feat: leader election callbacks

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/LeaderElectionManager.java

@@ -66,19 +66,28 @@ private void init(LeaderElectionConfiguration config) {
                 config.getLeaseDuration(),
                 config.getRenewDeadline(),
                 config.getRetryPeriod(),
-                leaderCallbacks(),
+                leaderCallbacks(config),
                 true,
                 config.getLeaseName()))
         .build();
   }
 
 
 
-  private LeaderCallbacks leaderCallbacks() {
+  private LeaderCallbacks leaderCallbacks(LeaderElectionConfiguration config) {
     return new LeaderCallbacks(
-        this::startLeading,
-        this::stopLeading,
-        leader -> log.info("New leader with identity: {}", leader));
+        () -> {
+          config.getLeaderCallbacks().ifPresent(LeaderCallbacks::onStartLeading);
+          LeaderElectionManager.this.startLeading();
+        },
+        () -> {
+          config.getLeaderCallbacks().ifPresent(LeaderCallbacks::onStopLeading);
+          LeaderElectionManager.this.stopLeading();
+        },
+        leader -> {
+          config.getLeaderCallbacks().ifPresent(cb -> cb.onNewLeader(leader));
+          log.info("New leader with identity: {}", leader);
+        });
   }
 
   private void startLeading() {

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

@@ -3,6 +3,8 @@
 import java.time.Duration;
 import java.util.Optional;
 
+import io.fabric8.kubernetes.client.extended.leaderelection.LeaderCallbacks;
+
 public class LeaderElectionConfiguration {
 
   public static final Duration LEASE_DURATION_DEFAULT_VALUE = Duration.ofSeconds(15);
@@ -17,13 +19,15 @@ public class LeaderElectionConfiguration {
   private final Duration renewDeadline;
   private final Duration retryPeriod;
 
+  private final LeaderCallbacks leaderCallbacks;
+
   public LeaderElectionConfiguration(String leaseName, String leaseNamespace, String identity) {
     this(
         leaseName,
         leaseNamespace,
         LEASE_DURATION_DEFAULT_VALUE,
         RENEW_DEADLINE_DEFAULT_VALUE,
-        RETRY_PERIOD_DEFAULT_VALUE, identity);
+        RETRY_PERIOD_DEFAULT_VALUE, identity, null);
   }
 
   public LeaderElectionConfiguration(String leaseName, String leaseNamespace) {
@@ -32,7 +36,7 @@ public LeaderElectionConfiguration(String leaseName, String leaseNamespace) {
         leaseNamespace,
         LEASE_DURATION_DEFAULT_VALUE,
         RENEW_DEADLINE_DEFAULT_VALUE,
-        RETRY_PERIOD_DEFAULT_VALUE, null);
+        RETRY_PERIOD_DEFAULT_VALUE, null, null);
   }
 
   public LeaderElectionConfiguration(String leaseName) {
@@ -41,7 +45,7 @@ public LeaderElectionConfiguration(String leaseName) {
         null,
         LEASE_DURATION_DEFAULT_VALUE,
         RENEW_DEADLINE_DEFAULT_VALUE,
-        RETRY_PERIOD_DEFAULT_VALUE, null);
+        RETRY_PERIOD_DEFAULT_VALUE, null, null);
   }
 
   public LeaderElectionConfiguration(
@@ -50,7 +54,7 @@ public LeaderElectionConfiguration(
       Duration leaseDuration,
       Duration renewDeadline,
       Duration retryPeriod) {
-    this(leaseName, leaseNamespace, leaseDuration, renewDeadline, retryPeriod, null);
+    this(leaseName, leaseNamespace, leaseDuration, renewDeadline, retryPeriod, null, null);
   }
 
   public LeaderElectionConfiguration(
@@ -59,13 +63,15 @@ public LeaderElectionConfiguration(
       Duration leaseDuration,
       Duration renewDeadline,
       Duration retryPeriod,
-      String identity) {
+      String identity,
+      LeaderCallbacks leaderCallbacks) {
     this.leaseName = leaseName;
     this.leaseNamespace = leaseNamespace;
     this.leaseDuration = leaseDuration;
     this.renewDeadline = renewDeadline;
     this.retryPeriod = retryPeriod;
     this.identity = identity;
+    this.leaderCallbacks = leaderCallbacks;
   }
 
   public Optional<String> getLeaseNamespace() {
@@ -91,4 +97,8 @@ public Duration getRetryPeriod() {
   public Optional<String> getIdentity() {
     return Optional.ofNullable(identity);
   }
+
+  public Optional<LeaderCallbacks> getLeaderCallbacks() {
+    return Optional.ofNullable(leaderCallbacks);
+  }
 }

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

@@ -0,0 +1,61 @@
+package io.javaoperatorsdk.operator.api.config;
+
+import java.time.Duration;
+
+import io.fabric8.kubernetes.client.extended.leaderelection.LeaderCallbacks;
+
+import static io.javaoperatorsdk.operator.api.config.LeaderElectionConfiguration.*;
+
+public final class LeaderElectionConfigurationBuilder {
+
+  private String leaseName;
+  private String leaseNamespace;
+  private String identity;
+  private Duration leaseDuration = LEASE_DURATION_DEFAULT_VALUE;
+  private Duration renewDeadline = RENEW_DEADLINE_DEFAULT_VALUE;
+  private Duration retryPeriod = RETRY_PERIOD_DEFAULT_VALUE;
+  private LeaderCallbacks leaderCallbacks;
+
+  private LeaderElectionConfigurationBuilder(String leaseName) {
+    this.leaseName = leaseName;
+  }
+
+  public static LeaderElectionConfigurationBuilder aLeaderElectionConfiguration(String leaseName) {
+    return new LeaderElectionConfigurationBuilder(leaseName);
+  }
+
+  public LeaderElectionConfigurationBuilder withLeaseNamespace(String leaseNamespace) {
+    this.leaseNamespace = leaseNamespace;
+    return this;
+  }
+
+  public LeaderElectionConfigurationBuilder withIdentity(String identity) {
+    this.identity = identity;
+    return this;
+  }
+
+  public LeaderElectionConfigurationBuilder withLeaseDuration(Duration leaseDuration) {
+    this.leaseDuration = leaseDuration;
+    return this;
+  }
+
+  public LeaderElectionConfigurationBuilder withRenewDeadline(Duration renewDeadline) {
+    this.renewDeadline = renewDeadline;
+    return this;
+  }
+
+  public LeaderElectionConfigurationBuilder withRetryPeriod(Duration retryPeriod) {
+    this.retryPeriod = retryPeriod;
+    return this;
+  }
+
+  public LeaderElectionConfigurationBuilder withLeaderCallbacks(LeaderCallbacks leaderCallbacks) {
+    this.leaderCallbacks = leaderCallbacks;
+    return this;
+  }
+
+  public LeaderElectionConfiguration build() {
+    return new LeaderElectionConfiguration(leaseName, leaseNamespace, leaseDuration, renewDeadline,
+        retryPeriod, identity, leaderCallbacks);
+  }
+}