From a4f91546605ba03243ced1dca45dcd6fbd41b996 Mon Sep 17 00:00:00 2001
From: csviri <csviri@gmail.com>
Date: Thu, 23 Jun 2022 15:49:35 +0200
Subject: [PATCH 01/12] feat: primary to secondary mapper

---
 .../informer/InformerConfiguration.java       | 18 ++++++
 .../InformerPrimaryToSecondaryMapper.java     | 11 ++++
 .../source/PrimaryToSecondaryMapper.java      | 11 ++++
 .../source/informer/InformerEventSource.java  | 45 ++++++++++----
 .../operator/PrimaryToSecondaryIT.java        | 59 ++++++++++++++++++
 .../sample/primarytosecondary/Cluster.java    | 15 +++++
 .../primarytosecondary/ClusterStatus.java     |  5 ++
 .../sample/primarytosecondary/Job.java        | 15 +++++
 .../primarytosecondary/JobReconciler.java     | 62 +++++++++++++++++++
 .../sample/primarytosecondary/JobSpec.java    | 15 +++++
 .../sample/primarytosecondary/JobStatus.java  |  5 ++
 11 files changed, 249 insertions(+), 12 deletions(-)
 create mode 100644 operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/InformerPrimaryToSecondaryMapper.java
 create mode 100644 operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/PrimaryToSecondaryMapper.java
 create mode 100644 operator-framework/src/test/java/io/javaoperatorsdk/operator/PrimaryToSecondaryIT.java
 create mode 100644 operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/Cluster.java
 create mode 100644 operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/ClusterStatus.java
 create mode 100644 operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/Job.java
 create mode 100644 operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobReconciler.java
 create mode 100644 operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobSpec.java
 create mode 100644 operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobStatus.java

diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/informer/InformerConfiguration.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/informer/InformerConfiguration.java
index 9cb0f1ee1d..4daa6e5644 100644
--- a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/informer/InformerConfiguration.java
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/informer/InformerConfiguration.java
@@ -8,6 +8,7 @@
 import io.javaoperatorsdk.operator.api.config.ResourceConfiguration;
 import io.javaoperatorsdk.operator.api.config.Utils;
 import io.javaoperatorsdk.operator.api.reconciler.EventSourceContext;
+import io.javaoperatorsdk.operator.processing.event.source.InformerPrimaryToSecondaryMapper;
 import io.javaoperatorsdk.operator.processing.event.source.SecondaryToPrimaryMapper;
 import io.javaoperatorsdk.operator.processing.event.source.informer.Mappers;
 
@@ -19,15 +20,18 @@ public interface InformerConfiguration<R extends HasMetadata>
   class DefaultInformerConfiguration<R extends HasMetadata> extends
       DefaultResourceConfiguration<R> implements InformerConfiguration<R> {
 
+    private final InformerPrimaryToSecondaryMapper<?> primaryToSecondaryMapper;
     private final SecondaryToPrimaryMapper<R> secondaryToPrimaryMapper;
     private final boolean followControllerNamespaceChanges;
 
     protected DefaultInformerConfiguration(String labelSelector,
         Class<R> resourceClass,
+        InformerPrimaryToSecondaryMapper<?> primaryToSecondaryMapper,
         SecondaryToPrimaryMapper<R> secondaryToPrimaryMapper,
         Set<String> namespaces, boolean followControllerNamespaceChanges) {
       super(labelSelector, resourceClass, namespaces);
       this.followControllerNamespaceChanges = followControllerNamespaceChanges;
+      this.primaryToSecondaryMapper = primaryToSecondaryMapper;
       this.secondaryToPrimaryMapper =
           Objects.requireNonNullElse(secondaryToPrimaryMapper,
               Mappers.fromOwnerReference());
@@ -41,6 +45,10 @@ public SecondaryToPrimaryMapper<R> getSecondaryToPrimaryMapper() {
       return secondaryToPrimaryMapper;
     }
 
+    @Override
+    public <P extends HasMetadata> InformerPrimaryToSecondaryMapper<P> getPrimaryToSecondaryMapper() {
+      return (InformerPrimaryToSecondaryMapper<P>) primaryToSecondaryMapper;
+    }
   }
 
   /**
@@ -53,9 +61,12 @@ public SecondaryToPrimaryMapper<R> getSecondaryToPrimaryMapper() {
 
   SecondaryToPrimaryMapper<R> getSecondaryToPrimaryMapper();
 
+  <P extends HasMetadata> InformerPrimaryToSecondaryMapper<P> getPrimaryToSecondaryMapper();
+
   @SuppressWarnings("unused")
   class InformerConfigurationBuilder<R extends HasMetadata> {
 
+    private InformerPrimaryToSecondaryMapper<?> primaryToSecondaryMapper;
     private SecondaryToPrimaryMapper<R> secondaryToPrimaryMapper;
     private Set<String> namespaces;
     private String labelSelector;
@@ -66,6 +77,12 @@ private InformerConfigurationBuilder(Class<R> resourceClass) {
       this.resourceClass = resourceClass;
     }
 
+    public <P extends HasMetadata> InformerConfigurationBuilder<R> withPrimaryToSecondaryMapper(
+        InformerPrimaryToSecondaryMapper<P> primaryToSecondaryMapper) {
+      this.primaryToSecondaryMapper = primaryToSecondaryMapper;
+      return this;
+    }
+
     public InformerConfigurationBuilder<R> withSecondaryToPrimaryMapper(
         SecondaryToPrimaryMapper<R> secondaryToPrimaryMapper) {
       this.secondaryToPrimaryMapper = secondaryToPrimaryMapper;
@@ -136,6 +153,7 @@ public InformerConfigurationBuilder<R> withLabelSelector(String labelSelector) {
 
     public InformerConfiguration<R> build() {
       return new DefaultInformerConfiguration<>(labelSelector, resourceClass,
+          primaryToSecondaryMapper,
           secondaryToPrimaryMapper,
           namespaces, inheritControllerNamespacesOnChange);
     }
diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/InformerPrimaryToSecondaryMapper.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/InformerPrimaryToSecondaryMapper.java
new file mode 100644
index 0000000000..ca3cd2a339
--- /dev/null
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/InformerPrimaryToSecondaryMapper.java
@@ -0,0 +1,11 @@
+package io.javaoperatorsdk.operator.processing.event.source;
+
+import java.util.Set;
+
+import io.fabric8.kubernetes.api.model.HasMetadata;
+import io.javaoperatorsdk.operator.processing.event.ResourceID;
+
+public interface InformerPrimaryToSecondaryMapper<P extends HasMetadata> {
+
+  Set<ResourceID> toSecondaryResourceIDs(P primary);
+}
diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/PrimaryToSecondaryMapper.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/PrimaryToSecondaryMapper.java
new file mode 100644
index 0000000000..069163001b
--- /dev/null
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/PrimaryToSecondaryMapper.java
@@ -0,0 +1,11 @@
+package io.javaoperatorsdk.operator.processing.event.source;
+
+import java.util.Set;
+
+import io.fabric8.kubernetes.api.model.HasMetadata;
+
+public interface PrimaryToSecondaryMapper<P extends HasMetadata> {
+
+  Set<String> toSecondaryResourceIdentifiers(P primary);
+
+}
diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerEventSource.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerEventSource.java
index 47fe4abcf3..9978473a64 100644
--- a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerEventSource.java
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerEventSource.java
@@ -16,6 +16,7 @@
 import io.javaoperatorsdk.operator.processing.event.Event;
 import io.javaoperatorsdk.operator.processing.event.EventHandler;
 import io.javaoperatorsdk.operator.processing.event.ResourceID;
+import io.javaoperatorsdk.operator.processing.event.source.InformerPrimaryToSecondaryMapper;
 
 /**
  * <p>
@@ -74,20 +75,23 @@ public class InformerEventSource<R extends HasMetadata, P extends HasMetadata>
   private final EventRecorder<R> eventRecorder = new EventRecorder<>();
   // we need direct control for the indexer to propagate the just update resource also to the index
   private final PrimaryToSecondaryIndex<R> primaryToSecondaryIndex;
+  private final InformerPrimaryToSecondaryMapper<P> primaryToSecondaryMapper;
 
   public InformerEventSource(
       InformerConfiguration<R> configuration, EventSourceContext<P> context) {
-    super(context.getClient().resources(configuration.getResourceClass()), configuration);
-    this.configuration = configuration;
-    primaryToSecondaryIndex =
-        new PrimaryToSecondaryIndex<>(configuration.getSecondaryToPrimaryMapper());
+    this(configuration, context.getClient());
   }
 
   public InformerEventSource(InformerConfiguration<R> configuration, KubernetesClient client) {
     super(client.resources(configuration.getResourceClass()), configuration);
     this.configuration = configuration;
-    primaryToSecondaryIndex =
-        new PrimaryToSecondaryIndex<>(configuration.getSecondaryToPrimaryMapper());
+    primaryToSecondaryMapper = configuration.getPrimaryToSecondaryMapper();
+    if (primaryToSecondaryMapper == null) {
+      primaryToSecondaryIndex =
+          new PrimaryToSecondaryIndex<>(configuration.getSecondaryToPrimaryMapper());
+    } else {
+      primaryToSecondaryIndex = null;
+    }
   }
 
   @Override
@@ -95,7 +99,9 @@ public void onAdd(R resource) {
     if (log.isDebugEnabled()) {
       log.debug("On add event received for resource id: {}", ResourceID.fromResource(resource));
     }
-    primaryToSecondaryIndex.onAddOrUpdate(resource);
+    if (useSecondaryToPrimaryIndex()) {
+      primaryToSecondaryIndex.onAddOrUpdate(resource);
+    }
     onAddOrUpdate("add", resource, () -> InformerEventSource.super.onAdd(resource));
   }
 
@@ -104,7 +110,9 @@ public void onUpdate(R oldObject, R newObject) {
     if (log.isDebugEnabled()) {
       log.debug("On update event received for resource id: {}", ResourceID.fromResource(newObject));
     }
-    primaryToSecondaryIndex.onAddOrUpdate(newObject);
+    if (useSecondaryToPrimaryIndex()) {
+      primaryToSecondaryIndex.onAddOrUpdate(newObject);
+    }
     onAddOrUpdate("update", newObject,
         () -> InformerEventSource.super.onUpdate(oldObject, newObject));
   }
@@ -114,7 +122,9 @@ public void onDelete(R resource, boolean b) {
     if (log.isDebugEnabled()) {
       log.debug("On delete event received for resource id: {}", ResourceID.fromResource(resource));
     }
-    primaryToSecondaryIndex.onDelete(resource);
+    if (useSecondaryToPrimaryIndex()) {
+      primaryToSecondaryIndex.onDelete(resource);
+    }
     super.onDelete(resource, b);
     propagateEvent(resource);
   }
@@ -177,8 +187,13 @@ private void propagateEvent(R object) {
 
   @Override
   public Set<R> getSecondaryResources(P primary) {
-    var secondaryIDs =
-        primaryToSecondaryIndex.getSecondaryResources(ResourceID.fromResource(primary));
+    Set<ResourceID> secondaryIDs;
+    if (useSecondaryToPrimaryIndex()) {
+      secondaryIDs =
+          primaryToSecondaryIndex.getSecondaryResources(ResourceID.fromResource(primary));
+    } else {
+      secondaryIDs = primaryToSecondaryMapper.toSecondaryResourceIDs(primary);
+    }
     return secondaryIDs.stream().map(this::get).flatMap(Optional::stream)
         .collect(Collectors.toSet());
   }
@@ -201,7 +216,9 @@ public synchronized void handleRecentResourceCreate(ResourceID resourceID, R res
   }
 
   private void handleRecentCreateOrUpdate(R resource, Runnable runnable) {
-    primaryToSecondaryIndex.onAddOrUpdate(resource);
+    if (useSecondaryToPrimaryIndex()) {
+      primaryToSecondaryIndex.onAddOrUpdate(resource);
+    }
     if (eventRecorder.isRecordingFor(ResourceID.fromResource(resource))) {
       handleRecentResourceOperationAndStopEventRecording(resource);
     } else {
@@ -247,6 +264,10 @@ private void handleRecentResourceOperationAndStopEventRecording(R resource) {
     }
   }
 
+  private boolean useSecondaryToPrimaryIndex() {
+    return this.primaryToSecondaryMapper == null;
+  }
+
   @Override
   public synchronized void prepareForCreateOrUpdateEventFiltering(ResourceID resourceID,
       R resource) {
diff --git a/operator-framework/src/test/java/io/javaoperatorsdk/operator/PrimaryToSecondaryIT.java b/operator-framework/src/test/java/io/javaoperatorsdk/operator/PrimaryToSecondaryIT.java
new file mode 100644
index 0000000000..cfba078293
--- /dev/null
+++ b/operator-framework/src/test/java/io/javaoperatorsdk/operator/PrimaryToSecondaryIT.java
@@ -0,0 +1,59 @@
+package io.javaoperatorsdk.operator;
+
+import java.time.Duration;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+import io.fabric8.kubernetes.api.model.ObjectMetaBuilder;
+import io.javaoperatorsdk.operator.junit.LocalOperatorExtension;
+import io.javaoperatorsdk.operator.sample.primarytosecondary.Cluster;
+import io.javaoperatorsdk.operator.sample.primarytosecondary.Job;
+import io.javaoperatorsdk.operator.sample.primarytosecondary.JobReconciler;
+import io.javaoperatorsdk.operator.sample.primarytosecondary.JobSpec;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.awaitility.Awaitility.await;
+
+class PrimaryToSecondaryIT {
+
+  public static final String CLUSTER_NAME = "cluster1";
+  public static final int MIN_DELAY = 150;
+  @RegisterExtension
+  LocalOperatorExtension operator =
+      LocalOperatorExtension.builder()
+
+          .withReconciler(new JobReconciler())
+          .build();
+
+  // todo load other CRD
+  @Test
+  void readsSecondaryInManyToOneCases() throws InterruptedException {
+    operator.create(Cluster.class, cluster());
+    Thread.sleep(MIN_DELAY);
+    operator.create(Job.class, job());
+
+    await().pollDelay(Duration.ofMillis(400)).untilAsserted(
+        () -> assertThat(operator.getReconcilerOfType(JobReconciler.class).getNumberOfExecutions())
+            .isEqualTo(1));
+  }
+
+  Job job() {
+    var job = new Job();
+    job.setMetadata(new ObjectMetaBuilder()
+        .withName("job1")
+        .build());
+    job.setSpec(new JobSpec());
+    job.getSpec().setClusterName(CLUSTER_NAME);
+    return job;
+  }
+
+  Cluster cluster() {
+    Cluster cluster = new Cluster();
+    cluster.setMetadata(new ObjectMetaBuilder()
+        .withName(CLUSTER_NAME)
+        .build());
+    return cluster;
+  }
+
+}
diff --git a/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/Cluster.java b/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/Cluster.java
new file mode 100644
index 0000000000..ffc43141a4
--- /dev/null
+++ b/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/Cluster.java
@@ -0,0 +1,15 @@
+package io.javaoperatorsdk.operator.sample.primarytosecondary;
+
+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("clu")
+public class Cluster
+    extends CustomResource<Void, ClusterStatus>
+    implements Namespaced {
+}
diff --git a/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/ClusterStatus.java b/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/ClusterStatus.java
new file mode 100644
index 0000000000..eac5c48b70
--- /dev/null
+++ b/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/ClusterStatus.java
@@ -0,0 +1,5 @@
+package io.javaoperatorsdk.operator.sample.primarytosecondary;
+
+public class ClusterStatus {
+
+}
diff --git a/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/Job.java b/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/Job.java
new file mode 100644
index 0000000000..5a3d43de79
--- /dev/null
+++ b/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/Job.java
@@ -0,0 +1,15 @@
+package io.javaoperatorsdk.operator.sample.primarytosecondary;
+
+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("cjo")
+public class Job
+    extends CustomResource<JobSpec, JobStatus>
+    implements Namespaced {
+}
diff --git a/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobReconciler.java b/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobReconciler.java
new file mode 100644
index 0000000000..c0c5188ea5
--- /dev/null
+++ b/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobReconciler.java
@@ -0,0 +1,62 @@
+package io.javaoperatorsdk.operator.sample.primarytosecondary;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.stream.Collectors;
+
+import io.javaoperatorsdk.operator.api.config.informer.InformerConfiguration;
+import io.javaoperatorsdk.operator.api.reconciler.*;
+import io.javaoperatorsdk.operator.processing.event.ResourceID;
+import io.javaoperatorsdk.operator.processing.event.source.EventSource;
+import io.javaoperatorsdk.operator.processing.event.source.InformerPrimaryToSecondaryMapper;
+import io.javaoperatorsdk.operator.processing.event.source.informer.InformerEventSource;
+
+@ControllerConfiguration()
+public class JobReconciler
+    implements Reconciler<Job>, EventSourceInitializer<Job> {
+
+  private static final String JOB_CLUSTER_INDEX = "job-cluster-index";
+
+  private final AtomicInteger numberOfExecutions = new AtomicInteger(0);
+
+  @Override
+  public UpdateControl<Job> reconcile(
+      Job resource, Context<Job> context) {
+
+    context.getSecondaryResource(Cluster.class)
+        .orElseThrow(() -> new IllegalStateException("Secondary resource should be present"));
+    numberOfExecutions.addAndGet(1);
+    return UpdateControl.noUpdate();
+  }
+
+  @Override
+  public Map<String, EventSource> prepareEventSources(EventSourceContext<Job> context) {
+    context.getPrimaryCache().addIndexer(JOB_CLUSTER_INDEX, (job -> List
+        .of(indexKey(job.getSpec().getClusterName(), job.getMetadata().getNamespace()))));
+
+    InformerConfiguration<Cluster> informerConfiguration =
+        InformerConfiguration.from(Cluster.class, context)
+            .withSecondaryToPrimaryMapper(cluster -> context.getPrimaryCache()
+                .byIndex(JOB_CLUSTER_INDEX, indexKey(cluster.getMetadata().getName(),
+                    cluster.getMetadata().getNamespace()))
+                .stream().map(ResourceID::fromResource).collect(Collectors.toSet()))
+            .withPrimaryToSecondaryMapper(
+                (InformerPrimaryToSecondaryMapper<Job>) primary -> Set.of(new ResourceID(
+                    primary.getSpec().getClusterName(), primary.getMetadata().getNamespace())))
+            .withNamespacesInheritedFromController(context)
+            .build();
+
+    return EventSourceInitializer
+        .nameEventSources(new InformerEventSource<>(informerConfiguration, context));
+  }
+
+  private String indexKey(String clusterName, String namespace) {
+    return clusterName + "#" + namespace;
+  }
+
+  public int getNumberOfExecutions() {
+    return numberOfExecutions.get();
+  }
+}
diff --git a/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobSpec.java b/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobSpec.java
new file mode 100644
index 0000000000..c7546dea71
--- /dev/null
+++ b/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobSpec.java
@@ -0,0 +1,15 @@
+package io.javaoperatorsdk.operator.sample.primarytosecondary;
+
+public class JobSpec {
+
+  private String clusterName;
+
+  public String getClusterName() {
+    return clusterName;
+  }
+
+  public JobSpec setClusterName(String clusterName) {
+    this.clusterName = clusterName;
+    return this;
+  }
+}
diff --git a/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobStatus.java b/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobStatus.java
new file mode 100644
index 0000000000..b2d7cf6259
--- /dev/null
+++ b/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobStatus.java
@@ -0,0 +1,5 @@
+package io.javaoperatorsdk.operator.sample.primarytosecondary;
+
+public class JobStatus {
+
+}

From 4df223b6ac5a4aafe46b6cf5398506de0dd26c54 Mon Sep 17 00:00:00 2001
From: csviri <csviri@gmail.com>
Date: Thu, 23 Jun 2022 15:53:59 +0200
Subject: [PATCH 02/12] cleanup

---
 .../config/informer/InformerConfiguration.java   | 16 ++++++++--------
 .../source/InformerPrimaryToSecondaryMapper.java | 11 -----------
 .../event/source/PrimaryToSecondaryMapper.java   |  4 ++--
 .../source/informer/InformerEventSource.java     |  4 ++--
 .../sample/primarytosecondary/JobReconciler.java |  4 ++--
 5 files changed, 14 insertions(+), 25 deletions(-)
 delete mode 100644 operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/InformerPrimaryToSecondaryMapper.java

diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/informer/InformerConfiguration.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/informer/InformerConfiguration.java
index 4daa6e5644..ddfae2919e 100644
--- a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/informer/InformerConfiguration.java
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/informer/InformerConfiguration.java
@@ -8,7 +8,7 @@
 import io.javaoperatorsdk.operator.api.config.ResourceConfiguration;
 import io.javaoperatorsdk.operator.api.config.Utils;
 import io.javaoperatorsdk.operator.api.reconciler.EventSourceContext;
-import io.javaoperatorsdk.operator.processing.event.source.InformerPrimaryToSecondaryMapper;
+import io.javaoperatorsdk.operator.processing.event.source.PrimaryToSecondaryMapper;
 import io.javaoperatorsdk.operator.processing.event.source.SecondaryToPrimaryMapper;
 import io.javaoperatorsdk.operator.processing.event.source.informer.Mappers;
 
@@ -20,13 +20,13 @@ public interface InformerConfiguration<R extends HasMetadata>
   class DefaultInformerConfiguration<R extends HasMetadata> extends
       DefaultResourceConfiguration<R> implements InformerConfiguration<R> {
 
-    private final InformerPrimaryToSecondaryMapper<?> primaryToSecondaryMapper;
+    private final PrimaryToSecondaryMapper<?> primaryToSecondaryMapper;
     private final SecondaryToPrimaryMapper<R> secondaryToPrimaryMapper;
     private final boolean followControllerNamespaceChanges;
 
     protected DefaultInformerConfiguration(String labelSelector,
         Class<R> resourceClass,
-        InformerPrimaryToSecondaryMapper<?> primaryToSecondaryMapper,
+        PrimaryToSecondaryMapper<?> primaryToSecondaryMapper,
         SecondaryToPrimaryMapper<R> secondaryToPrimaryMapper,
         Set<String> namespaces, boolean followControllerNamespaceChanges) {
       super(labelSelector, resourceClass, namespaces);
@@ -46,8 +46,8 @@ public SecondaryToPrimaryMapper<R> getSecondaryToPrimaryMapper() {
     }
 
     @Override
-    public <P extends HasMetadata> InformerPrimaryToSecondaryMapper<P> getPrimaryToSecondaryMapper() {
-      return (InformerPrimaryToSecondaryMapper<P>) primaryToSecondaryMapper;
+    public <P extends HasMetadata> PrimaryToSecondaryMapper<P> getPrimaryToSecondaryMapper() {
+      return (PrimaryToSecondaryMapper<P>) primaryToSecondaryMapper;
     }
   }
 
@@ -61,12 +61,12 @@ public <P extends HasMetadata> InformerPrimaryToSecondaryMapper<P> getPrimaryToS
 
   SecondaryToPrimaryMapper<R> getSecondaryToPrimaryMapper();
 
-  <P extends HasMetadata> InformerPrimaryToSecondaryMapper<P> getPrimaryToSecondaryMapper();
+  <P extends HasMetadata> PrimaryToSecondaryMapper<P> getPrimaryToSecondaryMapper();
 
   @SuppressWarnings("unused")
   class InformerConfigurationBuilder<R extends HasMetadata> {
 
-    private InformerPrimaryToSecondaryMapper<?> primaryToSecondaryMapper;
+    private PrimaryToSecondaryMapper<?> primaryToSecondaryMapper;
     private SecondaryToPrimaryMapper<R> secondaryToPrimaryMapper;
     private Set<String> namespaces;
     private String labelSelector;
@@ -78,7 +78,7 @@ private InformerConfigurationBuilder(Class<R> resourceClass) {
     }
 
     public <P extends HasMetadata> InformerConfigurationBuilder<R> withPrimaryToSecondaryMapper(
-        InformerPrimaryToSecondaryMapper<P> primaryToSecondaryMapper) {
+        PrimaryToSecondaryMapper<P> primaryToSecondaryMapper) {
       this.primaryToSecondaryMapper = primaryToSecondaryMapper;
       return this;
     }
diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/InformerPrimaryToSecondaryMapper.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/InformerPrimaryToSecondaryMapper.java
deleted file mode 100644
index ca3cd2a339..0000000000
--- a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/InformerPrimaryToSecondaryMapper.java
+++ /dev/null
@@ -1,11 +0,0 @@
-package io.javaoperatorsdk.operator.processing.event.source;
-
-import java.util.Set;
-
-import io.fabric8.kubernetes.api.model.HasMetadata;
-import io.javaoperatorsdk.operator.processing.event.ResourceID;
-
-public interface InformerPrimaryToSecondaryMapper<P extends HasMetadata> {
-
-  Set<ResourceID> toSecondaryResourceIDs(P primary);
-}
diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/PrimaryToSecondaryMapper.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/PrimaryToSecondaryMapper.java
index 069163001b..37f31e2e3e 100644
--- a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/PrimaryToSecondaryMapper.java
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/PrimaryToSecondaryMapper.java
@@ -3,9 +3,9 @@
 import java.util.Set;
 
 import io.fabric8.kubernetes.api.model.HasMetadata;
+import io.javaoperatorsdk.operator.processing.event.ResourceID;
 
 public interface PrimaryToSecondaryMapper<P extends HasMetadata> {
 
-  Set<String> toSecondaryResourceIdentifiers(P primary);
-
+  Set<ResourceID> toSecondaryResourceIDs(P primary);
 }
diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerEventSource.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerEventSource.java
index 9978473a64..7cb71597ba 100644
--- a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerEventSource.java
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerEventSource.java
@@ -16,7 +16,7 @@
 import io.javaoperatorsdk.operator.processing.event.Event;
 import io.javaoperatorsdk.operator.processing.event.EventHandler;
 import io.javaoperatorsdk.operator.processing.event.ResourceID;
-import io.javaoperatorsdk.operator.processing.event.source.InformerPrimaryToSecondaryMapper;
+import io.javaoperatorsdk.operator.processing.event.source.PrimaryToSecondaryMapper;
 
 /**
  * <p>
@@ -75,7 +75,7 @@ public class InformerEventSource<R extends HasMetadata, P extends HasMetadata>
   private final EventRecorder<R> eventRecorder = new EventRecorder<>();
   // we need direct control for the indexer to propagate the just update resource also to the index
   private final PrimaryToSecondaryIndex<R> primaryToSecondaryIndex;
-  private final InformerPrimaryToSecondaryMapper<P> primaryToSecondaryMapper;
+  private final PrimaryToSecondaryMapper<P> primaryToSecondaryMapper;
 
   public InformerEventSource(
       InformerConfiguration<R> configuration, EventSourceContext<P> context) {
diff --git a/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobReconciler.java b/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobReconciler.java
index c0c5188ea5..1ac7676265 100644
--- a/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobReconciler.java
+++ b/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/primarytosecondary/JobReconciler.java
@@ -10,7 +10,7 @@
 import io.javaoperatorsdk.operator.api.reconciler.*;
 import io.javaoperatorsdk.operator.processing.event.ResourceID;
 import io.javaoperatorsdk.operator.processing.event.source.EventSource;
-import io.javaoperatorsdk.operator.processing.event.source.InformerPrimaryToSecondaryMapper;
+import io.javaoperatorsdk.operator.processing.event.source.PrimaryToSecondaryMapper;
 import io.javaoperatorsdk.operator.processing.event.source.informer.InformerEventSource;
 
 @ControllerConfiguration()
@@ -43,7 +43,7 @@ public Map<String, EventSource> prepareEventSources(EventSourceContext<Job> cont
                     cluster.getMetadata().getNamespace()))
                 .stream().map(ResourceID::fromResource).collect(Collectors.toSet()))
             .withPrimaryToSecondaryMapper(
-                (InformerPrimaryToSecondaryMapper<Job>) primary -> Set.of(new ResourceID(
+                (PrimaryToSecondaryMapper<Job>) primary -> Set.of(new ResourceID(
                     primary.getSpec().getClusterName(), primary.getMetadata().getNamespace())))
             .withNamespacesInheritedFromController(context)
             .build();

From cabafc7881e10945abc954f22e984c8dc3ea56e5 Mon Sep 17 00:00:00 2001
From: csviri <csviri@gmail.com>
Date: Thu, 23 Jun 2022 16:48:55 +0200
Subject: [PATCH 03/12] additional CRD support in IT

---
 .../junit/LocalOperatorExtension.java         | 58 +++++++++++++------
 .../operator/PrimaryToSecondaryIT.java        |  3 +-
 2 files changed, 41 insertions(+), 20 deletions(-)

diff --git a/operator-framework-junit5/src/main/java/io/javaoperatorsdk/operator/junit/LocalOperatorExtension.java b/operator-framework-junit5/src/main/java/io/javaoperatorsdk/operator/junit/LocalOperatorExtension.java
index edccd025a6..2eb0fa5900 100644
--- a/operator-framework-junit5/src/main/java/io/javaoperatorsdk/operator/junit/LocalOperatorExtension.java
+++ b/operator-framework-junit5/src/main/java/io/javaoperatorsdk/operator/junit/LocalOperatorExtension.java
@@ -15,8 +15,10 @@
 import org.slf4j.LoggerFactory;
 
 import io.fabric8.kubernetes.api.model.HasMetadata;
+import io.fabric8.kubernetes.client.CustomResource;
 import io.fabric8.kubernetes.client.LocalPortForward;
 import io.javaoperatorsdk.operator.Operator;
+import io.javaoperatorsdk.operator.ReconcilerUtils;
 import io.javaoperatorsdk.operator.RegisteredController;
 import io.javaoperatorsdk.operator.api.config.ConfigurationService;
 import io.javaoperatorsdk.operator.api.config.ControllerConfigurationOverrider;
@@ -32,15 +34,17 @@ public class LocalOperatorExtension extends AbstractOperatorExtension {
 
   private final Operator operator;
   private final List<ReconcilerSpec> reconcilers;
-  private final List<PortFowardSpec> portForwards;
+  private final List<PortForwardSpec> portForwards;
   private final List<LocalPortForward> localPortForwards;
+  private final List<Class<? extends CustomResource>> additionalCustomResourceDefinitions;
   private final Map<Reconciler, RegisteredController> registeredControllers;
 
   private LocalOperatorExtension(
       ConfigurationService configurationService,
       List<ReconcilerSpec> reconcilers,
       List<HasMetadata> infrastructure,
-      List<PortFowardSpec> portForwards,
+      List<PortForwardSpec> portForwards,
+      List<Class<? extends CustomResource>> additionalCustomResourceDefinitions,
       Duration infrastructureTimeout,
       boolean preserveNamespaceOnError,
       boolean waitForNamespaceDeletion,
@@ -55,6 +59,7 @@ private LocalOperatorExtension(
     this.reconcilers = reconcilers;
     this.portForwards = portForwards;
     this.localPortForwards = new ArrayList<>(portForwards.size());
+    this.additionalCustomResourceDefinitions = additionalCustomResourceDefinitions;
     this.operator = new Operator(getKubernetesClient(), this.configurationService);
     this.registeredControllers = new HashMap<>();
   }
@@ -114,10 +119,12 @@ protected void before(ExtensionContext context) {
           .withName(podName).portForward(ref.getPort(), ref.getLocalPort()));
     }
 
+    additionalCustomResourceDefinitions
+        .forEach(cr -> applyCrd(ReconcilerUtils.getResourceTypeName(cr)));
+
     for (var ref : reconcilers) {
       final var config = configurationService.getConfigurationFor(ref.reconciler);
       final var oconfig = override(config).settingNamespace(namespace);
-      final var path = "/META-INF/fabric8/" + config.getResourceTypeName() + "-v1.yml";
 
       if (ref.retry != null) {
         oconfig.withRetry(ref.retry);
@@ -126,17 +133,7 @@ protected void before(ExtensionContext context) {
         ref.controllerConfigurationOverrider.accept(oconfig);
       }
 
-      try (InputStream is = getClass().getResourceAsStream(path)) {
-        final var crd = kubernetesClient.load(is);
-        crd.createOrReplace();
-        Thread.sleep(CRD_READY_WAIT); // readiness is not applicable for CRD, just wait a little
-        LOGGER.debug("Applied CRD with name: {}", config.getResourceTypeName());
-      } catch (InterruptedException ex) {
-        LOGGER.error("Interrupted.", ex);
-        Thread.currentThread().interrupt();
-      } catch (Exception ex) {
-        throw new IllegalStateException("Cannot apply CRD yaml: " + path, ex);
-      }
+      applyCrd(config.getResourceTypeName());
 
       if (ref.reconciler instanceof KubernetesClientAware) {
         ((KubernetesClientAware) ref.reconciler).setKubernetesClient(kubernetesClient);
@@ -150,6 +147,21 @@ protected void before(ExtensionContext context) {
     this.operator.start();
   }
 
+  private void applyCrd(String resourceTypeName) {
+    String path = "/META-INF/fabric8/" + resourceTypeName + "-v1.yml";
+    try (InputStream is = getClass().getResourceAsStream(path)) {
+      final var crd = getKubernetesClient().load(is);
+      crd.createOrReplace();
+      Thread.sleep(CRD_READY_WAIT); // readiness is not applicable for CRD, just wait a little
+      LOGGER.debug("Applied CRD with path: {}", path);
+    } catch (InterruptedException ex) {
+      LOGGER.error("Interrupted.", ex);
+      Thread.currentThread().interrupt();
+    } catch (Exception ex) {
+      throw new IllegalStateException("Cannot apply CRD yaml: " + path, ex);
+    }
+  }
+
   protected void after(ExtensionContext context) {
     super.after(context);
 
@@ -172,12 +184,14 @@ protected void after(ExtensionContext context) {
   @SuppressWarnings("rawtypes")
   public static class Builder extends AbstractBuilder<Builder> {
     private final List<ReconcilerSpec> reconcilers;
-    private final List<PortFowardSpec> portForwards;
+    private final List<PortForwardSpec> portForwards;
+    private final List<Class<? extends CustomResource>> additionalCustomResourceDefinitions;
 
     protected Builder() {
       super();
       this.reconcilers = new ArrayList<>();
       this.portForwards = new ArrayList<>();
+      this.additionalCustomResourceDefinitions = new ArrayList<>();
     }
 
     public Builder withReconciler(
@@ -217,16 +231,24 @@ public Builder withReconciler(Class<? extends Reconciler> value) {
 
     public Builder withPortForward(String namespace, String labelKey, String labelValue, int port,
         int localPort) {
-      portForwards.add(new PortFowardSpec(namespace, labelKey, labelValue, port, localPort));
+      portForwards.add(new PortForwardSpec(namespace, labelKey, labelValue, port, localPort));
       return this;
     }
 
+    public Builder withAdditionalCustomResourceDefinition(
+        Class<? extends CustomResource> customResource) {
+      additionalCustomResourceDefinitions.add(customResource);
+      return this;
+    }
+
+
     public LocalOperatorExtension build() {
       return new LocalOperatorExtension(
           configurationService,
           reconcilers,
           infrastructure,
           portForwards,
+          additionalCustomResourceDefinitions,
           infrastructureTimeout,
           preserveNamespaceOnError,
           waitForNamespaceDeletion,
@@ -234,14 +256,14 @@ public LocalOperatorExtension build() {
     }
   }
 
-  private static class PortFowardSpec {
+  private static class PortForwardSpec {
     final String namespace;
     final String labelKey;
     final String labelValue;
     final int port;
     final int localPort;
 
-    public PortFowardSpec(String namespace, String labelKey, String labelValue, int port,
+    public PortForwardSpec(String namespace, String labelKey, String labelValue, int port,
         int localPort) {
       this.namespace = namespace;
       this.labelKey = labelKey;
diff --git a/operator-framework/src/test/java/io/javaoperatorsdk/operator/PrimaryToSecondaryIT.java b/operator-framework/src/test/java/io/javaoperatorsdk/operator/PrimaryToSecondaryIT.java
index cfba078293..7da755113e 100644
--- a/operator-framework/src/test/java/io/javaoperatorsdk/operator/PrimaryToSecondaryIT.java
+++ b/operator-framework/src/test/java/io/javaoperatorsdk/operator/PrimaryToSecondaryIT.java
@@ -22,11 +22,10 @@ class PrimaryToSecondaryIT {
   @RegisterExtension
   LocalOperatorExtension operator =
       LocalOperatorExtension.builder()
-
+          .withAdditionalCustomResourceDefinition(Cluster.class)
           .withReconciler(new JobReconciler())
           .build();
 
-  // todo load other CRD
   @Test
   void readsSecondaryInManyToOneCases() throws InterruptedException {
     operator.create(Cluster.class, cluster());

From 80fb6fc4430f2e1ba9a874e0327f148b4a0d1873 Mon Sep 17 00:00:00 2001
From: csviri <csviri@gmail.com>
Date: Thu, 23 Jun 2022 16:57:05 +0200
Subject: [PATCH 04/12] IT improvements

---
 .../operator/MappingNoPrimaryToSecondaryIT.java               | 4 ++++
 .../io/javaoperatorsdk/operator/PrimaryToSecondaryIT.java     | 3 ++-
 2 files changed, 6 insertions(+), 1 deletion(-)
 create mode 100644 operator-framework/src/test/java/io/javaoperatorsdk/operator/MappingNoPrimaryToSecondaryIT.java

diff --git a/operator-framework/src/test/java/io/javaoperatorsdk/operator/MappingNoPrimaryToSecondaryIT.java b/operator-framework/src/test/java/io/javaoperatorsdk/operator/MappingNoPrimaryToSecondaryIT.java
new file mode 100644
index 0000000000..e5d921a752
--- /dev/null
+++ b/operator-framework/src/test/java/io/javaoperatorsdk/operator/MappingNoPrimaryToSecondaryIT.java
@@ -0,0 +1,4 @@
+package io.javaoperatorsdk.operator;
+
+public class MappingNoPrimaryToSecondaryIT {
+}
diff --git a/operator-framework/src/test/java/io/javaoperatorsdk/operator/PrimaryToSecondaryIT.java b/operator-framework/src/test/java/io/javaoperatorsdk/operator/PrimaryToSecondaryIT.java
index 7da755113e..b54923c6e6 100644
--- a/operator-framework/src/test/java/io/javaoperatorsdk/operator/PrimaryToSecondaryIT.java
+++ b/operator-framework/src/test/java/io/javaoperatorsdk/operator/PrimaryToSecondaryIT.java
@@ -19,6 +19,7 @@ class PrimaryToSecondaryIT {
 
   public static final String CLUSTER_NAME = "cluster1";
   public static final int MIN_DELAY = 150;
+
   @RegisterExtension
   LocalOperatorExtension operator =
       LocalOperatorExtension.builder()
@@ -32,7 +33,7 @@ void readsSecondaryInManyToOneCases() throws InterruptedException {
     Thread.sleep(MIN_DELAY);
     operator.create(Job.class, job());
 
-    await().pollDelay(Duration.ofMillis(400)).untilAsserted(
+    await().pollDelay(Duration.ofMillis(300)).untilAsserted(
         () -> assertThat(operator.getReconcilerOfType(JobReconciler.class).getNumberOfExecutions())
             .isEqualTo(1));
   }

From 74e265f0b51a37f511c2a3e249d0fee649155902 Mon Sep 17 00:00:00 2001
From: csviri <csviri@gmail.com>
Date: Thu, 23 Jun 2022 17:30:25 +0200
Subject: [PATCH 05/12] cleanup

---
 .../operator/MappingNoPrimaryToSecondaryIT.java               | 4 ----
 1 file changed, 4 deletions(-)
 delete mode 100644 operator-framework/src/test/java/io/javaoperatorsdk/operator/MappingNoPrimaryToSecondaryIT.java

diff --git a/operator-framework/src/test/java/io/javaoperatorsdk/operator/MappingNoPrimaryToSecondaryIT.java b/operator-framework/src/test/java/io/javaoperatorsdk/operator/MappingNoPrimaryToSecondaryIT.java
deleted file mode 100644
index e5d921a752..0000000000
--- a/operator-framework/src/test/java/io/javaoperatorsdk/operator/MappingNoPrimaryToSecondaryIT.java
+++ /dev/null
@@ -1,4 +0,0 @@
-package io.javaoperatorsdk.operator;
-
-public class MappingNoPrimaryToSecondaryIT {
-}

From c18f14f9df166480b591e4e1f3063cddb2a524a2 Mon Sep 17 00:00:00 2001
From: csviri <csviri@gmail.com>
Date: Fri, 24 Jun 2022 09:13:44 +0200
Subject: [PATCH 06/12] docs wip

---
 docs/documentation/features.md                            | 4 ++++
 .../processing/event/source/PrimaryToSecondaryMapper.java | 8 ++++++++
 2 files changed, 12 insertions(+)

diff --git a/docs/documentation/features.md b/docs/documentation/features.md
index 8cbf9ec841..a68f091073 100644
--- a/docs/documentation/features.md
+++ b/docs/documentation/features.md
@@ -520,6 +520,10 @@ for this feature.
 
 ## Monitoring with Micrometer
 
+## Managing Relation between Primary and Secondary Resources
+
+
+
 ## Automatic Generation of CRDs
 
 Note that this is feature of [Fabric8 Kubernetes Client](https://github.com/fabric8io/kubernetes-client) not the JOSDK.
diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/PrimaryToSecondaryMapper.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/PrimaryToSecondaryMapper.java
index 37f31e2e3e..866a2b2251 100644
--- a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/PrimaryToSecondaryMapper.java
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/PrimaryToSecondaryMapper.java
@@ -5,6 +5,14 @@
 import io.fabric8.kubernetes.api.model.HasMetadata;
 import io.javaoperatorsdk.operator.processing.event.ResourceID;
 
+/**
+ * Primary to Secondary mapper only needed in some cases, typically when there it many-to-one or
+ * many-to-many relation between primary and secondary resources. If there is owner reference (or
+ * reference with annotations) from secondary to primary this is not needed. See
+ * PrimaryToSecondaryIT integration tests that handles many-to-many relationship.
+ *
+ * @param <P> primary resource type
+ */
 public interface PrimaryToSecondaryMapper<P extends HasMetadata> {
 
   Set<ResourceID> toSecondaryResourceIDs(P primary);

From b7720f974ad2c450c9df6ac5297847af150b33d1 Mon Sep 17 00:00:00 2001
From: csviri <csviri@gmail.com>
Date: Fri, 24 Jun 2022 09:43:02 +0200
Subject: [PATCH 07/12] docs

---
 docs/documentation/features.md | 55 ++++++++++++++++++----------------
 1 file changed, 29 insertions(+), 26 deletions(-)

diff --git a/docs/documentation/features.md b/docs/documentation/features.md
index a68f091073..7a604dc14e 100644
--- a/docs/documentation/features.md
+++ b/docs/documentation/features.md
@@ -377,22 +377,12 @@ public class TomcatReconciler implements Reconciler<Tomcat>, EventSourceInitiali
 
     @Override
     public List<EventSource> prepareEventSources(EventSourceContext<Tomcat> context) {
-        SharedIndexInformer<Deployment> deploymentInformer =
-                kubernetesClient.apps()
-                        .deployments()
-                        .inAnyNamespace()
-                        .withLabel("app.kubernetes.io/managed-by", "tomcat-operator")
-                        .runnableInformer(0);
-
-        return List.of(
-                new InformerEventSource<>(deploymentInformer, d -> {
-                    var ownerReferences = d.getMetadata().getOwnerReferences();
-                    if (!ownerReferences.isEmpty()) {
-                        return Set.of(new ResourceID(ownerReferences.get(0).getName(), d.getMetadata().getNamespace()));
-                    } else {
-                        return EMPTY_SET;
-                    }
-                }));
+        var configMapEventSource =
+                new InformerEventSource<>(InformerConfiguration.from(Deployment.class, context)
+                        .withLabelSelector(SELECTOR)
+                        .withSecondaryToPrimaryMapper(Mappers.fromAnnotation(ANNOTATION_NAME,ANNOTATION_NAMESPACE)
+                        .build(), context));
+        return EventSourceInitializer.nameEventSources(configMapEventSource);
     }
   ...
 }
@@ -401,21 +391,38 @@ public class TomcatReconciler implements Reconciler<Tomcat>, EventSourceInitiali
 In the example above an `InformerEventSource` is registered (more on this specific eventsource later). Multiple things
 are going on here:
 
-1. An `SharedIndexInformer` (class from fabric8 Kubernetes client) is created. This will watch and produce events for
+1. In the background `SharedIndexInformer` (class from fabric8 Kubernetes client) is created. This will watch and produce events for
    `Deployments` in every namespace, but will filter them based on label. So `Deployments` which are not managed by
    `tomcat-operator` (the label is not present on them) will not trigger a reconciliation.
 2. In the next step
    an [InformerEventSource](https://github.com/java-operator-sdk/java-operator-sdk/blob/main/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerEventSource.java)
-   is created, which wraps the `SharedIndexInformer`. In addition to that a mapping functions is provided, **this maps
-   the event of the watched resource (in this case `Deployment`) to the custom resources to reconcile**. Not that in
-   this case this is a simple task, since `Deployment` is already created with an owner reference. Therefore,
-   the `ResourceID`
-   what identifies the custom resource to reconcile is created from the owner reference. 
+   is created, which wraps the `SharedIndexInformer`. In addition to that a mapping functions is provided,
+   with `withSecondaryToPrimaryMapper`, this maps  the event of the watched resource (in this case `Deployment`) to the
+   custom resources to reconcile. Note that usually this is covered by a default mapper , when `Deployment` 
+   is created with an owner reference, the default mapper gets the mapping information from there. Thus,
+   the `ResourceID` what identifies the custom resource to reconcile is created from the owner reference. 
+   For sake of the example a mapper is added that maps secondary to primary resource based on annotations. 
 
 Note that a set of `ResourceID` is returned, this is usually just a set with one element. The possibility to specify
 multiple values are there to cover some rare corner cases. If an irrelevant resource is observed, an empty set can 
 be returned to not reconcile any custom resource.
 
+### Managing Relation between Primary and Secondary Resources
+
+As already touched in previous section, a `SecondaryToPrimaryMapper` is required to map events to trigger reconciliation
+of the primary resource. By default, this is handled with a mapper that utilizes owner references. If an owner reference
+cannot be used (for example resources are in different namespace), other mapper can be provided, typically an annotation
+based on is provided.
+
+Adding a `SecondaryToPrimaryMapper` is typically sufficient when there is a one-to-many relationship between primary and
+secondary resources. The secondary resources can be mapped to its primary owner, and this is enough information to also
+get the resource using the API from the context in reconciler: `context.getSecondaryResources(...)`. There are however
+cases when to map the other way around this mapper is not enough, a `PrimaryToSecondaryMapper` is required. 
+This is typically when there is a many-to-one or many-to-many relationship between resources, thus the primary resource 
+is referencing a secondary resources. In these cases the mentioned reverse mapper is required to work properly. 
+See [PrimaryToSecondaryIT](https://github.com/java-operator-sdk/java-operator-sdk/blob/main/operator-framework/src/test/java/io/javaoperatorsdk/operator/PrimaryToSecondaryIT.java)
+integration test for a sample.
+
 ### Built-in EventSources
 
 There are multiple event-sources provided out of the box, the following are some more central ones:
@@ -520,10 +527,6 @@ for this feature.
 
 ## Monitoring with Micrometer
 
-## Managing Relation between Primary and Secondary Resources
-
-
-
 ## Automatic Generation of CRDs
 
 Note that this is feature of [Fabric8 Kubernetes Client](https://github.com/fabric8io/kubernetes-client) not the JOSDK.

From 92540da2db4bac8127848c10f36aed61b2a84ffe Mon Sep 17 00:00:00 2001
From: csviri <csviri@gmail.com>
Date: Fri, 24 Jun 2022 13:05:06 +0200
Subject: [PATCH 08/12] NO OP primary to secondary index

---
 .../DefaultPrimaryToSecondaryIndex.java       | 52 +++++++++++++++++++
 .../source/informer/InformerEventSource.java  | 20 +++----
 .../informer/NOOPPrimaryToSecondaryIndex.java | 32 ++++++++++++
 .../informer/PrimaryToSecondaryIndex.java     | 44 ++--------------
 ...> DefaultPrimaryToSecondaryIndexTest.java} |  6 +--
 5 files changed, 98 insertions(+), 56 deletions(-)
 create mode 100644 operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/DefaultPrimaryToSecondaryIndex.java
 create mode 100644 operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java
 rename operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/informer/{PrimaryToSecondaryIndexTest.java => DefaultPrimaryToSecondaryIndexTest.java} (94%)

diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/DefaultPrimaryToSecondaryIndex.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/DefaultPrimaryToSecondaryIndex.java
new file mode 100644
index 0000000000..65434cf53d
--- /dev/null
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/DefaultPrimaryToSecondaryIndex.java
@@ -0,0 +1,52 @@
+package io.javaoperatorsdk.operator.processing.event.source.informer;
+
+import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
+
+import io.fabric8.kubernetes.api.model.HasMetadata;
+import io.javaoperatorsdk.operator.processing.event.ResourceID;
+import io.javaoperatorsdk.operator.processing.event.source.SecondaryToPrimaryMapper;
+
+class DefaultPrimaryToSecondaryIndex<R extends HasMetadata> implements PrimaryToSecondaryIndex<R> {
+
+  private SecondaryToPrimaryMapper<R> secondaryToPrimaryMapper;
+  private Map<ResourceID, Set<ResourceID>> index = new HashMap<>();
+
+  public DefaultPrimaryToSecondaryIndex(SecondaryToPrimaryMapper<R> secondaryToPrimaryMapper) {
+    this.secondaryToPrimaryMapper = secondaryToPrimaryMapper;
+  }
+
+  @Override
+  public synchronized void onAddOrUpdate(R resource) {
+    Set<ResourceID> primaryResources = secondaryToPrimaryMapper.toPrimaryResourceIDs(resource);
+    primaryResources.forEach(
+        primaryResource -> {
+          var resourceSet =
+              index.computeIfAbsent(primaryResource, pr -> ConcurrentHashMap.newKeySet());
+          resourceSet.add(ResourceID.fromResource(resource));
+        });
+  }
+
+  @Override
+  public synchronized void onDelete(R resource) {
+    Set<ResourceID> primaryResources = secondaryToPrimaryMapper.toPrimaryResourceIDs(resource);
+    primaryResources.forEach(
+        primaryResource -> {
+          var secondaryResources = index.get(primaryResource);
+          secondaryResources.remove(ResourceID.fromResource(resource));
+          if (secondaryResources.isEmpty()) {
+            index.remove(primaryResource);
+          }
+        });
+  }
+
+  @Override
+  public synchronized Set<ResourceID> getSecondaryResources(ResourceID primary) {
+    var resourceIDs = index.get(primary);
+    if (resourceIDs == null) {
+      return Collections.emptySet();
+    } else {
+      return Collections.unmodifiableSet(resourceIDs);
+    }
+  }
+}
diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerEventSource.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerEventSource.java
index 7cb71597ba..4e0d96d5d9 100644
--- a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerEventSource.java
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerEventSource.java
@@ -88,9 +88,9 @@ public InformerEventSource(InformerConfiguration<R> configuration, KubernetesCli
     primaryToSecondaryMapper = configuration.getPrimaryToSecondaryMapper();
     if (primaryToSecondaryMapper == null) {
       primaryToSecondaryIndex =
-          new PrimaryToSecondaryIndex<>(configuration.getSecondaryToPrimaryMapper());
+          new DefaultPrimaryToSecondaryIndex<>(configuration.getSecondaryToPrimaryMapper());
     } else {
-      primaryToSecondaryIndex = null;
+      primaryToSecondaryIndex = NOOPPrimaryToSecondaryIndex.getInstance();
     }
   }
 
@@ -99,9 +99,7 @@ public void onAdd(R resource) {
     if (log.isDebugEnabled()) {
       log.debug("On add event received for resource id: {}", ResourceID.fromResource(resource));
     }
-    if (useSecondaryToPrimaryIndex()) {
-      primaryToSecondaryIndex.onAddOrUpdate(resource);
-    }
+    primaryToSecondaryIndex.onAddOrUpdate(resource);
     onAddOrUpdate("add", resource, () -> InformerEventSource.super.onAdd(resource));
   }
 
@@ -110,9 +108,7 @@ public void onUpdate(R oldObject, R newObject) {
     if (log.isDebugEnabled()) {
       log.debug("On update event received for resource id: {}", ResourceID.fromResource(newObject));
     }
-    if (useSecondaryToPrimaryIndex()) {
-      primaryToSecondaryIndex.onAddOrUpdate(newObject);
-    }
+    primaryToSecondaryIndex.onAddOrUpdate(newObject);
     onAddOrUpdate("update", newObject,
         () -> InformerEventSource.super.onUpdate(oldObject, newObject));
   }
@@ -122,9 +118,7 @@ public void onDelete(R resource, boolean b) {
     if (log.isDebugEnabled()) {
       log.debug("On delete event received for resource id: {}", ResourceID.fromResource(resource));
     }
-    if (useSecondaryToPrimaryIndex()) {
-      primaryToSecondaryIndex.onDelete(resource);
-    }
+    primaryToSecondaryIndex.onDelete(resource);
     super.onDelete(resource, b);
     propagateEvent(resource);
   }
@@ -216,9 +210,7 @@ public synchronized void handleRecentResourceCreate(ResourceID resourceID, R res
   }
 
   private void handleRecentCreateOrUpdate(R resource, Runnable runnable) {
-    if (useSecondaryToPrimaryIndex()) {
-      primaryToSecondaryIndex.onAddOrUpdate(resource);
-    }
+    primaryToSecondaryIndex.onAddOrUpdate(resource);
     if (eventRecorder.isRecordingFor(ResourceID.fromResource(resource))) {
       handleRecentResourceOperationAndStopEventRecording(resource);
     } else {
diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java
new file mode 100644
index 0000000000..46e7cd0f63
--- /dev/null
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java
@@ -0,0 +1,32 @@
+package io.javaoperatorsdk.operator.processing.event.source.informer;
+
+import java.util.Set;
+
+import io.fabric8.kubernetes.api.model.HasMetadata;
+import io.javaoperatorsdk.operator.processing.event.ResourceID;
+
+
+class NOOPPrimaryToSecondaryIndex<R extends HasMetadata>
+    implements PrimaryToSecondaryIndex<R> {
+
+  @SuppressWarnings("rawtypes")
+  private final static NOOPPrimaryToSecondaryIndex instance = new NOOPPrimaryToSecondaryIndex();
+
+  public static <T extends HasMetadata> NOOPPrimaryToSecondaryIndex<T> getInstance() {
+    return instance;
+  }
+
+  private NOOPPrimaryToSecondaryIndex() {
+  }
+
+  @Override
+  public void onAddOrUpdate(R resource) {}
+
+  @Override
+  public void onDelete(R resource) {}
+
+  @Override
+  public Set<ResourceID> getSecondaryResources(ResourceID primary) {
+    throw new IllegalStateException("Should not be called");
+  }
+}
diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/PrimaryToSecondaryIndex.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/PrimaryToSecondaryIndex.java
index 8918895aa1..7a87b23272 100644
--- a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/PrimaryToSecondaryIndex.java
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/PrimaryToSecondaryIndex.java
@@ -1,49 +1,15 @@
 package io.javaoperatorsdk.operator.processing.event.source.informer;
 
-import java.util.*;
-import java.util.concurrent.ConcurrentHashMap;
+import java.util.Set;
 
 import io.fabric8.kubernetes.api.model.HasMetadata;
 import io.javaoperatorsdk.operator.processing.event.ResourceID;
-import io.javaoperatorsdk.operator.processing.event.source.SecondaryToPrimaryMapper;
 
-class PrimaryToSecondaryIndex<R extends HasMetadata> {
+public interface PrimaryToSecondaryIndex<R extends HasMetadata> {
 
-  private SecondaryToPrimaryMapper<R> secondaryToPrimaryMapper;
-  private Map<ResourceID, Set<ResourceID>> index = new HashMap<>();
+  void onAddOrUpdate(R resource);
 
-  public PrimaryToSecondaryIndex(SecondaryToPrimaryMapper<R> secondaryToPrimaryMapper) {
-    this.secondaryToPrimaryMapper = secondaryToPrimaryMapper;
-  }
+  void onDelete(R resource);
 
-  public synchronized void onAddOrUpdate(R resource) {
-    Set<ResourceID> primaryResources = secondaryToPrimaryMapper.toPrimaryResourceIDs(resource);
-    primaryResources.forEach(
-        primaryResource -> {
-          var resourceSet =
-              index.computeIfAbsent(primaryResource, pr -> ConcurrentHashMap.newKeySet());
-          resourceSet.add(ResourceID.fromResource(resource));
-        });
-  }
-
-  public synchronized void onDelete(R resource) {
-    Set<ResourceID> primaryResources = secondaryToPrimaryMapper.toPrimaryResourceIDs(resource);
-    primaryResources.forEach(
-        primaryResource -> {
-          var secondaryResources = index.get(primaryResource);
-          secondaryResources.remove(ResourceID.fromResource(resource));
-          if (secondaryResources.isEmpty()) {
-            index.remove(primaryResource);
-          }
-        });
-  }
-
-  public synchronized Set<ResourceID> getSecondaryResources(ResourceID primary) {
-    var resourceIDs = index.get(primary);
-    if (resourceIDs == null) {
-      return Collections.emptySet();
-    } else {
-      return Collections.unmodifiableSet(resourceIDs);
-    }
-  }
+  Set<ResourceID> getSecondaryResources(ResourceID primary);
 }
diff --git a/operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/informer/PrimaryToSecondaryIndexTest.java b/operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/informer/DefaultPrimaryToSecondaryIndexTest.java
similarity index 94%
rename from operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/informer/PrimaryToSecondaryIndexTest.java
rename to operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/informer/DefaultPrimaryToSecondaryIndexTest.java
index ca73b135a7..da2d1b7cf0 100644
--- a/operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/informer/PrimaryToSecondaryIndexTest.java
+++ b/operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/informer/DefaultPrimaryToSecondaryIndexTest.java
@@ -15,12 +15,12 @@
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
-class PrimaryToSecondaryIndexTest {
+class DefaultPrimaryToSecondaryIndexTest {
 
   private SecondaryToPrimaryMapper<ConfigMap> secondaryToPrimaryMapperMock =
       mock(SecondaryToPrimaryMapper.class);
-  private PrimaryToSecondaryIndex<ConfigMap> primaryToSecondaryIndex =
-      new PrimaryToSecondaryIndex<>(secondaryToPrimaryMapperMock);
+  private DefaultPrimaryToSecondaryIndex<ConfigMap> primaryToSecondaryIndex =
+      new DefaultPrimaryToSecondaryIndex<>(secondaryToPrimaryMapperMock);
 
   private ResourceID primaryID1 = new ResourceID("id1", "default");
   private ResourceID primaryID2 = new ResourceID("id2", "default");

From 8d785d9d9750967c92ed324bbca7247aef9cc2aa Mon Sep 17 00:00:00 2001
From: csviri <csviri@gmail.com>
Date: Fri, 24 Jun 2022 13:30:30 +0200
Subject: [PATCH 09/12] format

---
 .../event/source/informer/NOOPPrimaryToSecondaryIndex.java    | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java
index 46e7cd0f63..2163f4e1ac 100644
--- a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java
@@ -5,7 +5,6 @@
 import io.fabric8.kubernetes.api.model.HasMetadata;
 import io.javaoperatorsdk.operator.processing.event.ResourceID;
 
-
 class NOOPPrimaryToSecondaryIndex<R extends HasMetadata>
     implements PrimaryToSecondaryIndex<R> {
 
@@ -16,8 +15,7 @@ public static <T extends HasMetadata> NOOPPrimaryToSecondaryIndex<T> getInstance
     return instance;
   }
 
-  private NOOPPrimaryToSecondaryIndex() {
-  }
+  private NOOPPrimaryToSecondaryIndex() {}
 
   @Override
   public void onAddOrUpdate(R resource) {}

From 42ecef7186c1647363b9ffd4137d9f5dc4811483 Mon Sep 17 00:00:00 2001
From: csviri <csviri@gmail.com>
Date: Fri, 24 Jun 2022 13:41:05 +0200
Subject: [PATCH 10/12] improvements

---
 .../source/informer/NOOPPrimaryToSecondaryIndex.java | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java
index 2163f4e1ac..0aedf1dc1e 100644
--- a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java
@@ -9,7 +9,7 @@ class NOOPPrimaryToSecondaryIndex<R extends HasMetadata>
     implements PrimaryToSecondaryIndex<R> {
 
   @SuppressWarnings("rawtypes")
-  private final static NOOPPrimaryToSecondaryIndex instance = new NOOPPrimaryToSecondaryIndex();
+  private static final NOOPPrimaryToSecondaryIndex instance = new NOOPPrimaryToSecondaryIndex();
 
   public static <T extends HasMetadata> NOOPPrimaryToSecondaryIndex<T> getInstance() {
     return instance;
@@ -18,13 +18,17 @@ public static <T extends HasMetadata> NOOPPrimaryToSecondaryIndex<T> getInstance
   private NOOPPrimaryToSecondaryIndex() {}
 
   @Override
-  public void onAddOrUpdate(R resource) {}
+  public void onAddOrUpdate(R resource) {
+    throw new UnsupportedOperationException();
+  }
 
   @Override
-  public void onDelete(R resource) {}
+  public void onDelete(R resource) {
+    throw new UnsupportedOperationException();
+  }
 
   @Override
   public Set<ResourceID> getSecondaryResources(ResourceID primary) {
-    throw new IllegalStateException("Should not be called");
+    throw new UnsupportedOperationException();
   }
 }

From b3216a3c5b33f638f42ef7c534632ff76e61aab2 Mon Sep 17 00:00:00 2001
From: csviri <csviri@gmail.com>
Date: Fri, 24 Jun 2022 13:41:26 +0200
Subject: [PATCH 11/12] revert no op

---
 .../event/source/informer/NOOPPrimaryToSecondaryIndex.java      | 2 --
 1 file changed, 2 deletions(-)

diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java
index 0aedf1dc1e..d894aaf07a 100644
--- a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java
@@ -19,12 +19,10 @@ private NOOPPrimaryToSecondaryIndex() {}
 
   @Override
   public void onAddOrUpdate(R resource) {
-    throw new UnsupportedOperationException();
   }
 
   @Override
   public void onDelete(R resource) {
-    throw new UnsupportedOperationException();
   }
 
   @Override

From 75fabcc8a34dfef6cdd6bffb014f2b44ace70f3c Mon Sep 17 00:00:00 2001
From: csviri <csviri@gmail.com>
Date: Fri, 24 Jun 2022 13:44:35 +0200
Subject: [PATCH 12/12] comments

---
 .../event/source/informer/NOOPPrimaryToSecondaryIndex.java      | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java
index d894aaf07a..ddc8cbec18 100644
--- a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/NOOPPrimaryToSecondaryIndex.java
@@ -19,10 +19,12 @@ private NOOPPrimaryToSecondaryIndex() {}
 
   @Override
   public void onAddOrUpdate(R resource) {
+    // empty method because of noop implementation
   }
 
   @Override
   public void onDelete(R resource) {
+    // empty method because of noop implementation
   }
 
   @Override