Disable leader election for webhook

[vincent-pli]

In knative/pkg, controller leverage leader election and buckets to support HA, but webhook has different approach, I mean webhook depends on hpa and pdb, so the webhook do not need any leader election, I mean do not need create lease,

Below is the case when I set buckets: "3" in config-leader-election.yaml, it's not make sense and useless.

tekton-pipelines-webhook.configmapwebhook.00-of-03                                                        tekton-pipelines-webhook-796fdf674c-nhwwb_f4c15288-0f1a-4eec-a0ca-f14b2a7dab4a      7m2s
tekton-pipelines-webhook.configmapwebhook.01-of-03                                                        tekton-pipelines-webhook-796fdf674c-nhwwb_f4c15288-0f1a-4eec-a0ca-f14b2a7dab4a      7m2s
tekton-pipelines-webhook.configmapwebhook.02-of-03                                                        tekton-pipelines-webhook-796fdf674c-nhwwb_f4c15288-0f1a-4eec-a0ca-f14b2a7dab4a      7m2s
tekton-pipelines-webhook.conversionwebhook.00-of-03                                                       tekton-pipelines-webhook-796fdf674c-nhwwb_1c3bdb72-0398-4310-a3ed-c3c30acf1ceb      7m2s
tekton-pipelines-webhook.conversionwebhook.01-of-03                                                       tekton-pipelines-webhook-796fdf674c-nhwwb_1c3bdb72-0398-4310-a3ed-c3c30acf1ceb      7m2s
tekton-pipelines-webhook.conversionwebhook.02-of-03                                                       tekton-pipelines-webhook-796fdf674c-nhwwb_1c3bdb72-0398-4310-a3ed-c3c30acf1ceb      7m2s
tekton-pipelines-webhook.defaultingwebhook.00-of-03                                                       tekton-pipelines-webhook-796fdf674c-nhwwb_6f471e5c-f136-46a2-82c2-bc04a7a3b0db      7m2s
tekton-pipelines-webhook.defaultingwebhook.01-of-03                                                       tekton-pipelines-webhook-796fdf674c-nhwwb_6f471e5c-f136-46a2-82c2-bc04a7a3b0db      7m2s
tekton-pipelines-webhook.defaultingwebhook.02-of-03                                                       tekton-pipelines-webhook-796fdf674c-nhwwb_6f471e5c-f136-46a2-82c2-bc04a7a3b0db      7m2s
tekton-pipelines-webhook.validationwebhook.00-of-03                                                       tekton-pipelines-webhook-796fdf674c-nhwwb_d16d6390-b989-4d7f-b951-17ba1d974783      7m2s
tekton-pipelines-webhook.validationwebhook.01-of-03                                                       tekton-pipelines-webhook-796fdf674c-nhwwb_d16d6390-b989-4d7f-b951-17ba1d974783      7m2s
tekton-pipelines-webhook.validationwebhook.02-of-03                                                       tekton-pipelines-webhook-796fdf674c-nhwwb_d16d6390-b989-4d7f-b951-17ba1d974783      7m2s
tekton-pipelines-webhook.webhookcertificates.00-of-03                                                     tekton-pipelines-webhook-796fdf674c-nhwwb_2272bb66-9d83-40b2-a874-011834ca781c      7m2s
tekton-pipelines-webhook.webhookcertificates.01-of-03                                                     tekton-pipelines-webhook-796fdf674c-nhwwb_2272bb66-9d83-40b2-a874-011834ca781c      7m2s
tekton-pipelines-webhook.webhookcertificates.02-of-03                                                     tekton-pipelines-webhook-796fdf674c-nhwwb_2272bb66-9d83-40b2-a874-011834ca781c      7m2s

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[vincent-pli]

/kind bug

[vincent-pli]

/release-note-none

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[vdemeester]

/cc @imjasonh @afrittoli
SGTM

[afrittoli]

In knative/pkg, controller leverage leader election and buckets to support HA, but webhook has different approach, I mean webhook depends on hpa and pdb, so the webhook do not need any leader election, I mean do not need create lease,

The webhook controller does use leader election, not the Admit part, but the Reconcile part does.
For instance for the certificate webhook, only one of the instances of the webhook needs to make sure that the certificate is up to date - if more than one did they'd step on their toes.

It's similar for all the other webhooks. They have an Admit path, which is used by k8s API for validation, defaulting and mutating, but they all have a 2nd Reconcile method which is responsible for the webhook configuration, and only one each need to be leader, only one should Reconcile.

See also: #2735 (comment)

[imjasonh]

@afrittoli this comment is great, can you propose it as official documentation in knative/pkg? I can definitely see other folks using that framework to have similar confusion.

[vincent-pli]

@afrittoli
Thanks point out the mechanism, I check the code, you are right.
It's not just a webhook but a reconciler to watch certification, configuration .etc.