RPC Client doesn't gracefully close Websocket Connections

[moorow]

System information

Geth version: 1.14.8
OS & Version: OSX

Expected behaviour

When rpc.Client Close() is called, I would expect a message like this to be sent

err := cli.writeMessage(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseNormalClosure, ""))

Actual behaviour

The client closes the TCP conn without sending a WS Close message, leading to websocket: close 1006 (abnormal closure): unexpected EOF on the server side.

Steps to reproduce the behaviour

Open a WS connection with the rpc.Client. Close the connection.

[holiman]

Odd. In rpc/client.go, the dispatch loop calls close on the underlying conn

	defer func() {
		close(c.closing)
		if reading {
			conn.close(ErrClientQuit, nil)
			c.drainRead()
		}
		close(c.didClose)
	}()

At some point, I'd have expected that to trickle down to the gorilla/websocket conn, which has the following default close-handler:

func (c *Conn) SetCloseHandler(h func(code int, text string) error) {
	if h == nil {
		h = func(code int, text string) error {
			message := FormatCloseMessage(code, "")
			c.WriteControl(CloseMessage, message, time.Now().Add(writeWait))
			return nil
		}
	}
	c.handleClose = h
}

[moorow]

So conn.close(ErrClientQuit, nil) eventually calls close on the jsonCodec

func (c *jsonCodec) close() {
	c.closer.Do(func() {
		close(c.closeCh)
		c.conn.Close()
	})
}

This in turn calls Close on the Gorrillas WS conn as you say.

// Close closes the underlying network connection without sending or waiting
// for a close message.
func (c *Conn) Close() error {
	return c.conn.Close()
}

This function unfortunately just closes the TPC connection.

The Close Handler only gets called if a CloseMessage is received.

[holiman]

Hm, it seems this is a long-standing issue in gorilla/websocket: gorilla/websocket#448

[moorow]

Yeah not sure if they are going to include or if they expect devs to implement themselves. When I use gorilla/websocket I tend to do something like this to solve the issue:

func (cli *Client) close() {
	// Gracefully close the connection by sending a close message
	if err := cli.WriteMessage(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseNormalClosure, "")); err != nil {
              //handle err
	}

	// Wait for the server to acknowledge the close
	select {
	case <-cli.done:
	case <-time.After(2 * time.Second):
	
            //Close the underlying connection
            if err := cli.conn.Close(); err != nil {
	            //handle err
            }
	}
}

Unfortunately this isn't possible with rpc Client as I don't have access to the WS conn itself.