/*
* 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.behaviors;
import akka.actor.ActorRef;
import akka.actor.ActorSelection;
import java.util.Set;
import org.opendaylight.controller.cluster.raft.RaftActorContext;
import org.opendaylight.controller.cluster.raft.RaftState;
import org.opendaylight.controller.cluster.raft.base.messages.ElectionTimeout;
import org.opendaylight.controller.cluster.raft.messages.AppendEntries;
import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
import org.opendaylight.controller.cluster.raft.messages.RaftRPC;
import org.opendaylight.controller.cluster.raft.messages.RequestVote;
import org.opendaylight.controller.cluster.raft.messages.RequestVoteReply;
/**
* The behavior of a RaftActor when it is in the CandidateState
*
* Candidates (§5.2):
*
* - On conversion to candidate, start election:
*
* - Increment currentTerm
*
- Vote for self
*
- Reset election timer
*
- Send RequestVote RPCs to all other servers
*
* - If votes received from majority of servers: become leader
*
- If AppendEntries RPC received from new leader: convert to
* follower
*
- If election timeout elapses: start new election
*
*/
public class Candidate extends AbstractRaftActorBehavior {
private int voteCount;
private final int votesRequired;
private final Set peers;
public Candidate(RaftActorContext context) {
super(context);
peers = context.getPeerAddresses().keySet();
if(LOG.isDebugEnabled()) {
LOG.debug("{}: Election: Candidate has following peers: {}", context.getId(), peers);
}
votesRequired = getMajorityVoteCount(peers.size());
startNewTerm();
scheduleElection(electionDuration());
}
@Override protected RaftActorBehavior handleAppendEntries(ActorRef sender,
AppendEntries appendEntries) {
if(LOG.isDebugEnabled()) {
LOG.debug("{}: handleAppendEntries: {}", context.getId(), appendEntries);
}
return this;
}
@Override protected RaftActorBehavior handleAppendEntriesReply(ActorRef sender,
AppendEntriesReply appendEntriesReply) {
return this;
}
@Override protected RaftActorBehavior handleRequestVoteReply(ActorRef sender,
RequestVoteReply requestVoteReply) {
if (requestVoteReply.isVoteGranted()) {
voteCount++;
}
if (voteCount >= votesRequired) {
return switchBehavior(new Leader(context));
}
return this;
}
@Override public RaftState state() {
return RaftState.Candidate;
}
@Override
public RaftActorBehavior handleMessage(ActorRef sender, Object originalMessage) {
Object message = fromSerializableMessage(originalMessage);
if (message instanceof RaftRPC) {
RaftRPC rpc = (RaftRPC) message;
if(LOG.isDebugEnabled()) {
LOG.debug("{}: RaftRPC message received {} my term is {}", context.getId(), rpc,
context.getTermInformation().getCurrentTerm());
}
// If RPC request or response contains term T > currentTerm:
// set currentTerm = T, convert to follower (§5.1)
// This applies to all RPC messages and responses
if (rpc.getTerm() > context.getTermInformation().getCurrentTerm()) {
context.getTermInformation().updateAndPersist(rpc.getTerm(), null);
return switchBehavior(new Follower(context));
}
}
if (message instanceof ElectionTimeout) {
if (votesRequired == 0) {
// If there are no peers then we should be a Leader
// We wait for the election timeout to occur before declare
// ourselves the leader. This gives enough time for a leader
// who we do not know about (as a peer)
// to send a message to the candidate
return switchBehavior(new Leader(context));
}
startNewTerm();
scheduleElection(electionDuration());
return this;
}
return super.handleMessage(sender, message);
}
private void startNewTerm() {
// set voteCount back to 1 (that is voting for self)
voteCount = 1;
// Increment the election term and vote for self
long currentTerm = context.getTermInformation().getCurrentTerm();
context.getTermInformation().updateAndPersist(currentTerm + 1,
context.getId());
if(LOG.isDebugEnabled()) {
LOG.debug("{}: Starting new term {}", context.getId(), (currentTerm + 1));
}
// Request for a vote
// TODO: Retry request for vote if replies do not arrive in a reasonable
// amount of time TBD
for (String peerId : peers) {
ActorSelection peerActor = context.getPeerActorSelection(peerId);
if(peerActor != null) {
peerActor.tell(new RequestVote(
context.getTermInformation().getCurrentTerm(),
context.getId(),
context.getReplicatedLog().lastIndex(),
context.getReplicatedLog().lastTerm()),
context.getActor()
);
}
}
}
@Override public void close() throws Exception {
stopElection();
}
}