Send a close to all websocket connections when server closes

[mcollina]

As noted by @franky47 in #45, the http server close callback does not fire until all connections are closed. This works extremely well for http requests, because it allows to wait until everything is done. It does not work well for websockets, because we need to call a method in each of them close(), hence I monkeypatch the server.close method.

I think we should send a PR to fastify to add the ability to handle this specific case.

This is a draft PR because the behavior should likely be customizable, i.e. the client.close() accepts a code and a message.

Fixes #45.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows Code of conduct

[delvedor]

I’m not sure if it is worth to add a new hook since this seems an edge case related to this module.
I’m wondering if we should be more aggressive when closing in fastify itself by using something like https://www.npmjs.com/package/stoppable.

[mcollina]

stoppable tracks all open sockets in a map. From my tests this lead to a significant overhead in term of throughput.

Note that we are already supporting that use case with the use of timeouts, so we don’t need stoppable for this to work.

We can land this and possibly add another hook or add prependHook to add an hook at the first position.

[Eomm]

Could we improve this feature request fastify/fastify#1795 with a TODO list?
If we manage the socket internally a preClose should not be necessary.

Anyway, I think a preClose hook cloud be useful for users to flush some data that are in memory and not persisted yet.

[mcollina]

@Eomm done, feel free to edit.

@delvedor @Eomm what do you think? Should we land this for v2?

[airhorns]

Have you folks further developed your thinking around this? It would be super awesome to have this just work by default -- happy to contribute if I can!

[mcollina]

I think we can land this.

@delvedor @Eomm what you think?

[Eomm]

Sorry for the delay

[delvedor]

LGTM