refactor: WebappReconciler doesn't use dependent resources anymore

This is meant to show that you can still write reconcilers without the
dependent resource support.

Author: metacosm

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/reconciler/dependent/KubernetesDependentResourceController.java

@@ -54,8 +54,7 @@ public String descriptionFor(R resource) {
   @Override
   public EventSource initEventSource(EventSourceContext<P> context) {
     this.client = context.getClient();
-    informer =
-        new InformerEventSource<>(client.resources(getResourceType()), configuration, context);
+    informer = new InformerEventSource<>(configuration, context);
     return informer;
   }
 

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerEventSource.java

@@ -5,9 +5,6 @@
 import java.util.stream.Stream;
 
 import io.fabric8.kubernetes.api.model.HasMetadata;
-import io.fabric8.kubernetes.api.model.KubernetesResourceList;
-import io.fabric8.kubernetes.client.dsl.MixedOperation;
-import io.fabric8.kubernetes.client.dsl.Resource;
 import io.fabric8.kubernetes.client.informers.ResourceEventHandler;
 import io.javaoperatorsdk.operator.api.reconciler.EventSourceContext;
 import io.javaoperatorsdk.operator.processing.event.Event;
@@ -21,22 +18,20 @@ public class InformerEventSource<T extends HasMetadata, P extends HasMetadata>
 
   private final InformerConfiguration<T, P> configuration;
 
-  public InformerEventSource(MixedOperation<T, KubernetesResourceList<T>, Resource<T>> client,
-      InformerConfiguration<T, P> configuration, EventSourceContext<P> context) {
-    super(client, configuration);
+  public InformerEventSource(InformerConfiguration<T, P> configuration,
+      EventSourceContext<P> context) {
+    super(context.getClient().resources(configuration.getResourceClass()), configuration);
     this.configuration = configuration;
 
     // init mappers with context if needed
-    if (context != null) {
-      final var primaryResourcesRetriever = configuration.getPrimaryResourcesRetriever();
-      if (primaryResourcesRetriever instanceof EventSourceContextAware) {
-        ((EventSourceContextAware) primaryResourcesRetriever).initWith(context);
-      }
+    final var primaryResourcesRetriever = configuration.getPrimaryResourcesRetriever();
+    if (primaryResourcesRetriever instanceof EventSourceContextAware) {
+      ((EventSourceContextAware) primaryResourcesRetriever).initWith(context);
+    }
 
-      final var associatedResourceIdentifier = configuration.getAssociatedResourceIdentifier();
-      if (associatedResourceIdentifier instanceof EventSourceContextAware) {
-        ((EventSourceContextAware) associatedResourceIdentifier).initWith(context);
-      }
+    final var associatedResourceIdentifier = configuration.getAssociatedResourceIdentifier();
+    if (associatedResourceIdentifier instanceof EventSourceContextAware) {
+      ((EventSourceContextAware) associatedResourceIdentifier).initWith(context);
     }
   }
 

sample-operators/tomcat-operator/src/main/java/io/javaoperatorsdk/operator/sample/WebappReconciler.java

@@ -7,6 +7,7 @@
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
+import java.util.stream.Collectors;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -16,26 +17,50 @@
 import io.fabric8.kubernetes.client.KubernetesClient;
 import io.fabric8.kubernetes.client.dsl.ExecListener;
 import io.fabric8.kubernetes.client.dsl.ExecWatch;
-import io.javaoperatorsdk.operator.api.config.Dependent;
 import io.javaoperatorsdk.operator.api.reconciler.Context;
 import io.javaoperatorsdk.operator.api.reconciler.ControllerConfiguration;
 import io.javaoperatorsdk.operator.api.reconciler.DeleteControl;
+import io.javaoperatorsdk.operator.api.reconciler.EventSourceContext;
+import io.javaoperatorsdk.operator.api.reconciler.EventSourceInitializer;
 import io.javaoperatorsdk.operator.api.reconciler.Reconciler;
 import io.javaoperatorsdk.operator.api.reconciler.UpdateControl;
+import io.javaoperatorsdk.operator.processing.event.ResourceID;
+import io.javaoperatorsdk.operator.processing.event.source.EventSource;
+import io.javaoperatorsdk.operator.processing.event.source.informer.InformerConfiguration;
+import io.javaoperatorsdk.operator.processing.event.source.informer.InformerEventSource;
 
-@ControllerConfiguration(
-    eventFilters = CustomFilter.class,
-    dependents = @Dependent(resourceType = Tomcat.class, type = TomcatDependentResource.class))
-public class WebappReconciler implements Reconciler<Webapp> {
+@ControllerConfiguration(eventFilters = {CustomFilter.class})
+public class WebappReconciler implements Reconciler<Webapp>, EventSourceInitializer<Webapp> {
 
-  private final KubernetesClient kubernetesClient;
+  private static final Logger log = LoggerFactory.getLogger(WebappReconciler.class);
 
-  private final Logger log = LoggerFactory.getLogger(getClass());
+  private final KubernetesClient kubernetesClient;
 
   public WebappReconciler(KubernetesClient kubernetesClient) {
     this.kubernetesClient = kubernetesClient;
   }
 
+  @Override
+  public List<EventSource> prepareEventSources(EventSourceContext<Webapp> context) {
+    return List.of(
+        new InformerEventSource<>(
+            new InformerConfiguration<>(context.getConfigurationService(),
+                null,
+                Tomcat.class,
+                // To create an event to a related WebApp resource and trigger the reconciliation
+                // we need to find which WebApp this Tomcat custom resource is related to.
+                // To find the related customResourceId of the WebApp resource we traverse the cache
+                // and identify it based on naming convention.
+                (Tomcat t) -> context.getPrimaryCache()
+                    .list(webApp -> webApp.getSpec().getTomcat().equals(t.getMetadata().getName()))
+                    .map(ResourceID::fromResource)
+                    .collect(Collectors.toSet()),
+                (Webapp webapp) -> new ResourceID(webapp.getSpec().getTomcat(),
+                    webapp.getMetadata().getNamespace()),
+                true),
+            context));
+  }
+
   /**
    * This method will be called not only on changes to Webapp objects but also when Tomcat objects
    * change.