org.apache.flink.runtime.leaderelection.StandaloneLeaderElectionService 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;
import org.apache.flink.runtime.highavailability.HighAvailabilityServices;
import org.apache.flink.util.Preconditions;
import javax.annotation.Nonnull;
import java.util.UUID;
/**
* Standalone implementation of the {@link LeaderElectionService} interface. The standalone
* implementation assumes that there is only a single {@link LeaderContender} and thus directly
* grants him the leadership upon start up. Furthermore, there is no communication needed between
* multiple standalone leader election services.
*/
public class StandaloneLeaderElectionService implements LeaderElectionService {
private LeaderContender contender = null;
@Override
public void start(LeaderContender newContender) throws Exception {
if (contender != null) {
// Service was already started
throw new IllegalArgumentException(
"Leader election service cannot be started multiple times.");
}
contender = Preconditions.checkNotNull(newContender);
// directly grant leadership to the given contender
contender.grantLeadership(HighAvailabilityServices.DEFAULT_LEADER_ID);
}
@Override
public void stop() {
if (contender != null) {
contender.revokeLeadership();
contender = null;
}
}
@Override
public void confirmLeadership(UUID leaderSessionID, String leaderAddress) {}
@Override
public boolean hasLeadership(@Nonnull UUID leaderSessionId) {
return (contender != null
&& HighAvailabilityServices.DEFAULT_LEADER_ID.equals(leaderSessionId));
}
}