org.opendaylight.controller.cluster.raft.policy.RaftPolicy Maven / Gradle / Ivy
/*
* Copyright (c) 2015 Cisco Systems, Inc. and others. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 which accompanies this distribution,
* and is available at http://www.eclipse.org/legal/epl-v10.html
*/
package org.opendaylight.controller.cluster.raft.policy;
/**
* The RaftPolicy is intended to change the default behavior of Raft. For example
* we may want to be able to determine which Raft replica should become the leader - with Raft elections are
* randomized so it is not possible to specify which replica should be the leader. The ability to specify
* the leader would be quite useful when testing a raft cluster.
*
*
* Similarly we may want to customize when exactly we apply a modification to the state - with Raft a modification
* is only applied to the state when the modification is replicated to a majority of the replicas. The ability to
* apply a modification to the state before consensus would be useful in scenarios where you have only 2 nodes
* in a Raft cluster and one of them is down but you still want the RaftActor to apply a modification to the state.
*/
public interface RaftPolicy {
/**
* According to Raft a Follower which does not receive a heartbeat (aka AppendEntries) in a given period should
* become a Candidate and trigger an election.
*
* @return true to enable automatic Raft elections, false to disable them
*/
boolean automaticElectionsEnabled();
/**
* According to Raft consensus on a Raft entry is achieved only after a Leader replicates a log entry to a
* majority of it's followers.
*
* @return true if modification should be applied before consensus, false to apply modification to state
* as per Raft
*/
boolean applyModificationToStateBeforeConsensus();
}