feat: add lifecycle hooks to EventSource (#368)

Author: lburgazzoli

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/DefaultEventSourceManager.java

@@ -5,6 +5,7 @@
 import io.javaoperatorsdk.operator.processing.event.internal.TimerEventSource;
 import java.util.Collections;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Optional;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.locks.ReentrantLock;
@@ -37,7 +38,9 @@ public void registerCustomResourceEventSource(
   }
 
   @Override
-  public <T extends EventSource> void registerEventSource(String name, T eventSource) {
+  public void registerEventSource(String name, EventSource eventSource) {
+    Objects.requireNonNull(eventSource, "EventSource must not be null");
+
     try {
       lock.lock();
       EventSource currentEventSource = eventSources.get(name);
@@ -47,6 +50,22 @@ public <T extends EventSource> void registerEventSource(String name, T eventSour
       }
       eventSources.put(name, eventSource);
       eventSource.setEventHandler(defaultEventHandler);
+      eventSource.start();
+    } finally {
+      lock.unlock();
+    }
+  }
+
+  @Override
+  public Optional<EventSource> deRegisterEventSource(String name) {
+    try {
+      lock.lock();
+      EventSource currentEventSource = eventSources.remove(name);
+      if (currentEventSource != null) {
+        currentEventSource.close();
+      }
+
+      return Optional.ofNullable(currentEventSource);
     } finally {
       lock.unlock();
     }

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/EventSource.java

@@ -1,6 +1,19 @@
 package io.javaoperatorsdk.operator.processing.event;
 
-public interface EventSource {
+public interface EventSource extends AutoCloseable {
+
+  /**
+   * This method is invoked when this {@link EventSource} instance is properly registered to a
+   * {@link EventSourceManager}.
+   */
+  default void start() {}
+
+  /**
+   * This method is invoked when this {@link EventSource} instance is de-registered from a {@link
+   * EventSourceManager}.
+   */
+  @Override
+  default void close() {}
 
   void setEventHandler(EventHandler eventHandler);
 

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/EventSourceManager.java

@@ -5,7 +5,25 @@
 
 public interface EventSourceManager {
 
-  <T extends EventSource> void registerEventSource(String name, T eventSource);
+  /**
+   * Add the {@link EventSource} identified by the given <code>name</code> to the event manager.
+   *
+   * @param name the name of the {@link EventSource} to add
+   * @param eventSource the {@link EventSource} to register
+   * @thorw IllegalStateException if an {@link EventSource} with the same name is already
+   *     registered.
+   */
+  void registerEventSource(String name, EventSource eventSource);
+
+  /**
+   * Remove the {@link EventSource} identified by the given <code>name</code> from the event
+   * manager.
+   *
+   * @param name the name of the {@link EventSource} to remove
+   * @return an optional {@link EventSource} which would be empty if no {@link EventSource} have
+   *     been registered with the given name.
+   */
+  Optional<EventSource> deRegisterEventSource(String name);
 
   Optional<EventSource> deRegisterCustomResourceFromEventSource(
       String name, String customResourceUid);