support label selector in MutatingWebhook

[ChenLingPeng]

What would you like to be added:
In webbook, I would like to add a labelSelector to filter which object should be called with webhook, just like namespaceSelector

Why is this needed:

In istio, we use MutatingWebhook to inject sidecar into pod. For now, webhook only supports namespaceSelector, so when the namespace match, all pods in the namespace will call webhook to check if inject is necessary. In the real world, not all pods in the namespace needs inject. And in some bad case, when the webhook service goes down, it will affect the pods which have no need to inject. So I suggest adding a labelSelector.

[ChenLingPeng]

/sig api-machinery

[liggitt]

this is planned in https://github.com/kubernetes/enhancements/blob/master/keps/sig-api-machinery/00xx-admission-webhooks-to-ga.md#object-selector and tracked in kubernetes/enhancements#492

/close

[k8s-ci-robot]

@liggitt: Closing this issue.

In response to this:

this is planned in https://github.com/kubernetes/enhancements/blob/master/keps/sig-api-machinery/00xx-admission-webhooks-to-ga.md#object-selector and tracked in kubernetes/enhancements#492

/close

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