refactor: avoid unneeded initializations in injection contexts (#2950)

* refactor: avoid unneeded initializations in injection contexts

Signed-off-by: Chris Laprun <claprun@redhat.com>

* docs: added javadoc and tests

Signed-off-by: Chris Laprun <claprun@redhat.com>

---------

Signed-off-by: Chris Laprun <claprun@redhat.com>

Author: metacosm

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

@@ -24,17 +24,17 @@
 public class Operator implements LifecycleAware {
   private static final Logger log = LoggerFactory.getLogger(Operator.class);
 
-  private final ControllerManager controllerManager;
-  private final LeaderElectionManager leaderElectionManager;
-  private final ConfigurationService configurationService;
+  private ControllerManager controllerManager;
+  private LeaderElectionManager leaderElectionManager;
+  private ConfigurationService configurationService;
   private volatile boolean started = false;
 
   public Operator() {
-    this((KubernetesClient) null);
+    init(initConfigurationService(null, null), true);
   }
 
   Operator(KubernetesClient kubernetesClient) {
-    this(initConfigurationService(kubernetesClient, null));
+    init(initConfigurationService(kubernetesClient, null), false);
   }
 
   /**
@@ -46,12 +46,7 @@ public Operator() {
    *     operator
    */
   public Operator(ConfigurationService configurationService) {
-    this.configurationService = configurationService;
-
-    final var executorServiceManager = configurationService.getExecutorServiceManager();
-    controllerManager = new ControllerManager(executorServiceManager);
-
-    leaderElectionManager = new LeaderElectionManager(controllerManager, configurationService);
+    init(configurationService, false);
   }
 
   /**
@@ -62,10 +57,55 @@ public Operator(ConfigurationService configurationService) {
    *     {@link ConfigurationService} values
    */
   public Operator(Consumer<ConfigurationServiceOverrider> overrider) {
-    this(initConfigurationService(null, overrider));
+    init(initConfigurationService(null, overrider), false);
+  }
+
+  /**
+   * In a deferred initialization scenario, the default constructor will typically be called to
+   * create a proxy instance, usually to be replaced at some later time when the dependents (in this
+   * case the ConfigurationService instance) are available. In this situation, we want to make it
+   * possible to not perform the initialization steps directly so this implementation makes it
+   * possible to not crash when a null ConfigurationService is passed only if deferred
+   * initialization is allowed
+   *
+   * @param configurationService the potentially {@code null} {@link ConfigurationService} to use
+   *     for this operator
+   * @param allowDeferredInit whether or not deferred initialization of the configuration service is
+   *     allowed
+   * @throws IllegalStateException if the specified configuration service is {@code null} but
+   *     deferred initialization is not allowed
+   */
+  private void init(ConfigurationService configurationService, boolean allowDeferredInit) {
+    if (configurationService == null) {
+      if (!allowDeferredInit) {
+        throw new IllegalStateException(
+            "Deferred initialization of ConfigurationService is not allowed");
+      }
+    } else {
+      this.configurationService = configurationService;
+
+      final var executorServiceManager = configurationService.getExecutorServiceManager();
+      controllerManager = new ControllerManager(executorServiceManager);
+
+      leaderElectionManager = new LeaderElectionManager(controllerManager, configurationService);
+    }
   }
 
-  private static ConfigurationService initConfigurationService(
+  /**
+   * Overridable by subclasses to enable deferred configuration, useful to avoid unneeded processing
+   * in injection scenarios, typically returning {@code null} here instead of performing any
+   * configuration
+   *
+   * @param client a potentially {@code null} {@link KubernetesClient} to initialize the operator's
+   *     {@link ConfigurationService} with
+   * @param overrider a potentially {@code null} {@link ConfigurationServiceOverrider} consumer to
+   *     override the default {@link ConfigurationService} with
+   * @return a ready to use {@link ConfigurationService} using values provided by the specified
+   *     overrides and kubernetes client, if provided or {@code null} in case deferred
+   *     initialization is possible, in which case it is up to the extension to ensure that the
+   *     {@link ConfigurationService} is properly set before the operator instance is used
+   */
+  protected ConfigurationService initConfigurationService(
       KubernetesClient client, Consumer<ConfigurationServiceOverrider> overrider) {
     // initialize the client if the user didn't provide one
     if (client == null) {
@@ -232,8 +272,8 @@ public <P extends HasMetadata> RegisteredController<P> register(
    *
    * @param reconciler part of the reconciler to register
    * @param configOverrider consumer to use to change config values
-   * @return registered controller
    * @param <P> the {@code HasMetadata} type associated with the reconciler
+   * @return registered controller
    */
   public <P extends HasMetadata> RegisteredController<P> register(
       Reconciler<P> reconciler, Consumer<ControllerConfigurationOverrider<P>> configOverrider) {
@@ -266,4 +306,14 @@ boolean isStarted() {
   public ConfigurationService getConfigurationService() {
     return configurationService;
   }
+
+  /**
+   * Make it possible for extensions to set the {@link ConfigurationService} after the operator has
+   * been initialized
+   *
+   * @param configurationService the {@link ConfigurationService} to use for this operator
+   */
+  protected void setConfigurationService(ConfigurationService configurationService) {
+    init(configurationService, false);
+  }
 }

operator-framework-core/src/test/java/io/javaoperatorsdk/operator/OperatorTest.java

@@ -1,31 +1,24 @@
 package io.javaoperatorsdk.operator;
 
-import org.junit.jupiter.api.BeforeEach;
+import java.util.function.Consumer;
+
 import org.junit.jupiter.api.Test;
 
 import io.fabric8.kubernetes.api.model.ConfigMap;
 import io.fabric8.kubernetes.client.KubernetesClient;
+import io.javaoperatorsdk.operator.api.config.ConfigurationService;
+import io.javaoperatorsdk.operator.api.config.ConfigurationServiceOverrider;
 import io.javaoperatorsdk.operator.api.reconciler.Context;
-import io.javaoperatorsdk.operator.api.reconciler.ControllerConfiguration;
 import io.javaoperatorsdk.operator.api.reconciler.Reconciler;
 import io.javaoperatorsdk.operator.api.reconciler.UpdateControl;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.*;
 
 @SuppressWarnings("rawtypes")
 class OperatorTest {
-
-  private final KubernetesClient kubernetesClient = MockKubernetesClient.client(ConfigMap.class);
-  private Operator operator;
-
-  @BeforeEach
-  void initOperator() {
-    operator = new Operator(kubernetesClient);
-  }
-
   @Test
   void shouldBePossibleToRetrieveNumberOfRegisteredControllers() {
+    final var operator = new Operator();
     assertEquals(0, operator.getRegisteredControllersNumber());
 
     operator.register(new FooReconciler());
@@ -34,6 +27,7 @@ void shouldBePossibleToRetrieveNumberOfRegisteredControllers() {
 
   @Test
   void shouldBePossibleToRetrieveRegisteredControllerByName() {
+    final var operator = new Operator();
     final var reconciler = new FooReconciler();
     final var name = ReconcilerUtils.getNameFor(reconciler);
 
@@ -51,12 +45,42 @@ void shouldBePossibleToRetrieveRegisteredControllerByName() {
     assertEquals(maybeController.get(), registeredControllers.stream().findFirst().orElseThrow());
   }
 
-  @ControllerConfiguration
-  private static class FooReconciler implements Reconciler<ConfigMap> {
+  @Test
+  void shouldThrowExceptionIf() {
+    final var operator = new OperatorExtension();
+    assertNotNull(operator);
+    operator.setConfigurationService(ConfigurationService.newOverriddenConfigurationService(null));
+    assertNotNull(operator.getConfigurationService());
+
+    // should fail because the implementation is not providing a valid configuration service when
+    // constructing the operator
+    assertThrows(
+        IllegalStateException.class,
+        () -> new OperatorExtension(MockKubernetesClient.client(ConfigMap.class)));
+  }
 
+  private static class FooReconciler implements Reconciler<ConfigMap> {
     @Override
     public UpdateControl<ConfigMap> reconcile(ConfigMap resource, Context context) {
       return UpdateControl.noUpdate();
     }
   }
+
+  private static class OperatorExtension extends Operator {
+    public OperatorExtension() {}
+
+    public OperatorExtension(KubernetesClient client) {
+      super(client);
+    }
+
+    /**
+     * Overridden to mimic deferred initialization (or rather the fact that we don't want to do that
+     * processing at this time so return null).
+     */
+    @Override
+    protected ConfigurationService initConfigurationService(
+        KubernetesClient client, Consumer<ConfigurationServiceOverrider> overrider) {
+      return null;
+    }
+  }
 }