package org.opendaylight.controller.cluster.raft.behaviors;
import akka.actor.ActorRef;
+import akka.actor.ActorSelection;
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;
-import java.util.List;
+import java.util.Set;
/**
* The behavior of a RaftActor when it is in the CandidateState
- * <p>
+ * <p/>
* Candidates (§5.2):
* <ul>
* <li> On conversion to candidate, start election:
* </ul>
*/
public class Candidate extends AbstractRaftActorBehavior {
- private final List<String> peers;
- public Candidate(RaftActorContext context, List<String> peers) {
+ private int voteCount;
+
+ private final int votesRequired;
+
+ private final Set<String> peers;
+
+ public Candidate(RaftActorContext context) {
super(context);
- this.peers = peers;
+
+ peers = context.getPeerAddresses().keySet();
+
+ if(LOG.isDebugEnabled()) {
+ LOG.debug("Election:Candidate has following peers: {}", peers);
+ }
+
+ if(peers.size() > 0) {
+ // Votes are required from a majority of the peers including self.
+ // The votesRequired field therefore stores a calculated value
+ // of the number of votes required for this candidate to win an
+ // election based on it's known peers.
+ // If a peer was added during normal operation and raft replicas
+ // came to know about them then the new peer would also need to be
+ // taken into consideration when calculating this value.
+ // Here are some examples for what the votesRequired would be for n
+ // peers
+ // 0 peers = 1 votesRequired (0 + 1) / 2 + 1 = 1
+ // 2 peers = 2 votesRequired (2 + 1) / 2 + 1 = 2
+ // 4 peers = 3 votesRequired (4 + 1) / 2 + 1 = 3
+ int noOfPeers = peers.size();
+ int self = 1;
+ votesRequired = (noOfPeers + self) / 2 + 1;
+ } else {
+ votesRequired = 0;
+ }
+
+ startNewTerm();
+ scheduleElection(electionDuration());
}
- @Override
- public RaftState handleMessage(ActorRef sender, Object message) {
+ @Override protected RaftActorBehavior handleAppendEntries(ActorRef sender,
+ AppendEntries appendEntries) {
+
+ if(LOG.isDebugEnabled()) {
+ LOG.debug(appendEntries.toString());
+ }
+
+ 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 {}", 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 {}", (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();
+ }
}
Code Review / controller.git / blobdiff