Provide a reconnect option to `yo ssh`?

[darrenkenny]

A common thing to do when working with VMs is to reboot them, it would be useful to have a reconnect option with yo ssh, to match the wait option, to be able to do something like:

yo ssh -w --reconnect myvm-1

or using shot name:

yo ssh -wr myvm-1

[brenns10]

I'm not sure how this would be implemented. How would yo know when to reconnect? By the exit status of ssh? Or by the runtime of the command? As far as I can tell, yo would need to distinguish between at least three cases:

1. Successful ssh session which is terminated by the user intentionally, with no desire to reconnect. In fact, there are two possibilities even here: (a) the user exits via the exit command or ctrl-D, both of which result in ssh exiting with status 0. But case (b) is where the user intentionally exits via the escape sequence <RET>~., and in this case, ssh exits with status 255.
2. Successful ssh session which is terminated due to a reboot, and the user would like ssh to reconnect. Since the connection typically drops here, I would assume ssh will terminate with status 255, but I have yet to test it.
3. An ssh session which failed to connect, either due to a permission issue, or a connection issue. This would also result in a status 255, but you could detect it via the runtime (permission failures usually result in very brief, sub-second runtimes). However, some connection issues could be timeouts, so you can't rely on runtime to detect this case.

As a result, I'm not sure I can come up with an approach that could separate out the case (2), where we'd like to have a reconnect, from the other cases, where we definitely wouldn't want Yo to enter an infinite loop.

[darrenkenny]

Almost certainly any reconnect would be entering a sleep pattern after the ssh connection drops - so it can always be interrupted by the user.

Personally, I don't see that as an issue in attempting to reconnect - as long as it isn't bombarding the server to try to reconnect, it seems reasonable.

The flow I'm be hoping to go with is quite simplistic, along the lines of:

• attempt to connect, waiting if needed
  • connected, an in-use
  • on disconnect, if in reconnect mode
    • wait a short while (5 or 10 sec?)
    • loop back to attempt to connect

I don't believe it needs to be any more complicated than that.

[brenns10]

So the idea would be that if the user wants to exit, they ctrl-d (or whatever) and then Yo gives them a few seconds of grace period to interrupt before it reconnects?

That seems reasonable.

[darrenkenny]

Well, I'd suggest Ctrl-C during the wait periods, but that's the general idea.

Given that it is an opt-in, i.e. not the default operation, it shouldn't be a surprise to people.

Maybe, it could be made more obvious to someone selecting it that they can Ctr-C while waiting, maybe via a message.