Gracefully close open WebSocket connections when server shuts down.

[aslakhellesoy]

When the server shuts down it should call WebSocketConnection.close() on all open connections. This will send a CLOSE frame to the connected client, preventing IO exceptions in the clients.

[aslakhellesoy]

Might be related to #41

[aslakhellesoy]

As part of doing this we should probably add a WebSokcetHandler.onError event, so that we can test how a connection is closed on the client (we'd expect a close event, but not an error event).

[KushalP]

Should this also attempt to "catch" exceptions and do WebSocketConnection.close() rather than just leaving them hanging as well?

[aslakhellesoy]

@KushalP do you mean IO exceptions or other exceptions? Got an example? What do you mean by leaving them hanging?

[KushalP]

Yes. In the case of IO exceptions, should we catch them (provisionally) to close the WebSocket connections and then throw the IO exception back out?

My thinking behind this is to prevent clients from attempting to communicate with a server that has failed.

[aslakhellesoy]

I'm still not sure I understand...

1. A client establishes a WebSocket connection.
2. The server catches an IO exception while trying to read from or write to the client's socket.
3. The server calls close() on the associated connection object so a CLOSE frame can be sent back to the client.

I don't understand how this would work. We wouldn't get an IO exception unless the socket is hosed, in which case we can't send a CLOSE frame at all.

Am I missing something here?

(IO exceptions are already caught and sent to the WebServer.connectionExceptionHandler)

[KushalP]

Perhaps this is a bit silly to try and pull off in practice.

Don't worry about this for the moment. I'll have a proper think (and look through the spec) and get back to you if this is feasible.