Canary should alert when it never becomes ready

[rvanoo]

Describe the feature

Canary should fire an alert if a canary never becomes ready. Happy to debate whether this should be an error or warn, but I'd prefer the former.

What problem are you trying to solve?

There are scenarios that I'm encountering where canary Pods will crash on startup for reasons that are environment-specific (configuration, data) which makes this difficult or impossible to detect earlier (in CI). I would like to be able to catch this happening in e.g. production environments when releases fail to roll out as a result.

Flagger currently rolls back silently which defeats the alerting I tried to configure to this end.

Proposed solution

Fire an alert when rolling back on account of canary not becoming ready.

Any alternatives you've considered?

None.