chore(deps): bump slf4j-api from 1.7.36 to 2.0.0

.github/workflows/e2e-test.yml

@@ -21,6 +21,7 @@ jobs:
           - "sample-operators/mysql-schema"
           - "sample-operators/tomcat-operator"
           - "sample-operators/webpage"
+          - "sample-operators/leader-election"
     runs-on: ubuntu-latest
     steps:
       - name: Checkout

.github/workflows/pr.yml

@@ -25,8 +25,8 @@ jobs:
           cache: 'maven'
       - name: Check code format
         run: |
-          ./mvnw ${MAVEN_ARGS} formatter:validate -Dconfigfile=$PWD/contributing/eclipse-google-style.xml --file pom.xml
-          ./mvnw ${MAVEN_ARGS} impsort:check --file pom.xml
+          ./mvnw ${MAVEN_ARGS} formatter:validate -Dconfigfile=$PWD/contributing/eclipse-google-style.xml -pl '!operator-framework-bom' --file pom.xml
+          ./mvnw ${MAVEN_ARGS} impsort:check -pl '!operator-framework-bom' --file pom.xml
       - name: Run unit tests
         run: ./mvnw ${MAVEN_ARGS} -B test --file pom.xml
 

docs/documentation/dependent-resources.md

@@ -86,6 +86,35 @@ possible to not implement any of these traits and therefore create read-only dep
 that will trigger your reconciler whenever a user interacts with them but that are never
 modified by your reconciler itself.
 
+[`AbstractSimpleDependentResource`](https://github.com/java-operator-sdk/java-operator-sdk/blob/main/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/dependent/external/AbstractSimpleDependentResource.java)
+and [`KubernetesDependentResource`](https://github.com/java-operator-sdk/java-operator-sdk/blob/main/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/dependent/kubernetes/KubernetesDependentResource.java)
+sub-classes can also implement
+the [`Matcher`](https://github.com/java-operator-sdk/java-operator-sdk/blob/main/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/dependent/Matcher.java)
+interface to customize how the SDK decides whether or not the actual state of the dependent
+matches the desired state. This makes it convenient to use these abstract base classes for your
+implementation, only customizing the matching logic. Note that in many cases, there is no need
+to customize that logic as the SDK already provides convenient default implementations in the
+form
+of [`DesiredEqualsMatcher`](https://github.com/java-operator-sdk/java-operator-sdk/blob/main/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/dependent/DesiredEqualsMatcher.java)
+and
+[`GenericKubernetesResourceMatcher`](https://github.com/java-operator-sdk/java-operator-sdk/blob/main/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/dependent/kubernetes/GenericKubernetesResourceMatcher.java)
+implementations, respectively. If you want to provide custom logic, you only need your
+`DependentResource` implementation to implement the `Matcher` interface as below, which shows
+how to customize the default matching logic for Kubernetes resource to also consider annotations
+and labels, which are ignored by default:
+
+```java
+public class MyDependentResource extends KubernetesDependentResource<MyDependent, MyPrimary>
+    implements Matcher<MyDependent, MyPrimary> {
+  // your implementation
+
+  public Result<MyDependent> match(MyDependent actualResource, MyPrimary primary,
+      Context<MyPrimary> context) {
+    return GenericKubernetesResourceMatcher.match(this, actualResource, primary, context, true);
+  }
+}
+```
+
 ### Batteries included: convenient DependentResource implementations!
 
 JOSDK also offers several other convenient implementations building on top of
@@ -116,7 +145,7 @@ Deleted (or set to be garbage collected). The following example shows how to cre
 @KubernetesDependent(labelSelector = WebPageManagedDependentsReconciler.SELECTOR)
 class DeploymentDependentResource extends CRUDKubernetesDependentResource<Deployment, WebPage> {
 
-   public DeploymentDependentResource() {
+  public DeploymentDependentResource() {
     super(Deployment.class);
   }
 
@@ -169,26 +198,26 @@ instances are managed by JOSDK, an example of which can be seen below:
 ```java
 
 @ControllerConfiguration(
-        labelSelector = SELECTOR,
-        dependents = {
-                @Dependent(type = ConfigMapDependentResource.class),
-                @Dependent(type = DeploymentDependentResource.class),
-                @Dependent(type = ServiceDependentResource.class)
-        })
+    labelSelector = SELECTOR,
+    dependents = {
+        @Dependent(type = ConfigMapDependentResource.class),
+        @Dependent(type = DeploymentDependentResource.class),
+        @Dependent(type = ServiceDependentResource.class)
+    })
 public class WebPageManagedDependentsReconciler
-        implements Reconciler<WebPage>, ErrorStatusHandler<WebPage> {
+    implements Reconciler<WebPage>, ErrorStatusHandler<WebPage> {
 
-   // omitted code
+  // omitted code
 
-   @Override
-   public UpdateControl<WebPage> reconcile(WebPage webPage, Context<WebPage> context)
-           throws Exception {
+  @Override
+  public UpdateControl<WebPage> reconcile(WebPage webPage, Context<WebPage> context)
+      throws Exception {
 
-      final var name = context.getSecondaryResource(ConfigMap.class).orElseThrow()
-              .getMetadata().getName();
-      webPage.setStatus(createStatus(name));
-      return UpdateControl.patchStatus(webPage);
-   }
+    final var name = context.getSecondaryResource(ConfigMap.class).orElseThrow()
+        .getMetadata().getName();
+    webPage.setStatus(createStatus(name));
+    return UpdateControl.patchStatus(webPage);
+  }
 
 }
 ```
@@ -215,69 +244,69 @@ an `Ingress`:
 
 @ControllerConfiguration
 public class WebPageStandaloneDependentsReconciler
-        implements Reconciler<WebPage>, ErrorStatusHandler<WebPage>,
-        EventSourceInitializer<WebPage> {
-
-   private KubernetesDependentResource<ConfigMap, WebPage> configMapDR;
-   private KubernetesDependentResource<Deployment, WebPage> deploymentDR;
-   private KubernetesDependentResource<Service, WebPage> serviceDR;
-   private KubernetesDependentResource<Service, WebPage> ingressDR;
-
-   public WebPageStandaloneDependentsReconciler(KubernetesClient kubernetesClient) {
-      // 1.
-      createDependentResources(kubernetesClient);
-   }
-
-   @Override
-   public List<EventSource> prepareEventSources(EventSourceContext<WebPage> context) {
-      // 2.  
-      return List.of(
-              configMapDR.initEventSource(context),
-              deploymentDR.initEventSource(context),
-              serviceDR.initEventSource(context));
-   }
-
-   @Override
-   public UpdateControl<WebPage> reconcile(WebPage webPage, Context<WebPage> context)
-           throws Exception {
-
-      // 3.
-      if (!isValidHtml(webPage.getHtml())) {
-         return UpdateControl.patchStatus(setInvalidHtmlErrorMessage(webPage));
-      }
-
-      // 4.  
-      configMapDR.reconcile(webPage, context);
-      deploymentDR.reconcile(webPage, context);
-      serviceDR.reconcile(webPage, context);
-
-      // 5.
-      if (Boolean.TRUE.equals(webPage.getSpec().getExposed())) {
-         ingressDR.reconcile(webPage, context);
-      } else {
-         ingressDR.delete(webPage, context);
-      }
-
-      // 6.
-      webPage.setStatus(
-              createStatus(configMapDR.getResource(webPage).orElseThrow().getMetadata().getName()));
-      return UpdateControl.patchStatus(webPage);
-   }
-
-   private void createDependentResources(KubernetesClient client) {
-      this.configMapDR = new ConfigMapDependentResource();
-      this.deploymentDR = new DeploymentDependentResource();
-      this.serviceDR = new ServiceDependentResource();
-      this.ingressDR = new IngressDependentResource();
-
-      Arrays.asList(configMapDR, deploymentDR, serviceDR, ingressDR).forEach(dr -> {
-         dr.setKubernetesClient(client);
-         dr.configureWith(new KubernetesDependentResourceConfig()
-                 .setLabelSelector(DEPENDENT_RESOURCE_LABEL_SELECTOR));
-      });
-   }
-
-   // omitted code
+    implements Reconciler<WebPage>, ErrorStatusHandler<WebPage>,
+    EventSourceInitializer<WebPage> {
+
+  private KubernetesDependentResource<ConfigMap, WebPage> configMapDR;
+  private KubernetesDependentResource<Deployment, WebPage> deploymentDR;
+  private KubernetesDependentResource<Service, WebPage> serviceDR;
+  private KubernetesDependentResource<Service, WebPage> ingressDR;
+
+  public WebPageStandaloneDependentsReconciler(KubernetesClient kubernetesClient) {
+    // 1.
+    createDependentResources(kubernetesClient);
+  }
+
+  @Override
+  public List<EventSource> prepareEventSources(EventSourceContext<WebPage> context) {
+    // 2.  
+    return List.of(
+        configMapDR.initEventSource(context),
+        deploymentDR.initEventSource(context),
+        serviceDR.initEventSource(context));
+  }
+
+  @Override
+  public UpdateControl<WebPage> reconcile(WebPage webPage, Context<WebPage> context)
+      throws Exception {
+
+    // 3.
+    if (!isValidHtml(webPage.getHtml())) {
+      return UpdateControl.patchStatus(setInvalidHtmlErrorMessage(webPage));
+    }
+
+    // 4.  
+    configMapDR.reconcile(webPage, context);
+    deploymentDR.reconcile(webPage, context);
+    serviceDR.reconcile(webPage, context);
+
+    // 5.
+    if (Boolean.TRUE.equals(webPage.getSpec().getExposed())) {
+      ingressDR.reconcile(webPage, context);
+    } else {
+      ingressDR.delete(webPage, context);
+    }
+
+    // 6.
+    webPage.setStatus(
+        createStatus(configMapDR.getResource(webPage).orElseThrow().getMetadata().getName()));
+    return UpdateControl.patchStatus(webPage);
+  }
+
+  private void createDependentResources(KubernetesClient client) {
+    this.configMapDR = new ConfigMapDependentResource();
+    this.deploymentDR = new DeploymentDependentResource();
+    this.serviceDR = new ServiceDependentResource();
+    this.ingressDR = new IngressDependentResource();
+
+    Arrays.asList(configMapDR, deploymentDR, serviceDR, ingressDR).forEach(dr -> {
+      dr.setKubernetesClient(client);
+      dr.configureWith(new KubernetesDependentResourceConfig()
+          .setLabelSelector(DEPENDENT_RESOURCE_LABEL_SELECTOR));
+    });
+  }
+
+  // omitted code
 }
 ```
 

docs/documentation/features.md

@@ -683,6 +683,19 @@ See also
 the [integration test](https://github.com/java-operator-sdk/java-operator-sdk/blob/ec37025a15046d8f409c77616110024bf32c3416/operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/changenamespace/ChangeNamespaceTestReconciler.java)
 for this feature.
 
+## Leader Election
+
+Operators are generally deployed with a single running or active instance. However, it is 
+possible to deploy multiple instances in such a way that only one, called the "leader", processes the 
+events. This is achieved via a mechanism called "leader election". While all the instances are 
+running, and even start their event sources to populate the caches, only the leader will process 
+the events. This means that should the leader change for any reason, for example because it 
+crashed, the other instances are already warmed up and ready to pick up where the previous 
+leader left off should one of them become elected leader.
+
+See sample configuration in the [E2E test](https://github.com/java-operator-sdk/java-operator-sdk/blob/144947d89323f1c65de6e86bd8b9a6a8ffe714ff/sample-operators/leader-election/src/main/java/io/javaoperatorsdk/operator/sample/LeaderElectionTestOperator.java#L26-L30)
+.
+
 ## Monitoring with Micrometer
 
 ## Automatic Generation of CRDs

micrometer-support/pom.xml

@@ -5,7 +5,7 @@
   <parent>
     <artifactId>java-operator-sdk</artifactId>
     <groupId>io.javaoperatorsdk</groupId>
-    <version>3.1.2-SNAPSHOT</version>
+    <version>3.2.0-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
 

operator-framework-bom/pom.xml

@@ -0,0 +1,43 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>io.javaoperatorsdk</groupId>
+    <artifactId>operator-framework-bom</artifactId>
+    <version>3.2.0-SNAPSHOT</version>
+    <name>Operator SDK - Bill of Materials</name>
+    <packaging>pom</packaging>
+
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>io.javaoperatorsdk</groupId>
+                <artifactId>operator-framework-core</artifactId>
+                <version>${project.version}</version>
+            </dependency>
+            <dependency>
+                <groupId>io.javaoperatorsdk</groupId>
+                <artifactId>operator-framework</artifactId>
+                <version>${project.version}</version>
+            </dependency>
+            <dependency>
+                <groupId>io.javaoperatorsdk</groupId>
+                <artifactId>micrometer-support</artifactId>
+                <version>${project.version}</version>
+            </dependency>
+            <dependency>
+                <groupId>io.javaoperatorsdk</groupId>
+                <artifactId>operator-framework-junit-5</artifactId>
+                <version>${project.version}</version>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
+    <distributionManagement>
+        <snapshotRepository>
+            <id>ossrh</id>
+            <url>https://oss.sonatype.org/content/repositories/snapshots</url>
+        </snapshotRepository>
+    </distributionManagement>
+</project>

operator-framework-core/pom.xml

@@ -6,7 +6,7 @@
   <parent>
     <groupId>io.javaoperatorsdk</groupId>
     <artifactId>java-operator-sdk</artifactId>
-    <version>3.1.2-SNAPSHOT</version>
+    <version>3.2.0-SNAPSHOT</version>
     <relativePath>../pom.xml</relativePath>
   </parent>
 
@@ -52,12 +52,10 @@
 
 
   <dependencies>
-    <!-- We use the OpenShift client, because functionally it is a superset of the Kubernetes client -->
     <dependency>
       <groupId>io.fabric8</groupId>
       <artifactId>kubernetes-client</artifactId>
     </dependency>
-
     <dependency>
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-api</artifactId>