Event on client disconnect/abort in a streaming response

[sommeeeer]

Im wondering if its possible to get any event emitted when a client aborts or disconnects during a streaming response with awslambda.streamifyResponse. I tried with this code, but from my testing it looks like theres no event emitted on the Lambda when that happens:

exports.handler = awslambda.streamifyResponse(
 async (event, responseStream, context) => {
 responseStream.setContentType('text/event-stream')
 responseStream.on("close", ()=> {
 // this never gets emitted at any point
 console.log("responseStream closed");
 });
 for (let i = 0; i < 20; i++) {
 await sleep(1000);
 responseStream.write(`event: ping\n`);
 responseStream.write(`data: ${i}\n\n`);
 }
 responseStream.end();
 }
);

This would be an awesome feature to add in the age of SSR streaming, LLM's and more.

[douniwan5788]

I’ve done some testing on this as well, and I can confirm your findings.

In my tests, the close event is indeed emitted when responseStream.end() is invoked (intentional closure), but it fails to trigger when the client disconnects (e.g., closing the browser tab or aborting the request).