/*
* 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.ArrayList;
import java.util.Collection;
import org.opendaylight.controller.cluster.raft.PeerInfo;
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 Collection votingPeers = new ArrayList<>();
public Candidate(RaftActorContext context) {
super(context, RaftState.Candidate);
for(PeerInfo peer: context.getPeers()) {
if(peer.isVoting()) {
votingPeers.add(peer.getId());
}
}
if(LOG.isDebugEnabled()) {
LOG.debug("{}: Election: Candidate has following voting peers: {}", logName(), votingPeers);
}
votesRequired = getMajorityVoteCount(votingPeers.size());
startNewTerm();
if(votingPeers.isEmpty()){
actor().tell(ELECTION_TIMEOUT, actor());
} else {
scheduleElection(electionDuration());
}
}
@Override protected RaftActorBehavior handleAppendEntries(ActorRef sender,
AppendEntries appendEntries) {
if(LOG.isDebugEnabled()) {
LOG.debug("{}: handleAppendEntries: {}", logName(), appendEntries);
}
// Some other candidate for the same term became a leader and sent us an append entry
if(currentTerm() == appendEntries.getTerm()){
LOG.debug("{}: New Leader sent an append entry to Candidate for term {} will switch to Follower",
logName(), currentTerm());
return switchBehavior(new Follower(context));
}
return this;
}
@Override protected RaftActorBehavior handleAppendEntriesReply(ActorRef sender,
AppendEntriesReply appendEntriesReply) {
return this;
}
@Override protected RaftActorBehavior handleRequestVoteReply(ActorRef sender,
RequestVoteReply requestVoteReply) {
LOG.debug("{}: handleRequestVoteReply: {}, current voteCount: {}", logName(), requestVoteReply,
voteCount);
if (requestVoteReply.isVoteGranted()) {
voteCount++;
}
if (voteCount >= votesRequired) {
return internalSwitchBehavior(RaftState.Leader);
}
return this;
}
@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 {}", logName(), 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 internalSwitchBehavior(RaftState.Follower);
}
}
if (message instanceof ElectionTimeout) {
LOG.debug("{}: Received ElectionTimeout", logName());
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 internalSwitchBehavior(RaftState.Leader);
}
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();
long newTerm = currentTerm + 1;
context.getTermInformation().updateAndPersist(newTerm, context.getId());
LOG.debug("{}: Starting new term {}", logName(), newTerm);
// Request for a vote
// TODO: Retry request for vote if replies do not arrive in a reasonable
// amount of time TBD
for (String peerId : votingPeers) {
ActorSelection peerActor = context.getPeerActorSelection(peerId);
if(peerActor != null) {
RequestVote requestVote = new RequestVote(
context.getTermInformation().getCurrentTerm(),
context.getId(),
context.getReplicatedLog().lastIndex(),
context.getReplicatedLog().lastTerm());
LOG.debug("{}: Sending {} to peer {}", logName(), requestVote, peerId);
peerActor.tell(requestVote, context.getActor());
}
}
}
@Override public void close() throws Exception {
stopElection();
}
}