package org.opendaylight.controller.cluster.raft.behaviors;
import akka.actor.ActorRef;
+import akka.actor.ActorSelection;
+import akka.actor.Cancellable;
import com.google.common.base.Preconditions;
+import org.opendaylight.controller.cluster.raft.ClientRequestTracker;
+import org.opendaylight.controller.cluster.raft.ClientRequestTrackerImpl;
+import org.opendaylight.controller.cluster.raft.FollowerLogInformation;
import org.opendaylight.controller.cluster.raft.FollowerLogInformationImpl;
import org.opendaylight.controller.cluster.raft.RaftActorContext;
-import org.opendaylight.controller.cluster.raft.RaftReplicator;
import org.opendaylight.controller.cluster.raft.RaftState;
-import org.opendaylight.controller.cluster.raft.internal.messages.SendHeartBeat;
+import org.opendaylight.controller.cluster.raft.ReplicatedLogEntry;
+import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
+import org.opendaylight.controller.cluster.raft.base.messages.Replicate;
+import org.opendaylight.controller.cluster.raft.base.messages.SendHeartBeat;
+import org.opendaylight.controller.cluster.raft.base.messages.SendInstallSnapshot;
import org.opendaylight.controller.cluster.raft.messages.AppendEntries;
import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
-import org.opendaylight.controller.cluster.raft.messages.RequestVote;
+import org.opendaylight.controller.cluster.raft.messages.InstallSnapshot;
+import org.opendaylight.controller.cluster.raft.messages.InstallSnapshotReply;
+import org.opendaylight.controller.cluster.raft.messages.RaftRPC;
import org.opendaylight.controller.cluster.raft.messages.RequestVoteReply;
+import scala.concurrent.duration.FiniteDuration;
+import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
/**
* The behavior of a RaftActor when it is in the Leader state
- * <p>
+ * <p/>
* Leaders:
* <ul>
* <li> Upon election: send initial empty AppendEntries RPCs
public class Leader extends AbstractRaftActorBehavior {
- private final Map<String, ActorRef> followerToReplicator = new HashMap<>();
+ private final Map<String, FollowerLogInformation> followerToLog =
+ new HashMap();
- public Leader(RaftActorContext context, List<String> followers){
+ private final Set<String> followers;
+
+ private Cancellable heartbeatSchedule = null;
+ private Cancellable appendEntriesSchedule = null;
+ private Cancellable installSnapshotSchedule = null;
+
+ private List<ClientRequestTracker> trackerList = new ArrayList<>();
+
+ private final int minReplicationCount;
+
+ public Leader(RaftActorContext context) {
super(context);
- for(String follower : followers) {
+ if (lastIndex() >= 0) {
+ context.setCommitIndex(lastIndex());
+ }
- ActorRef replicator = context.actorOf(
- RaftReplicator.props(
- new FollowerLogInformationImpl(follower,
- new AtomicLong(0),
- new AtomicLong(0)),
- context.getActor()
- )
- );
+ followers = context.getPeerAddresses().keySet();
+
+ for (String followerId : followers) {
+ FollowerLogInformation followerLogInformation =
+ new FollowerLogInformationImpl(followerId,
+ new AtomicLong(lastIndex()),
+ new AtomicLong(-1));
+
+ followerToLog.put(followerId, followerLogInformation);
+ }
- // Create a replicator for each follower
- followerToReplicator.put(follower, replicator);
+ context.getLogger().debug("Election:Leader has following peers:"+ followers);
+ if (followers.size() > 0) {
+ minReplicationCount = (followers.size() + 1) / 2 + 1;
+ } else {
+ minReplicationCount = 0;
}
+
+ // Immediately schedule a heartbeat
+ // Upon election: send initial empty AppendEntries RPCs
+ // (heartbeat) to each server; repeat during idle periods to
+ // prevent election timeouts (§5.2)
+ scheduleHeartBeat(new FiniteDuration(0, TimeUnit.SECONDS));
+
+ scheduleInstallSnapshotCheck(
+ new FiniteDuration(context.getConfigParams().getHeartBeatInterval().length() * 1000,
+ context.getConfigParams().getHeartBeatInterval().unit())
+ );
+
}
@Override protected RaftState handleAppendEntries(ActorRef sender,
- AppendEntries appendEntries, RaftState suggestedState) {
- return suggestedState;
+ AppendEntries appendEntries) {
+
+ context.getLogger().info("Leader: Received {}", appendEntries.toString());
+
+ return state();
}
@Override protected RaftState handleAppendEntriesReply(ActorRef sender,
- AppendEntriesReply appendEntriesReply, RaftState suggestedState) {
- return suggestedState;
+ AppendEntriesReply appendEntriesReply) {
+
+ if(! appendEntriesReply.isSuccess()) {
+ context.getLogger()
+ .info("Leader: Received {}", appendEntriesReply.toString());
+ }
+
+ // Update the FollowerLogInformation
+ String followerId = appendEntriesReply.getFollowerId();
+ FollowerLogInformation followerLogInformation =
+ followerToLog.get(followerId);
+
+ if(followerLogInformation == null){
+ context.getLogger().error("Unknown follower {}", followerId);
+ return state();
+ }
+
+ if (appendEntriesReply.isSuccess()) {
+ followerLogInformation
+ .setMatchIndex(appendEntriesReply.getLogLastIndex());
+ followerLogInformation
+ .setNextIndex(appendEntriesReply.getLogLastIndex() + 1);
+ } else {
+
+ // TODO: When we find that the follower is out of sync with the
+ // Leader we simply decrement that followers next index by 1.
+ // Would it be possible to do better than this? The RAFT spec
+ // does not explicitly deal with it but may be something for us to
+ // think about
+
+ followerLogInformation.decrNextIndex();
+ }
+
+ // Now figure out if this reply warrants a change in the commitIndex
+ // If there exists an N such that N > commitIndex, a majority
+ // of matchIndex[i] ≥ N, and log[N].term == currentTerm:
+ // set commitIndex = N (§5.3, §5.4).
+ for (long N = context.getCommitIndex() + 1; ; N++) {
+ int replicatedCount = 1;
+
+ for (FollowerLogInformation info : followerToLog.values()) {
+ if (info.getMatchIndex().get() >= N) {
+ replicatedCount++;
+ }
+ }
+
+ if (replicatedCount >= minReplicationCount) {
+ ReplicatedLogEntry replicatedLogEntry =
+ context.getReplicatedLog().get(N);
+ if (replicatedLogEntry != null
+ && replicatedLogEntry.getTerm()
+ == currentTerm()) {
+ context.setCommitIndex(N);
+ }
+ } else {
+ break;
+ }
+ }
+
+ // Apply the change to the state machine
+ if (context.getCommitIndex() > context.getLastApplied()) {
+ applyLogToStateMachine(context.getCommitIndex());
+ }
+
+ return state();
}
- @Override protected RaftState handleRequestVote(ActorRef sender,
- RequestVote requestVote, RaftState suggestedState) {
- return suggestedState;
+ protected ClientRequestTracker findClientRequestTracker(long logIndex) {
+ for (ClientRequestTracker tracker : trackerList) {
+ if (tracker.getIndex() == logIndex) {
+ return tracker;
+ }
+ }
+
+ return null;
}
@Override protected RaftState handleRequestVoteReply(ActorRef sender,
- RequestVoteReply requestVoteReply, RaftState suggestedState) {
- return suggestedState;
+ RequestVoteReply requestVoteReply) {
+ return state();
}
- @Override protected RaftState state() {
+ @Override public RaftState state() {
return RaftState.Leader;
}
- @Override public RaftState handleMessage(ActorRef sender, Object message) {
+ @Override public RaftState handleMessage(ActorRef sender, Object originalMessage) {
Preconditions.checkNotNull(sender, "sender should not be null");
- if(message instanceof SendHeartBeat) {
- sender.tell(new AppendEntries(
- context.getTermInformation().getCurrentTerm().get() , context.getId(),
- context.getReplicatedLog().last().getIndex(),
- context.getReplicatedLog().last().getTerm(),
- Collections.EMPTY_LIST, context.getCommitIndex().get()), context.getActor());
- return state();
+ Object message = fromSerializableMessage(originalMessage);
+
+ if (message instanceof RaftRPC) {
+ RaftRPC rpc = (RaftRPC) message;
+ // If RPC request or response contains term T > currentTerm:
+ // set currentTerm = T, convert to follower (§5.1)
+ // This applies to all RPC messages and responses
+ if (rpc.getTerm() > context.getTermInformation().getCurrentTerm()) {
+ context.getTermInformation().updateAndPersist(rpc.getTerm(), null);
+ return RaftState.Follower;
+ }
}
+
+ try {
+ if (message instanceof SendHeartBeat) {
+ return sendHeartBeat();
+ } else if(message instanceof SendInstallSnapshot) {
+ installSnapshotIfNeeded();
+ } else if (message instanceof Replicate) {
+ replicate((Replicate) message);
+ } else if (message instanceof InstallSnapshotReply){
+ handleInstallSnapshotReply(
+ (InstallSnapshotReply) message);
+ }
+ } finally {
+ scheduleHeartBeat(context.getConfigParams().getHeartBeatInterval());
+ }
+
return super.handleMessage(sender, message);
}
+
+ private void handleInstallSnapshotReply(InstallSnapshotReply message) {
+ InstallSnapshotReply reply = message;
+ String followerId = reply.getFollowerId();
+ FollowerLogInformation followerLogInformation =
+ followerToLog.get(followerId);
+
+ followerLogInformation
+ .setMatchIndex(context.getReplicatedLog().getSnapshotIndex());
+ followerLogInformation
+ .setNextIndex(context.getReplicatedLog().getSnapshotIndex() + 1);
+ }
+
+ private void replicate(Replicate replicate) {
+ long logIndex = replicate.getReplicatedLogEntry().getIndex();
+
+ context.getLogger().debug("Replicate message " + logIndex);
+
+ if (followers.size() == 0) {
+ context.setCommitIndex(
+ replicate.getReplicatedLogEntry().getIndex());
+
+ context.getActor()
+ .tell(new ApplyState(replicate.getClientActor(),
+ replicate.getIdentifier(),
+ replicate.getReplicatedLogEntry()),
+ context.getActor()
+ );
+ } 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 : followers) {
+ ActorSelection followerActor =
+ context.getPeerActorSelection(followerId);
+
+ if (followerActor != null) {
+ 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 : followers) {
+ ActorSelection followerActor =
+ context.getPeerActorSelection(followerId);
+
+ if(followerActor != null) {
+ 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()
+ );
+ }
+ }
+ }
+ }
+
+ private RaftState sendHeartBeat() {
+ if (followers.size() > 0) {
+ sendAppendEntries();
+ }
+ return state();
+ }
+
+ private void stopHeartBeat() {
+ if (heartbeatSchedule != null && !heartbeatSchedule.isCancelled()) {
+ heartbeatSchedule.cancel();
+ }
+ }
+
+ private void stopInstallSnapshotSchedule() {
+ if (installSnapshotSchedule != null && !installSnapshotSchedule.isCancelled()) {
+ installSnapshotSchedule.cancel();
+ }
+ }
+
+ private void scheduleHeartBeat(FiniteDuration interval) {
+ if(followers.size() == 0){
+ // Optimization - do not bother scheduling a heartbeat as there are
+ // no followers
+ return;
+ }
+
+ stopHeartBeat();
+
+ // Schedule a heartbeat. When the scheduler triggers a SendHeartbeat
+ // message is sent to itself.
+ // Scheduling the heartbeat only once here because heartbeats do not
+ // need to be sent if there are other messages being sent to the remote
+ // actor.
+ heartbeatSchedule =
+ context.getActorSystem().scheduler().scheduleOnce(
+ interval,
+ context.getActor(), new SendHeartBeat(),
+ context.getActorSystem().dispatcher(), context.getActor());
+ }
+
+
+ private void scheduleInstallSnapshotCheck(FiniteDuration interval) {
+ if(followers.size() == 0){
+ // Optimization - do not bother scheduling a heartbeat as there are
+ // no followers
+ return;
+ }
+
+ stopInstallSnapshotSchedule();
+
+ // Schedule a message to send append entries to followers that can
+ // accept an append entries with some data in it
+ installSnapshotSchedule =
+ context.getActorSystem().scheduler().scheduleOnce(
+ interval,
+ context.getActor(), new SendInstallSnapshot(),
+ context.getActorSystem().dispatcher(), context.getActor());
+ }
+
+
+
+ @Override public void close() throws Exception {
+ stopHeartBeat();
+ }
+
+ @Override public String getLeaderId() {
+ return context.getId();
+ }
+
}
Code Review / controller.git / blobdiff