System metrics support

[kerthcet]

What would you like to be added:

We should add some metrics for tracking the health of the system, some of them like:

• Rolling update duration
• Recreate group times
• HPA related? Like scaling up/down times & duration?

Please add more if you think so.

Why is this needed:

Providing insight of the system

Completion requirements:

This enhancement requires the following artifacts:

• Design doc
• API change
• Docs update

The artifacts should be linked in subsequent comments.

[liurupeng]

+1 this should be pretty useful. How about "latency for pod be scheduled and become ready"?

[kerthcet]

Or do you mean Replica? Pod seems not that important.

[liurupeng]

Or do you mean Replica? Pod seems not that important.

yep, Replica makes sense

[Edwinhr716]

/assign

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/lifecycle stale

[kerthcet]

/remove-lifecycle stale

[googs1025]

"Hey, do we still need this feature? I'm not sure why the PR got closed back then and nothing happened afterwards. If it is still needed, I can take a shot at it." @kerthcet @liurupeng @Edwinhr716
Or, it would be great if Edwinhr716 is willing to re-promote this PR

[Edwinhr716]

The PR got closed due to lack of clarity on what each metric was measuring. If we want to continue with the issue, it would be good to agree on what metrics we want to be added and what each metric entails

[kerthcet]

Yes, we do. I'll categorize them once I had time and submit a pr as a demo.