org.apache.pulsar.metadata.api.coordination.LeaderElection Maven / Gradle / Ivy
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* 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
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* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.pulsar.metadata.api.coordination;
import java.util.Optional;
import java.util.concurrent.CompletableFuture;
/**
* Leader election controller.
*/
public interface LeaderElection extends AutoCloseable {
/**
* Try to become the leader.
*
* Warning: because of the distributed nature of the leader election, having been promoted to "leader" status will
* never provide a strong guarantee that no one else also thinks it's the leader. The caller will have to deal with
* these race conditions when using the resource itself (eg. using compareAndSet() or fencing mechanisms).
*
* @param proposedValue
* the value to set for the leader, in the case this instance succeeds in becoming leader
* @return a future that will track the completion of the operation
* if there's a failure in the leader election
*/
CompletableFuture elect(T proposedValue);
/**
* Get the current leader election state.
*/
LeaderElectionState getState();
/**
* Get the value set by the elected leader, or empty if there's currently no leader.
*
* @return a future that will track the completion of the operation
*/
CompletableFuture> getLeaderValue();
/**
* Get the value set by the elected leader, or empty if there's currently no leader.
*
* The call is non blocking and in certain cases can return Optional.empty() even though a leader is
* technically elected.
*
* @return a future that will track the completion of the operation
*/
Optional getLeaderValueIfPresent();
/**
* Close the leader election controller and release the leadership (if it was acquired).
*
* @return a future that will track the completion of the operation
*/
CompletableFuture asyncClose();
}