/*
* 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.slider.core.main;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.service.Service;
import org.apache.hadoop.util.ShutdownHookManager;
import java.lang.ref.WeakReference;
/**
* JVM Shutdown hook for Service which will stop the
* Service gracefully in case of JVM shutdown.
* This hook uses a weak reference to the service, so
* does not cause services to be retained after they have
* been stopped and deferenced elsewhere.
*/
public class ServiceShutdownHook implements Runnable {
private static final Log LOG = LogFactory.getLog(ServiceShutdownHook.class);
private WeakReference<Service> serviceRef;
private Runnable hook;
public ServiceShutdownHook(Service service) {
serviceRef = new WeakReference<>(service);
}
public void register(int priority) {
unregister();
hook = this;
ShutdownHookManager.get().addShutdownHook(hook, priority);
}
public void unregister() {
if (hook != null) {
try {
ShutdownHookManager.get().removeShutdownHook(hook);
} catch (IllegalStateException e) {
LOG.info("Failed to unregister shutdown hook",e);
}
hook = null;
}
}
// @Override
public void run() {
Service service = serviceRef.get();
if (service == null) {
return;
}
try {
// Stop the Service
service.stop();
} catch (Throwable t) {
LOG.info("Error stopping " + service.getName(), t);
}
}
}