Issue #1595 ---Part2 --- Add namespace denied list

[mallow111]

What this PR does / why we need it:
Details: #1593

How does this change affect the cardinality of KSM: (increases, decreases or does not change cardinality)

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #1593

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[mallow111]

@dgrisonnet any idea how to fix the ci-validate-docs check?

[fpetkovski]

Thanks for the contribution @mallow111! To fix the docs, you can run make generate.

Besides that, the PR seems to need a bit more work. Currently, the namespace-denylist option only excludes namespaces from the namespaces list. If the namespaces list is empty, KSM will export metrics from all namespaces, regardless of what is in the namespace denylist.

One way to get namespace exclusion to work when watching all namespaces is to propagate the namespace denylist all the way down to the listwatchers. Here is an example of how the createConfigMapListWatch could end up looking like:

func createConfigMapListWatch(kubeClient clientset.Interface, ns string, nsDenylist []string) cache.ListerWatcher {
	fieldSelector := excludeNamespacesFieldSelector(nsDenylist)
	return &cache.ListWatch{
		ListFunc: func(opts metav1.ListOptions) (runtime.Object, error) {
			opts.FieldSelector = fieldSelector
			return kubeClient.CoreV1().ConfigMaps(ns).List(context.TODO(), opts)
		},
		WatchFunc: func(opts metav1.ListOptions) (watch.Interface, error) {
			opts.FieldSelector = fieldSelector
			return kubeClient.CoreV1().ConfigMaps(ns).Watch(context.TODO(), opts)
		},
	}
}

func excludeNamespacesFieldSelector(nsDenylist []string) string {
	if len(nsDenylist) == 0 {
		return ""
	}

	namespaceExcludeSelectors := make([]fields.Selector, len(nsDenylist))
	for i, ns := range nsDenylist {
		selector := fields.OneTermNotEqualSelector("metadata.namespace", ns)
		namespaceExcludeSelectors[i] = selector
	}
	return fields.AndSelectors(namespaceExcludeSelectors...).String()
}

[mallow111]

@fpetkovski Please take a look at the PR for the listwatcher change, once it is done, I can go back to this pr and address the rest, trying to break big PR into smaller ones.
#1596

[mallow111]

@fpetkovski
@mrueg
PR #1596 is merged, now I am back to this PR again, once this is approved, I will work on the TODO part, which is the last bit of this issue, it might involve a few unit test update to make sure the flow is working.

[mallow111]

@fpetkovski updated, can you check again, thanks!

[fpetkovski]

Thanks @mallow111, this looks good so far. Any reason why you don't want to use the GetExcludeNSFieldSelector function now instead of the empty fieldselector?

[mallow111]

@fabriziopandini updated, check again please

[fpetkovski]

Great stuff!

/lgtm

[mallow111]

@mrueg can you help to approve, thanks!

[mrueg]

/lgtm

Thanks for your work!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: fpetkovski, mallow111, mrueg

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[mallow111]

It is merged, thank you!