+ } else {
+
+ // Create a tracker entry we will use this later to notify the
+ // client actor
+ trackerList.add(
+ new ClientRequestTrackerImpl(replicate.getClientActor(),
+ replicate.getIdentifier(),
+ logIndex)
+ );
+
+ sendAppendEntries();
+ }
+ }
+
+ private void sendAppendEntries() {
+ // Send an AppendEntries to all followers
+ for (String followerId : followerToActor.keySet()) {
+ ActorSelection followerActor =
+ followerToActor.get(followerId);
+
+ FollowerLogInformation followerLogInformation =
+ followerToLog.get(followerId);
+
+ long nextIndex = followerLogInformation.getNextIndex().get();
+
+ List<ReplicatedLogEntry> entries = Collections.emptyList();
+
+ if(context.getReplicatedLog().isPresent(nextIndex)){
+ // TODO: Instead of sending all entries from nextIndex
+ // only send a fixed number of entries to each follower
+ // This is to avoid the situation where there are a lot of
+ // entries to install for a fresh follower or to a follower
+ // that has fallen too far behind with the log but yet is not
+ // eligible to receive a snapshot
+ entries =
+ context.getReplicatedLog().getFrom(nextIndex);
+ }
+
+ followerActor.tell(
+ new AppendEntries(currentTerm(), context.getId(), prevLogIndex(nextIndex),
+ prevLogTerm(nextIndex), entries, context.getCommitIndex()).toSerializable(),
+ actor());
+ }
+ }
+
+ /**
+ * An installSnapshot is scheduled at a interval that is a multiple of
+ * a HEARTBEAT_INTERVAL. This is to avoid the need to check for installing
+ * snapshots at every heartbeat.
+ */
+ private void installSnapshotIfNeeded(){
+ for (String followerId : followerToActor.keySet()) {
+ ActorSelection followerActor =
+ followerToActor.get(followerId);
+
+ FollowerLogInformation followerLogInformation =
+ followerToLog.get(followerId);
+
+ long nextIndex = followerLogInformation.getNextIndex().get();
+
+ if(!context.getReplicatedLog().isPresent(nextIndex) && context.getReplicatedLog().isInSnapshot(nextIndex)){
+ followerActor.tell(
+ new InstallSnapshot(currentTerm(), context.getId(),
+ context.getReplicatedLog().getSnapshotIndex(),
+ context.getReplicatedLog().getSnapshotTerm(),
+ context.getReplicatedLog().getSnapshot()
+ ),
+ actor()
+ );