org.apache.flink.runtime.leaderelection.LeaderElectionEventHandler 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.flink.runtime.leaderelection;
/**
* Interface which should be implemented to respond to leader changes in {@link
* LeaderElectionDriver}.
*
* Important: The {@link LeaderElectionDriver} could not guarantee that there is
* no {@link LeaderElectionEventHandler} callbacks happen after {@link
* LeaderElectionDriver#close()}. This means that the implementor of {@link
* LeaderElectionEventHandler} is responsible for filtering out spurious callbacks(e.g. after close
* has been called on {@link LeaderElectionDriver}).
*/
public interface LeaderElectionEventHandler {
/** Called by specific {@link LeaderElectionDriver} when the leadership is granted. */
void onGrantLeadership();
/** Called by specific {@link LeaderElectionDriver} when the leadership is revoked. */
void onRevokeLeadership();
/**
* Called by specific {@link LeaderElectionDriver} when the leader information is changed. Then
* the {@link LeaderElectionService} could write the leader information again if necessary. This
* method should only be called when {@link LeaderElectionDriver#hasLeadership()} is true.
* Duplicated leader change events could happen, so the implementation should check whether the
* passed leader information is really different with internal confirmed leader information.
*
* @param leaderInformation leader information which contains leader session id and leader
* address.
*/
void onLeaderInformationChange(LeaderInformation leaderInformation);
}