org.apache.hadoop.service.CompositeService Maven / Gradle / Ivy
/**
* 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.hadoop.service;
import java.util.ArrayList;
import java.util.List;
import org.apache.hadoop.classification.InterfaceAudience.Public;
import org.apache.hadoop.classification.InterfaceStability.Evolving;
import org.apache.hadoop.conf.Configuration;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Composition of services.
*/
@Public
@Evolving
public class CompositeService extends AbstractService {
private static final Logger LOG =
LoggerFactory.getLogger(CompositeService.class);
/**
* Policy on shutdown: attempt to close everything (purest) or
* only try to close started services (which assumes
* that the service implementations may not handle the stop() operation
* except when started.
* Irrespective of this policy, if a child service fails during
* its init() or start() operations, it will have stop() called on it.
*/
protected static final boolean STOP_ONLY_STARTED_SERVICES = false;
private final List serviceList = new ArrayList();
public CompositeService(String name) {
super(name);
}
/**
* Get a cloned list of services
* @return a list of child services at the time of invocation -
* added services will not be picked up.
*/
public List getServices() {
synchronized (serviceList) {
return new ArrayList(serviceList);
}
}
/**
* Add the passed {@link Service} to the list of services managed by this
* {@link CompositeService}
* @param service the {@link Service} to be added
*/
protected void addService(Service service) {
if (LOG.isDebugEnabled()) {
LOG.debug("Adding service " + service.getName());
}
synchronized (serviceList) {
serviceList.add(service);
}
}
/**
* If the passed object is an instance of {@link Service},
* add it to the list of services managed by this {@link CompositeService}
* @param object
* @return true if a service is added, false otherwise.
*/
protected boolean addIfService(Object object) {
if (object instanceof Service) {
addService((Service) object);
return true;
} else {
return false;
}
}
protected boolean removeService(Service service) {
LOG.debug("Removing service {}", service.getName());
synchronized (serviceList) {
return serviceList.remove(service);
}
}
protected void serviceInit(Configuration conf) throws Exception {
List services = getServices();
if (LOG.isDebugEnabled()) {
LOG.debug(getName() + ": initing services, size=" + services.size());
}
for (Service service : services) {
service.init(conf);
}
super.serviceInit(conf);
}
protected void serviceStart() throws Exception {
List services = getServices();
if (LOG.isDebugEnabled()) {
LOG.debug(getName() + ": starting services, size=" + services.size());
}
for (Service service : services) {
// start the service. If this fails that service
// will be stopped and an exception raised
service.start();
}
super.serviceStart();
}
protected void serviceStop() throws Exception {
//stop all services that were started
int numOfServicesToStop = serviceList.size();
if (LOG.isDebugEnabled()) {
LOG.debug(getName() + ": stopping services, size=" + numOfServicesToStop);
}
stop(numOfServicesToStop, STOP_ONLY_STARTED_SERVICES);
super.serviceStop();
}
/**
* Stop the services in reverse order
*
* @param numOfServicesStarted index from where the stop should work
* @param stopOnlyStartedServices flag to say "only start services that are
* started, not those that are NOTINITED or INITED.
* @throws RuntimeException the first exception raised during the
* stop process -after all services are stopped
*/
private void stop(int numOfServicesStarted, boolean stopOnlyStartedServices) {
// stop in reverse order of start
Exception firstException = null;
List services = getServices();
for (int i = numOfServicesStarted - 1; i >= 0; i--) {
Service service = services.get(i);
if (LOG.isDebugEnabled()) {
LOG.debug("Stopping service #" + i + ": " + service);
}
STATE state = service.getServiceState();
//depending on the stop police
if (state == STATE.STARTED
|| (!stopOnlyStartedServices && state == STATE.INITED)) {
Exception ex = ServiceOperations.stopQuietly(LOG, service);
if (ex != null && firstException == null) {
firstException = ex;
}
}
}
//after stopping all services, rethrow the first exception raised
if (firstException != null) {
throw ServiceStateException.convert(firstException);
}
}
/**
* JVM Shutdown hook for CompositeService which will stop the give
* CompositeService gracefully in case of JVM shutdown.
*/
public static class CompositeServiceShutdownHook implements Runnable {
private CompositeService compositeService;
public CompositeServiceShutdownHook(CompositeService compositeService) {
this.compositeService = compositeService;
}
@Override
public void run() {
ServiceOperations.stopQuietly(compositeService);
}
}
}