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 context.getLogger().debug("Election:Candidate has following peers:"+ peers);
57 if(peers.size() > 0) {
58 // Votes are required from a majority of the peers including self.
59 // The votesRequired field therefore stores a calculated value
60 // of the number of votes required for this candidate to win an
61 // election based on it's known peers.
62 // If a peer was added during normal operation and raft replicas
63 // came to know about them then the new peer would also need to be
64 // taken into consideration when calculating this value.
65 // Here are some examples for what the votesRequired would be for n
67 // 0 peers = 1 votesRequired (0 + 1) / 2 + 1 = 1
68 // 2 peers = 2 votesRequired (2 + 1) / 2 + 1 = 2
69 // 4 peers = 3 votesRequired (4 + 1) / 2 + 1 = 3
70 int noOfPeers = peers.size();
72 votesRequired = (noOfPeers + self) / 2 + 1;
78 scheduleElection(electionDuration());
81 @Override protected RaftState handleAppendEntries(ActorRef sender,
82 AppendEntries appendEntries) {
84 context.getLogger().info("Candidate: Received {}", appendEntries.toString());
89 @Override protected RaftState handleAppendEntriesReply(ActorRef sender,
90 AppendEntriesReply appendEntriesReply) {
95 @Override protected RaftState handleRequestVoteReply(ActorRef sender,
96 RequestVoteReply requestVoteReply) {
98 if (requestVoteReply.isVoteGranted()) {
102 if (voteCount >= votesRequired) {
103 return RaftState.Leader;
109 @Override public RaftState state() {
110 return RaftState.Candidate;
114 public RaftState handleMessage(ActorRef sender, Object originalMessage) {
116 Object message = fromSerializableMessage(originalMessage);
118 if (message instanceof RaftRPC) {
120 RaftRPC rpc = (RaftRPC) message;
122 context.getLogger().debug("RaftRPC message received {} my term is {}", rpc.toString(), context.getTermInformation().getCurrentTerm());
124 // If RPC request or response contains term T > currentTerm:
125 // set currentTerm = T, convert to follower (§5.1)
126 // This applies to all RPC messages and responses
127 if (rpc.getTerm() > context.getTermInformation().getCurrentTerm()) {
128 context.getTermInformation().updateAndPersist(rpc.getTerm(), null);
129 return RaftState.Follower;
133 if (message instanceof ElectionTimeout) {
134 if (votesRequired == 0) {
135 // If there are no peers then we should be a Leader
136 // We wait for the election timeout to occur before declare
137 // ourselves the leader. This gives enough time for a leader
138 // who we do not know about (as a peer)
139 // to send a message to the candidate
140 return RaftState.Leader;
143 scheduleElection(electionDuration());
147 return super.handleMessage(sender, message);
151 private void startNewTerm() {
154 // set voteCount back to 1 (that is voting for self)
157 // Increment the election term and vote for self
158 long currentTerm = context.getTermInformation().getCurrentTerm();
159 context.getTermInformation().updateAndPersist(currentTerm + 1,
162 context.getLogger().debug("Starting new term " + (currentTerm + 1));
164 // Request for a vote
165 // TODO: Retry request for vote if replies do not arrive in a reasonable
166 // amount of time TBD
167 for (String peerId : peers) {
168 ActorSelection peerActor = context.getPeerActorSelection(peerId);
169 if(peerActor != null) {
170 peerActor.tell(new RequestVote(
171 context.getTermInformation().getCurrentTerm(),
173 context.getReplicatedLog().lastIndex(),
174 context.getReplicatedLog().lastTerm()),
183 @Override public void close() throws Exception {