Does Fabric8io K8s java client support patch() or rollingupdate() using YAML snippets?

Question

I am trying to program the patching/rolling upgrade of k8s apps by taking deployment snippets as input. I use patch() method to apply the snippet onto an existing deployment as part of rollingupdate using fabric8io's k8s client APIS.. Fabric8.io kubernetes-client version 4.10.1 I'm also using some loadYaml helper methods from kubernetes-api 3.0.12.

Here is my sample snippet - adminpatch.yaml file:

    kind: Deployment   
    spec:
      strategy:
        type: RollingUpdate
        rollingUpdate:
          maxSurge: 1
          maxUnavailable: 0     
      template:
        spec:
          containers:
            - name: ${PATCH_IMAGE_NAME}
              image: ${PATCH_IMAGE_URL}
              imagePullPolicy: Always

I'm sending the above file content (with all the placeholders replaced) to patchDeployment() method as string. Here is my call to fabric8 patch() method:

     public static String patchDeployment(String deploymentName, String namespace, String deploymentYaml) {
    try {
    Deployment deploymentSnippet = (Deployment) getK8sObject(deploymentYaml);
    if(deploymentSnippet instanceof Deployment) {
            logger.debug("Valid deployment object.");
    Deployment deployment = getK8sClient().apps().deployments().inNamespace(namespace).withName(deploymentName)
        .rolling().patch(deploymentSnippet);
    System.out.println(deployment.toString());
    return getLastConfig(deployment.getMetadata(), deployment);
    }
    } catch (Exception Ex) {
      Ex.printStackTrace();
    }
      return "Failed";
  }

It throws the below exception:

> io.fabric8.kubernetes.client.KubernetesClientException: Failure
> executing: PATCH at:
> https://10.44.4.126:6443/apis/apps/v1/namespaces/default/deployments/patch-demo.
> Message: Deployment.apps "patch-demo" is invalid: spec.selector:
> Invalid value:
> v1.LabelSelector{MatchLabels:map[string]string{"app":"nginx",
> "deployment":"3470574ffdbd6e88d426a77dd951ed45"},
> MatchExpressions:[]v1.LabelSelectorRequirement(nil)}: field is
> immutable. Received status: Status(apiVersion=v1, code=422,
> details=StatusDetails(causes=[StatusCause(field=spec.selector,
> message=Invalid value:
> v1.LabelSelector{MatchLabels:map[string]string{"app":"nginx",
> "deployment":"3470574ffdbd6e88d426a77dd951ed45"},
> MatchExpressions:[]v1.LabelSelectorRequirement(nil)}: field is
> immutable, reason=FieldValueInvalid, additionalProperties={})],
> group=apps, kind=Deployment, name=patch-demo, retryAfterSeconds=null,
> uid=null, additionalProperties={}), kind=Status,
> message=Deployment.apps "patch-demo" is invalid: spec.selector:
> Invalid value:
> v1.LabelSelector{MatchLabels:map[string]string{"app":"nginx",
> "deployment":"3470574ffdbd6e88d426a77dd951ed45"},
> MatchExpressions:[]v1.LabelSelectorRequirement(nil)}: field is
> immutable, metadata=ListMeta(_continue=null, remainingItemCount=null,
> resourceVersion=null, selfLink=null, additionalProperties={}),
> reason=Invalid, status=Failure, additionalProperties={}).

I also tried the original snippet(with labels and selectors) with kubectl patch deployment <DEPLOYMENT_NAME> -n <MY_NAMESPACE> --patch "$(cat adminpatch.yaml) and this applies the same snippet fine.

I could not get much documentation on fabric8io k8s client patch() java API. Any help will be appreciated.

Answer 1

Here is the related bug in Fabric8io rolling API: https://github.com/fabric8io/kubernetes-client/issues/1868

As of now, one way I found to achieve patching with fabri8io APIs is to :

1. Get the running deployment object
2. add/replace containers in it with new containers
3. use the createOrReplace() API to redeploy the deployment object

But your patch understandably could be more than just an update to the containers field. In that case, processing each editable field becomes messy.

I went ahead with using the official K8s client's patchNamespacedDeployment() API to implement patching. https://github.com/kubernetes-client/java/blob/356109457499862a581a951a710cd808d0b9c622/examples/src/main/java/io/kubernetes/client/examples/PatchExample.java