What can I do to intercept ws

[zzkkui]

Hi,
I need to disconnect after inactivity to release resources. So I want to know how to get the inactive state. At present, I have an idea to intercept ws and determine whether it is active based on the information inside, but I have not found a way to intercept it.

If there is currently no method, I think the message parameter should be added in the following method

theia/packages/core/src/common/messaging/abstract-connection-provider.ts

Line 51 in 7d3b1d3

protected readonly onIncomingMessageActivityEmitter: Emitter<void> = new Emitter();

theia/packages/core/src/common/messaging/abstract-connection-provider.ts

Line 115 in 7d3b1d3

this.onIncomingMessageActivityEmitter.fire(undefined);

Thanks

[msujew]

Hi @zzkkui thank you for your question,

I assume the resources you want to release are on the backend? Correct me if I'm wrong there. So basically, the MessagingContribution will call terminate on the web socket once it doesn't answer for 30 seconds. See here:

theia/packages/core/src/node/messaging/messaging-contribution.ts

Lines 109 to 117 in 33dea9b

	setInterval(() => {
	this.webSocketServer!.clients.forEach((socket: CheckAliveWS) => {
	if (socket.alive === false) {
	socket.terminate();
	return;
	}
	socket.alive = false;
	socket.ping();
	});

In order to use that to release your resources, you will have to add your own function to the onClose callback of the WebSocketChannel which is created for each user. I think the best way to add that onClose callback is to create your custom MessagingContribution and override the createChannel method. Just add your callback to the WebSocketChannel before returning it:

theia/packages/core/src/node/messaging/messaging-contribution.ts

Lines 217 to 227 in 33dea9b

	protected createChannel(id: number, socket: ws): WebSocketChannel {
	return new WebSocketChannel(id, content => {
	if (socket.readyState < ws.CLOSING) {
	socket.send(content, err => {
	if (err) {
	throw err;
	}
	});
	}
	});
	}

[msujew]

Oh I see, that's how it is. Alright then, the actual approach isn't that different compared to what I proposed earlier. However, instead of adding your callback to the onClose method of the WebSocketChannel, you can simply add a callback to onMessage, which contains the parsed json data: (At least I think that this should work)

theia/packages/core/src/common/messaging/web-socket-channel.ts

Lines 118 to 122 in 6550934

	onMessage(cb: (data: any) => void): void {
	this.checkNotDisposed();
	this.fireMessage = cb;
	this.toDispose.push(Disposable.create(() => this.fireMessage = () => { }));
	}

[zzkkui]

Yes, I was also studying here before, but I want to modify and overwrite onMessage through extensions instead of directly modifying the source code of theia. Unfortunately, I did not find a way to achieve it through extensions. This makes me very frustrated.
So I hope to get some help, thank you very much

[msujew]

Yeah, you should be easily able to overwrite onMessage callback for your own extension without the need to change the Theia source code. See the following example:

export class CustomMessagingContribution extends MessagingContribution {
    protected createChannel(id: number, socket: ws): WebSocketChannel { 
        const channel = super.createChannel(id, socket);
        channel.onMessage(data => {
            // insert your custom logic in here
        };
        return channel;
    } 
}

You would also have to rebind the MessagingContribution in your backend module:

rebind(MessagingContribution).to(CustomMessagingContribution).inSingleton();

[zzkkui]

Oh !!! Thank you for your answer. I tried to use your method and did get the right to process the message, but there is a difference, I can't get the message in onMessage, I get the message in handleMessage. It's all because of your help, thank you very much!

following example:

protected createChannel(id: number, socket: ws) {
        const channel = super.createChannel(id, socket);
        const handleMessage = channel.handleMessage.bind(channel);
        channel.handleMessage = (message: WebSocketChannel.Message) => {
            handleMessage(message);
            if(message.kind === 'data') {
                console.log(message.content);
            }
        };
        return channel;
    }

and then rebind

rebind<MessagingContribution>(MessagingService.Identifier).to(CustomMessagingContribution).inSingletonScope();

[msujew]

Oh, I see, I didn't notice that the kind property of your message is data in the example you provided. onMessage only handles the message kind, but not data. Glad you figured that out on your own, good job!