/*
* Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 which accompanies this distribution,
* and is available at http://www.eclipse.org/legal/epl-v10.html
*/
package org.opendaylight.controller.cluster.raft.behaviors;
import akka.actor.ActorRef;
import akka.actor.ActorSelection;
import akka.actor.Cancellable;
import com.google.common.base.Preconditions;
import org.opendaylight.controller.cluster.raft.FollowerLogInformation;
import org.opendaylight.controller.cluster.raft.FollowerLogInformationImpl;
import org.opendaylight.controller.cluster.raft.RaftActorContext;
import org.opendaylight.controller.cluster.raft.RaftState;
import org.opendaylight.controller.cluster.raft.internal.messages.SendHeartBeat;
import org.opendaylight.controller.cluster.raft.messages.AppendEntries;
import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
import org.opendaylight.controller.cluster.raft.messages.RequestVote;
import org.opendaylight.controller.cluster.raft.messages.RequestVoteReply;
import scala.concurrent.duration.FiniteDuration;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
/**
* The behavior of a RaftActor when it is in the Leader state
*
* Leaders:
*
* - Upon election: send initial empty AppendEntries RPCs
* (heartbeat) to each server; repeat during idle periods to
* prevent election timeouts (§5.2)
*
- If command received from client: append entry to local log,
* respond after entry applied to state machine (§5.3)
*
- If last log index ≥ nextIndex for a follower: send
* AppendEntries RPC with log entries starting at nextIndex
*
* - If successful: update nextIndex and matchIndex for
* follower (§5.3)
*
- If AppendEntries fails because of log inconsistency:
* decrement nextIndex and retry (§5.3)
*
* - If there exists an N such that N > commitIndex, a majority
* of matchIndex[i] ≥ N, and log[N].term == currentTerm:
* set commitIndex = N (§5.3, §5.4).
*/
public class Leader extends AbstractRaftActorBehavior {
/**
* The interval at which a heart beat message will be sent to the remote
* RaftActor
*
* Since this is set to 100 milliseconds the Election timeout should be
* at least 200 milliseconds
*/
private static final FiniteDuration HEART_BEAT_INTERVAL =
new FiniteDuration(100, TimeUnit.MILLISECONDS);
private final Map followerToReplicator = new HashMap<>();
private final Map followerToLog =
new HashMap();
private final Map followerToActor = new HashMap<>();
private Cancellable heartbeatCancel = null;
public Leader(RaftActorContext context, List followers) {
super(context);
for (String follower : followers) {
FollowerLogInformation followerLogInformation =
new FollowerLogInformationImpl(follower,
new AtomicLong(0),
new AtomicLong(0));
followerToActor.put(follower,
context.actorSelection(followerLogInformation.getId()));
followerToLog.put(follower, followerLogInformation);
}
// Immediately schedule a heartbeat
// Upon election: send initial empty AppendEntries RPCs
// (heartbeat) to each server; repeat during idle periods to
// prevent election timeouts (§5.2)
scheduleHeartBeat(new FiniteDuration(0, TimeUnit.SECONDS));
}
@Override protected RaftState handleAppendEntries(ActorRef sender,
AppendEntries appendEntries, RaftState suggestedState) {
return suggestedState;
}
@Override protected RaftState handleAppendEntriesReply(ActorRef sender,
AppendEntriesReply appendEntriesReply, RaftState suggestedState) {
return suggestedState;
}
@Override protected RaftState handleRequestVote(ActorRef sender,
RequestVote requestVote, RaftState suggestedState) {
return suggestedState;
}
@Override protected RaftState handleRequestVoteReply(ActorRef sender,
RequestVoteReply requestVoteReply, RaftState suggestedState) {
return suggestedState;
}
@Override protected RaftState state() {
return RaftState.Leader;
}
@Override public RaftState handleMessage(ActorRef sender, Object message) {
Preconditions.checkNotNull(sender, "sender should not be null");
scheduleHeartBeat(HEART_BEAT_INTERVAL);
if (message instanceof SendHeartBeat) {
for (ActorSelection follower : followerToActor.values()) {
follower.tell(new AppendEntries(
context.getTermInformation().getCurrentTerm().get(),
context.getId(),
context.getReplicatedLog().last().getIndex(),
context.getReplicatedLog().last().getTerm(),
Collections.EMPTY_LIST, context.getCommitIndex().get()),
context.getActor());
}
return state();
}
return super.handleMessage(sender, message);
}
private void scheduleHeartBeat(FiniteDuration interval) {
if (heartbeatCancel != null && !heartbeatCancel.isCancelled()) {
heartbeatCancel.cancel();
}
// Schedule a heartbeat. When the scheduler triggers the replicator
// will let the RaftActor (leader) know that a new heartbeat needs to be sent
// Scheduling the heartbeat only once here because heartbeats do not
// need to be sent if there are other messages being sent to the remote
// actor.
heartbeatCancel =
context.getActorSystem().scheduler().scheduleOnce(interval,
context.getActor(), new SendHeartBeat(),
context.getActorSystem().dispatcher(), context.getActor());
}
}