Polish apache#4807 : [Feature] Add the callback mechanism ShutdownHook …

…apache#4807

dubbo-common/src/main/java/org/apache/dubbo/common/lang/Prioritized.java

@@ -0,0 +1,52 @@
+/*
+ * 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.dubbo.common.lang;
+
+import static java.lang.Integer.compare;
+
+/**
+ * {@code Prioritized} interface can be implemented by objects that
+ * should be sorted, for example the tasks in executable queue.
+ *
+ * @since 2.7.4
+ */
+public interface Prioritized extends Comparable<Prioritized> {
+
+    /**
+     * The maximum priority
+     */
+    int MAX_PRIORITY = Integer.MIN_VALUE;
+
+    /**
+     * The minimum priority
+     */
+    int MIN_PRIORITY = Integer.MAX_VALUE;
+
+    /**
+     * Get the priority
+     *
+     * @return the default is {@link #MIN_PRIORITY minimum one}
+     */
+    default int getPriority() {
+        return MIN_PRIORITY;
+    }
+
+    @Override
+    default int compareTo(Prioritized that) {
+        return compare(this.getPriority(), that.getPriority());
+    }
+}

dubbo-common/src/main/java/org/apache/dubbo/common/lang/ShutdownHookCallback.java

@@ -0,0 +1,32 @@
+/*
+ * 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.dubbo.common.lang;
+
+/**
+ * Dubbo ShutdownHook callback interface
+ *
+ * @since 2.7.4
+ */
+public interface ShutdownHookCallback extends Prioritized {
+
+    /**
+     * Callback execution
+     *
+     * @throws Throwable if met with some errors
+     */
+    void callback() throws Throwable;
+}

dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/DubboShutdownHook.java

@@ -17,6 +17,7 @@
 package org.apache.dubbo.config;
 
 import org.apache.dubbo.common.extension.ExtensionLoader;
+import org.apache.dubbo.common.lang.ShutdownHookCallback;
 import org.apache.dubbo.common.logger.Logger;
 import org.apache.dubbo.common.logger.LoggerFactory;
 import org.apache.dubbo.config.event.DubboServiceDestroyedEvent;
@@ -27,8 +28,14 @@
 import org.apache.dubbo.registry.support.AbstractRegistryFactory;
 import org.apache.dubbo.rpc.Protocol;
 
+import java.util.Collection;
+import java.util.LinkedList;
+import java.util.List;
 import java.util.concurrent.atomic.AtomicBoolean;
 
+import static java.util.Collections.sort;
+import static java.util.ServiceLoader.load;
+
 /**
  * The shutdown hook thread to do the clean up stuff.
  * This is a singleton in order to ensure there is only one shutdown hook registered.
@@ -40,19 +47,29 @@ public class DubboShutdownHook extends Thread {
     private static final Logger logger = LoggerFactory.getLogger(DubboShutdownHook.class);
 
     private static final DubboShutdownHook DUBBO_SHUTDOWN_HOOK = new DubboShutdownHook("DubboShutdownHook");
+
     /**
      * Has it already been registered or not?
      */
     private final AtomicBoolean registered = new AtomicBoolean(false);
+
     /**
      * Has it already been destroyed or not?
      */
     private final AtomicBoolean destroyed = new AtomicBoolean(false);
 
     private final EventDispatcher eventDispatcher = EventDispatcher.getDefaultExtension();
 
+    private final List<ShutdownHookCallback> callbacks = new LinkedList<>();
+
     private DubboShutdownHook(String name) {
         super(name);
+        loadCallbacks();
+    }
+
+    public DubboShutdownHook addCallback(ShutdownHookCallback callback) {
+        this.callbacks.add(callback);
+        return this;
     }
 
     public static DubboShutdownHook getDubboShutdownHook() {
@@ -64,9 +81,41 @@ public void run() {
         if (logger.isInfoEnabled()) {
             logger.info("Run shutdown hook now.");
         }
+        callback();
         doDestroy();
     }
 
+    /**
+     * For testing purpose
+     */
+    Collection<ShutdownHookCallback> getCallbacks() {
+        sort(callbacks);
+        return callbacks;
+    }
+
+    /**
+     * For testing purpose
+     */
+    void clear() {
+        callbacks.clear();
+    }
+
+    private void loadCallbacks() {
+        load(ShutdownHookCallback.class).forEach(callbacks::add);
+    }
+
+    private void callback() {
+        getCallbacks().forEach(callback -> {
+            try {
+                callback.callback();
+            } catch (Throwable e) {
+                if (logger.isErrorEnabled()) {
+                    logger.error(e.getMessage(), e);
+                }
+            }
+        });
+    }
+
     /**
      * Register the ShutdownHook
      */

dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/config/DubboShutdownHookTest.java

@@ -0,0 +1,62 @@
+/*
+ * 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.dubbo.config;
+
+import org.apache.dubbo.common.lang.ShutdownHookCallback;
+import org.apache.dubbo.event.EventDispatcher;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * {@link DubboShutdownHook} Test
+ *
+ * @since 2.7.4
+ */
+public class DubboShutdownHookTest implements ShutdownHookCallback {
+
+    private final DubboShutdownHook dubboShutdownHook = DubboShutdownHook.getDubboShutdownHook();
+
+    private final EventDispatcher eventDispatcher = EventDispatcher.getDefaultExtension();
+
+
+    @BeforeEach
+    public void before() {
+
+    }
+
+    @AfterEach
+    public void after() {
+        eventDispatcher.removeAllEventListeners();
+        dubboShutdownHook.clear();
+    }
+
+    @Test
+    public void testCallback() {
+        assertEquals(this.getClass(), dubboShutdownHook.getCallbacks().iterator().next().getClass());
+        dubboShutdownHook.addCallback(this);
+        assertEquals(2, dubboShutdownHook.getCallbacks().size());
+    }
+
+    @Override
+    public void callback() throws Throwable {
+
+    }
+}

dubbo-config/dubbo-config-api/src/test/resources/META-INF/services/org.apache.dubbo.common.lang.ShutdownHookCallback

@@ -0,0 +1 @@
+org.apache.dubbo.config.DubboShutdownHookTest