/* * Copyright (c) 2014 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; import akka.persistence.UntypedEventsourcedProcessor; import org.opendaylight.controller.cluster.raft.behaviors.Candidate; import org.opendaylight.controller.cluster.raft.behaviors.Follower; import org.opendaylight.controller.cluster.raft.behaviors.Leader; import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior; import java.util.Collections; import java.util.concurrent.atomic.AtomicLong; /** * RaftActor encapsulates a state machine that needs to be kept synchronized * in a cluster. It implements the RAFT algorithm as described in the paper * * In Search of an Understandable Consensus Algorithm *
* RaftActor has 3 states and each state has a certain behavior associated * with it. A Raft actor can behave as, *
* A RaftActor MUST be a Leader in order to accept requests from clients to * change the state of it's encapsulated state machine. Once a RaftActor becomes * a Leader it is also responsible for ensuring that all followers ultimately * have the same log and therefore the same state machine as itself. * *
* The current behavior of a RaftActor determines how election for leadership * is initiated and how peer RaftActors react to request for votes. * *
* Each RaftActor also needs to know the current election term. It uses this * information for a couple of things. One is to simply figure out who it * voted for in the last election. Another is to figure out if the message * it received to update it's state is stale. * *
* The RaftActor uses akka-persistence to store it's replicated log. * Furthermore through it's behaviors a Raft Actor determines * *