Introduce `PodNeverStarted` as a reason when pod fails to come up

[vaibhavtiwari33]

Introduce a check to establish whether the pod is in running (or error) state, based on which if the pod never started in the first place, we should have:

PodsHealthy = false, Reason=NeverStarted

[whynowy]

Instead of NeverStarted, shall we just surface the reason for pod not in running state?

So basically:

1. Pod in bad state (Error, ImgPullFailur, etc, excluding states like Pending) - Unhealthy, and reason;
2. Pod in Running state - check if there's OOM caused restart in the last 2 mins.

[juliev0]

(Error, ImgPullFailur, etc, excluding states like Pending)

ImagePullFailure is in fact a Pod which is in Pending state

[juliev0]

@whynowy can you clarify in your question the specific MonoVertex/Vertex Condition key/value pairs that you have in mind for the various cases?

I believe we are only talking about Condition of type=PodsHealthy, and can you clarify reason value and message value for the cases?

[juliev0]

Are you mainly saying to use the existing Reason “Unhealthy” instead of creating a new Reason? That’s good with me.