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.RequestVoteReply;
  23 import scala.concurrent.duration.FiniteDuration;
  24
  25 import java.util.Collections;
  26 import java.util.HashMap;
  27 import java.util.List;
  28 import java.util.Map;
  29 import java.util.concurrent.TimeUnit;
  30 import java.util.concurrent.atomic.AtomicLong;
  31
  32 /**
  33  * The behavior of a RaftActor when it is in the Leader state
  34  * <p/>
  35  * Leaders:
  36  * <ul>
  37  * <li> Upon election: send initial empty AppendEntries RPCs
  38  * (heartbeat) to each server; repeat during idle periods to
  39  * prevent election timeouts (§5.2)
  40  * <li> If command received from client: append entry to local log,
  41  * respond after entry applied to state machine (§5.3)
  42  * <li> If last log index ≥ nextIndex for a follower: send
  43  * AppendEntries RPC with log entries starting at nextIndex
  44  * <ul>
  45  * <li> If successful: update nextIndex and matchIndex for
  46  * follower (§5.3)
  47  * <li> If AppendEntries fails because of log inconsistency:
  48  * decrement nextIndex and retry (§5.3)
  49  * </ul>
  50  * <li> If there exists an N such that N > commitIndex, a majority
  51  * of matchIndex[i] ≥ N, and log[N].term == currentTerm:
  52  * set commitIndex = N (§5.3, §5.4).
  53  */
  54 public class Leader extends AbstractRaftActorBehavior {
  55
  56
  57     private final Map<String, FollowerLogInformation> followerToLog =
  58         new HashMap();
  59
  60     private final Map<String, ActorSelection> followerToActor = new HashMap<>();
  61
  62     private Cancellable heartbeatCancel = null;
  63
  64     public Leader(RaftActorContext context, List<String> followerPaths) {
  65         super(context);
  66
  67         for (String followerPath : followerPaths) {
  68             FollowerLogInformation followerLogInformation =
  69                 new FollowerLogInformationImpl(followerPath,
  70                     new AtomicLong(0),
  71                     new AtomicLong(0));
  72
  73             followerToActor.put(followerPath,
  74                 context.actorSelection(followerLogInformation.getId()));
  75             followerToLog.put(followerPath, followerLogInformation);
  76
  77         }
  78
  79         // Immediately schedule a heartbeat
  80         // Upon election: send initial empty AppendEntries RPCs
  81         // (heartbeat) to each server; repeat during idle periods to
  82         // prevent election timeouts (§5.2)
  83         scheduleHeartBeat(new FiniteDuration(0, TimeUnit.SECONDS));
  84
  85
  86     }
  87
  88     @Override protected RaftState handleAppendEntries(ActorRef sender,
  89         AppendEntries appendEntries, RaftState suggestedState) {
  90         return suggestedState;
  91     }
  92
  93     @Override protected RaftState handleAppendEntriesReply(ActorRef sender,
  94         AppendEntriesReply appendEntriesReply, RaftState suggestedState) {
  95         return suggestedState;
  96     }
  97
  98     @Override protected RaftState handleRequestVoteReply(ActorRef sender,
  99         RequestVoteReply requestVoteReply, RaftState suggestedState) {
 100         return suggestedState;
 101     }
 102
 103     @Override protected RaftState state() {
 104         return RaftState.Leader;
 105     }
 106
 107     @Override public RaftState handleMessage(ActorRef sender, Object message) {
 108         Preconditions.checkNotNull(sender, "sender should not be null");
 109
 110         scheduleHeartBeat(HEART_BEAT_INTERVAL);
 111
 112         if (message instanceof SendHeartBeat) {
 113             for (ActorSelection follower : followerToActor.values()) {
 114                 follower.tell(new AppendEntries(
 115                     context.getTermInformation().getCurrentTerm(),
 116                     context.getId(),
 117                     context.getReplicatedLog().last().getIndex(),
 118                     context.getReplicatedLog().last().getTerm(),
 119                     Collections.EMPTY_LIST, context.getCommitIndex()),
 120                     context.getActor());
 121             }
 122             return state();
 123         }
 124         return super.handleMessage(sender, message);
 125     }
 126
 127     private void scheduleHeartBeat(FiniteDuration interval) {
 128         if (heartbeatCancel != null && !heartbeatCancel.isCancelled()) {
 129             heartbeatCancel.cancel();
 130         }
 131
 132         // Schedule a heartbeat. When the scheduler triggers a SendHeartbeat
 133         // message is sent to itself.
 134         // Scheduling the heartbeat only once here because heartbeats do not
 135         // need to be sent if there are other messages being sent to the remote
 136         // actor.
 137         heartbeatCancel =
 138             context.getActorSystem().scheduler().scheduleOnce(interval,
 139                 context.getActor(), new SendHeartBeat(),
 140                 context.getActorSystem().dispatcher(), context.getActor());
 141     }
 142
 143 }