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/*
* ============LICENSE_START=======================================================
* feature-server-pool
* ================================================================================
* Copyright (C) 2020 AT&T Intellectual Property. All rights reserved.
* ================================================================================
* Licensed 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.
* ============LICENSE_END=========================================================
*/
package org.onap.policy.drools.serverpool;
import java.util.Collection;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
/**
* This interface is used to distribute notifications of various system
* events, such as new 'Server' instances, or a server failing.
*/
public class Events {
// set of listeners receiving event notifications
private static final Queue<Events> listeners =
new ConcurrentLinkedQueue<>();
/**
* add a listener to the set of listeners receiving events.
*
* @param handler the listener
*/
public static void register(Events handler) {
// if it is already here, remove it first
listeners.remove(handler);
// add to the end of the queue
listeners.add(handler);
}
/**
* remove a listener from the set of listeners.
*/
public static boolean unregister(Events handler) {
return listeners.remove(handler);
}
public static Collection<Events> getListeners() {
return listeners;
}
/* ============================================================ */
/**
* Notification that a new server has been discovered.
*
* @param server this is the new server
*/
public void newServer(Server server) {
// do nothing
}
/**
* Notification that a server has failed.
*
* @param server this is the server that failed
*/
public void serverFailed(Server server) {
// do nothing
}
/**
* Notification that a new lead server has been selected.
*
* @param server this is the new lead server
*/
public void newLeader(Server server) {
// do nothing
}
/**
* Notification that the lead server has gone down.
*
* @param server the lead server that failed
*/
public void leaderFailed(Server server) {
// do nothing
}
/**
* Notification that a new selection just completed, but the same
* leader has been chosen (this may be in response to a new server
* joining earlier).
*
* @param server the current leader, which has been confirmed
*/
public void leaderConfirmed(Server server) {
// do nothing
}
}
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