ReadableStream cancel is not called when client disconnects

[luccas40]

What version of Bun is running?

1.0.7

What platform is your computer?

Debian Bullseye x64

What steps can reproduce the bug?

Running Bun with Svelte, in a API GET function:

    let keepAlive = true;
    const stream = new ReadableStream({
        start: async controller =>{
            while(keepAlive){           
                await new Promise(r => setTimeout(r, 1000));
            }
        },
        cancel: () =>{
            console.log("cancelled");
            keepAlive = false;
        }
    });
    return new Response(stream, {
        headers: {
            "Cache-Control": "no-store",
            "Content-Type": "text/event-stream",
            "Connection": "keep-alive",
        }
    });

What is the expected behavior?

Everytime the page is closed or the connection is closed by the client we should see a log on the server "cancelled".

What do you see instead?

Nothing is logged and the loop keeps running even if the page is fully closed.

Additional information

It works just fine with Node

[giesf]

Any news on this? :/

[ksmithut]

@giesf I'm not exactly sure how it's supposed to work, but I got something working going off of the request abort signal rather than relying on the response cancel callback:

const server = Bun.serve({
  async fetch(req) {
    const stream = new ReadableStream({
      async start(controller) {
        const encoder = new TextEncoder()
        let count = 0
        const interval = setInterval(() => {
          controller.enqueue(encoder.encode(`${count++}\n`))
        }, 1000)
        let closed = false
        function close() {
          if (closed) return
          console.log('aborted')
          closed = true
          clearInterval(interval)
          req.signal.removeEventListener('abort', close)
          controller.close()
        }
        req.signal.addEventListener('abort', close)
        if (req.signal.aborted) return close()
      }
    })
    return new Response(stream)
  }
})

Now running curl localhost:3000 will get a stream of numbers, and when you ctrl + c you get the aborted log and the request artifacts get cleaned up.

Is that what you're looking for?

[TheArmagan]

Any updates?

[pekeler]

We're using SSE for the "realtime" aspect of our SPA. Once these ReadableStreams are used up, the app freezes (because server event listeners don't get unregistered). So this isn't just a blocker for going to prod, but it's making development super annoying. Can we please have an ETA for a bug fix?

[Jarred-Sumner]

This will be fixed in Bun v1.1.27