docs: Add best practice for reducing memory usage

[blkperl]

Signed-off-by: William Van Hevelingen william.vanhevelingen@acquia.com

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3.6% Duplication

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Go Published Test Results

1 834 tests   1 834 ✔️  2m 32s ⏱️
   105 suites         0 💤
       1 files           0 ❌

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    2 files      2 suites   1h 37m 21s ⏱️
  95 tests   90 ✔️ 3 💤 2 ❌
192 runs  184 ✔️ 6 💤 2 ❌

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Results for commit 36c46fd.

[blkperl]

@zachaller Thanks for the review! Let me know if you have questions or suggestions on changing the wording.

We could also mention that operators may wish to do the same for Deployments as the argo-controller watches all ReplicaSets on the clusters. One way to avoid this is to use NewCache which I don't think the controller uses. I can open a new issue for this if you think that makes sense. The tigera operator uses NewCache with a filter for NetworkPolicies if you are looking for an example.

• https://github.com/tigera/operator/blob/master/main.go#L231-L235
• https://github.com/argoproj-labs/argocd-operator/blob/master/main.go#L123
• https://master.sdk.operatorframework.io/docs/best-practices/designing-lean-operators/

[zachaller]

Yea I would love a new issue for looking into using that cache to get an informer that is more limited in scope that say all replicasets to reduce memory usage. Rollouts was created before a lot of the kubebuilder stuff so there is quite a few things done a little lower level but I took a quick peak at that cache package and it looks like I can get an informer still off of it so I would like to spend time looking into that and would use the issue to help track that.

[zachaller]

I think rollouts might need to do something like this instead of the cache

kubeInformerFactory := kubeinformers.NewSharedInformerFactoryWithOptions(
				kubeClient,
				resyncDuration,
				kubeinformers.WithNamespace(namespace), kubeinformers.WithTweakListOptions(func(options *metav1.ListOptions) {
					options.LabelSelector = "rollouts-managed=managed-key"
				}))

The key being WithTweakListOptions, and we would also probably need to add some managed by label to the rs

We might even be able to just use a LabelSelector="rollouts-pod-template-hash" meaning just to have the key and match any value

[blkperl]

Thanks, I filed #2552