#16717 defer provider instantiation in Kubernetes Module (#16726)

* #16717 defer provider instatiation

* add license header

* fix style, ignore new class in jacoco as it is still initialization code

---------

Co-authored-by: Alberto Lago Alvarado <albl@sitecore.net>

extensions-core/kubernetes-extensions/pom.xml

@@ -158,10 +158,12 @@
           <excludes>
             <!-- Initialization code -->
             <exclude>org/apache/druid/k8s/discovery/K8sDiscoveryModule*</exclude>
+            <exclude>org/apache/druid/k8s/discovery/K8sDruidLeaderSelectorProvider*</exclude>
 
             <!-- K8S Api Glue, not unit testable -->
             <exclude>org/apache/druid/k8s/discovery/DefaultK8sApiClient*</exclude>
             <exclude>org/apache/druid/k8s/discovery/DefaultK8sLeaderElectorFactory*</exclude>
+
           </excludes>
         </configuration>
       </plugin>

extensions-core/kubernetes-extensions/src/main/java/org/apache/druid/k8s/discovery/K8sDiscoveryModule.java

@@ -21,9 +21,7 @@ package org.apache.druid.k8s.discovery;
 
 import com.fasterxml.jackson.databind.Module;
 import com.google.inject.Binder;
-import com.google.inject.Inject;
 import com.google.inject.Key;
-import com.google.inject.Provider;
 import io.kubernetes.client.openapi.ApiClient;
 import io.kubernetes.client.util.Config;
 import org.apache.druid.client.coordinator.Coordinator;
@@ -34,9 +32,7 @@ import org.apache.druid.discovery.DruidNodeDiscoveryProvider;
 import org.apache.druid.guice.JsonConfigProvider;
 import org.apache.druid.guice.LazySingleton;
 import org.apache.druid.guice.PolyBind;
-import org.apache.druid.guice.annotations.Self;
 import org.apache.druid.initialization.DruidModule;
-import org.apache.druid.server.DruidNode;
 
 import java.io.IOException;
 import java.util.Collections;
@@ -88,65 +84,15 @@ public class K8sDiscoveryModule implements DruidModule
     PolyBind.optionBinder(binder, Key.get(DruidLeaderSelector.class, Coordinator.class))
             .addBinding(K8S_KEY)
             .toProvider(
-                new DruidLeaderSelectorProvider(true)
+                K8sDruidLeaderSelectorProvider.K8sCoordinatorDruidLeaderSelectorProvider.class
             )
             .in(LazySingleton.class);
 
     PolyBind.optionBinder(binder, Key.get(DruidLeaderSelector.class, IndexingService.class))
             .addBinding(K8S_KEY)
             .toProvider(
-                new DruidLeaderSelectorProvider(false)
+                K8sDruidLeaderSelectorProvider.K8sIndexingServiceDruidLeaderSelectorProvider.class
             )
             .in(LazySingleton.class);
   }
-
-  private static class DruidLeaderSelectorProvider implements Provider<DruidLeaderSelector>
-  {
-    @Inject
-    @Self
-    private DruidNode druidNode;
-
-    @Inject
-    private PodInfo podInfo;
-
-    @Inject
-    private K8sDiscoveryConfig discoveryConfig;
-
-    @Inject
-    private Provider<ApiClient> k8sApiClientProvider;
-
-    private boolean isCoordinator;
-
-    DruidLeaderSelectorProvider(boolean isCoordinator)
-    {
-      this.isCoordinator = isCoordinator;
-    }
-
-    @Override
-    public DruidLeaderSelector get()
-    {
-      // Note: these can not be setup in the constructor because injected K8sDiscoveryConfig and PodInfo
-      // are not available at that time.
-      String lockResourceName;
-      String lockResourceNamespace;
-
-      if (isCoordinator) {
-        lockResourceName = discoveryConfig.getClusterIdentifier() + "-leaderelection-coordinator";
-        lockResourceNamespace = discoveryConfig.getCoordinatorLeaderElectionConfigMapNamespace() == null ?
-                                     podInfo.getPodNamespace() : discoveryConfig.getCoordinatorLeaderElectionConfigMapNamespace();
-      } else {
-        lockResourceName = discoveryConfig.getClusterIdentifier() + "-leaderelection-overlord";
-        lockResourceNamespace = discoveryConfig.getOverlordLeaderElectionConfigMapNamespace() == null ?
-                                     podInfo.getPodNamespace() : discoveryConfig.getOverlordLeaderElectionConfigMapNamespace();
-      }
-
-      return new K8sDruidLeaderSelector(
-          druidNode,
-          lockResourceName,
-          lockResourceNamespace,
-          discoveryConfig,
-          new DefaultK8sLeaderElectorFactory(k8sApiClientProvider.get(), discoveryConfig)
-      );
-    }
-  }
 }

extensions-core/kubernetes-extensions/src/main/java/org/apache/druid/k8s/discovery/K8sDruidLeaderSelectorProvider.java

@@ -0,0 +1,97 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.druid.k8s.discovery;
+
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+import io.kubernetes.client.openapi.ApiClient;
+import org.apache.druid.discovery.DruidLeaderSelector;
+import org.apache.druid.guice.annotations.Self;
+import org.apache.druid.server.DruidNode;
+
+public abstract class K8sDruidLeaderSelectorProvider implements Provider<DruidLeaderSelector>
+{
+  @Inject
+  @Self
+  private DruidNode druidNode;
+
+  @Inject
+  private PodInfo podInfo;
+
+  @Inject
+  private K8sDiscoveryConfig discoveryConfig;
+
+  @Inject
+  private Provider<ApiClient> k8sApiClientProvider;
+
+  private boolean isCoordinator;
+
+  K8sDruidLeaderSelectorProvider(boolean isCoordinator)
+  {
+    this.isCoordinator = isCoordinator;
+  }
+
+  @Override
+  public DruidLeaderSelector get()
+  {
+    // Note: these can not be setup in the constructor because injected K8sDiscoveryConfig and PodInfo
+    // are not available at that time.
+    String lockResourceName;
+    String lockResourceNamespace;
+
+    if (isCoordinator) {
+      lockResourceName = discoveryConfig.getClusterIdentifier() + "-leaderelection-coordinator";
+      lockResourceNamespace = discoveryConfig.getCoordinatorLeaderElectionConfigMapNamespace() == null
+                              ?
+                              podInfo.getPodNamespace()
+                              : discoveryConfig.getCoordinatorLeaderElectionConfigMapNamespace();
+    } else {
+      lockResourceName = discoveryConfig.getClusterIdentifier() + "-leaderelection-overlord";
+      lockResourceNamespace = discoveryConfig.getOverlordLeaderElectionConfigMapNamespace() == null ?
+                              podInfo.getPodNamespace() : discoveryConfig.getOverlordLeaderElectionConfigMapNamespace();
+    }
+
+    return new K8sDruidLeaderSelector(
+        druidNode,
+        lockResourceName,
+        lockResourceNamespace,
+        discoveryConfig,
+        new DefaultK8sLeaderElectorFactory(k8sApiClientProvider.get(), discoveryConfig)
+    );
+  }
+
+  static class K8sCoordinatorDruidLeaderSelectorProvider extends K8sDruidLeaderSelectorProvider
+  {
+    @Inject
+    public K8sCoordinatorDruidLeaderSelectorProvider()
+    {
+      super(true);
+    }
+  }
+
+  static class K8sIndexingServiceDruidLeaderSelectorProvider extends K8sDruidLeaderSelectorProvider
+  {
+    @Inject
+    public K8sIndexingServiceDruidLeaderSelectorProvider()
+    {
+      super(false);
+    }
+  }
+}