Unknown namespace for the cache error while Getting cluster scoped for MultiNamespacedCache

[vinod-patil]

While using MultiNamespacedCache with manager, if we try to get a cluster scoped resource as
cluster scoped resource doesn't have any namespace (empty namespace), it's returning unknown namespace error

func (c *multiNamespaceCache) Get(ctx context.Context, key client.ObjectKey, obj client.Object) error {
	cache, ok := c.namespaceToCache[key.Namespace]
	if !ok {
		return fmt.Errorf("unable to get: %v because of unknown namespace for the cache", key)
	}
	return cache.Get(ctx, key, obj)
}

[alvaroaleman]

/kind bug
/help

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[varshaprasad96]

@alvaroaleman, would this be the right approach to solve the issue with cluster scoped objects:

1. In namespaceToCache mapping, we add an entry for a mapping between no namespace and global cache (say an empty string as the key). When there is no namespace provided in the object key, we call the global cache to get the cluster scoped object.
2. In case of listing the objects in multinamespace cache - if listOptions does provide anything, we call the global cache, without any specified namespace to list the objects. Currently, by default if namespace is not provided we are looking for objects across all namespaces and listing them.

Maybe we can have a separate const defined for multiNamespaceCache to identify a "no namespace" condition.

cc: @estroz

[estroz]

One problem that will likely result in a breaking change comes from point (2). As @varshaprasad96 alluded to, listOpts.Namespace == corev1.NamespaceAll means "only look up objects within the known namespace set", even though looking up objects across all namespaces/cluster scoped objects is still allowed via a multiNamespaceCache. That will probably have to change.

[madhurtrilio]

Having same issue. Any tentative timelines on when this will be fixed?

[alvaroaleman]

@madhurtrilio #1418 will fix this