opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/behaviors/Leader.java

   1 /*
   2  * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
   3  *
   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
   7  */
   8
   9 package org.opendaylight.controller.cluster.raft.behaviors;
  10
  11 import akka.actor.ActorRef;
  12 import akka.actor.ActorSelection;
  13 import akka.actor.Cancellable;
  14 import com.google.common.base.Preconditions;
  15 import org.opendaylight.controller.cluster.raft.FollowerLogInformation;
  16 import org.opendaylight.controller.cluster.raft.FollowerLogInformationImpl;
  17 import org.opendaylight.controller.cluster.raft.RaftActorContext;
  18 import org.opendaylight.controller.cluster.raft.RaftState;
  19 import org.opendaylight.controller.cluster.raft.internal.messages.SendHeartBeat;
  20 import org.opendaylight.controller.cluster.raft.messages.AppendEntries;
  21 import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
  22 import org.opendaylight.controller.cluster.raft.messages.RequestVote;
  23 import org.opendaylight.controller.cluster.raft.messages.RequestVoteReply;
  24 import scala.concurrent.duration.FiniteDuration;
  25
  26 import java.util.Collections;
  27 import java.util.HashMap;
  28 import java.util.List;
  29 import java.util.Map;
  30 import java.util.concurrent.TimeUnit;
  31 import java.util.concurrent.atomic.AtomicLong;
  32
  33 /**
  34  * The behavior of a RaftActor when it is in the Leader state
  35  * <p/>
  36  * Leaders:
  37  * <ul>
  38  * <li> Upon election: send initial empty AppendEntries RPCs
  39  * (heartbeat) to each server; repeat during idle periods to
  40  * prevent election timeouts (§5.2)
  41  * <li> If command received from client: append entry to local log,
  42  * respond after entry applied to state machine (§5.3)
  43  * <li> If last log index ≥ nextIndex for a follower: send
  44  * AppendEntries RPC with log entries starting at nextIndex
  45  * <ul>
  46  * <li> If successful: update nextIndex and matchIndex for
  47  * follower (§5.3)
  48  * <li> If AppendEntries fails because of log inconsistency:
  49  * decrement nextIndex and retry (§5.3)
  50  * </ul>
  51  * <li> If there exists an N such that N > commitIndex, a majority
  52  * of matchIndex[i] ≥ N, and log[N].term == currentTerm:
  53  * set commitIndex = N (§5.3, §5.4).
  54  */
  55 public class Leader extends AbstractRaftActorBehavior {
  56
  57     /**
  58      * The interval at which a heart beat message will be sent to the remote
  59      * RaftActor
  60      * <p/>
  61      * Since this is set to 100 milliseconds the Election timeout should be
  62      * at least 200 milliseconds
  63      */
  64     private static final FiniteDuration HEART_BEAT_INTERVAL =
  65         new FiniteDuration(100, TimeUnit.MILLISECONDS);
  66
  67     private final Map<String, ActorRef> followerToReplicator = new HashMap<>();
  68
  69     private final Map<String, FollowerLogInformation> followerToLog =
  70         new HashMap();
  71
  72     private final Map<String, ActorSelection> followerToActor = new HashMap<>();
  73
  74     private Cancellable heartbeatCancel = null;
  75
  76     public Leader(RaftActorContext context, List<String> followers) {
  77         super(context);
  78
  79         for (String follower : followers) {
  80
  81             FollowerLogInformation followerLogInformation =
  82                 new FollowerLogInformationImpl(follower,
  83                     new AtomicLong(0),
  84                     new AtomicLong(0));
  85
  86             followerToActor.put(follower,
  87                 context.actorSelection(followerLogInformation.getId()));
  88             followerToLog.put(follower, followerLogInformation);
  89
  90         }
  91
  92         // Immediately schedule a heartbeat
  93         // Upon election: send initial empty AppendEntries RPCs
  94         // (heartbeat) to each server; repeat during idle periods to
  95         // prevent election timeouts (§5.2)
  96         scheduleHeartBeat(new FiniteDuration(0, TimeUnit.SECONDS));
  97
  98
  99     }
 100
 101     @Override protected RaftState handleAppendEntries(ActorRef sender,
 102         AppendEntries appendEntries, RaftState suggestedState) {
 103         return suggestedState;
 104     }
 105
 106     @Override protected RaftState handleAppendEntriesReply(ActorRef sender,
 107         AppendEntriesReply appendEntriesReply, RaftState suggestedState) {
 108         return suggestedState;
 109     }
 110
 111     @Override protected RaftState handleRequestVote(ActorRef sender,
 112         RequestVote requestVote, RaftState suggestedState) {
 113         return suggestedState;
 114     }
 115
 116     @Override protected RaftState handleRequestVoteReply(ActorRef sender,
 117         RequestVoteReply requestVoteReply, RaftState suggestedState) {
 118         return suggestedState;
 119     }
 120
 121     @Override protected RaftState state() {
 122         return RaftState.Leader;
 123     }
 124
 125     @Override public RaftState handleMessage(ActorRef sender, Object message) {
 126         Preconditions.checkNotNull(sender, "sender should not be null");
 127
 128         scheduleHeartBeat(HEART_BEAT_INTERVAL);
 129
 130         if (message instanceof SendHeartBeat) {
 131             for (ActorSelection follower : followerToActor.values()) {
 132                 follower.tell(new AppendEntries(
 133                     context.getTermInformation().getCurrentTerm().get(),
 134                     context.getId(),
 135                     context.getReplicatedLog().last().getIndex(),
 136                     context.getReplicatedLog().last().getTerm(),
 137                     Collections.EMPTY_LIST, context.getCommitIndex().get()),
 138                     context.getActor());
 139             }
 140             return state();
 141         }
 142         return super.handleMessage(sender, message);
 143     }
 144
 145     private void scheduleHeartBeat(FiniteDuration interval) {
 146         if (heartbeatCancel != null && !heartbeatCancel.isCancelled()) {
 147             heartbeatCancel.cancel();
 148         }
 149
 150         // Schedule a heartbeat. When the scheduler triggers the replicator
 151         // will let the RaftActor (leader) know that a new heartbeat needs to be sent
 152         // Scheduling the heartbeat only once here because heartbeats do not
 153         // need to be sent if there are other messages being sent to the remote
 154         // actor.
 155         heartbeatCancel =
 156             context.getActorSystem().scheduler().scheduleOnce(interval,
 157                 context.getActor(), new SendHeartBeat(),
 158                 context.getActorSystem().dispatcher(), context.getActor());
 159     }
 160
 161 }