Add argument to remove only pods violating allowlisted taints

[etoster]

Fixes #1353.

Adds the option to apply the RemovePodsViolatingNodeTaints strategy only for an explicitly allowlisted set of taints.

When a list of includedTaints is provided, a taint will be considered if and only if it matches an included key or key=value from the list. Otherwise it will be ignored. Leaving includedTaints unset will include any taint by default.

[linux-foundation-easycla]

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• ✅ login: etoster / name: Tobias Ostermann (b769786)

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[knelasevero]

/ok-to-test

[knelasevero]

should we let users set both included and excluded taints? When we look at namespace inclusion/exclusion we make inclusion be something like: "this and nothing else". Shouldn't we keep consistency here?

@a7i @damemi @ingvagabund

[damemi]

should we let users set both included and excluded taints? When we look at namespace inclusion/exclusion we make inclusion be something like: "this and nothing else". Shouldn't we keep consistency here?

@a7i @damemi @ingvagabund

I'm for using one or the other until there's a use case for both. I had mentioned in the original issue that it didn't seem harmful to do both, but I agree that it's safer and more consistent to make them exclusive for now.

[etoster]

should we let users set both included and excluded taints? When we look at namespace inclusion/exclusion we make inclusion be something like: "this and nothing else". Shouldn't we keep consistency here?

@damemi also pointed this out in the issue.

I started looking into how it's done for namespaces, but I wasn't sure where would be the right place to check in this case. If it would be within the strategy plugin or if there is some linter parsing the deschedulerPolicy resource before (which I didn't find). So I proposed the change without it, but I'm happy to add it, if you could give me some guidance on what you consider the best practice for it!

[ingvagabund]

+1 for allowing to set only one of include/exclude lists, not both.

[ingvagabund]

If it would be within the strategy plugin

Yeap. Each strategy/plugin is responsible for its own arg validation. E.g. https://github.com/kubernetes-sigs/descheduler/blob/master/pkg/framework/plugins/removeduplicates/validation.go

[etoster]

Thanks @ingvagabund! I added the validation to allow only one of include/exclude taints. Please have a look.
cc @knelasevero @damemi

[ingvagabund]

One last nit.

The changes are not that significant so they can be part of a single commit (will leave this up to you). Multiple commits are ok as well. In which case would you please integrate the last commit into the first one?

[knelasevero]

After Jan's comments are addressed I think this lgtm

[ingvagabund]

/approve
/lgtm

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[etoster]

Thank you all for your quick responses and helpful feedback! This was a great experience as a first time contributor. :)