import akka.actor.ActorRef;
import akka.actor.ActorSelection;
-import akka.actor.Cancellable;
+import java.util.Set;
import org.opendaylight.controller.cluster.raft.RaftActorContext;
import org.opendaylight.controller.cluster.raft.RaftState;
-import org.opendaylight.controller.cluster.raft.internal.messages.ElectionTimeout;
+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 scala.concurrent.duration.FiniteDuration;
-
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.Random;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicLong;
/**
* The behavior of a RaftActor when it is in the CandidateState
- * <p>
+ * <p/>
* Candidates (§5.2):
* <ul>
* <li> On conversion to candidate, start election:
*/
public class Candidate extends AbstractRaftActorBehavior {
- /**
- * The maximum election time variance
- */
- private static final int ELECTION_TIME_MAX_VARIANCE = 100;
+ private int voteCount;
- /**
- * The interval in which a new election would get triggered if no leader is found
- */
- private static final long ELECTION_TIME_INTERVAL = Leader.HEART_BEAT_INTERVAL.toMillis() * 2;
+ private final int votesRequired;
- /**
- *
- */
- private final Map<String, ActorSelection> peerToActor = new HashMap<>();
+ private final Set<String> peers;
- private Cancellable electionCancel = null;
+ public Candidate(RaftActorContext context) {
+ super(context, RaftState.Candidate);
- private int voteCount;
+ peers = context.getPeerAddresses().keySet();
- private final int votesRequired;
+ if(LOG.isDebugEnabled()) {
+ LOG.debug("{}: Election: Candidate has following peers: {}", logName(), peers);
+ }
- public Candidate(RaftActorContext context, List<String> peerPaths) {
- super(context);
+ votesRequired = getMajorityVoteCount(peers.size());
- for (String peerPath : peerPaths) {
- peerToActor.put(peerPath,
- context.actorSelection(peerPath));
- }
+ startNewTerm();
- if(peerPaths.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 = peerPaths.size();
- int self = 1;
- votesRequired = (noOfPeers + self) / 2 + 1;
+ if(context.getPeerAddresses().isEmpty()){
+ actor().tell(ELECTION_TIMEOUT, actor());
} else {
- votesRequired = 0;
+ scheduleElection(electionDuration());
}
- scheduleElection(randomizedDuration());
- }
-
- @Override protected RaftState handleAppendEntries(ActorRef sender,
- AppendEntries appendEntries, RaftState suggestedState) {
-
- // There is some peer who thinks it's a leader but is not
- // I will not accept this append entries
- sender.tell(new AppendEntriesReply(
- context.getTermInformation().getCurrentTerm().get(), false),
- context.getActor());
- return suggestedState;
}
- @Override protected RaftState handleAppendEntriesReply(ActorRef sender,
- AppendEntriesReply appendEntriesReply, RaftState suggestedState) {
+ @Override protected RaftActorBehavior handleAppendEntries(ActorRef sender,
+ AppendEntries appendEntries) {
- // Some peer thinks I was a leader and sent me a reply
+ if(LOG.isDebugEnabled()) {
+ LOG.debug("{}: handleAppendEntries: {}", logName(), appendEntries);
+ }
- return suggestedState;
+ return this;
}
- @Override protected RaftState handleRequestVote(ActorRef sender,
- RequestVote requestVote, RaftState suggestedState) {
-
- // We got this RequestVote because the term in there is less than
- // or equal to our current term, so do not grant the vote
- sender.tell(new RequestVoteReply(
- context.getTermInformation().getCurrentTerm().get(), false),
- context.getActor());
+ @Override protected RaftActorBehavior handleAppendEntriesReply(ActorRef sender,
+ AppendEntriesReply appendEntriesReply) {
- return suggestedState;
+ return this;
}
- @Override protected RaftState handleRequestVoteReply(ActorRef sender,
- RequestVoteReply requestVoteReply, RaftState suggestedState) {
- if(suggestedState == RaftState.Follower) {
- // If base class thinks I should be follower then I am
- return suggestedState;
- }
+ @Override protected RaftActorBehavior handleRequestVoteReply(ActorRef sender,
+ RequestVoteReply requestVoteReply) {
- if(requestVoteReply.isVoteGranted()){
+ LOG.debug("{}: handleRequestVoteReply: {}, current voteCount: {}", logName(), requestVoteReply,
+ voteCount);
+
+ if (requestVoteReply.isVoteGranted()) {
voteCount++;
}
- if(voteCount >= votesRequired){
- return RaftState.Leader;
+ if (voteCount >= votesRequired) {
+ return switchBehavior(new Leader(context));
}
- return state();
- }
-
- @Override protected RaftState state() {
- return RaftState.Candidate;
+ return this;
}
@Override
- public RaftState handleMessage(ActorRef sender, Object message) {
- if(message instanceof ElectionTimeout){
- if(votesRequired == 0){
+ 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 switchBehavior(new Follower(context));
+ }
+ }
+
+ 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 RaftState.Leader;
+
+ return switchBehavior(new Leader(context));
}
- scheduleElection(randomizedDuration());
- return state();
+ startNewTerm();
+ scheduleElection(electionDuration());
+ return this;
}
+
return super.handleMessage(sender, message);
}
- private FiniteDuration randomizedDuration(){
- long variance = new Random().nextInt(ELECTION_TIME_MAX_VARIANCE);
- return new FiniteDuration(ELECTION_TIME_INTERVAL + variance, TimeUnit.MILLISECONDS);
- }
- private void scheduleElection(FiniteDuration interval) {
+ private void startNewTerm() {
+
// set voteCount back to 1 (that is voting for self)
voteCount = 1;
// Increment the election term and vote for self
- AtomicLong currentTerm = context.getTermInformation().getCurrentTerm();
- context.getTermInformation().update(currentTerm.incrementAndGet(), context.getId());
+ long currentTerm = context.getTermInformation().getCurrentTerm();
+ long newTerm = currentTerm + 1;
+ context.getTermInformation().updateAndPersist(newTerm, context.getId());
- // Request for a vote
- for(ActorSelection peerActor : peerToActor.values()){
- peerActor.tell(new RequestVote(
- context.getTermInformation().getCurrentTerm().get(),
- context.getId(), context.getReplicatedLog().last().getIndex(),
- context.getReplicatedLog().last().getTerm()),
- context.getActor());
- }
+ LOG.debug("{}: Starting new term {}", logName(), newTerm);
- if (electionCancel != null && !electionCancel.isCancelled()) {
- electionCancel.cancel();
+ // 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) {
+ 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());
+ }
}
-
- // Schedule an election. When the scheduler triggers an ElectionTimeout
- // message is sent to itself
- electionCancel =
- context.getActorSystem().scheduler().scheduleOnce(interval,
- context.getActor(), new ElectionTimeout(),
- context.getActorSystem().dispatcher(), context.getActor());
}
+ @Override public void close() throws Exception {
+ stopElection();
+ }
}
Code Review / controller.git / blobdiff