* terms of the Eclipse Public License v1.0 which accompanies this distribution,
* and is available at http://www.eclipse.org/legal/epl-v10.html
*/
-
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.Optional;
import com.google.common.base.Preconditions;
-import org.opendaylight.controller.cluster.raft.FollowerLogInformationImpl;
+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.RaftReplicator;
+import org.opendaylight.controller.cluster.raft.RaftActorLeadershipTransferCohort;
import org.opendaylight.controller.cluster.raft.RaftState;
-import org.opendaylight.controller.cluster.raft.internal.messages.SendHeartBeat;
-import org.opendaylight.controller.cluster.raft.messages.AppendEntries;
+import org.opendaylight.controller.cluster.raft.base.messages.TimeoutNow;
import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
-import org.opendaylight.controller.cluster.raft.messages.RequestVote;
-import org.opendaylight.controller.cluster.raft.messages.RequestVoteReply;
-
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.concurrent.atomic.AtomicLong;
/**
- * The behavior of a RaftActor when it is in the Leader state
+ * The behavior of a RaftActor when it is in the Leader state.
+ *
* <p>
* Leaders:
* <ul>
* respond after entry applied to state machine (§5.3)
* <li> If last log index ≥ nextIndex for a follower: send
* AppendEntries RPC with log entries starting at nextIndex
- * <ul>
* <li> If successful: update nextIndex and matchIndex for
* follower (§5.3)
* <li> If AppendEntries fails because of log inconsistency:
* decrement nextIndex and retry (§5.3)
- * </ul>
- * <li> If there exists an N such that N > commitIndex, a majority
+ * <li> 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).
+ * </ul>
*/
-public class Leader extends AbstractRaftActorBehavior {
-
-
- private final Map<String, ActorRef> followerToReplicator = new HashMap<>();
+public class Leader extends AbstractLeader {
+ /**
+ * 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();
+ @Nullable private LeadershipTransferContext leadershipTransferContext;
+
+ Leader(RaftActorContext context, @Nullable AbstractLeader initializeFromLeader) {
+ super(context, RaftState.Leader, initializeFromLeader);
+ }
- public Leader(RaftActorContext context, List<String> followers){
- super(context);
+ public Leader(RaftActorContext context) {
+ this(context, null);
+ }
- for(String follower : followers) {
+ @Override
+ public RaftActorBehavior handleMessage(ActorRef sender, Object originalMessage) {
+ Preconditions.checkNotNull(sender, "sender should not be null");
- ActorRef replicator = context.actorOf(
- RaftReplicator.props(
- new FollowerLogInformationImpl(follower,
- new AtomicLong(0),
- new AtomicLong(0)),
- context.getActor()
- )
- );
+ if (ISOLATED_LEADER_CHECK.equals(originalMessage)) {
+ if (isLeaderIsolated()) {
+ log.warn("{}: At least {} followers need to be active, Switching {} from Leader to IsolatedLeader",
+ context.getId(), getMinIsolatedLeaderPeerCount(), getLeaderId());
+ return internalSwitchBehavior(new IsolatedLeader(context, this));
+ } else {
+ return this;
+ }
+ } else {
+ return super.handleMessage(sender, originalMessage);
+ }
+ }
- // Create a replicator for each follower
- followerToReplicator.put(follower, replicator);
+ @Override
+ protected void beforeSendHeartbeat() {
+ if (isolatedLeaderCheck.elapsed(TimeUnit.MILLISECONDS)
+ > context.getConfigParams().getIsolatedCheckIntervalInMillis()) {
+ context.getActor().tell(ISOLATED_LEADER_CHECK, context.getActor());
+ 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;
}
- @Override protected RaftState handleAppendEntries(ActorRef sender,
- AppendEntries appendEntries, RaftState suggestedState) {
- return suggestedState;
+ /**
+ * 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,
+ * <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>
+ * <li>Otherwise if the election time out period elapses, notify
+ * {@link RaftActorLeadershipTransferCohort#abortTransfer}.</li>
+ * </ul>
+ *
+ * @param leadershipTransferCohort the cohort participating in the leadership transfer
+ */
+ 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);
}
- @Override protected RaftState handleAppendEntriesReply(ActorRef sender,
- AppendEntriesReply appendEntriesReply, RaftState suggestedState) {
- return suggestedState;
+ private void tryToCompleteLeadershipTransfer(String followerId) {
+ if (leadershipTransferContext == null) {
+ return;
+ }
+
+ final Optional<String> requestedFollowerIdOptional
+ = leadershipTransferContext.transferCohort.getRequestedFollowerId();
+ if (requestedFollowerIdOptional.isPresent() && !requestedFollowerIdOptional.get().equals(followerId)) {
+ // we want to transfer leadership to specific follower
+ 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 a TimeoutNow message to the matching follower to immediately start an election.
+ ActorSelection followerActor = context.getPeerActorSelection(followerId);
+ followerActor.tell(TimeoutNow.INSTANCE, context.getActor());
+
+ log.debug("{}: Leader transfer complete", logName());
+
+ leadershipTransferContext.transferCohort.transferComplete();
+ leadershipTransferContext = null;
+ }
}
- @Override protected RaftState handleRequestVote(ActorRef sender,
- RequestVote requestVote, RaftState suggestedState) {
- return suggestedState;
+ @Override
+ public void close() {
+ if (leadershipTransferContext != null) {
+ LeadershipTransferContext localLeadershipTransferContext = leadershipTransferContext;
+ leadershipTransferContext = null;
+ localLeadershipTransferContext.transferCohort.abortTransfer();
+ }
+
+ super.close();
}
- @Override protected RaftState handleRequestVoteReply(ActorRef sender,
- RequestVoteReply requestVoteReply, RaftState suggestedState) {
- return suggestedState;
+ @VisibleForTesting
+ void markFollowerActive(String followerId) {
+ getFollower(followerId).markFollowerActive();
}
- @Override protected RaftState state() {
- return RaftState.Leader;
+ @VisibleForTesting
+ void markFollowerInActive(String followerId) {
+ getFollower(followerId).markFollowerInActive();
}
- @Override public RaftState handleMessage(ActorRef sender, Object message) {
- Preconditions.checkNotNull(sender, "sender should not be null");
+ 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;
+ }
- 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();
+ return false;
}
- return super.handleMessage(sender, message);
}
}
Code Review / controller.git / blobdiff