close before stop or stop before close in embedded etcd?

[bluebrown]

Hi, I am playing around with https://pkg.go.dev/go.etcd.io/etcd/server/v3/embed. I am confused by the etcd.Close method and etcdserver.Stop method.

When shutting down the program, in which order are they supposed to be called?

i.e. like below, or the other way around?

e, _ := embed.StartEtcd(cfg)
...
e.Server.Stop()
e.Close()
return <-e.Err()

From the example here it seems like stop comes first, since the close call is deferred. https://github.com/etcd-io/etcd/blob/main/server/embed/doc.go#L27

But from my testing, e.Err may block until close is actually called. So deferring it may lead to the program hanging. For example see this https://go.dev/play/p/Trmcy9TV4ag.

[tjungblu]

If you look at the code, the Close method will also stop:
https://github.com/etcd-io/etcd/blob/server/v3.5.8/server/embed/etcd.go#L423-L426

So it's enough to just Close.

[ahrtr]

I agree with @tjungblu . User application just needs to call Close(), and it's recommended to follow the same way as etcdserver talks to the embed package. FYI.

etcd/server/etcdmain/etcd.go

Lines 185 to 199 in b27dec8

	osutil.HandleInterrupts(lg)
	// At this point, the initialization of etcd is done.
	// The listeners are listening on the TCP ports and ready
	// for accepting connections. The etcd instance should be
	// joined with the cluster and ready to serve incoming
	// connections.
	notifySystemd(lg)
	select {
	case lerr := <-errc:
	// fatal out on listener errors
	lg.Fatal("listener failed", zap.Error(lerr))
	case <-stopped:
	}

Also please feel free to raise a PR to fix the incorrect doc.