HADOOP-8071. Avoid an extra packet in client code when nagling is disabled. Contributed by Todd Lipcon.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1244189 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -166,6 +166,8 @@ Release 0.23.2 - UNRELEASED
     (szetszwo)
 
   OPTIMIZATIONS
+    HADOOP-8071. Avoid an extra packet in client code when nagling is
+    disabled. (todd)
 
   BUG FIXES
 

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java

@@ -794,14 +794,18 @@ public class Client {
           //for serializing the
           //data to be written
           d = new DataOutputBuffer();
+          d.writeInt(0); // placeholder for data length
           RpcPayloadHeader header = new RpcPayloadHeader(
               call.rpcKind, RpcPayloadOperation.RPC_FINAL_PAYLOAD, call.id);
           header.write(d);
           call.rpcRequest.write(d);
           byte[] data = d.getData();
-          int dataLength = d.getLength();
-          out.writeInt(dataLength);      //first put the data length
-          out.write(data, 0, dataLength);//write the data
+          int dataLength = d.getLength() - 4;
+          data[0] = (byte)((dataLength >>> 24) & 0xff);
+          data[1] = (byte)((dataLength >>> 16) & 0xff);
+          data[2] = (byte)((dataLength >>> 8) & 0xff);
+          data[3] = (byte)(dataLength & 0xff);
+          out.write(data, 0, dataLength + 4);//write the data
           out.flush();
         }
       } catch(IOException e) {