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 package org.opendaylight.controller.cluster.raft.behaviors;
   9
  10 import akka.actor.ActorRef;
  11 import akka.actor.Cancellable;
  12 import com.google.common.annotations.VisibleForTesting;
  13 import com.google.common.base.Preconditions;
  14 import org.opendaylight.controller.cluster.raft.RaftActorContext;
  15 import org.opendaylight.controller.cluster.raft.base.messages.InitiateInstallSnapshot;
  16 import org.opendaylight.controller.cluster.raft.base.messages.IsolatedLeaderCheck;
  17 import scala.concurrent.duration.FiniteDuration;
  18
  19 /**
  20  * The behavior of a RaftActor when it is in the Leader state
  21  * <p/>
  22  * Leaders:
  23  * <ul>
  24  * <li> Upon election: send initial empty AppendEntries RPCs
  25  * (heartbeat) to each server; repeat during idle periods to
  26  * prevent election timeouts (§5.2)
  27  * <li> If command received from client: append entry to local log,
  28  * respond after entry applied to state machine (§5.3)
  29  * <li> If last log index ≥ nextIndex for a follower: send
  30  * AppendEntries RPC with log entries starting at nextIndex
  31  * <ul>
  32  * <li> If successful: update nextIndex and matchIndex for
  33  * follower (§5.3)
  34  * <li> If AppendEntries fails because of log inconsistency:
  35  * decrement nextIndex and retry (§5.3)
  36  * </ul>
  37  * <li> If there exists an N such that N > commitIndex, a majority
  38  * of matchIndex[i] ≥ N, and log[N].term == currentTerm:
  39  * set commitIndex = N (§5.3, §5.4).
  40  */
  41 public class Leader extends AbstractLeader {
  42     private Cancellable installSnapshotSchedule = null;
  43     private Cancellable isolatedLeaderCheckSchedule = null;
  44
  45     public Leader(RaftActorContext context) {
  46         super(context);
  47
  48         scheduleInstallSnapshotCheck(context.getConfigParams().getIsolatedCheckInterval());
  49
  50         scheduleIsolatedLeaderCheck(
  51             new FiniteDuration(context.getConfigParams().getHeartBeatInterval().length() * 10,
  52                 context.getConfigParams().getHeartBeatInterval().unit()));
  53     }
  54
  55     @Override public RaftActorBehavior handleMessage(ActorRef sender, Object originalMessage) {
  56         Preconditions.checkNotNull(sender, "sender should not be null");
  57
  58         if (originalMessage instanceof IsolatedLeaderCheck) {
  59             if (isLeaderIsolated()) {
  60                 LOG.info("At least {} followers need to be active, Switching {} from Leader to IsolatedLeader",
  61                     minIsolatedLeaderPeerCount, leaderId);
  62                 return switchBehavior(new IsolatedLeader(context));
  63             }
  64         }
  65
  66         return super.handleMessage(sender, originalMessage);
  67     }
  68
  69     protected void stopInstallSnapshotSchedule() {
  70         if (installSnapshotSchedule != null && !installSnapshotSchedule.isCancelled()) {
  71             installSnapshotSchedule.cancel();
  72         }
  73     }
  74
  75     protected void scheduleInstallSnapshotCheck(FiniteDuration interval) {
  76         if (getFollowerIds().isEmpty()) {
  77             // Optimization - do not bother scheduling a heartbeat as there are
  78             // no followers
  79             return;
  80         }
  81
  82         stopInstallSnapshotSchedule();
  83
  84         // Schedule a message to send append entries to followers that can
  85         // accept an append entries with some data in it
  86         installSnapshotSchedule =
  87             context.getActorSystem().scheduler().scheduleOnce(
  88                 interval,
  89                 context.getActor(), new InitiateInstallSnapshot(),
  90                 context.getActorSystem().dispatcher(), context.getActor());
  91     }
  92
  93     protected void stopIsolatedLeaderCheckSchedule() {
  94         if (isolatedLeaderCheckSchedule != null && !isolatedLeaderCheckSchedule.isCancelled()) {
  95             isolatedLeaderCheckSchedule.cancel();
  96         }
  97     }
  98
  99     protected void scheduleIsolatedLeaderCheck(FiniteDuration isolatedCheckInterval) {
 100         isolatedLeaderCheckSchedule = context.getActorSystem().scheduler().schedule(isolatedCheckInterval, isolatedCheckInterval,
 101             context.getActor(), new IsolatedLeaderCheck(),
 102             context.getActorSystem().dispatcher(), context.getActor());
 103     }
 104
 105     @Override
 106     public void close() throws Exception {
 107         stopInstallSnapshotSchedule();
 108         stopIsolatedLeaderCheckSchedule();
 109         super.close();
 110     }
 111
 112     @VisibleForTesting
 113     void markFollowerActive(String followerId) {
 114         getFollower(followerId).markFollowerActive();
 115     }
 116
 117     @VisibleForTesting
 118     void markFollowerInActive(String followerId) {
 119         getFollower(followerId).markFollowerInActive();
 120     }
 121 }