feat: allow image list to be empty

[konturn]

My use case involves initializing an ImageCache resource out of band, and then having a separate service dynamically add and remove images from the cache. As part of this, I think it would be nice to have the option to initialize the ImageCache resource with CacheSpecs with empty Images lists.

[senthilrch]

This would be a useful feature.

The PR doesn't addresses actions taken by the controller on such ImageCache resources + the status update for such resources.

[konturn]

Is there any further change to the controller logic required? It looks like the loop here already accounts for the possibility of an empty image list.

[senthilrch]

The ImageCache status is updated to Processing in below code:-

kube-fledged/cmd/controller/app/controller.go

Line 507 in aadfdcd

if err = c.updateImageCacheStatus(imageCache, status); err != nil {

If the ImageCache CR has an empty image list, the CR will get stuck in the Processing status. So updating the status should be skipped when image list is empty.

[senthilrch]

A more robust solution for this use case would be to implement something on the lines of Pod scheduling gates introduced in K8s 1.26.

https://kubernetes.io/blog/2022/12/26/pod-scheduling-readiness-alpha/

[konturn]

Ah I see--okay, I'll go ahead and make the necessary changes to the status processing logic