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✨ Add predicate for Generation change on update event #553

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merged 1 commit into from
Aug 13, 2019
Merged

✨ Add predicate for Generation change on update event #553

merged 1 commit into from
Aug 13, 2019

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hasbro17
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@hasbro17 hasbro17 commented Aug 7, 2019

Adds a GenerationChangedPredicate predicate similar to the ResourceVersionChangedPredicate that will filter out update events if an object's metadata.generation is unchanged.

This predicate is needed since the CRD status subresource is more commonly enabled now which allows users to filter out updates that have no spec changes.

Since this is a common ask, this predicate is better suited as a helper in the predicate library rather than having users write it themselves or being somewhere downstream in the operator-sdk.

Side note: For CRD objects the Generation increment is skipped on metatdata updates as expected. But this behavior isn't consistent for other APIs e.g Deployments where annotation updates will cause a Generation bump. kubernetes/kubernetes#67428 (comment)
I wasn't sure if this is worth pointing out in the comments though.

@k8s-ci-robot k8s-ci-robot added the cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. label Aug 7, 2019
@k8s-ci-robot k8s-ci-robot added the size/L Denotes a PR that changes 100-499 lines, ignoring generated files. label Aug 7, 2019
@hasbro17 hasbro17 changed the title ✨ Add predicate for Generation change on update event ✨ Add predicate for Generation change on update event Aug 7, 2019
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hasbro17 commented Aug 7, 2019

/assign @droot

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droot reviewed Aug 7, 2019
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Looks good, have a couple of minor comments.

pkg/predicate/predicate.go Outdated
@@ -116,3 +116,32 @@ func (ResourceVersionChangedPredicate) Update(e event.UpdateEvent) bool {
}
return true
}

// GenerationChangedPredicate implements a default update predicate function on generation change
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It will be good to add the details that you specified in the PR description especially mentioning status sub-resource. That sort of explains when this predicate is useful.

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I would also like to see an update to the examples to show how to use the predicate? WDYT?

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Did you mean showing how to use one of the pre-defined predicates as an argument to the controller's Watch()?
I guess I could add that since I don't see it in any of the other examples:
https://godoc.org/github.com/kubernetes-sigs/controller-runtime/pkg/controller#ex-Controller

There's also an existing example in the predicate godoc, outlining how to define a new predicate.
Interestingly enough it's using generation change as the example.
https://github.com/kubernetes-sigs/controller-runtime/blob/master/pkg/predicate/example_test.go#L27-L33
https://godoc.org/github.com/kubernetes-sigs/controller-runtime/pkg/predicate#ex-Funcs

I could update that to be more complete like the one written here. Or leave that as it is if it's meant to be just a short example.

@droot Let me know what you think.

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I'd prefer to keep that example as-is.

In addition to a "why", I think this needs a "caveats" section -- like "this means you won't self-correct when someone else wipes your status".

pkg/predicate/predicate_test.go Outdated Show resolved Hide resolved
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Updated the godocs for GenerationChangedPredicate to explain how the Generation field works and the purpose of the predicate, along with a caveats section on the gotchas with using the predicate.
PTAL to see if the comments need to be more elaborate or concise. Or if there are any other caveats.

@shawn-hurley Based on the comments above I haven't updated the existing example. Let me know if you think we still need another example.

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/lgtm
/approve

@k8s-ci-robot k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Aug 13, 2019
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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: DirectXMan12, hasbro17

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@k8s-ci-robot k8s-ci-robot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Aug 13, 2019
@k8s-ci-robot k8s-ci-robot merged commit d7467fc into kubernetes-sigs:master Aug 13, 2019
@hasbro17 hasbro17 deleted the add-generation-predicate branch August 15, 2019 00:24
@DirectXMan12 DirectXMan12 mentioned this pull request Aug 28, 2019
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metral added a commit to pulumi/pulumi-kubernetes-operator that referenced this pull request Jul 10, 2020
@metral
stack-cntlr(Reconcile): skip extra loop if status updated
abe714d 
See:
 - operator-framework/operator-sdk#2795
 - kubernetes-sigs/kubebuilder#1103
 - kubernetes-sigs/controller-runtime#553
 - https://book-v1.book.kubebuilder.io/basics/status_subresource.html
@hiddeco hiddeco mentioned this pull request Sep 12, 2020
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@zcahana zcahana mentioned this pull request Nov 9, 2020
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@danaradg danaradg mentioned this pull request Apr 6, 2022
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