/**
* 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 org.apache.hadoop.classification.InterfaceAudience.Public;
import org.apache.hadoop.classification.InterfaceStability.Stable;
/**
* Interface to notify state changes of a service.
*/
@Public
@Stable
public interface ServiceStateChangeListener {
/**
* Callback to notify of a state change. The service will already
* have changed state before this callback is invoked.
*
* This operation is invoked on the thread that initiated the state change,
* while the service itself in in a sychronized section.
* <ol>
* <li>Any long-lived operation here will prevent the service state
* change from completing in a timely manner.</li>
* <li>If another thread is somehow invoked from the listener, and
* that thread invokes the methods of the service (including
* subclass-specific methods), there is a risk of a deadlock.</li>
* </ol>
*
*
* @param service the service that has changed.
*/
void stateChanged(Service service);
}