As I mentioned in my previous post, I am trying to use the rust-websocket library to implement a prototype debugger server for Servo.
The main server thread needs to wait for one of the following events: 1. An incoming WebSocket connection. 2. A message from the browser Unfortunately, the former uses a TCP socket, and the latter a mpsc receiver, and it is not possible to select on both. To avoid this, we listen for incoming WebSocket connections on a separate acceptor thread, and then send the connection in a message over the mpsc channel. This way, the main server thread can wait for both types of event. Note that this is exactly what we do in the existing devtools server. One message that the browser should send to the server is a request to shutdown the server. When the server receives a shutdown request, it should close all open connections, and then shut down the server. Unfortunately, as far as I can tell, the rust-websocket library does not provide a way to shut down a server. This means we have no way to break the acceptor thread out of its loop; we can't send it a notification, since it is blocked waiting on an incoming connection. The result is that we end up leaking the acceptor thread on shutdown. I can see the following options here. I am leaning towards option 2, but option 3 is also something we could consider. What are your opinions? 1. Ignore the problem. This is what we do in the existing devtools server. After all, what is a leaked thread among friends? 2. Write a pull request to add this functionality to rust-websocket. Since the library uses TCP sockets under the hood, this should be as simple as closing the listener socket (is it possible to do this from another thread?). Doing so should break the acceptor thread out of its loop. 3. I found another websocket library for Rust, called "ws". Unlike rust-websocket, ws seems to have a proper shutdown story (one can call a shutdown() method on a Sender, which can be cloned between threads). It also seems to be a bit more robustly designed than rust-websocket, so it might be worth considering. On the other hand, like rust-websocket, ws also does not provide a way to upgrade HTTP requests to WebSocket. And unlike rust-websocket, there doesn't seem to be a pending pull request to add this functionality, which means we might have to implement it ourselves. _______________________________________________ dev-servo mailing list [email protected] https://lists.mozilla.org/listinfo/dev-servo
