fix: check serving webhook readiness through endpoint lookup

[linkvt]

Changes

• Checks the serving webhook readiness by looking at the endpoints and not ready pods
  • The failure scenario is a bit hard to reproduce, appreciate some testing/feedback

I see this issue consistently, almost every run of kn quickstart kind ... fails for me without this check due to the webhook being recognized as ready when it isn't reachable.

/kind bug

Fixes #610
Related to #607

Release Note

Fix webhook connection errors occuring sometimes after the webhook readiness check has passed.

[linkvt]

Hi @psschwei , would appreciate if you could take a look on this small PR based on your recent one that added the webhook readiness check, thanks!

[psschwei]

Thanks!
/lgtm
/approve

I stepped down as a maintainer here a while back, so will need @dsimansk or @dprotaso for final approval.

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: linkvt, psschwei

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[psschwei]

I stepped down as a maintainer here a while back, so will need dsimansk or dprotaso for final approval.

Or not, it seems... 🤷

[dprotaso]

Or not, it seems... 🤷

huh yeah that's odd

[dprotaso]

my working theory is that vincent had approver status as a release lead? and when you commented prow checked and updated the label

https://github.com/knative/community/pull/1735/files

[joebowbeer]

@psschwei When will this be released?

[psschwei]

Seems that Knative 1.21 comes out January 20: https://github.com/knative/community/blob/ad9257bad1fc0a737e041e16438f60bf78e045be/mechanics/RELEASE-SCHEDULE.md?plain=1#L25

[linkvt]

I just added a follow-up PR as my original implementation in this PR used the deprecated Endpoint resource instead of EndpointSlices, not sure how I missed that.

Edit: I'm also open to backporting it to release-1.20, IIRC its basically just adding a comment, prow creates the PR, PR gets merged and auto release happens.

[joebowbeer]

@linkvt Thanks. I run kn quickstart kind --registry fairly often in automation and it fails periodically due to #610, which also aborts the Kourier install.