package org.opendaylight.controller.cluster.raft.behaviors;
import akka.actor.ActorRef;
+import akka.actor.ActorSelection;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.common.base.Stopwatch;
import java.util.concurrent.TimeUnit;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import org.opendaylight.controller.cluster.raft.FollowerLogInformation;
import org.opendaylight.controller.cluster.raft.RaftActorContext;
+import org.opendaylight.controller.cluster.raft.RaftActorLeadershipTransferCohort;
import org.opendaylight.controller.cluster.raft.RaftState;
-import org.opendaylight.controller.cluster.raft.base.messages.IsolatedLeaderCheck;
+import org.opendaylight.controller.cluster.raft.base.messages.ElectionTimeout;
+import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
/**
* The behavior of a RaftActor when it is in the Leader state
* set commitIndex = N (§5.3, §5.4).
*/
public class Leader extends AbstractLeader {
- private static final IsolatedLeaderCheck ISOLATED_LEADER_CHECK = new IsolatedLeaderCheck();
- private final Stopwatch isolatedLeaderCheck;
+ /**
+ * Internal message sent to periodically check if this leader has become isolated and should transition
+ * to {@link IsolatedLeader}.
+ */
+ @VisibleForTesting
+ static final Object ISOLATED_LEADER_CHECK = new Object();
+
+ private final Stopwatch isolatedLeaderCheck = Stopwatch.createStarted();
+ private @Nullable LeadershipTransferContext leadershipTransferContext;
public Leader(RaftActorContext context) {
- super(context);
- isolatedLeaderCheck = Stopwatch.createStarted();
+ super(context, RaftState.Leader);
}
- @Override public RaftActorBehavior handleMessage(ActorRef sender, Object originalMessage) {
+ @Override
+ public RaftActorBehavior handleMessage(ActorRef sender, Object originalMessage) {
Preconditions.checkNotNull(sender, "sender should not be null");
- if (originalMessage instanceof IsolatedLeaderCheck) {
+ if (ISOLATED_LEADER_CHECK.equals(originalMessage)) {
if (isLeaderIsolated()) {
LOG.warn("{}: At least {} followers need to be active, Switching {} from Leader to IsolatedLeader",
- context.getId(), minIsolatedLeaderPeerCount, leaderId);
-
+ context.getId(), getMinIsolatedLeaderPeerCount(), getLeaderId());
return internalSwitchBehavior(RaftState.IsolatedLeader);
+ } else {
+ return this;
}
+ } else {
+ return super.handleMessage(sender, originalMessage);
}
-
- return super.handleMessage(sender, originalMessage);
}
@Override
isolatedLeaderCheck.reset().start();
}
+ if(leadershipTransferContext != null && leadershipTransferContext.isExpired(
+ context.getConfigParams().getElectionTimeOutInterval().toMillis())) {
+ LOG.debug("{}: Leadership transfer expired", logName());
+ leadershipTransferContext = null;
+ }
+ }
+
+ @Override
+ protected RaftActorBehavior handleAppendEntriesReply(ActorRef sender, AppendEntriesReply appendEntriesReply) {
+ RaftActorBehavior returnBehavior = super.handleAppendEntriesReply(sender, appendEntriesReply);
+ tryToCompleteLeadershipTransfer(appendEntriesReply.getFollowerId());
+ return returnBehavior;
+ }
+
+ /**
+ * Attempts to transfer leadership to a follower as per the raft paper (§3.10) as follows:
+ * <ul>
+ * <li>Start a timer (Stopwatch).</li>
+ * <li>Send an initial AppendEntries heartbeat to all followers.</li>
+ * <li>On AppendEntriesReply, check if the follower's new match Index matches the leader's last index</li>
+ * <li>If it matches, </li>
+ * <ul>
+ * <li>Send an additional AppendEntries to ensure the follower has applied all its log entries to its state.</li>
+ * <li>Send an ElectionTimeout to the follower to immediately start an election.</li>
+ * <li>Notify {@link RaftActorLeadershipTransferCohort#transferComplete}.</li>
+ * </ul>
+ * <li>Otherwise if the election time out period elapses, notify
+ * {@link RaftActorLeadershipTransferCohort#abortTtransfer}.</li>
+ * </ul>
+ *
+ * @param leadershipTransferCohort
+ */
+ public void transferLeadership(@Nonnull RaftActorLeadershipTransferCohort leadershipTransferCohort) {
+ LOG.debug("{}: Attempting to transfer leadership", logName());
+
+ leadershipTransferContext = new LeadershipTransferContext(leadershipTransferCohort);
+
+ // Send an immediate heart beat to the followers.
+ sendAppendEntries(0, false);
+ }
+
+ private void tryToCompleteLeadershipTransfer(String followerId) {
+ if(leadershipTransferContext == null) {
+ return;
+ }
+
+ FollowerLogInformation followerInfo = getFollower(followerId);
+ if(followerInfo == null) {
+ return;
+ }
+
+ long lastIndex = context.getReplicatedLog().lastIndex();
+ boolean isVoting = context.getPeerInfo(followerId).isVoting();
+
+ LOG.debug("{}: tryToCompleteLeadershipTransfer: followerId: {}, matchIndex: {}, lastIndex: {}, isVoting: {}",
+ logName(), followerId, followerInfo.getMatchIndex(), lastIndex, isVoting);
+
+ if(isVoting && followerInfo.getMatchIndex() == lastIndex) {
+ LOG.debug("{}: Follower's log matches - sending ElectionTimeout", logName());
+
+ // We can't be sure if the follower has applied all its log entries to its state so send an
+ // additional AppendEntries with the latest commit index.
+ sendAppendEntries(0, false);
+
+ // Now send an ElectionTimeout to the matching follower to immediately start an election.
+ ActorSelection followerActor = context.getPeerActorSelection(followerId);
+ followerActor.tell(ElectionTimeout.INSTANCE, context.getActor());
+
+ LOG.debug("{}: Leader transfer complete", logName());
+
+ leadershipTransferContext.transferCohort.transferComplete();
+ leadershipTransferContext = null;
+ }
}
@Override
- public void close() throws Exception {
+ public void close() {
+ if(leadershipTransferContext != null) {
+ leadershipTransferContext.transferCohort.abortTransfer();
+ }
+
super.close();
}
void markFollowerInActive(String followerId) {
getFollower(followerId).markFollowerInActive();
}
+
+ private static class LeadershipTransferContext {
+ RaftActorLeadershipTransferCohort transferCohort;
+ Stopwatch timer = Stopwatch.createStarted();
+
+ LeadershipTransferContext(RaftActorLeadershipTransferCohort transferCohort) {
+ this.transferCohort = transferCohort;
+ }
+
+ boolean isExpired(long timeout) {
+ if(timer.elapsed(TimeUnit.MILLISECONDS) >= timeout) {
+ transferCohort.abortTransfer();
+ return true;
+ }
+
+ return false;
+ }
+ }
}
Code Review / controller.git / blobdiff