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.Cancellable;
  13 import com.google.common.annotations.VisibleForTesting;
  14 import com.google.common.base.Preconditions;
  15 import org.opendaylight.controller.cluster.raft.RaftActorContext;
  16 import org.opendaylight.controller.cluster.raft.base.messages.InitiateInstallSnapshot;
  17 import org.opendaylight.controller.cluster.raft.base.messages.IsolatedLeaderCheck;
  18 import scala.concurrent.duration.FiniteDuration;
  19
  20 /**
  21  * The behavior of a RaftActor when it is in the Leader state
  22  * <p/>
  23  * Leaders:
  24  * <ul>
  25  * <li> Upon election: send initial empty AppendEntries RPCs
  26  * (heartbeat) to each server; repeat during idle periods to
  27  * prevent election timeouts (§5.2)
  28  * <li> If command received from client: append entry to local log,
  29  * respond after entry applied to state machine (§5.3)
  30  * <li> If last log index ≥ nextIndex for a follower: send
  31  * AppendEntries RPC with log entries starting at nextIndex
  32  * <ul>
  33  * <li> If successful: update nextIndex and matchIndex for
  34  * follower (§5.3)
  35  * <li> If AppendEntries fails because of log inconsistency:
  36  * decrement nextIndex and retry (§5.3)
  37  * </ul>
  38  * <li> If there exists an N such that N > commitIndex, a majority
  39  * of matchIndex[i] ≥ N, and log[N].term == currentTerm:
  40  * set commitIndex = N (§5.3, §5.4).
  41  */
  42 public class Leader extends AbstractLeader {
  43     private Cancellable installSnapshotSchedule = null;
  44     private Cancellable isolatedLeaderCheckSchedule = null;
  45
  46     public Leader(RaftActorContext context) {
  47         super(context);
  48
  49         scheduleInstallSnapshotCheck(context.getConfigParams().getIsolatedCheckInterval());
  50
  51         scheduleIsolatedLeaderCheck(
  52             new FiniteDuration(context.getConfigParams().getHeartBeatInterval().length() * 10,
  53                 context.getConfigParams().getHeartBeatInterval().unit()));
  54     }
  55
  56     @Override public RaftActorBehavior handleMessage(ActorRef sender, Object originalMessage) {
  57         Preconditions.checkNotNull(sender, "sender should not be null");
  58
  59         if (originalMessage instanceof IsolatedLeaderCheck) {
  60             if (isLeaderIsolated()) {
  61                 LOG.info("At least {} followers need to be active, Switching {} from Leader to IsolatedLeader",
  62                     minIsolatedLeaderPeerCount, leaderId);
  63                 return switchBehavior(new IsolatedLeader(context));
  64             }
  65         }
  66
  67         return super.handleMessage(sender, originalMessage);
  68     }
  69
  70     protected void stopInstallSnapshotSchedule() {
  71         if (installSnapshotSchedule != null && !installSnapshotSchedule.isCancelled()) {
  72             installSnapshotSchedule.cancel();
  73         }
  74     }
  75
  76     protected void scheduleInstallSnapshotCheck(FiniteDuration interval) {
  77         if(followers.size() == 0){
  78             // Optimization - do not bother scheduling a heartbeat as there are
  79             // no followers
  80             return;
  81         }
  82
  83         stopInstallSnapshotSchedule();
  84
  85         // Schedule a message to send append entries to followers that can
  86         // accept an append entries with some data in it
  87         installSnapshotSchedule =
  88             context.getActorSystem().scheduler().scheduleOnce(
  89                 interval,
  90                 context.getActor(), new InitiateInstallSnapshot(),
  91                 context.getActorSystem().dispatcher(), context.getActor());
  92     }
  93
  94     protected void stopIsolatedLeaderCheckSchedule() {
  95         if (isolatedLeaderCheckSchedule != null && !isolatedLeaderCheckSchedule.isCancelled()) {
  96             isolatedLeaderCheckSchedule.cancel();
  97         }
  98     }
  99
 100     protected void scheduleIsolatedLeaderCheck(FiniteDuration isolatedCheckInterval) {
 101         isolatedLeaderCheckSchedule = context.getActorSystem().scheduler().schedule(isolatedCheckInterval, isolatedCheckInterval,
 102             context.getActor(), new IsolatedLeaderCheck(),
 103             context.getActorSystem().dispatcher(), context.getActor());
 104     }
 105
 106     @Override public void close() throws Exception {
 107         stopInstallSnapshotSchedule();
 108         stopIsolatedLeaderCheckSchedule();
 109         super.close();
 110     }
 111
 112     @VisibleForTesting
 113     void markFollowerActive(String followerId) {
 114         followerToLog.get(followerId).markFollowerActive();
 115     }
 116 }