerDefaults() throws IOException {
-    GetServerDefaultsRequestProto req = GetServerDefaultsRequestProto.newBuilder().build();
+    GetServerDefaultsRequestProto req = VOID_GET_SERVER_DEFAULT_REQUEST;
     try {
       return PBHelper
           .convert(rpcProxy.getServerDefaults(null, req).getServerDefaults());
@@ -473,9 +496,9 @@ public class ClientNamenodeProtocolTranslatorPB implements
 
   @Override
   public long[] getStats() throws IOException {
-    GetFsStatusRequestProto req = GetFsStatusRequestProto.newBuilder().build();
     try {
-      return PBHelper.convert(rpcProxy.getFsStats(null, req));
+      return PBHelper.convert(rpcProxy.getFsStats(null,
+          VOID_GET_FSSTATUS_REQUEST));
     } catch (ServiceException e) {
       throw ProtobufHelper.getRemoteException(e);
     }
@@ -522,10 +545,8 @@ public class ClientNamenodeProtocolTranslatorPB implements
 
   @Override
   public void saveNamespace() throws AccessControlException, IOException {
-    SaveNamespaceRequestProto req = SaveNamespaceRequestProto.newBuilder()
-        .build();
     try {
-      rpcProxy.saveNamespace(null, req);
+      rpcProxy.saveNamespace(null, VOID_SAVE_NAMESPACE_REQUEST);
     } catch (ServiceException e) {
       throw ProtobufHelper.getRemoteException(e);
     }
@@ -533,9 +554,9 @@ public class ClientNamenodeProtocolTranslatorPB implements
   
   @Override
   public long rollEdits() throws AccessControlException, IOException {
-    RollEditsRequestProto req = RollEditsRequestProto.getDefaultInstance();
     try {
-      RollEditsResponseProto resp = rpcProxy.rollEdits(null, req);
+      RollEditsResponseProto resp = rpcProxy.rollEdits(null,
+          VOID_ROLLEDITS_REQUEST);
       return resp.getNewSegmentTxId();
     } catch (ServiceException se) {
       throw ProtobufHelper.getRemoteException(se);
@@ -557,9 +578,8 @@ public class ClientNamenodeProtocolTranslatorPB implements
 
   @Override
   public void refreshNodes() throws IOException {
-    RefreshNodesRequestProto req = RefreshNodesRequestProto.newBuilder().build();
     try {
-      rpcProxy.refreshNodes(null, req);
+      rpcProxy.refreshNodes(null, VOID_REFRESH_NODES_REQUEST);
     } catch (ServiceException e) {
       throw ProtobufHelper.getRemoteException(e);
     }
@@ -567,9 +587,8 @@ public class ClientNamenodeProtocolTranslatorPB implements
 
   @Override
   public void finalizeUpgrade() throws IOException {
-    FinalizeUpgradeRequestProto req = FinalizeUpgradeRequestProto.newBuilder().build();
     try {
-      rpcProxy.finalizeUpgrade(null, req);
+      rpcProxy.finalizeUpgrade(null, VOID_FINALIZE_UPGRADE_REQUEST);
     } catch (ServiceException e) {
       throw ProtobufHelper.getRemoteException(e);
     }
@@ -818,12 +837,10 @@ public class ClientNamenodeProtocolTranslatorPB implements
   
   @Override
   public DataEncryptionKey getDataEncryptionKey() throws IOException {
-    GetDataEncryptionKeyRequestProto req = GetDataEncryptionKeyRequestProto
-        .newBuilder().build();
     try {
-      GetDataEncryptionKeyResponseProto rsp = 
+      GetDataEncryptionKeyResponseProto rsp = rpcProxy.getDataEncryptionKey(
-          rpcProxy.getDataEncryptionKey(null, req);
+          null, VOID_GET_DATA_ENCRYPTIONKEY_REQUEST);
-      return rsp.hasDataEncryptionKey() ? 
+     return rsp.hasDataEncryptionKey() ? 
           PBHelper.convert(rsp.getDataEncryptionKey()) : null;
     } catch (ServiceException e) {
       throw ProtobufHelper.getRemoteException(e);

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/DatanodeProtocolClientSideTranslatorPB.java

@@ -84,7 +84,7 @@ public class DatanodeProtocolClientSideTranslatorPB implements
   
   /** RpcController is not used and hence is set to null */
   private final DatanodeProtocolPB rpcProxy;
-  private static final VersionRequestProto VERSION_REQUEST = 
+  private static final VersionRequestProto VOID_VERSION_REQUEST = 
       VersionRequestProto.newBuilder().build();
   private final static RpcController NULL_CONTROLLER = null;
   
@@ -243,7 +243,7 @@ public class DatanodeProtocolClientSideTranslatorPB implements
   public NamespaceInfo versionRequest() throws IOException {
     try {
       return PBHelper.convert(rpcProxy.versionRequest(NULL_CONTROLLER,
-          VERSION_REQUEST).getInfo());
+          VOID_VERSION_REQUEST).getInfo());
     } catch (ServiceException e) {
       throw ProtobufHelper.getRemoteException(e);
     }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/DatanodeProtocolServerSideTranslatorPB.java

@@ -62,15 +62,17 @@ public class DatanodeProtocolServerSideTranslatorPB implements
     DatanodeProtocolPB {
 
   private final DatanodeProtocol impl;
-  private static final ErrorReportResponseProto ERROR_REPORT_RESPONSE_PROTO = 
+  private static final ErrorReportResponseProto
-      ErrorReportResponseProto.newBuilder().build();
+      VOID_ERROR_REPORT_RESPONSE_PROTO = 
+          ErrorReportResponseProto.newBuilder().build();
   private static final BlockReceivedAndDeletedResponseProto 
-      BLOCK_RECEIVED_AND_DELETE_RESPONSE = 
+      VOID_BLOCK_RECEIVED_AND_DELETE_RESPONSE = 
           BlockReceivedAndDeletedResponseProto.newBuilder().build();
-  private static final ReportBadBlocksResponseProto REPORT_BAD_BLOCK_RESPONSE = 
+  private static final ReportBadBlocksResponseProto
-      ReportBadBlocksResponseProto.newBuilder().build();
+      VOID_REPORT_BAD_BLOCK_RESPONSE = 
+          ReportBadBlocksResponseProto.newBuilder().build();
   private static final CommitBlockSynchronizationResponseProto 
-      COMMIT_BLOCK_SYNCHRONIZATION_RESPONSE_PROTO =
+      VOID_COMMIT_BLOCK_SYNCHRONIZATION_RESPONSE_PROTO =
           CommitBlockSynchronizationResponseProto.newBuilder().build();
 
   public DatanodeProtocolServerSideTranslatorPB(DatanodeProtocol impl) {
@@ -180,7 +182,7 @@ public class DatanodeProtocolServerSideTranslatorPB implements
     } catch (IOException e) {
       throw new ServiceException(e);
     }
-    return BLOCK_RECEIVED_AND_DELETE_RESPONSE;
+    return VOID_BLOCK_RECEIVED_AND_DELETE_RESPONSE;
   }
 
   @Override
@@ -192,7 +194,7 @@ public class DatanodeProtocolServerSideTranslatorPB implements
     } catch (IOException e) {
       throw new ServiceException(e);
     }
-    return ERROR_REPORT_RESPONSE_PROTO;
+    return VOID_ERROR_REPORT_RESPONSE_PROTO;
   }
 
   @Override
@@ -221,7 +223,7 @@ public class DatanodeProtocolServerSideTranslatorPB implements
     } catch (IOException e) {
       throw new ServiceException(e);
     }
-    return REPORT_BAD_BLOCK_RESPONSE;
+    return VOID_REPORT_BAD_BLOCK_RESPONSE;
   }
 
   @Override
@@ -242,6 +244,6 @@ public class DatanodeProtocolServerSideTranslatorPB implements
     } catch (IOException e) {
       throw new ServiceException(e);
     }
-    return COMMIT_BLOCK_SYNCHRONIZATION_RESPONSE_PROTO;
+    return VOID_COMMIT_BLOCK_SYNCHRONIZATION_RESPONSE_PROTO;
   }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/JournalProtocolServerSideTranslatorPB.java

@@ -42,6 +42,13 @@ public class JournalProtocolServerSideTranslatorPB implements JournalProtocolPB
   /** Server side implementation to delegate the requests to */
   private final JournalProtocol impl;
 
+  private final static JournalResponseProto VOID_JOURNAL_RESPONSE = 
+  JournalResponseProto.newBuilder().build();
+
+  private final static StartLogSegmentResponseProto
+  VOID_START_LOG_SEGMENT_RESPONSE =
+      StartLogSegmentResponseProto.newBuilder().build();
+
   public JournalProtocolServerSideTranslatorPB(JournalProtocol impl) {
     this.impl = impl;
   }
@@ -56,7 +63,7 @@ public class JournalProtocolServerSideTranslatorPB implements JournalProtocolPB
     } catch (IOException e) {
       throw new ServiceException(e);
     }
-    return JournalResponseProto.newBuilder().build();
+    return VOID_JOURNAL_RESPONSE;
   }
 
   /** @see JournalProtocol#startLogSegment */
@@ -69,7 +76,7 @@ public class JournalProtocolServerSideTranslatorPB implements JournalProtocolPB
     } catch (IOException e) {
       throw new ServiceException(e);
     }
-    return StartLogSegmentResponseProto.newBuilder().build();
+    return VOID_START_LOG_SEGMENT_RESPONSE;
   }
 
   @Override

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/NamenodeProtocolServerSideTranslatorPB.java

@@ -63,6 +63,12 @@ public class NamenodeProtocolServerSideTranslatorPB implements
     NamenodeProtocolPB {
   private final NamenodeProtocol impl;
 
+  private final static ErrorReportResponseProto VOID_ERROR_REPORT_RESPONSE = 
+  ErrorReportResponseProto.newBuilder().build();
+
+  private final static EndCheckpointResponseProto VOID_END_CHECKPOINT_RESPONSE =
+  EndCheckpointResponseProto.newBuilder().build();
+
   public NamenodeProtocolServerSideTranslatorPB(NamenodeProtocol impl) {
     this.impl = impl;
   }
@@ -147,7 +153,7 @@ public class NamenodeProtocolServerSideTranslatorPB implements
     } catch (IOException e) {
       throw new ServiceException(e);
     }
-    return ErrorReportResponseProto.newBuilder().build();
+    return VOID_ERROR_REPORT_RESPONSE;
   }
 
   @Override
@@ -185,7 +191,7 @@ public class NamenodeProtocolServerSideTranslatorPB implements
     } catch (IOException e) {
       throw new ServiceException(e);
     }
-    return EndCheckpointResponseProto.newBuilder().build();
+    return VOID_END_CHECKPOINT_RESPONSE;
   }
 
   @Override

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/NamenodeProtocolTranslatorPB.java

@@ -68,13 +68,13 @@ public class NamenodeProtocolTranslatorPB implements NamenodeProtocol,
   /*
    * Protobuf requests with no parameters instantiated only once
    */
-  private static final GetBlockKeysRequestProto GET_BLOCKKEYS = 
+  private static final GetBlockKeysRequestProto VOID_GET_BLOCKKEYS_REQUEST = 
       GetBlockKeysRequestProto.newBuilder().build();
-  private static final GetTransactionIdRequestProto GET_TRANSACTIONID = 
+  private static final GetTransactionIdRequestProto VOID_GET_TRANSACTIONID_REQUEST = 
       GetTransactionIdRequestProto.newBuilder().build();
-  private static final RollEditLogRequestProto ROLL_EDITLOG = 
+  private static final RollEditLogRequestProto VOID_ROLL_EDITLOG_REQUEST = 
       RollEditLogRequestProto.newBuilder().build();
-  private static final VersionRequestProto VERSION_REQUEST = 
+  private static final VersionRequestProto VOID_VERSION_REQUEST = 
       VersionRequestProto.newBuilder().build();
 
   final private NamenodeProtocolPB rpcProxy;
@@ -106,7 +106,7 @@ public class NamenodeProtocolTranslatorPB implements NamenodeProtocol,
   public ExportedBlockKeys getBlockKeys() throws IOException {
     try {
       GetBlockKeysResponseProto rsp = rpcProxy.getBlockKeys(NULL_CONTROLLER,
-          GET_BLOCKKEYS);
+          VOID_GET_BLOCKKEYS_REQUEST);
       return rsp.hasKeys() ? PBHelper.convert(rsp.getKeys()) : null;
     } catch (ServiceException e) {
       throw ProtobufHelper.getRemoteException(e);
@@ -116,8 +116,8 @@ public class NamenodeProtocolTranslatorPB implements NamenodeProtocol,
   @Override
   public long getTransactionID() throws IOException {
     try {
-      return rpcProxy.getTransactionId(NULL_CONTROLLER, GET_TRANSACTIONID)
+      return rpcProxy.getTransactionId(NULL_CONTROLLER,
-          .getTxId();
+          VOID_GET_TRANSACTIONID_REQUEST).getTxId();
     } catch (ServiceException e) {
       throw ProtobufHelper.getRemoteException(e);
     }
@@ -137,7 +137,7 @@ public class NamenodeProtocolTranslatorPB implements NamenodeProtocol,
   public CheckpointSignature rollEditLog() throws IOException {
     try {
       return PBHelper.convert(rpcProxy.rollEditLog(NULL_CONTROLLER,
-          ROLL_EDITLOG).getSignature());
+          VOID_ROLL_EDITLOG_REQUEST).getSignature());
     } catch (ServiceException e) {
       throw ProtobufHelper.getRemoteException(e);
     }
@@ -147,7 +147,7 @@ public class NamenodeProtocolTranslatorPB implements NamenodeProtocol,
   public NamespaceInfo versionRequest() throws IOException {
     try {
       return PBHelper.convert(rpcProxy.versionRequest(NULL_CONTROLLER,
-          VERSION_REQUEST).getInfo());
+          VOID_VERSION_REQUEST).getInfo());
     } catch (ServiceException e) {
       throw ProtobufHelper.getRemoteException(e);
     }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/RefreshAuthorizationPolicyProtocolClientSideTranslatorPB.java

@@ -38,6 +38,10 @@ public class RefreshAuthorizationPolicyProtocolClientSideTranslatorPB implements
   private final static RpcController NULL_CONTROLLER = null;
   private final RefreshAuthorizationPolicyProtocolPB rpcProxy;
   
+  private final static RefreshServiceAclRequestProto
+  VOID_REFRESH_SERVICE_ACL_REQUEST =
+      RefreshServiceAclRequestProto.newBuilder().build();
+
   public RefreshAuthorizationPolicyProtocolClientSideTranslatorPB(
       RefreshAuthorizationPolicyProtocolPB rpcProxy) {
     this.rpcProxy = rpcProxy;
@@ -50,10 +54,9 @@ public class RefreshAuthorizationPolicyProtocolClientSideTranslatorPB implements
 
   @Override
   public void refreshServiceAcl() throws IOException {
-    RefreshServiceAclRequestProto request = RefreshServiceAclRequestProto
-        .newBuilder().build();
     try {
-      rpcProxy.refreshServiceAcl(NULL_CONTROLLER, request);
+      rpcProxy.refreshServiceAcl(NULL_CONTROLLER,
+          VOID_REFRESH_SERVICE_ACL_REQUEST);
     } catch (ServiceException se) {
       throw ProtobufHelper.getRemoteException(se);
     }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/RefreshAuthorizationPolicyProtocolServerSideTranslatorPB.java

@@ -32,6 +32,10 @@ public class RefreshAuthorizationPolicyProtocolServerSideTranslatorPB implements
 
   private final RefreshAuthorizationPolicyProtocol impl;
 
+  private final static RefreshServiceAclResponseProto
+  VOID_REFRESH_SERVICE_ACL_RESPONSE = RefreshServiceAclResponseProto
+      .newBuilder().build();
+
   public RefreshAuthorizationPolicyProtocolServerSideTranslatorPB(
       RefreshAuthorizationPolicyProtocol impl) {
     this.impl = impl;
@@ -46,6 +50,6 @@ public class RefreshAuthorizationPolicyProtocolServerSideTranslatorPB implements
     } catch (IOException e) {
       throw new ServiceException(e);
     }
-    return RefreshServiceAclResponseProto.newBuilder().build();
+    return VOID_REFRESH_SERVICE_ACL_RESPONSE;
   }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/RefreshUserMappingsProtocolClientSideTranslatorPB.java

@@ -39,6 +39,14 @@ public class RefreshUserMappingsProtocolClientSideTranslatorPB implements
   private final static RpcController NULL_CONTROLLER = null;
   private final RefreshUserMappingsProtocolPB rpcProxy;
   
+  private final static RefreshUserToGroupsMappingsRequestProto 
+  VOID_REFRESH_USER_TO_GROUPS_MAPPING_REQUEST = 
+      RefreshUserToGroupsMappingsRequestProto.newBuilder().build();
+
+  private final static RefreshSuperUserGroupsConfigurationRequestProto
+  VOID_REFRESH_SUPERUSER_GROUPS_CONFIGURATION_REQUEST = 
+      RefreshSuperUserGroupsConfigurationRequestProto.newBuilder().build();
+
   public RefreshUserMappingsProtocolClientSideTranslatorPB(
       RefreshUserMappingsProtocolPB rpcProxy) {
     this.rpcProxy = rpcProxy;
@@ -51,10 +59,9 @@ public class RefreshUserMappingsProtocolClientSideTranslatorPB implements
 
   @Override
   public void refreshUserToGroupsMappings() throws IOException {
-    RefreshUserToGroupsMappingsRequestProto request = 
-        RefreshUserToGroupsMappingsRequestProto.newBuilder().build();
     try {
-      rpcProxy.refreshUserToGroupsMappings(NULL_CONTROLLER, request);
+      rpcProxy.refreshUserToGroupsMappings(NULL_CONTROLLER,
+          VOID_REFRESH_USER_TO_GROUPS_MAPPING_REQUEST);
     } catch (ServiceException se) {
       throw ProtobufHelper.getRemoteException(se);
     }
@@ -62,10 +69,9 @@ public class RefreshUserMappingsProtocolClientSideTranslatorPB implements
 
   @Override
   public void refreshSuperUserGroupsConfiguration() throws IOException {
-    RefreshSuperUserGroupsConfigurationRequestProto request = 
-        RefreshSuperUserGroupsConfigurationRequestProto.newBuilder().build();
     try {
-      rpcProxy.refreshSuperUserGroupsConfiguration(NULL_CONTROLLER, request);
+      rpcProxy.refreshSuperUserGroupsConfiguration(NULL_CONTROLLER,
+          VOID_REFRESH_SUPERUSER_GROUPS_CONFIGURATION_REQUEST);
     } catch (ServiceException se) {
       throw ProtobufHelper.getRemoteException(se);
     }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/RefreshUserMappingsProtocolServerSideTranslatorPB.java

@@ -33,6 +33,15 @@ public class RefreshUserMappingsProtocolServerSideTranslatorPB implements Refres
 
   private final RefreshUserMappingsProtocol impl;
   
+  private final static RefreshUserToGroupsMappingsResponseProto 
+  VOID_REFRESH_USER_GROUPS_MAPPING_RESPONSE =
+      RefreshUserToGroupsMappingsResponseProto.newBuilder().build();
+
+  private final static RefreshSuperUserGroupsConfigurationResponseProto
+  VOID_REFRESH_SUPERUSER_GROUPS_CONFIGURATION_RESPONSE = 
+      RefreshSuperUserGroupsConfigurationResponseProto.newBuilder()
+      .build();
+
   public RefreshUserMappingsProtocolServerSideTranslatorPB(RefreshUserMappingsProtocol impl) {
     this.impl = impl;
   }
@@ -47,7 +56,7 @@ public class RefreshUserMappingsProtocolServerSideTranslatorPB implements Refres
     } catch (IOException e) {
       throw new ServiceException(e);
     }
-    return RefreshUserToGroupsMappingsResponseProto.newBuilder().build();
+    return VOID_REFRESH_USER_GROUPS_MAPPING_RESPONSE;
   }
 
   @Override
@@ -60,7 +69,6 @@ public class RefreshUserMappingsProtocolServerSideTranslatorPB implements Refres
     } catch (IOException e) {
       throw new ServiceException(e);
     }
-    return RefreshSuperUserGroupsConfigurationResponseProto.newBuilder()
+    return VOID_REFRESH_SUPERUSER_GROUPS_CONFIGURATION_RESPONSE;
-        .build();
   }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/qjournal/protocolPB/QJournalProtocolServerSideTranslatorPB.java

@@ -65,6 +65,13 @@ public class QJournalProtocolServerSideTranslatorPB implements QJournalProtocolP
   /** Server side implementation to delegate the requests to */
   private final QJournalProtocol impl;
 
+  private final static JournalResponseProto VOID_JOURNAL_RESPONSE =
+  JournalResponseProto.newBuilder().build();
+
+  private final static StartLogSegmentResponseProto
+  VOID_START_LOG_SEGMENT_RESPONSE =
+      StartLogSegmentResponseProto.newBuilder().build();
+
   public QJournalProtocolServerSideTranslatorPB(QJournalProtocol impl) {
     this.impl = impl;
   }
@@ -135,7 +142,7 @@ public class QJournalProtocolServerSideTranslatorPB implements QJournalProtocolP
     } catch (IOException e) {
       throw new ServiceException(e);
     }
-    return JournalResponseProto.newBuilder().build();
+    return VOID_JOURNAL_RESPONSE;
   }
 
   /** @see JournalProtocol#heartbeat */
@@ -160,7 +167,7 @@ public class QJournalProtocolServerSideTranslatorPB implements QJournalProtocolP
     } catch (IOException e) {
       throw new ServiceException(e);
     }
-    return StartLogSegmentResponseProto.newBuilder().build();
+    return VOID_START_LOG_SEGMENT_RESPONSE;
   }
   
   @Override

hadoop-hdfs-project/hadoop-hdfs/src/main/proto/ClientNamenodeProtocol.proto

@@ -168,7 +168,7 @@ message RenameRequestProto {
   required string dst = 2;
 }
 
-message RenameResponseProto { // void response
+message RenameResponseProto {
   required bool result = 1;
 }