[#327] rpc: Fix mem leak

gRPC stream must be closed by `cancel` to prevent memleak.

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

api/rpc/client/flows.go

@@ -38,18 +38,27 @@ type MessageWriterCloser interface {
 }
 
 type clientStreamWriterCloser struct {
-	MessageReadWriter
-
+	sw   *streamWrapper
 	resp message.Message
 }
 
+// WriteMessage implements MessageWriterCloser.
+func (c *clientStreamWriterCloser) WriteMessage(m message.Message) error {
+	return c.sw.WriteMessage(m)
+}
+
 func (c *clientStreamWriterCloser) Close() error {
-	err := c.MessageReadWriter.Close()
+	err := c.sw.closeSend()
 	if err != nil {
+		c.sw.cancel()
 		return err
 	}
 
-	return c.ReadMessage(c.resp)
+	if err = c.sw.ReadMessage(c.resp); err != nil {
+		return err
+	}
+
+	return c.sw.Close()
 }
 
 // OpenClientStream initializes communication session by RPC info, opens client-side stream
@@ -57,13 +66,13 @@ func (c *clientStreamWriterCloser) Close() error {
 //
 // All stream writes must be performed before the closing. Close must be called once.
 func OpenClientStream(cli *Client, info common.CallMethodInfo, resp message.Message, opts ...CallOption) (MessageWriterCloser, error) {
-	rw, err := cli.Init(info, opts...)
+	rw, err := cli.initInternal(info, opts...)
 	if err != nil {
 		return nil, err
 	}
 
 	return &clientStreamWriterCloser{
-		MessageReadWriter: rw,
+		sw:   rw,
 		resp: resp,
 	}, nil
 }
@@ -112,7 +121,7 @@ func (s *serverStreamReaderCloser) ReadMessage(msg message.Message) error {
 //
 // All stream reads must be performed before the closing. Close must be called once.
 func OpenServerStream(cli *Client, info common.CallMethodInfo, req message.Message, opts ...CallOption) (MessageReader, error) {
-	rw, err := cli.Init(info, opts...)
+	rw, err := cli.initInternal(info, opts...)
 	if err != nil {
 		return nil, err
 	}

api/rpc/client/init.go

@@ -41,6 +41,10 @@ type MessageReadWriter interface {
 
 // Init initiates a messaging session and returns the interface for message transmitting.
 func (c *Client) Init(info common.CallMethodInfo, opts ...CallOption) (MessageReadWriter, error) {
+	return c.initInternal(info, opts...)
+}
+
+func (c *Client) initInternal(info common.CallMethodInfo, opts ...CallOption) (*streamWrapper, error) {
 	prm := defaultCallParameters()
 
 	for _, opt := range opts {
@@ -52,7 +56,6 @@ func (c *Client) Init(info common.CallMethodInfo, opts ...CallOption) (MessageRe
 	}
 
 	ctx, cancel := context.WithCancel(prm.ctx)
-	defer cancel()
 
 	// `conn.NewStream` doesn't check if `conn` may turn up invalidated right before this invocation.
 	// In such cases, the operation can hang indefinitely, with the context timeout being the only

api/rpc/client/stream_wrapper.go

@@ -34,10 +34,15 @@ func (w streamWrapper) WriteMessage(m message.Message) error {
 	})
 }
 
-func (w *streamWrapper) Close() error {
+func (w *streamWrapper) closeSend() error {
 	return w.withTimeout(w.ClientStream.CloseSend)
 }
 
+func (w *streamWrapper) Close() error {
+	w.cancel()
+	return nil
+}
+
 func (w *streamWrapper) withTimeout(closure func() error) error {
 	ch := make(chan error, 1)
 	go func() {
@@ -50,6 +55,10 @@ func (w *streamWrapper) withTimeout(closure func() error) error {
 	select {
 	case err := <-ch:
 		tt.Stop()
+		select {
+		case <-tt.C:
+		default:
+		}
 		return err
 	case <-tt.C:
 		w.cancel()