Introduce RemoveFailedPods strategy

[a7i]

Closes issue #596

[k8s-ci-robot]

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[damemi]

/ok-to-test

[damemi]

looks pretty thorough, a couple notes but fundamentally solid imo

[a7i]

/assign @seanmalloy

[damemi]

This looks good to squash, then I can approve

One nit though, which I'd like your input on, is maybe the new StrategyParam validator should be in its own package? It's minor but it would be nice to keep the strategies package to strategy code.

I was also not really sure about the way it wraps the "common" params inside another struct for the new strategy, but I suppose that's the best way to accomplish that (with the common params embedded). Hopefully we can start moving other strategies to use this function too and clean up their duped code

[a7i]

I was also not really sure about the way it wraps the "common" params inside another struct for the new strategy, but I suppose that's the best way to accomplish that (with the common params embedded). Hopefully we can start moving other strategies to use this function too and clean up their duped code

Ok, I can do that. something like pkg/descheduler/internal/validators/? (hence internal to reduce public API surface).

As far as wrapping the common params, I don't have a clever idea. If it was just a validator, could use interface. But it's also a parser that returns the parsed params so the return type gets tricky.

[damemi]

@a7i maybe just pkg/descheduler/strategies/validation?

[damemi]

/approve
I think the validation package will have some room to evolve as we implement it in other strategies but it looks good now. Thanks @a7i

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: a7i, damemi

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[ingvagabund]

Given all strategies use the same StrategyParameters type it makes sense to put all the validation under the same package as all the params are shared across multiple strategies. On the other hand each strategy accesses a subset of the parameters so some part of the validation needs to stay as close to each strategy as possible.

The rest looks good.

[ingvagabund]

/lgtm