/*
* Copyright 2014-2016 the original author or authors.
*
* 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.
*/
package org.springframework.integration.leader;
/**
* Interface that defines the contract for candidates to participate
* in a leader election. The callback methods {@link #onGranted(Context)}
* and {@link #onRevoked(Context)} are invoked when leadership is
* granted and revoked.
*
* @author Patrick Peralta
* @author Janne Valkealahti
*
*/
public interface Candidate {
/**
* Gets the role.
*
* @return a string indicating the name of the leadership role
* this candidate is participating in; other candidates
* present in the system with the same name will contend
* for leadership
*/
String getRole();
/**
* Gets the identifier.
*
* @return a unique ID for this candidate; no other candidate for
* leader election should return the same id
*/
String getId();
/**
* Callback method invoked when this candidate is elected leader.
* Implementations may chose to launch a background thread to
* perform leadership roles and return immediately. Another option
* is for implementations to perform all leadership work in the
* thread invoking this method. In the latter case, the
* method <em>must</em> respond to thread interrupts by throwing
* {@link java.lang.InterruptedException}. When the thread
* is interrupted, this indicates that this candidate is no
* longer leader.
*
* @param ctx leadership context
* @throws InterruptedException when this candidate is no longer leader
*/
void onGranted(Context ctx) throws InterruptedException;
/**
* Callback method invoked when this candidate is no longer leader.
* Implementations should use this to shut down any resources
* (threads, network connections, etc) used to perform leadership work.
*
* @param ctx leadership context
*/
void onRevoked(Context ctx);
}