clientv3: how watch know the remote etcd is closed?

[siddontang]

Hi
I start on etcd node and use the simple watch example here https://godoc.org/github.com/coreos/etcd/clientv3#example-Watcher--Watch

but when I kill etcd server, I find that we can't know the server is down and watch still hangs up.
Do we have any way to check server is down in watch?

[xiang90]

You should kill the listener, then the stream will be shutdown. Or you can enable progressNotify to do application level heartbeat.

[heyitsanthony]

Watch isn't really meant for detecting disconnects. Maybe use a Session?

[siddontang]

@xiang90

I call embed etcd Close, and I think it will close the listener too, but watch doesn't know it.
I use clientv3.WithProgressNotify() in watch, but seem no help too.

[xiang90]

@siddontang After enabling with progress notify, the watcher should expect to receive notification at least every minute. If it cannot receive anything, you should kill it. Watch is designed to handle connection failures, so it just keep on retrying. @heyitsanthony Shall we expose the errors by adding a errc chan?

[xiang90]

@siddontang Also as @heyitsanthony mentioned, watch is not really designed for detecting connection issues.

[heyitsanthony]

@xiang90 I don't think Watch should say anything about disconnects; it's at the wrong network layer. The feature probably belongs in the balancer.

[xiang90]

@heyitsanthony I do not mean watcher API. I mean for the client interface, we probably should expose some errorc. So the user can know the client is experiencing connection errors.

[heyitsanthony]

@xiang90 sure, agreed

[xiang90]

Answers are provided. So I am closing this.

[siddontang]

Hi @xiang90
Can we know the connection error in watch now?

[heyitsanthony]

@siddontang is there a reason why Session wouldn't work for your use case? I don't think Watch should ever report transport errors.

[siddontang]

@heyitsanthony we need to watch a key changed, Session may be not ok.
But we are refactoring our code, maybe we will remove watch don't need this later. :-)