Should app.listen also return a promise?

[blai]

https://github.com/koajs/koa/blob/master/lib/application.js#L62 currently returning server.listen(), thoughts?

[jonathanong]

What would that accomplish?

[blai]

well, in Node.js server.listen() also take a callback, with the first argument being error. There has not been an easy way to doing something like: wait for the server to start listening (some app might take a bit to instantiate all the middleware dependencies, e.g. a db connection). Or something like, if the server failed to start listening because the port is in use, try start in a different port. I guess this (returning promise) opens up some possibilities, just a random thought.

[tj]

I'd like to defer that sort of boot logic, ideally you'd get everything ready and then .listen() for connections, but thankfully most database drivers buffer requests and so on so usually .listen() at the bottom without a callback is just fine

[jonathanong]

@visionmedia why not just remove app.listen()? people are inevitably going to ask for more like with Express. ie i wanted expect: 100-continue support, but it's easier just to create the server myself. you use http.createServer(app.callback()) in half your tests and examples anyways.

[tj]

I find it useful, just need to be certain that it's not going to change and turn into some giant wtf