/*
 * 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.logging.log4j.core.util;

import org.apache.logging.log4j.Marker;
import org.apache.logging.log4j.MarkerManager;

Registry used for Runnable shutdown callback instances. Due to differing requirements of how late in the JVM lifecycle Log4j should be shut down, this interface is provided for customizing how to register shutdown hook callbacks. Implementations may optionally implement LifeCycle. 
Since:
2.1/**
 * Registry used for Runnable shutdown callback instances. Due to differing requirements of how late in the JVM
 * lifecycle Log4j should be shut down, this interface is provided for customizing how to register shutdown hook
 * callbacks. Implementations may optionally implement {@link org.apache.logging.log4j.core.LifeCycle}.
 *
 * @since 2.1
 */
public interface ShutdownCallbackRegistry {

    
System property to set to choose the ShutdownCallbackRegistry.
/**
     * System property to set to choose the ShutdownCallbackRegistry.
     */
    String SHUTDOWN_CALLBACK_REGISTRY = "log4j.shutdownCallbackRegistry";

    
System property to set to override the global ability to register shutdown hooks.
/**
     * System property to set to override the global ability to register shutdown hooks.
     */
    String SHUTDOWN_HOOK_ENABLED = "log4j.shutdownHookEnabled";

    
Shared Marker to indicate log messages corresponding to shutdown hooks.
/**
     * Shared Marker to indicate log messages corresponding to shutdown hooks.
     */
    Marker SHUTDOWN_HOOK_MARKER = MarkerManager.getMarker("SHUTDOWN HOOK");

    
Adds a Runnable shutdown callback to this class.
Params:
callback – the shutdown callback to be executed upon shutdown.
Returns:
a Cancellable wrapper of the provided callback or null if the shutdown hook is disabled and cannot be added.
Since:
2.1/**
     * Adds a Runnable shutdown callback to this class.
     *
     * @param callback the shutdown callback to be executed upon shutdown.
     * @return a Cancellable wrapper of the provided callback or {@code null} if the shutdown hook is disabled and
     * cannot be added.
     * @since 2.1
     */
    Cancellable addShutdownCallback(Runnable callback);
}