HBASE-15202 Reduce garbage while setting response (Ram)

hbase-server/src/main/java/org/apache/hadoop/hbase/ipc/RpcServer.java

@@ -136,6 +136,7 @@ import org.apache.htrace.TraceInfo;
 import com.google.common.util.concurrent.ThreadFactoryBuilder;
 import com.google.protobuf.BlockingService;
 import com.google.protobuf.CodedInputStream;
+import com.google.protobuf.CodedOutputStream;
 import com.google.protobuf.Descriptors.MethodDescriptor;
 import com.google.protobuf.Message;
 import com.google.protobuf.ServiceException;
@@ -431,14 +432,10 @@ public class RpcServer implements RpcServerInterface, ConfigurationObserver {
         }
         Message header = headerBuilder.build();
 
-        // Organize the response as a set of bytebuffers rather than collect it all together inside
+        byte[] b = createHeaderAndMessageBytes(result, header);
-        // one big byte array; save on allocations.
+
-        ByteBuffer bbHeader = IPCUtil.getDelimitedMessageAsByteBuffer(header);
+        bc = new BufferChain(ByteBuffer.wrap(b), this.cellBlock);
-        ByteBuffer bbResult = IPCUtil.getDelimitedMessageAsByteBuffer(result);
+
-        int totalSize = bbHeader.capacity() + (bbResult == null? 0: bbResult.limit()) +
-          (this.cellBlock == null? 0: this.cellBlock.limit());
-        ByteBuffer bbTotalSize = ByteBuffer.wrap(Bytes.toBytes(totalSize));
-        bc = new BufferChain(bbTotalSize, bbHeader, bbResult, this.cellBlock);
         if (connection.useWrap) {
           bc = wrapWithSasl(bc);
         }
@@ -448,6 +445,44 @@ public class RpcServer implements RpcServerInterface, ConfigurationObserver {
       this.response = bc;
     }
 
+    private byte[] createHeaderAndMessageBytes(Message result, Message header)
+        throws IOException {
+      // Organize the response as a set of bytebuffers rather than collect it all together inside
+      // one big byte array; save on allocations.
+      int headerSerializedSize = 0, resultSerializedSize = 0, headerVintSize = 0,
+          resultVintSize = 0;
+      if (header != null) {
+        headerSerializedSize = header.getSerializedSize();
+        headerVintSize = CodedOutputStream.computeRawVarint32Size(headerSerializedSize);
+      }
+      if (result != null) {
+        resultSerializedSize = result.getSerializedSize();
+        resultVintSize = CodedOutputStream.computeRawVarint32Size(resultSerializedSize);
+      }
+      // calculate the total size
+      int totalSize = headerSerializedSize + headerVintSize
+          + (resultSerializedSize + resultVintSize)
+          + (this.cellBlock == null ? 0 : this.cellBlock.limit());
+      // The byte[] should also hold the totalSize of the header, message and the cellblock
+      byte[] b = new byte[headerSerializedSize + headerVintSize + resultSerializedSize
+          + resultVintSize + Bytes.SIZEOF_INT];
+      // The RpcClient expects the int to be in a format that code be decoded by
+      // the DataInputStream#readInt(). Hence going with the Bytes.toBytes(int)
+      // form of writing int.
+      Bytes.putInt(b, 0, totalSize);
+      CodedOutputStream cos = CodedOutputStream.newInstance(b, Bytes.SIZEOF_INT,
+          b.length - Bytes.SIZEOF_INT);
+      if (header != null) {
+        cos.writeMessageNoTag(header);
+      }
+      if (result != null) {
+        cos.writeMessageNoTag(result);
+      }
+      cos.flush();
+      cos.checkNoSpaceLeft();
+      return b;
+    }
+
     private BufferChain wrapWithSasl(BufferChain bc)
         throws IOException {
       if (!this.connection.useSasl) return bc;