Hey @Arinji

Sup

Ok so

Hmm, it's not possible to directly stop a server action in the middle of it's invocation

What are you trying to do anyways

You can't just stop an ongoing process, be it an api route or a server action

Well, I was actually using ai lib and the conte xt is very much the same as this template: https://github.com/vercel/ai-chatbot/blob/main/lib/chat/actions.tsx#L109

simple server action that further calls the streamUI function from the lib.

Interestingly enough, this function has an abort param. Ref: https://sdk.vercel.ai/docs/reference/ai-sdk-rsc/stream-ui

But then how do you control it if not from the UI (an interface is that I am building)

And what I am specifically doing is a 'stop' button that stops the llm from outputting text

As far as I know, there's no way to abort a server action

Well, theoretically you could have multiple server actions, one for starting an action, one for stopping an action. combining this with some state management and you'll have what your looking for.

Super simple example (its not exactly 'cancelling' a server action, kind of a bypass), this code will not directly work bcuz of multiple reasons, its just for demonstration purposes:

"use server"

let isRunning = false;
let conditionX = false;
let controller: ReadableStreamDefaultController<string> | null = null;

export function startAction(streamController: ReadableStreamDefaultController<string>) {
    if (conditionX) {
        isRunning = true;
        controller = streamController;
        streamText();
    } else {
        streamController.close();
    }
}

export function stopAction() {
    isRunning = false;
    if (controller) {
        controller.close();
        controller = null;
    }
}

function streamText() { // for example purposes
    if (isRunning && controller) {
        controller.enqueue('Streaming some text...\n');
        setTimeout(streamText, 1000); // Stream text every second
    }
}

It's a good point and I will try it myself. I am worried if the requests would always go to the same server, and perhaps there is a one-function cleaner solution for this.

Maybe

A signal is not serializable

You could have a table in a db, with a id to an action, and before the server makes any changes to the db it checks if there exists any like record in the db to stop?

Well, the point of the 'stop generating' button is to also reduce costs (since the response so for isn't appropriate) and to end it right there.

The db is updated after the entire message is streamed to client

Tell me if that's what you suggested, cause I think it doesn't end it on the spot

this is a work around, but its still a pretty clean solution.
@Alexandru If you dont need any more help, please mark a solution.

This is what I understood from what you suggested. However, on abortUserMessage the controller aborts as it should, but then the entire app crashes and the client disconnects from the call with the error: This operation was aborted. Here's the main bits of my code:

Im not sure why that happens but maybe try a final cleanup when everything is done.
Add this after the catch statement.

      ...
      abortSignal: abortController.signal
    })
  } catch (error) {
    console.log(error)
  } finally {
    abortController = null; // Ensure the abort controller is reset
 }

Unfortunately, this doesn't help it. This is the error I am getting and in my opinion it makes no sense.. The abort action is intentional, it is meant to interrupt the streamUI function and I can see that at the right moment in the logs of my LLM API local provider (i.e. LMStudio). The error is vague and it feels like it is meaningless, but there might be something deeper going on that prevents this fundamentally.

I'm waiting to hear other ideas and would really appreciate any opinions you have. The issue stays that I am trying to provide an abortSignal to cancel or abort streaming UI on the server from the client.

The source code looks something like this, but it's mostly what you get with the chatbot Vercel template.

Hmm, do you have react strict mode enabled? (its enabled by default)

I do. However, I don't see any difference with reactStrictMode: false either, with the current implementation.

well, its calling the abort twice, the second time it tries to do it theres a chance that it shows the error that you are getting because the abortController is already aborted. you know what i mean? (https://tryitands.ee/ set reactStrictMode to false )

I doubt that's the case since strictMode is about double rendering and not double function calling (that are on the server)

well, the events are called twice

so onFormSubmit

is called twice

i think

in my opinion, u are right

I've come across an issue on Vercel's ai package that hasn't been addressed yet, but it's closely tied to Nextjs functionality. I truly believe there must be a way to enable the implementation of the stop button.
https://github.com/vercel/ai/issues/1122

Let me know what you think and how we can continue forward