Listing / loading a CAPI Cluster resource throws an exception

[lion7]

Describe the bug

The KubernetesDeserializer does a lookup for internally defined classes when deserializing JSON/YAML.

I have a CRD where the kind is Cluster (definition can be found here). This gets resolved as class io.fabric8.kubernetes.api.model.Cluster, which is used internally to describe a cluster as part of the kubeconfig (why is this even implementing KubernetesResource?). This class does not match my resource at all, so I expected the deserializer to return a GenericKubernetesResource. Right now this loading behaviour results in all kind of weird exceptions later on.

Code analysis
I noticed that in io.fabric8.kubernetes.internal.KubernetesDeserializer.Mapping#getInternalTypeForName, there is actually a check that the complete apiVersion + kind matches the found class. This check is however only done if there are more than 1 possible classes found, which is not the case here. I would suggest to always do this check to be on the safe side. Part of the code:

            // If only one class found, return it
            if (possibleResults.size() == 1) {
                return possibleResults.get(0);
            } else if (possibleResults.size() > 1) {
              // Compare with apiVersions being compared for set of classes found
              for (Class<? extends KubernetesResource> result : possibleResults) {
                String defaultKeyFromClass = getKeyFromClass(result);
                if (key.equals(defaultKeyFromClass)) {
                  return result;
                }
              }
              return possibleResults.get(0);
            } else {
              return null;
            }

Fabric8 Kubernetes Client version

next (development version)

Steps to reproduce

When listing CAPI cluster resources as generic kubernetes resources, like so

kubernetesClient.genericKubernetesResources("cluster.x-k8s.io/v1beta1", "Cluster").list()

The following exception is thrown:

java.lang.NullPointerException: Cannot invoke "String.length()" because "this.input" is null
	at java.base/java.net.URI$Parser.parse(URI.java:3165)
	at java.base/java.net.URI.<init>(URI.java:623)
	at io.fabric8.kubernetes.client.utils.URLUtils.join(URLUtils.java:89)
	at io.fabric8.kubernetes.client.dsl.base.OperationSupport.getRootUrl(OperationSupport.java:146)
	at io.fabric8.kubernetes.client.dsl.base.OperationSupport.getNamespacedUrl(OperationSupport.java:153)
	at io.fabric8.kubernetes.client.dsl.base.OperationSupport.getNamespacedUrl(OperationSupport.java:164)
	at io.fabric8.kubernetes.client.dsl.base.BaseOperation.list(BaseOperation.java:414)
	at io.fabric8.kubernetes.client.dsl.base.BaseOperation.list(BaseOperation.java:402)
	at io.fabric8.kubernetes.client.dsl.base.BaseOperation.list(BaseOperation.java:83)
	at dev.ruddur.operator.clusterapi.SideroClient.clusterExists(SideroClient.kt:19)

Same goes for loading a resource of this kind:

val s = """
apiVersion: cluster.x-k8s.io/v1beta1
kind: Cluster
metadata:
  name: test
spec:
  clusterNetwork:
    pods:
      cidrBlocks:
        - 10.244.0.0/16
    services:
      cidrBlocks:
        - 10.96.0.0/12
  infrastructureRef:
    apiVersion: infrastructure.cluster.x-k8s.io/v1alpha3
    kind: MetalCluster
    name: test
  controlPlaneRef:
    apiVersion: controlplane.cluster.x-k8s.io/v1alpha3
    kind: TalosControlPlane
    name: test-cp
"""
val r = kubernetesClient.resource(s).get()
println(r)

Which throws:

Exception in thread "main" java.lang.ClassCastException: class io.fabric8.kubernetes.api.model.Cluster cannot be cast to class io.fabric8.kubernetes.api.model.HasMetadata (io.fabric8.kubernetes.api.model.Cluster and io.fabric8.kubernetes.api.model.HasMetadata are in unnamed module of loader 'app')
	at io.fabric8.kubernetes.client.BaseKubernetesClient.resource(BaseKubernetesClient.java:235)
	at dev.ruddur.operator.Main.main(Main.kt:55)

Expected behavior

That I would be able to list and/or create Cluster resources using the GenericKubernetesResource APIs.

Runtime

Kubernetes (vanilla)

Kubernetes API Server version

1.22.3@latest

Environment

Linux

Fabric8 Kubernetes Client Logs

No response

Additional context

Current workaround is to explicitly register this resource as a GenericKubernetesResource:

KubernetesDeserializer.registerCustomKind("cluster.x-k8s.io/v1beta1", "Cluster", GenericKubernetesResource.class)

[shawkins]

I noticed that in io.fabric8.kubernetes.internal.KubernetesDeserializer.Mapping#getInternalTypeForName, there is actually a check that the complete apiVersion + kind matches the found class.

I think we talked about this a little with #3785 but it didn't end up being needed to resolve that issue. Yes a change is need to prevent this kind of resolution conflict.

The following exception is thrown:
...
Which throws:

The logic will default to using a built-in handler if possible, so it's again resolving to wrong Cluster resource. Since it's not a HasMetadata resource we're generating invalid metadata from its class - the class has neither a Version nor a Group annotation, and the logic in

kubernetes-client/kubernetes-client/src/main/java/io/fabric8/kubernetes/client/dsl/base/OperationSupport.java

Line 100 in 5d5ff8e

this.apiGroupVersion = ctx.getConfig().getApiVersion();

assumes that if there's a config, it will specify a default apiVersion - which is not required. So in addition to the deserializer change there are a couple of sanity checks needed that will make for better exceptions.

[shawkins]

A separate pr will still be needed for the deserializer change.