Server crash when client disconnect: "Can\'t set headers after they are sent."

[sylvain101010]

Hi,
When a client disconnect, the server crash with the following error:

Error: Can't set headers after they are sent.

here is a stacktrace

server listening on 3000
_http_outgoing.js:504
throw new Error('Can't set headers after they are sent.');
^
Error: Can't set headers after they are sent.
at validateHeader (_http_outgoing.js:504:11)
at ServerResponse.setHeader (_http_outgoing.js:511:3)
at Immediate.wrapReplyEnd [as _onImmediate] (/Users/test/fastifyy/node_modules/fastify/lib/reply.js:145:15)
at runCallback (timers.js:785:20)
at tryOnImmediate (timers.js:743:5)
at processImmediate [as _immediateCallback] (timers.js:714:5)

How to reproduce:

just run example.js
node example.js
then
curl localhost:3000/sse2
And quit the running curl job
Ctrl+c

[YerkoPalma]

I just had this very same issue. You must ensure to call reply.sse() (with no arguments) before closing your server. This works for me

fastify.addHook('onClose', (instance, done) => {
  instance._Reply.sse()
  done()
})

try adding that hook, then running your server and stop it with Ctrl + c

[piranna]

He is talking about when clients disconnect, that's the same problem I have, NOT when server close...