Better way to stop supervisor service *if it exists*

[estebistec]

For a deploy I have, I'm looking to shut down a supervisord during the nodes upgrade because there are multiple nodes of this specific type. So I have HA and can do a "rolling upgrade" to avoid the currently upgrading server from serving requests with partially updated state.

The problem is that for a fully idempotent upgrade/install, I cannot assume that the service has even been created yet. So during the stop, it will blow up if the service doesn't exist.

Now, I can catch that exception and roll on, but the problem is that the exception is not typed, so I cannot be confident that the known exception is even what occurred as I allow it to happen while trying a stop. So...

• Should there be a more specific exception type for this?
• Is there a better way to try a stop where the service may not yet exist and am I just doing it wrong?

[jontrainor]

I stumbled on your question and have been wondering the same thing. This is how I handle the case where the service has not been created yet:

  supervisor_service someService do
    only_if { ::File.exists?("/etc/supervisor.d/" + someService + ".conf") }
    action :stop
  end

I would love to know if there is a better way though.

[whizz]

In my opinion the correct way is to change the cookbook behavior and not to raise the error when attempting to stop a service that does not exist. It's idempotent, because since the service does not exist it's stopped by definition. I can submit a trivial one-line PR, if the author agrees that is a correct way to handle this. We have done this in our local version. Our use case is a bit different, but similar in result.