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/**
* 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.hive.service;
import java.util.ArrayList;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hive.conf.HiveConf;
/**
* AbstractService.
*
*/
public abstract class AbstractService implements Service {
private static final Log LOG = LogFactory.getLog(AbstractService.class);
/**
* Service state: initially {@link STATE#NOTINITED}.
*/
private STATE state = STATE.NOTINITED;
/**
* Service name.
*/
private final String name;
/**
* Service start time. Will be zero until the service is started.
*/
private long startTime;
/**
* The configuration. Will be null until the service is initialized.
*/
private HiveConf hiveConf;
/**
* List of state change listeners; it is final to ensure
* that it will never be null.
*/
private final List<ServiceStateChangeListener> listeners =
new ArrayList<ServiceStateChangeListener>();
/**
* Construct the service.
*
* @param name
* service name
*/
public AbstractService(String name) {
this.name = name;
}
@Override
public synchronized STATE getServiceState() {
return state;
}
/**
* {@inheritDoc}
*
* @throws IllegalStateException
* if the current service state does not permit
* this action
*/
@Override
public synchronized void init(HiveConf hiveConf) {
ensureCurrentState(STATE.NOTINITED);
this.hiveConf = hiveConf;
changeState(STATE.INITED);
LOG.info("Service:" + getName() + " is inited.");
}
/**
* {@inheritDoc}
*
* @throws IllegalStateException
* if the current service state does not permit
* this action
*/
@Override
public synchronized void start() {
startTime = System.currentTimeMillis();
ensureCurrentState(STATE.INITED);
changeState(STATE.STARTED);
LOG.info("Service:" + getName() + " is started.");
}
/**
* {@inheritDoc}
*
* @throws IllegalStateException
* if the current service state does not permit
* this action
*/
@Override
public synchronized void stop() {
if (state == STATE.STOPPED ||
state == STATE.INITED ||
state == STATE.NOTINITED) {
// already stopped, or else it was never
// started (eg another service failing canceled startup)
return;
}
ensureCurrentState(STATE.STARTED);
changeState(STATE.STOPPED);
LOG.info("Service:" + getName() + " is stopped.");
}
@Override
public synchronized void register(ServiceStateChangeListener l) {
listeners.add(l);
}
@Override
public synchronized void unregister(ServiceStateChangeListener l) {
listeners.remove(l);
}
@Override
public String getName() {
return name;
}
@Override
public synchronized HiveConf getHiveConf() {
return hiveConf;
}
@Override
public long getStartTime() {
return startTime;
}
/**
* Verify that that a service is in a given state.
*
* @param currentState
* the desired state
* @throws IllegalStateException
* if the service state is different from
* the desired state
*/
private void ensureCurrentState(STATE currentState) {
ServiceOperations.ensureCurrentState(state, currentState);
}
/**
* Change to a new state and notify all listeners.
* This is a private method that is only invoked from synchronized methods,
* which avoid having to clone the listener list. It does imply that
* the state change listener methods should be short lived, as they
* will delay the state transition.
*
* @param newState
* new service state
*/
private void changeState(STATE newState) {
state = newState;
// notify listeners
for (ServiceStateChangeListener l : listeners) {
l.stateChanged(this);
}
}
}
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