*/
package org.opendaylight.controller.cluster.raft;
+import akka.actor.ActorRef;
+import akka.actor.ActorSelection;
+import akka.actor.Cancellable;
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Optional;
+import com.google.common.base.Stopwatch;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+import org.opendaylight.controller.cluster.raft.base.messages.LeaderTransitioning;
import org.opendaylight.controller.cluster.raft.behaviors.Leader;
import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import scala.concurrent.duration.FiniteDuration;
/**
- * A helper class that participates in raft actor leadership transfer. An instance is created upon
+ * A raft actor support class that participates in leadership transfer. An instance is created upon
* initialization of leadership transfer.
* <p>
- * NOTE: All methods on this class must be called on the actor's thread dispatcher as they modify internal state.
+ * The transfer process is as follows:
+ * <ol>
+ * <li>Send a LeaderStateChanged message with a null leader Id to the local RoleChangeNotifier to notify
+ * clients that we no longer have a working leader.</li>
+ * <li>Send a LeaderTransitioning message to each follower so each can send LeaderStateChanged messages to
+ * their local RoleChangeNotifiers.</li>
+ * <li>Call {@link RaftActor#pauseLeader} passing this RaftActorLeadershipTransferCohort
+ * instance. This allows derived classes to perform work prior to transferring leadership.</li>
+ * <li>When the pause is complete, the {@link #run} method is called which in turn calls
+ * {@link Leader#transferLeadership}.</li>
+ * <li>The Leader calls {@link #transferComplete} on successful completion.</li>
+ * <li>Wait a short period of time for the new leader to be elected to give the derived class a chance to
+ * possibly complete work that was suspended while we were transferring.</li>
+ * <li>On notification of the new leader from the RaftActor or on time out, notify {@link OnComplete} callbacks.</li>
+ * </ol>
+ * <p>
+ * NOTE: All methods on this class must be called on the actor's thread dispatcher as they may access/modify
+ * internal state.
*
* @author Thomas Pantelis
*/
-public abstract class RaftActorLeadershipTransferCohort {
+public class RaftActorLeadershipTransferCohort implements Runnable {
+ private static final Logger LOG = LoggerFactory.getLogger(RaftActorLeadershipTransferCohort.class);
+
private final RaftActor raftActor;
+ private final ActorRef replyTo;
+ private Cancellable newLeaderTimer;
+ private final List<OnComplete> onCompleteCallbacks = new ArrayList<>();
+ private long newLeaderTimeoutInMillis = 2000;
+ private final Stopwatch transferTimer = Stopwatch.createUnstarted();
- protected RaftActorLeadershipTransferCohort(RaftActor raftActor) {
+ RaftActorLeadershipTransferCohort(RaftActor raftActor, ActorRef replyTo) {
this.raftActor = raftActor;
+ this.replyTo = replyTo;
+ }
+
+ void init() {
+ RaftActorContext context = raftActor.getRaftActorContext();
+ RaftActorBehavior currentBehavior = raftActor.getCurrentBehavior();
+
+ transferTimer.start();
+
+ Optional<ActorRef> roleChangeNotifier = raftActor.getRoleChangeNotifier();
+ if(roleChangeNotifier.isPresent()) {
+ roleChangeNotifier.get().tell(raftActor.newLeaderStateChanged(context.getId(), null,
+ currentBehavior.getLeaderPayloadVersion()), raftActor.self());
+ }
+
+ LeaderTransitioning leaderTransitioning = new LeaderTransitioning();
+ for(String peerId: context.getPeerIds()) {
+ ActorSelection followerActor = context.getPeerActorSelection(peerId);
+ if(followerActor != null) {
+ followerActor.tell(leaderTransitioning, context.getActor());
+ }
+ }
+
+ raftActor.pauseLeader(this);
}
/**
- * This method is invoked to start leadership transfer.
+ * This method is invoked to run the leadership transfer.
*/
- public void startTransfer() {
+ @Override
+ public void run() {
RaftActorBehavior behavior = raftActor.getCurrentBehavior();
+ // Sanity check...
if(behavior instanceof Leader) {
((Leader)behavior).transferLeadership(this);
+ } else {
+ LOG.debug("{}: No longer the leader - skipping transfer", raftActor.persistenceId());
+ finish(true);
}
}
/**
- * This method is invoked to abort leadership transfer.
+ * This method is invoked to abort leadership transfer on failure.
*/
public void abortTransfer() {
- transferComplete();
+ LOG.debug("{}: leader transfer aborted", raftActor.persistenceId());
+ finish(false);
}
/**
- * This method is invoked when leadership transfer is complete.
+ * This method is invoked when leadership transfer was carried out and complete.
*/
- public abstract void transferComplete();
+ public void transferComplete() {
+ LOG.debug("{}: leader transfer complete - waiting for new leader", raftActor.persistenceId());
+
+ // We'll give it a little time for the new leader to be elected to give the derived class a
+ // chance to possibly complete work that was suspended while we were transferring. The
+ // RequestVote message from the new leader candidate should cause us to step down as leader
+ // and convert to follower due to higher term. We should then get an AppendEntries heart
+ // beat with the new leader id.
+
+ // Add a timer in case we don't get a leader change - 2 sec should be plenty of time if a new
+ // leader is elected. Note: the Runnable is sent as a message to the raftActor which executes it
+ // safely run on actor's thread dispatcher.
+ FiniteDuration timeout = FiniteDuration.create(newLeaderTimeoutInMillis, TimeUnit.MILLISECONDS);
+ newLeaderTimer = raftActor.getContext().system().scheduler().scheduleOnce(timeout, raftActor.self(),
+ new Runnable() {
+ @Override
+ public void run() {
+ LOG.debug("{}: leader not elected in time", raftActor.persistenceId());
+ finish(true);
+ }
+ }, raftActor.getContext().system().dispatcher(), raftActor.self());
+ }
+
+ void onNewLeader(String newLeader) {
+ if(newLeader != null && newLeaderTimer != null) {
+ LOG.debug("{}: leader changed to {}", raftActor.persistenceId(), newLeader);
+ newLeaderTimer.cancel();
+ finish(true);
+ }
+ }
+
+ private void finish(boolean success) {
+ if(transferTimer.isRunning()) {
+ transferTimer.stop();
+ if(success) {
+ LOG.info("{}: Successfully transferred leadership to {} in {}", raftActor.persistenceId(),
+ raftActor.getLeaderId(), transferTimer.toString());
+ } else {
+ LOG.info("{}: Failed to transfer leadership in {}", raftActor.persistenceId(),
+ transferTimer.toString());
+ }
+ }
+
+ for(OnComplete onComplete: onCompleteCallbacks) {
+ if(success) {
+ onComplete.onSuccess(raftActor.self(), replyTo);
+ } else {
+ onComplete.onFailure(raftActor.self(), replyTo);
+ }
+ }
+ }
+
+ void addOnComplete(OnComplete onComplete) {
+ onCompleteCallbacks.add(onComplete);
+ }
+
+ @VisibleForTesting
+ void setNewLeaderTimeoutInMillis(long newLeaderTimeoutInMillis) {
+ this.newLeaderTimeoutInMillis = newLeaderTimeoutInMillis;
+ }
+
+ interface OnComplete {
+ void onSuccess(ActorRef raftActorRef, ActorRef replyTo);
+ void onFailure(ActorRef raftActorRef, ActorRef replyTo);
+ }
}
Code Review / controller.git / blobdiff