org.apache.flink.runtime.leaderelection.LeaderElectionDriver Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
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* 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,
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*/
package org.apache.flink.runtime.leaderelection;
/**
* A {@link LeaderElectionDriver} is responsible for performing the leader election and storing the
* leader information. All the leader internal state is guarded by lock in {@link
* LeaderElectionService}. Different driver implementations do not need to care about the lock. And
* it should use {@link LeaderElectionEventHandler} if it want to respond to the leader change
* events.
*
* Important: The {@link LeaderElectionDriver} could not guarantee that there is
* no {@link LeaderElectionEventHandler} callbacks happen after {@link #close()}.
*/
public interface LeaderElectionDriver {
/**
* Write the current leader information to external persistent storage(e.g. Zookeeper,
* Kubernetes ConfigMap). This is a blocking IO operation. The write operation takes effect only
* when the driver still has the leadership.
*
* @param leaderInformation current leader information. It could be {@link
* LeaderInformation#empty()}, which means the caller want to clear the leader information
* on external storage. Please remember that the clear operation should only happen before a
* new leader is elected and has written his leader information on the storage. Otherwise,
* we may have a risk to wrongly update the storage with empty leader information.
*/
void writeLeaderInformation(LeaderInformation leaderInformation);
/**
* Check whether the driver still have the leadership in the distributed coordination system.
*
* @return Return whether the driver has leadership.
*/
boolean hasLeadership();
/** Close the services used for leader election. */
void close() throws Exception;
}