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 java.util.ArrayList;
14 import java.util.Collection;
15 import org.opendaylight.controller.cluster.raft.PeerInfo;
16 import org.opendaylight.controller.cluster.raft.RaftActorContext;
17 import org.opendaylight.controller.cluster.raft.RaftState;
18 import org.opendaylight.controller.cluster.raft.base.messages.ElectionTimeout;
19 import org.opendaylight.controller.cluster.raft.messages.AppendEntries;
20 import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
21 import org.opendaylight.controller.cluster.raft.messages.RaftRPC;
22 import org.opendaylight.controller.cluster.raft.messages.RequestVote;
23 import org.opendaylight.controller.cluster.raft.messages.RequestVoteReply;
26 * The behavior of a RaftActor when it is in the Candidate raft state.
30 * <li> On conversion to candidate, start election:
32 * <li> Increment currentTerm
34 * <li> Reset election timer
35 * <li> Send RequestVote RPCs to all other servers
37 * <li> If votes received from majority of servers: become leader
38 * <li> If AppendEntries RPC received from new leader: convert to
40 * <li> If election timeout elapses: start new election
43 public class Candidate extends AbstractRaftActorBehavior {
45 private int voteCount;
47 private final int votesRequired;
49 private final Collection<String> votingPeers = new ArrayList<>();
51 public Candidate(RaftActorContext context) {
52 super(context, RaftState.Candidate);
54 for (PeerInfo peer: context.getPeers()) {
55 if (peer.isVoting()) {
56 votingPeers.add(peer.getId());
60 log.debug("{}: Election: Candidate has following voting peers: {}", logName(), votingPeers);
62 votesRequired = getMajorityVoteCount(votingPeers.size());
66 if (votingPeers.isEmpty()) {
67 actor().tell(ElectionTimeout.INSTANCE, actor());
69 scheduleElection(electionDuration());
74 public final String getLeaderId() {
79 public final short getLeaderPayloadVersion() {
84 protected RaftActorBehavior handleAppendEntries(ActorRef sender, AppendEntries appendEntries) {
86 log.debug("{}: handleAppendEntries: {}", logName(), appendEntries);
88 // Some other candidate for the same term became a leader and sent us an append entry
89 if (currentTerm() == appendEntries.getTerm()) {
90 log.debug("{}: New Leader sent an append entry to Candidate for term {} will switch to Follower",
91 logName(), currentTerm());
93 return switchBehavior(new Follower(context));
100 protected RaftActorBehavior handleAppendEntriesReply(ActorRef sender, AppendEntriesReply appendEntriesReply) {
105 protected RaftActorBehavior handleRequestVoteReply(ActorRef sender, RequestVoteReply requestVoteReply) {
106 log.debug("{}: handleRequestVoteReply: {}, current voteCount: {}", logName(), requestVoteReply, voteCount);
108 if (requestVoteReply.isVoteGranted()) {
112 if (voteCount >= votesRequired) {
113 if (context.getLastApplied() < context.getReplicatedLog().lastIndex()) {
114 log.debug("{}: LastApplied index {} is behind last index {}", logName(), context.getLastApplied(),
115 context.getReplicatedLog().lastIndex());
116 return internalSwitchBehavior(RaftState.PreLeader);
118 return internalSwitchBehavior(RaftState.Leader);
126 public RaftActorBehavior handleMessage(ActorRef sender, Object message) {
127 if (message instanceof ElectionTimeout) {
128 log.debug("{}: Received ElectionTimeout", logName());
130 if (votesRequired == 0) {
131 // If there are no peers then we should be a Leader
132 // We wait for the election timeout to occur before declare
133 // ourselves the leader. This gives enough time for a leader
134 // who we do not know about (as a peer)
135 // to send a message to the candidate
137 return internalSwitchBehavior(RaftState.Leader);
141 scheduleElection(electionDuration());
145 if (message instanceof RaftRPC) {
147 RaftRPC rpc = (RaftRPC) message;
149 log.debug("{}: RaftRPC message received {}, my term is {}", logName(), rpc,
150 context.getTermInformation().getCurrentTerm());
152 // If RPC request or response contains term T > currentTerm:
153 // set currentTerm = T, convert to follower (§5.1)
154 // This applies to all RPC messages and responses
155 if (rpc.getTerm() > context.getTermInformation().getCurrentTerm()) {
156 context.getTermInformation().updateAndPersist(rpc.getTerm(), null);
158 // The raft paper does not say whether or not a Candidate can/should process a RequestVote in
159 // this case but doing so gains quicker convergence when the sender's log is more up-to-date.
160 if (message instanceof RequestVote) {
161 super.handleMessage(sender, message);
164 return internalSwitchBehavior(RaftState.Follower);
168 return super.handleMessage(sender, message);
172 private void startNewTerm() {
175 // set voteCount back to 1 (that is voting for self)
178 // Increment the election term and vote for self
179 long currentTerm = context.getTermInformation().getCurrentTerm();
180 long newTerm = currentTerm + 1;
181 context.getTermInformation().updateAndPersist(newTerm, context.getId());
183 log.debug("{}: Starting new term {}", logName(), newTerm);
185 // Request for a vote
186 // TODO: Retry request for vote if replies do not arrive in a reasonable
187 // amount of time TBD
188 for (String peerId : votingPeers) {
189 ActorSelection peerActor = context.getPeerActorSelection(peerId);
190 if (peerActor != null) {
191 RequestVote requestVote = new RequestVote(
192 context.getTermInformation().getCurrentTerm(),
194 context.getReplicatedLog().lastIndex(),
195 context.getReplicatedLog().lastTerm());
197 log.debug("{}: Sending {} to peer {}", logName(), requestVote, peerId);
199 peerActor.tell(requestVote, context.getActor());
205 public void close() {