1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache license, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the license for the specific language governing permissions and
15 * limitations under the license.
16 */
17
18 package org.apache.logging.log4j.core.util;
19
20 import org.apache.logging.log4j.Marker;
21 import org.apache.logging.log4j.MarkerManager;
22
23 /**
24 * Registry used for Runnable shutdown callback instances. Due to differing requirements of how late in the JVM
25 * lifecycle Log4j should be shut down, this interface is provided for customizing how to register shutdown hook
26 * callbacks. Implementations may optionally implement {@link org.apache.logging.log4j.core.LifeCycle}.
27 *
28 * @since 2.1
29 */
30 public interface ShutdownCallbackRegistry {
31
32 /**
33 * System property to set to choose the ShutdownCallbackRegistry.
34 */
35 String SHUTDOWN_CALLBACK_REGISTRY = "log4j.shutdownCallbackRegistry";
36
37 /**
38 * System property to set to override the global ability to register shutdown hooks.
39 */
40 String SHUTDOWN_HOOK_ENABLED = "log4j.shutdownHookEnabled";
41
42 /**
43 * Shared Marker to indicate log messages corresponding to shutdown hooks.
44 */
45 Marker SHUTDOWN_HOOK_MARKER = MarkerManager.getMarker("SHUTDOWN HOOK");
46
47 /**
48 * Adds a Runnable shutdown callback to this class.
49 *
50 * @param callback the shutdown callback to be executed upon shutdown.
51 * @return a Cancellable wrapper of the provided callback or {@code null} if the shutdown hook is disabled and
52 * cannot be added.
53 * @since 2.1
54 */
55 Cancellable addShutdownCallback(Runnable callback);
56 }