HDFS-4364. GetLinkTargetResponseProto does not handle null path. Contributed by Suresh Srinivas.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1433202 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -13,6 +13,9 @@ Release 2.0.3-alpha - Unreleased
     HDFS-4367. GetDataEncryptionKeyResponseProto does not handle null
     response. (suresh)
 
+    HDFS-4364. GetLinkTargetResponseProto does not handle null path. (suresh)
+
+
   NEW FEATURES
 
     HDFS-2656. Add libwebhdfs, a pure C client based on WebHDFS.

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

@@ -729,8 +729,12 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
       GetLinkTargetRequestProto req) throws ServiceException {
     try {
       String result = server.getLinkTarget(req.getPath());
-      return GetLinkTargetResponseProto.newBuilder().setTargetPath(result)
-          .build();
+      GetLinkTargetResponseProto.Builder builder = GetLinkTargetResponseProto
+          .newBuilder();
+      if (result != null) {
+        builder.setTargetPath(result);
+      }
+      return builder.build();
     } catch (IOException e) {
       throw new ServiceException(e);
     }

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

@@ -74,6 +74,7 @@ import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetFil
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetFileLinkInfoResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetFsStatusRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetLinkTargetRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetLinkTargetResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetListingRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetListingResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetPreferredBlockSizeRequestProto;
@@ -714,7 +715,8 @@ public class ClientNamenodeProtocolTranslatorPB implements
     GetLinkTargetRequestProto req = GetLinkTargetRequestProto.newBuilder()
         .setPath(path).build();
     try {
-      return rpcProxy.getLinkTarget(null, req).getTargetPath();
+      GetLinkTargetResponseProto rsp = rpcProxy.getLinkTarget(null, req);
+      return rsp.hasTargetPath() ? rsp.getTargetPath() : null;
     } catch (ServiceException e) {
       throw ProtobufHelper.getRemoteException(e);
     }

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

@@ -387,7 +387,7 @@ message GetLinkTargetRequestProto {
   required string path = 1;
 }
 message GetLinkTargetResponseProto {
-  required string targetPath = 1;
+  optional string targetPath = 1;
 }
 
 message UpdateBlockForPipelineRequestProto {