rpc/http: improve request handling

rpc/server.go

@@ -117,14 +117,12 @@ func (s *Server) RegisterName(name string, rcvr interface{}) error {
 	return nil
 }
 
-// ServeCodec reads incoming requests from codec, calls the appropriate callback and writes the
-// response back using the given codec. It will block until the codec is closed.
-//
-// This server will:
-// 1. allow for asynchronous and parallel request execution
-// 2. supports notifications (pub/sub)
-// 3. supports request batches
-func (s *Server) ServeCodec(codec ServerCodec) {
+// serveRequest will reads requests from the codec, calls the RPC callback and
+// writes the response to the given codec.
+// If singleShot is true it will process a single request, otherwise it will handle
+// requests until the codec returns an error when reading a request (in most cases
+// an EOF). It executes requests in parallel when singleShot is false.
+func (s *Server) serveRequest(codec ServerCodec, singleShot bool) error {
 	defer func() {
 		if err := recover(); err != nil {
 			const size = 64 << 10
@@ -132,7 +130,12 @@ func (s *Server) ServeCodec(codec ServerCodec) {
 			buf = buf[:runtime.Stack(buf, false)]
 			glog.Errorln(string(buf))
 		}
-		codec.Close()
+
+		s.codecsMu.Lock()
+		s.codecs.Remove(codec)
+		s.codecsMu.Unlock()
+
+		return
 	}()
 
 	ctx, cancel := context.WithCancel(context.Background())
@@ -141,20 +144,22 @@ func (s *Server) ServeCodec(codec ServerCodec) {
 	s.codecsMu.Lock()
 	if atomic.LoadInt32(&s.run) != 1 { // server stopped
 		s.codecsMu.Unlock()
-		return
+		return &shutdownError{}
 	}
 	s.codecs.Add(codec)
 	s.codecsMu.Unlock()
 
+	// test if the server is ordered to stop
 	for atomic.LoadInt32(&s.run) == 1 {
 		reqs, batch, err := s.readRequest(codec)
-
 		if err != nil {
 			glog.V(logger.Debug).Infof("%v\n", err)
 			codec.Write(codec.CreateErrorResponse(nil, err))
-			break
+			return nil
 		}
 
+		// check if server is ordered to shutdown and return an error
+		// telling the client that his request failed.
 		if atomic.LoadInt32(&s.run) != 1 {
 			err = &shutdownError{}
 			if batch {
@@ -166,15 +171,42 @@ func (s *Server) ServeCodec(codec ServerCodec) {
 			} else {
 				codec.Write(codec.CreateErrorResponse(&reqs[0].id, err))
 			}
-			break
+			return nil
 		}
 
-		if batch {
+		if singleShot && batch {
+			s.execBatch(ctx, codec, reqs)
+			return nil
+		} else if singleShot && !batch {
+			s.exec(ctx, codec, reqs[0])
+			return nil
+		} else if !singleShot && batch {
 			go s.execBatch(ctx, codec, reqs)
 		} else {
 			go s.exec(ctx, codec, reqs[0])
 		}
 	}
+
+	return nil
+}
+
+// ServeCodec reads incoming requests from codec, calls the appropriate callback and writes the
+// response back using the given codec. It will block until the codec is closed or the server is
+// stopped. In either case the codec is closed.
+//
+// This server will:
+// 1. allow for asynchronous and parallel request execution
+// 2. supports notifications (pub/sub)
+// 3. supports request batches
+func (s *Server) ServeCodec(codec ServerCodec) {
+	defer codec.Close()
+	s.serveRequest(codec, false)
+}
+
+// ServeSingleRequest reads and processes a single RPC request from the given codec. It will not
+// close the codec unless a non-recoverable error has occurred.
+func (s *Server) ServeSingleRequest(codec ServerCodec) {
+	s.serveRequest(codec, true)
 }
 
 // Stop will stop reading new requests, wait for stopPendingRequestTimeout to allow pending requests to finish,