2 * Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
9 package org.opendaylight.controller.cluster.raft.behaviors;
11 import akka.actor.ActorRef;
12 import akka.actor.ActorSelection;
13 import org.opendaylight.controller.cluster.raft.RaftActorContext;
14 import org.opendaylight.controller.cluster.raft.RaftState;
15 import org.opendaylight.controller.cluster.raft.base.messages.ElectionTimeout;
16 import org.opendaylight.controller.cluster.raft.messages.AppendEntries;
17 import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
18 import org.opendaylight.controller.cluster.raft.messages.RaftRPC;
19 import org.opendaylight.controller.cluster.raft.messages.RequestVote;
20 import org.opendaylight.controller.cluster.raft.messages.RequestVoteReply;
25 * The behavior of a RaftActor when it is in the CandidateState
29 * <li> On conversion to candidate, start election:
31 * <li> Increment currentTerm
33 * <li> Reset election timer
34 * <li> Send RequestVote RPCs to all other servers
36 * <li> If votes received from majority of servers: become leader
37 * <li> If AppendEntries RPC received from new leader: convert to
39 * <li> If election timeout elapses: start new election
42 public class Candidate extends AbstractRaftActorBehavior {
44 private int voteCount;
46 private final int votesRequired;
48 private final Set<String> peers;
50 public Candidate(RaftActorContext context) {
53 peers = context.getPeerAddresses().keySet();
55 if(LOG.isDebugEnabled()) {
56 LOG.debug("Election:Candidate has following peers: {}", peers);
59 if(peers.size() > 0) {
60 // Votes are required from a majority of the peers including self.
61 // The votesRequired field therefore stores a calculated value
62 // of the number of votes required for this candidate to win an
63 // election based on it's known peers.
64 // If a peer was added during normal operation and raft replicas
65 // came to know about them then the new peer would also need to be
66 // taken into consideration when calculating this value.
67 // Here are some examples for what the votesRequired would be for n
69 // 0 peers = 1 votesRequired (0 + 1) / 2 + 1 = 1
70 // 2 peers = 2 votesRequired (2 + 1) / 2 + 1 = 2
71 // 4 peers = 3 votesRequired (4 + 1) / 2 + 1 = 3
72 int noOfPeers = peers.size();
74 votesRequired = (noOfPeers + self) / 2 + 1;
80 scheduleElection(electionDuration());
83 @Override protected RaftActorBehavior handleAppendEntries(ActorRef sender,
84 AppendEntries appendEntries) {
86 if(LOG.isDebugEnabled()) {
87 LOG.debug(appendEntries.toString());
93 @Override protected RaftActorBehavior handleAppendEntriesReply(ActorRef sender,
94 AppendEntriesReply appendEntriesReply) {
99 @Override protected RaftActorBehavior handleRequestVoteReply(ActorRef sender,
100 RequestVoteReply requestVoteReply) {
102 if (requestVoteReply.isVoteGranted()) {
106 if (voteCount >= votesRequired) {
107 return switchBehavior(new Leader(context));
113 @Override public RaftState state() {
114 return RaftState.Candidate;
118 public RaftActorBehavior handleMessage(ActorRef sender, Object originalMessage) {
120 Object message = fromSerializableMessage(originalMessage);
122 if (message instanceof RaftRPC) {
124 RaftRPC rpc = (RaftRPC) message;
126 if(LOG.isDebugEnabled()) {
127 LOG.debug("RaftRPC message received {} my term is {}", rpc, context.getTermInformation().getCurrentTerm());
130 // If RPC request or response contains term T > currentTerm:
131 // set currentTerm = T, convert to follower (§5.1)
132 // This applies to all RPC messages and responses
133 if (rpc.getTerm() > context.getTermInformation().getCurrentTerm()) {
134 context.getTermInformation().updateAndPersist(rpc.getTerm(), null);
136 return switchBehavior(new Follower(context));
140 if (message instanceof ElectionTimeout) {
141 if (votesRequired == 0) {
142 // If there are no peers then we should be a Leader
143 // We wait for the election timeout to occur before declare
144 // ourselves the leader. This gives enough time for a leader
145 // who we do not know about (as a peer)
146 // to send a message to the candidate
148 return switchBehavior(new Leader(context));
151 scheduleElection(electionDuration());
155 return super.handleMessage(sender, message);
159 private void startNewTerm() {
162 // set voteCount back to 1 (that is voting for self)
165 // Increment the election term and vote for self
166 long currentTerm = context.getTermInformation().getCurrentTerm();
167 context.getTermInformation().updateAndPersist(currentTerm + 1,
170 if(LOG.isDebugEnabled()) {
171 LOG.debug("Starting new term {}", (currentTerm + 1));
174 // Request for a vote
175 // TODO: Retry request for vote if replies do not arrive in a reasonable
176 // amount of time TBD
177 for (String peerId : peers) {
178 ActorSelection peerActor = context.getPeerActorSelection(peerId);
179 if(peerActor != null) {
180 peerActor.tell(new RequestVote(
181 context.getTermInformation().getCurrentTerm(),
183 context.getReplicatedLog().lastIndex(),
184 context.getReplicatedLog().lastTerm()),
193 @Override public void close() throws Exception {