feat: support to handle different cluster for InformerEventSource

docs/content/en/docs/features/_index.md

@@ -606,6 +606,25 @@ parts of reconciliation logic and during the execution of the controller:
 
 For more information about MDC see this [link](https://www.baeldung.com/mdc-in-log4j-2-logback).
 
+## InformerEventSource Multi-Cluster Support
+
+It is possible to handle resources for remote cluster with `InformerEventSource`. To do so,
+simply set a client that connects to a remote cluster:
+
+```java
+
+InformerEventSourceConfiguration<Tomcat> configuration =
+        InformerEventSourceConfiguration.from(SecondaryResource.class, PrimaryResource.class)
+            .withKubernetesClient(remoteClusterClient)
+            .withSecondaryToPrimaryMapper(Mappers.fromDefaultAnnotations());
+
+```
+
+You will also need to specify a `SecondaryToPrimaryMapper`, since the default one
+is based on owner references and won't work across cluster instances. You could, for example, use the provided implementation that relies on annotations added to the secondary resources to identify the associated primary resource.
+
+See related [integration test](https://github.com/operator-framework/java-operator-sdk/tree/main/operator-framework/src/test/java/io/javaoperatorsdk/operator/baseapi/informerremotecluster).
+
 ## Dynamically Changing Target Namespaces
 
 A controller can be configured to watch a specific set of namespaces in addition of the

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/informer/InformerEventSourceConfiguration.java

@@ -6,6 +6,7 @@
 
 import io.fabric8.kubernetes.api.model.GenericKubernetesResource;
 import io.fabric8.kubernetes.api.model.HasMetadata;
+import io.fabric8.kubernetes.client.KubernetesClient;
 import io.javaoperatorsdk.operator.api.config.Informable;
 import io.javaoperatorsdk.operator.processing.GroupVersionKind;
 import io.javaoperatorsdk.operator.processing.event.source.PrimaryToSecondaryMapper;
@@ -57,22 +58,33 @@ default String name() {
     return getInformerConfig().getName();
   }
 
+  /**
+   * Optional, specific kubernetes client, typically to connect to a different cluster than the rest
+   * of the operator. Note that this is solely for multi cluster support.
+   */
+  default Optional<KubernetesClient> getKubernetesClient() {
+    return Optional.empty();
+  }
+
   class DefaultInformerEventSourceConfiguration<R extends HasMetadata>
       implements InformerEventSourceConfiguration<R> {
     private final PrimaryToSecondaryMapper<?> primaryToSecondaryMapper;
     private final SecondaryToPrimaryMapper<R> secondaryToPrimaryMapper;
     private final GroupVersionKind groupVersionKind;
     private final InformerConfiguration<R> informerConfig;
+    private final KubernetesClient kubernetesClient;
 
     protected DefaultInformerEventSourceConfiguration(
         GroupVersionKind groupVersionKind,
         PrimaryToSecondaryMapper<?> primaryToSecondaryMapper,
         SecondaryToPrimaryMapper<R> secondaryToPrimaryMapper,
-        InformerConfiguration<R> informerConfig) {
+        InformerConfiguration<R> informerConfig,
+        KubernetesClient kubernetesClient) {
       this.informerConfig = Objects.requireNonNull(informerConfig);
       this.groupVersionKind = groupVersionKind;
       this.primaryToSecondaryMapper = primaryToSecondaryMapper;
       this.secondaryToPrimaryMapper = secondaryToPrimaryMapper;
+      this.kubernetesClient = kubernetesClient;
     }
 
     @Override
@@ -95,8 +107,12 @@ public <P extends HasMetadata> PrimaryToSecondaryMapper<P> getPrimaryToSecondary
     public Optional<GroupVersionKind> getGroupVersionKind() {
       return Optional.ofNullable(groupVersionKind);
     }
-  }
 
+    @Override
+    public Optional<KubernetesClient> getKubernetesClient() {
+      return Optional.ofNullable(kubernetesClient);
+    }
+  }
 
   @SuppressWarnings({"unused", "UnusedReturnValue"})
   class Builder<R extends HasMetadata> {
@@ -108,6 +124,7 @@ class Builder<R extends HasMetadata> {
     private String name;
     private PrimaryToSecondaryMapper<?> primaryToSecondaryMapper;
     private SecondaryToPrimaryMapper<R> secondaryToPrimaryMapper;
+    private KubernetesClient kubernetesClient;
 
     private Builder(Class<R> resourceClass,
         Class<? extends HasMetadata> primaryResourceClass) {
@@ -152,6 +169,16 @@ public Builder<R> withSecondaryToPrimaryMapper(
       return this;
     }
 
+    /**
+     * Use this is case want to create an InformerEventSource that handles resources from different
+     * cluster.
+     */
+    public Builder<R> withKubernetesClient(
+        KubernetesClient kubernetesClient) {
+      this.kubernetesClient = kubernetesClient;
+      return this;
+    }
+
     public String getName() {
       return name;
     }
@@ -192,7 +219,7 @@ public InformerEventSourceConfiguration<R> build() {
           Objects.requireNonNullElse(secondaryToPrimaryMapper,
               Mappers.fromOwnerReferences(HasMetadata.getApiVersion(primaryResourceClass),
                   HasMetadata.getKind(primaryResourceClass), false)),
-          config.buildForInformerEventSource());
+          config.buildForInformerEventSource(), kubernetesClient);
     }
   }
 }

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

@@ -1,6 +1,8 @@
 package io.javaoperatorsdk.operator.processing.event.source.informer;
 
-import java.util.*;
+import java.util.Optional;
+import java.util.Set;
+import java.util.UUID;
 import java.util.stream.Collectors;
 
 import org.slf4j.Logger;
@@ -67,18 +69,17 @@ public class InformerEventSource<R extends HasMetadata, P extends HasMetadata>
     extends ManagedInformerEventSource<R, P, InformerEventSourceConfiguration<R>>
     implements ResourceEventHandler<R> {
 
-  public static String PREVIOUS_ANNOTATION_KEY = "javaoperatorsdk.io/previous";
-
   private static final Logger log = LoggerFactory.getLogger(InformerEventSource.class);
-
+  public static final String PREVIOUS_ANNOTATION_KEY = "javaoperatorsdk.io/previous";
   // we need direct control for the indexer to propagate the just update resource also to the index
   private final PrimaryToSecondaryIndex<R> primaryToSecondaryIndex;
   private final PrimaryToSecondaryMapper<P> primaryToSecondaryMapper;
   private final String id = UUID.randomUUID().toString();
 
   public InformerEventSource(
       InformerEventSourceConfiguration<R> configuration, EventSourceContext<P> context) {
-    this(configuration, context.getClient(),
+    this(configuration,
+        configuration.getKubernetesClient().orElse(context.getClient()),
         context.getControllerConfiguration().getConfigurationService()
             .parseResourceVersionsForEventFilteringAndCaching());
   }
@@ -287,10 +288,6 @@ private boolean eventAcceptedByFilter(Operation operation, R newObject, R oldObj
     }
   }
 
-  private enum Operation {
-    ADD, UPDATE
-  }
-
   private boolean acceptedByDeleteFilters(R resource, boolean b) {
     return (onDeleteFilter == null || onDeleteFilter.accept(resource, b)) &&
         (genericFilter == null || genericFilter.accept(resource));
@@ -307,4 +304,8 @@ public R addPreviousAnnotation(String resourceVersion, R target) {
         id + Optional.ofNullable(resourceVersion).map(rv -> "," + rv).orElse(""));
     return target;
   }
+
+  private enum Operation {
+    ADD, UPDATE
+  }
 }

operator-framework/src/test/java/io/javaoperatorsdk/operator/baseapi/informerremotecluster/InformerRemoteClusterCustomResource.java

@@ -0,0 +1,14 @@
+package io.javaoperatorsdk.operator.baseapi.informerremotecluster;
+
+import io.fabric8.kubernetes.api.model.Namespaced;
+import io.fabric8.kubernetes.client.CustomResource;
+import io.fabric8.kubernetes.model.annotation.Group;
+import io.fabric8.kubernetes.model.annotation.ShortNames;
+import io.fabric8.kubernetes.model.annotation.Version;
+
+@Group("sample.javaoperatorsdk")
+@Version("v1")
+@ShortNames("irc")
+public class InformerRemoteClusterCustomResource
+    extends CustomResource<Void, InformerRemoteClusterStatus> implements Namespaced {
+}

operator-framework/src/test/java/io/javaoperatorsdk/operator/baseapi/informerremotecluster/InformerRemoteClusterIT.java

@@ -0,0 +1,88 @@
+package io.javaoperatorsdk.operator.baseapi.informerremotecluster;
+
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+import io.fabric8.kubeapitest.junit.EnableKubeAPIServer;
+import io.fabric8.kubernetes.api.model.ConfigMap;
+import io.fabric8.kubernetes.api.model.ConfigMapBuilder;
+import io.fabric8.kubernetes.api.model.ObjectMetaBuilder;
+import io.fabric8.kubernetes.client.KubernetesClient;
+import io.javaoperatorsdk.operator.junit.LocallyRunOperatorExtension;
+import io.javaoperatorsdk.operator.processing.event.source.informer.Mappers;
+
+import static io.javaoperatorsdk.operator.baseapi.informerremotecluster.InformerRemoteClusterReconciler.DATA_KEY;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.awaitility.Awaitility.await;
+
+@EnableKubeAPIServer
+class InformerRemoteClusterIT {
+
+  public static final String NAME = "test1";
+  public static final String CONFIG_MAP_NAME = "testcm";
+  public static final String INITIAL_VALUE = "initial_value";
+  public static final String CHANGED_VALUE = "changed_value";
+  public static final String CM_NAMESPACE = "default";
+
+  // injected by Kube API Test. Client for another cluster.
+  static KubernetesClient kubernetesClient;
+
+  @RegisterExtension
+  LocallyRunOperatorExtension extension =
+      LocallyRunOperatorExtension.builder()
+          .withReconciler(new InformerRemoteClusterReconciler(kubernetesClient))
+          .build();
+
+  @Test
+  void testRemoteClusterInformer() {
+    var r = extension.create(testCustomResource());
+
+    var cm = kubernetesClient.configMaps()
+        .resource(remoteConfigMap(r.getMetadata().getName(),
+            r.getMetadata().getNamespace()))
+        .create();
+
+    // config map does not exist on the primary resource cluster
+    assertThat(extension.getKubernetesClient().configMaps()
+        .inNamespace(CM_NAMESPACE)
+        .withName(CONFIG_MAP_NAME).get()).isNull();
+
+    await().untilAsserted(() -> {
+      var cr = extension.get(InformerRemoteClusterCustomResource.class, NAME);
+      assertThat(cr.getStatus()).isNotNull();
+      assertThat(cr.getStatus().getRemoteConfigMapMessage()).isEqualTo(INITIAL_VALUE);
+    });
+
+    cm.getData().put(DATA_KEY, CHANGED_VALUE);
+    kubernetesClient.configMaps().resource(cm).update();
+
+    await().untilAsserted(() -> {
+      var cr = extension.get(InformerRemoteClusterCustomResource.class, NAME);
+      assertThat(cr.getStatus().getRemoteConfigMapMessage()).isEqualTo(CHANGED_VALUE);
+    });
+  }
+
+  InformerRemoteClusterCustomResource testCustomResource() {
+    var res = new InformerRemoteClusterCustomResource();
+    res.setMetadata(new ObjectMetaBuilder()
+        .withName(NAME)
+        .build());
+    return res;
+  }
+
+  ConfigMap remoteConfigMap(String ownerName, String ownerNamespace) {
+    return new ConfigMapBuilder()
+        .withMetadata(new ObjectMetaBuilder()
+            .withName(CONFIG_MAP_NAME)
+            .withNamespace(CM_NAMESPACE)
+            .withAnnotations(Map.of(
+                Mappers.DEFAULT_ANNOTATION_FOR_NAME, ownerName,
+                Mappers.DEFAULT_ANNOTATION_FOR_NAMESPACE, ownerNamespace))
+            .build())
+        .withData(Map.of(DATA_KEY, INITIAL_VALUE))
+        .build();
+  }
+
+}

operator-framework/src/test/java/io/javaoperatorsdk/operator/baseapi/informerremotecluster/InformerRemoteClusterReconciler.java

@@ -0,0 +1,65 @@
+package io.javaoperatorsdk.operator.baseapi.informerremotecluster;
+
+import java.util.List;
+
+import io.fabric8.kubernetes.api.model.ConfigMap;
+import io.fabric8.kubernetes.api.model.ObjectMetaBuilder;
+import io.fabric8.kubernetes.client.KubernetesClient;
+import io.javaoperatorsdk.operator.api.config.informer.InformerConfiguration;
+import io.javaoperatorsdk.operator.api.config.informer.InformerEventSourceConfiguration;
+import io.javaoperatorsdk.operator.api.reconciler.Context;
+import io.javaoperatorsdk.operator.api.reconciler.ControllerConfiguration;
+import io.javaoperatorsdk.operator.api.reconciler.EventSourceContext;
+import io.javaoperatorsdk.operator.api.reconciler.Reconciler;
+import io.javaoperatorsdk.operator.api.reconciler.UpdateControl;
+import io.javaoperatorsdk.operator.processing.event.source.EventSource;
+import io.javaoperatorsdk.operator.processing.event.source.informer.InformerEventSource;
+import io.javaoperatorsdk.operator.processing.event.source.informer.Mappers;
+
+@ControllerConfiguration
+public class InformerRemoteClusterReconciler
+    implements Reconciler<InformerRemoteClusterCustomResource> {
+
+  public static final String DATA_KEY = "key";
+
+  private final KubernetesClient remoteClient;
+
+  public InformerRemoteClusterReconciler(KubernetesClient remoteClient) {
+    this.remoteClient = remoteClient;
+  }
+
+  @Override
+  public UpdateControl<InformerRemoteClusterCustomResource> reconcile(
+      InformerRemoteClusterCustomResource resource,
+      Context<InformerRemoteClusterCustomResource> context) throws Exception {
+
+    return context.getSecondaryResource(ConfigMap.class).map(cm -> {
+      var r = new InformerRemoteClusterCustomResource();
+      r.setMetadata(new ObjectMetaBuilder()
+          .withName(resource.getMetadata().getName())
+          .withNamespace(resource.getMetadata().getNamespace())
+          .build());
+      r.setStatus(new InformerRemoteClusterStatus());
+      r.getStatus().setRemoteConfigMapMessage(cm.getData().get(DATA_KEY));
+      return UpdateControl.patchStatus(r);
+    }).orElseGet(UpdateControl::noUpdate);
+  }
+
+  @Override
+  public List<EventSource<?, InformerRemoteClusterCustomResource>> prepareEventSources(
+      EventSourceContext<InformerRemoteClusterCustomResource> context) {
+
+    var es = new InformerEventSource<>(InformerEventSourceConfiguration
+        .from(ConfigMap.class, InformerRemoteClusterCustomResource.class)
+        // owner references do not work cross cluster, using
+        // annotations here to reference primary resource
+        .withSecondaryToPrimaryMapper(Mappers.fromDefaultAnnotations())
+        // setting remote client for informer
+        .withKubernetesClient(remoteClient)
+        .withInformerConfiguration(
+            InformerConfiguration.Builder::withWatchAllNamespaces)
+        .build(), context);
+
+    return List.of(es);
+  }
+}

operator-framework/src/test/java/io/javaoperatorsdk/operator/baseapi/informerremotecluster/InformerRemoteClusterStatus.java

@@ -0,0 +1,14 @@
+package io.javaoperatorsdk.operator.baseapi.informerremotecluster;
+
+public class InformerRemoteClusterStatus {
+
+  private String remoteConfigMapMessage;
+
+  public String getRemoteConfigMapMessage() {
+    return remoteConfigMapMessage;
+  }
+
+  public void setRemoteConfigMapMessage(String remoteConfigMapMessage) {
+    this.remoteConfigMapMessage = remoteConfigMapMessage;
+  }
+}

operator-framework/src/test/java/io/javaoperatorsdk/operator/baseapi/labelselector/LabelSelectorTestReconciler.java

@@ -22,6 +22,7 @@ public class LabelSelectorTestReconciler
   @Override
   public UpdateControl<LabelSelectorTestCustomResource> reconcile(
       LabelSelectorTestCustomResource resource, Context<LabelSelectorTestCustomResource> context) {
+
     numberOfExecutions.addAndGet(1);
     return UpdateControl.noUpdate();
   }