[Question] `desired` method of `CRUDKubernetesDependentResource` called twice when dependent resource exists

[michaelkoepf]

Hi,

I have an operator that uses a standalone dependent resource. The dependent resource is of type CRUDKubernetesDependentResource<ConfigMap, T> and only overrides method protected ConfigMap desired(T primary, Context<T> context). When the dependent resource does not exist yet, desired is called once. However, when the dependent resource exists, desired is called twice in a row. Why is that? According to the flowchart in the docs, I would have expected only one call.

Minimal reproducible example based on the WebPage Example Operator

Full source code can be found here: https://github.com/michaelkoepf/dependent-resource-test. Most important classes can be found below.

@ControllerConfiguration
public class WebPageStandaloneDependentsReconciler implements Reconciler<WebPage> {

  private static final Logger LOG = LoggerFactory.getLogger(WebPageStandaloneDependentsReconciler.class);

  private final Workflow<WebPage> workflow;

  public WebPageStandaloneDependentsReconciler() {
    workflow = createDependentResourcesAndWorkflow();
  }

  @Override
  public List<EventSource<?, WebPage>> prepareEventSources(EventSourceContext<WebPage> context) {
    return EventSourceUtils.eventSourcesFromWorkflow(context, workflow);
  }

  @Override
  public UpdateControl<WebPage> reconcile(WebPage webPage, Context<WebPage> context)
      throws Exception {
    LOG.info("Starting reconciliation at {}", System.currentTimeMillis());
    workflow.reconcile(webPage, context);

    return UpdateControl.noUpdate();
  }

  @SuppressWarnings({"unchecked", "rawtypes"})
  private Workflow<WebPage> createDependentResourcesAndWorkflow() {
    // create the dependent resources
    var configMapDR = new ConfigMapDependentResource();

    // configure them with our label selector
    Arrays.asList(configMapDR)
        .forEach(
            dr ->
                dr.configureWith(
                    new KubernetesDependentResourceConfigBuilder()
                        .withKubernetesDependentInformerConfig(
                            InformerConfiguration.builder(dr.resourceType())
                                .withLabelSelector("managed=true")
                                .build())
                        .build()));

    return new WorkflowBuilder<WebPage>()
        .addDependentResource(configMapDR)
        .build();
  }
}

public class ConfigMapDependentResource
    extends CRUDKubernetesDependentResource<ConfigMap, WebPage> {

  private static final Logger LOG = LoggerFactory.getLogger(ConfigMapDependentResource.class);

  @Override
  protected ConfigMap desired(WebPage webPage, Context<WebPage> context) {
    LOG.info("Evaluating desired state at {}", System.currentTimeMillis());

    Map<String, String> data = new HashMap<>();
    data.put("index.html", webPage.getSpec().getHtml());
    Map<String, String> labels = new HashMap<>();
    labels.put("managed", "true");
    return new ConfigMapBuilder()
        .withMetadata(
            new ObjectMetaBuilder()
                .withName("webpage-configmap")
                .withNamespace(webPage.getMetadata().getNamespace())
                .withLabels(labels)
                .build())
        .withData(data)
        .build();
  }
}

Example

1. Trigger reconciliation by kubectl apply -f k8s/webpage-v1.yaml. Dependent resource does not exist yet. Log:

2025-08-11 13:32:02,237 INFO  [com.exa.WebPageStandaloneDependentsReconciler] (ReconcilerExecutor-webpagestandalonedependentsreconciler-185) Starting reconciliation at 1754911922237
2025-08-11 13:32:02,240 INFO  [com.exa.ConfigMapDependentResource] (pool-16-thread-1) Evaluating desired state at 1754911922240

2. Dependent resource now exists. Trigger reconciliation again by kubectl apply -f k8s/webpage-v2.yaml. Log:

2025-08-11 13:32:04,816 INFO  [com.exa.WebPageStandaloneDependentsReconciler] (ReconcilerExecutor-webpagestandalonedependentsreconciler-188) Starting reconciliation at 1754911924816
2025-08-11 13:32:04,817 INFO  [com.exa.ConfigMapDependentResource] (pool-16-thread-2) Evaluating desired state at 1754911924817
2025-08-11 13:32:04,818 INFO  [com.exa.ConfigMapDependentResource] (pool-16-thread-2) Evaluating desired state at 1754911924818

3. Trigger reconciliation again by kubectl apply -f k8s/webpage-v3.yaml. Log:

2025-08-11 13:32:06,888 INFO  [com.exa.WebPageStandaloneDependentsReconciler] (ReconcilerExecutor-webpagestandalonedependentsreconciler-191) Starting reconciliation at 1754911926888
2025-08-11 13:32:06,889 INFO  [com.exa.ConfigMapDependentResource] (pool-16-thread-3) Evaluating desired state at 1754911926889
2025-08-11 13:32:06,889 INFO  [com.exa.ConfigMapDependentResource] (pool-16-thread-3) Evaluating desired state at 1754911926889

[metacosm]

Which version of the SDK are you using?

[michaelkoepf]

@metacosm

[csviri]

Hi @michaelkoepf ,

see here: https://javaoperatorsdk.io/blog/2025/01/06/version-5-released/#resourcediscriminator-is-removed-and-related-changes

java-operator-sdk/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/dependent/AbstractDependentResource.java

Line 139 in 03a0949

R desired = desired(primary, context);

java-operator-sdk/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/dependent/kubernetes/KubernetesDependentResource.java

Lines 266 to 290 in 03a0949

	@Override
	protected Optional<R> selectTargetSecondaryResource(
	Set<R> secondaryResources, P primary, Context<P> context) {
	ResourceID managedResourceID = targetSecondaryResourceID(primary, context);
	return secondaryResources.stream()
	.filter(
	r ->
	r.getMetadata().getName().equals(managedResourceID.getName())
	&& Objects.equals(
	r.getMetadata().getNamespace(),
	managedResourceID.getNamespace().orElse(null)))
	.findFirst();
	}
	/**
	* Override this method in order to optimize and not compute the desired when selecting the target
	* secondary resource. Simply, a static ResourceID can be returned.
	*
	* @param primary resource
	* @param context of current reconciliation
	* @return id of the target managed resource
	*/
	protected ResourceID targetSecondaryResourceID(P primary, Context<P> context) {
	return ResourceID.fromResource(desired(primary, context));
	}

Basically by default calls desired to select the target resource. you can easily optimize this by overriding:

java-operator-sdk/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/dependent/kubernetes/KubernetesDependentResource.java

Lines 288 to 290 in 03a0949

	protected ResourceID targetSecondaryResourceID(P primary, Context<P> context) {
	return ResourceID.fromResource(desired(primary, context));
	}