org.graylog2.system.shutdown.GracefulShutdownHook Maven / Gradle / Ivy
/*
* Copyright (C) 2020 Graylog, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* .
*/
package org.graylog2.system.shutdown;
/**
* Services can implement this to participate in a graceful shutdown of the server.
*
* A service can register itself with the {@link GracefulShutdownService} like this:
*
*
{@code
* class MyService implements GracefulShutdownHook {
* private final GracefulShutdownService shutdownService;
*
* @Inject
* public MyService(GracefulShutdownService shutdownService) {
* this.shutdownService = shutdownService;
* }
*
* // This will be executed by the GracefulShutdownService on server shutdown
* @Override
* void doGracefulShutdown() throws Exception {
* runShutdownTasks();
* }
*
* public void start() {
* // Let the GracefulShutdownService know about this service
* this.shutdownService.register(this);
* }
*
* // This will be executed by some service manager when this service is stopped
* public void stop() {
* // Remove this service from the GracefulShutdownService because it's stopped before server shutdown and
* // we don't need any graceful shutdown for it anymore
* this.shutdownService.unregister(this);
* runShutdownTasks();
* }
*
* private void runShutdownTasks() {
* // Run the actual shutdown tasks for the service here
* }
* }
* }
*/
public interface GracefulShutdownHook {
/**
* Execute shutdown tasks for the service that implements this interface.
* Warning:
*
* - This method is called from another thread so the class that implements {@link GracefulShutdownHook} must be thread-safe.
* - The server shutdown is waiting for this method call to complete. Blocking this method will block the server
* shutdown!
*
*
* @throws Exception
*/
void doGracefulShutdown() throws Exception;
}