* RaftActor has 3 states and each state has a certain behavior associated * with it. A Raft actor can behave as, *
* A RaftActor MUST be a Leader in order to accept requests from clients to * change the state of it's encapsulated state machine. Once a RaftActor becomes * a Leader it is also responsible for ensuring that all followers ultimately * have the same log and therefore the same state machine as itself. - *
- * + * + ** The current behavior of a RaftActor determines how election for leadership * is initiated and how peer RaftActors react to request for votes. - *
- * + * + ** Each RaftActor also needs to know the current election term. It uses this * information for a couple of things. One is to simply figure out who it * voted for in the last election. Another is to figure out if the message * it received to update it's state is stale. - *
- * + * + ** The RaftActor uses akka-persistence to store it's replicated log. * Furthermore through it's behaviors a Raft Actor determines - *
** This is to account for situations where a we know that a peer * exists but we do not know an address up-front. This may also be used in * situations where a known peer starts off in a different location and we * need to change it's address + * *
* Note that if the peerId does not match the list of peers passed to
* this actor during construction an IllegalStateException will be thrown.
- *
- * @param peerId
- * @param peerAddress
*/
- protected void setPeerAddress(String peerId, String peerAddress){
+ protected void setPeerAddress(final String peerId, final String peerAddress) {
context.setPeerAddress(peerId, peerAddress);
}
/**
* The applyState method will be called by the RaftActor when some data
- * needs to be applied to the actor's state
+ * needs to be applied to the actor's state.
*
* @param clientActor A reference to the client who sent this message. This
* is the same reference that was passed to persistData
@@ -512,14 +809,12 @@ public abstract class RaftActor extends AbstractUntypedPersistentActor {
* @param data A piece of data that was persisted by the persistData call.
* This should NEVER be null.
*/
- protected abstract void applyState(ActorRef clientActor, String identifier,
- Object data);
+ protected abstract void applyState(ActorRef clientActor, Identifier identifier, Object data);
/**
* Returns the RaftActorRecoveryCohort to participate in persistence recovery.
*/
- @Nonnull
- protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
+ protected abstract @NonNull RaftActorRecoveryCohort getRaftActorRecoveryCohort();
/**
* This method is called when recovery is complete.
@@ -527,10 +822,9 @@ public abstract class RaftActor extends AbstractUntypedPersistentActor {
protected abstract void onRecoveryComplete();
/**
- * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
+ * Returns the RaftActorSnapshotCohort to participate in snapshot captures.
*/
- @Nonnull
- protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
+ protected abstract @NonNull RaftActorSnapshotCohort getRaftActorSnapshotCohort();
/**
* This method will be called by the RaftActor when the state of the
@@ -540,87 +834,207 @@ public abstract class RaftActor extends AbstractUntypedPersistentActor {
protected abstract void onStateChanged();
/**
- * Notifier Actor for this RaftActor to notify when a role change happens
+ * Notifier Actor for this RaftActor to notify when a role change happens.
+ *
* @return ActorRef - ActorRef of the notifier or Optional.absent if none.
*/
protected abstract Optional
+ * The default implementation immediately runs the operation.
+ *
+ * @param operation the operation to run
+ */
+ protected void pauseLeader(final Runnable operation) {
+ operation.run();
+ }
+
+ /**
+ * This method is invoked when the actions hooked to the leader becoming paused failed to execute and the leader
+ * should resume normal operations.
+ *
+ *
+ * Note this method can be invoked even before the operation supplied to {@link #pauseLeader(Runnable)} is invoked.
+ */
+ protected void unpauseLeader() {
+
+ }
+
+ protected void onLeaderChanged(final String oldLeader, final String newLeader) {
+ }
+
+ private String getLeaderAddress() {
+ if (isLeader()) {
return getSelf().path().toString();
}
- String leaderId = currentBehavior.getLeaderId();
+ String leaderId = getLeaderId();
if (leaderId == null) {
return null;
}
String peerAddress = context.getPeerAddress(leaderId);
- if(LOG.isDebugEnabled()) {
- LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
- persistenceId(), leaderId, peerAddress);
- }
+ LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}", persistenceId(), leaderId, peerAddress);
return peerAddress;
}
- protected boolean hasFollowers(){
+ protected boolean hasFollowers() {
return getRaftActorContext().hasFollowers();
}
+ private void captureSnapshot() {
+ SnapshotManager snapshotManager = context.getSnapshotManager();
+
+ if (!snapshotManager.isCapturing()) {
+ final long idx = getCurrentBehavior().getReplicatedToAllIndex();
+ LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
+ replicatedLog().last(), idx);
+
+ snapshotManager.capture(replicatedLog().last(), idx);
+ }
+ }
+
/**
- * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntriesTest}
- * whose type for fromIndex is long instead of int. This class was kept for backwards
- * compatibility with Helium.
+ * Switch this member to non-voting status. This is a no-op for all behaviors except when we are the leader,
+ * in which case we need to step down.
*/
- @Deprecated
- static class DeleteEntries implements Serializable {
- private static final long serialVersionUID = 1L;
- private final int fromIndex;
+ void becomeNonVoting() {
+ if (isLeader()) {
+ initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
+ @Override
+ public void onSuccess(final ActorRef raftActorRef) {
+ LOG.debug("{}: leader transfer succeeded after change to non-voting", persistenceId());
+ ensureFollowerState();
+ }
- public DeleteEntries(int fromIndex) {
- this.fromIndex = fromIndex;
- }
+ @Override
+ public void onFailure(final ActorRef raftActorRef) {
+ LOG.debug("{}: leader transfer failed after change to non-voting", persistenceId());
+ ensureFollowerState();
+ }
- public int getFromIndex() {
- return fromIndex;
+ private void ensureFollowerState() {
+ // Whether or not leadership transfer succeeded, we have to step down as leader and
+ // switch to Follower so ensure that.
+ if (getRaftState() != RaftState.Follower) {
+ initializeBehavior();
+ }
+ }
+ }, null, RaftActorLeadershipTransferCohort.USE_DEFAULT_LEADER_TIMEOUT);
}
}
- static class UpdateElectionTerm implements Serializable {
- private static final long serialVersionUID = 1L;
- private final long currentTerm;
- private final String votedFor;
+ /**
+ * A point-in-time capture of {@link RaftActorBehavior} state critical for transitioning between behaviors.
+ */
+ private abstract static class BehaviorState implements Immutable {
+ @Nullable abstract RaftActorBehavior getBehavior();
- public UpdateElectionTerm(long currentTerm, String votedFor) {
- this.currentTerm = currentTerm;
- this.votedFor = votedFor;
- }
+ @Nullable abstract String getLastValidLeaderId();
- public long getCurrentTerm() {
- return currentTerm;
- }
+ @Nullable abstract String getLastLeaderId();
- public String getVotedFor() {
- return votedFor;
- }
+ abstract short getLeaderPayloadVersion();
}
- private static class BehaviorStateHolder {
- private RaftActorBehavior behavior;
- private String leaderId;
-
- void init(RaftActorBehavior behavior) {
- this.behavior = behavior;
- this.leaderId = behavior != null ? behavior.getLeaderId() : null;
+ /**
+ * A {@link BehaviorState} corresponding to non-null {@link RaftActorBehavior} state.
+ */
+ private static final class SimpleBehaviorState extends BehaviorState {
+ private final RaftActorBehavior behavior;
+ private final String lastValidLeaderId;
+ private final String lastLeaderId;
+ private final short leaderPayloadVersion;
+
+ SimpleBehaviorState(final String lastValidLeaderId, final String lastLeaderId,
+ final RaftActorBehavior behavior) {
+ this.lastValidLeaderId = lastValidLeaderId;
+ this.lastLeaderId = lastLeaderId;
+ this.behavior = requireNonNull(behavior);
+ this.leaderPayloadVersion = behavior.getLeaderPayloadVersion();
}
+ @Override
RaftActorBehavior getBehavior() {
return behavior;
}
- String getLeaderId() {
- return leaderId;
+ @Override
+ String getLastValidLeaderId() {
+ return lastValidLeaderId;
+ }
+
+ @Override
+ short getLeaderPayloadVersion() {
+ return leaderPayloadVersion;
+ }
+
+ @Override
+ String getLastLeaderId() {
+ return lastLeaderId;
+ }
+ }
+
+ /**
+ * Class tracking behavior-related information, which we need to keep around and pass across behavior switches.
+ * An instance is created for each RaftActor. It has two functions:
+ * - it keeps track of the last leader ID we have encountered since we have been created
+ * - it creates state capture needed to transition from one behavior to the next
+ */
+ private static final class BehaviorStateTracker {
+ /**
+ * A {@link BehaviorState} corresponding to null {@link RaftActorBehavior} state. Since null behavior is only
+ * allowed before we receive the first message, we know the leader ID to be null.
+ */
+ private static final BehaviorState NULL_BEHAVIOR_STATE = new BehaviorState() {
+ @Override
+ RaftActorBehavior getBehavior() {
+ return null;
+ }
+
+ @Override
+ String getLastValidLeaderId() {
+ return null;
+ }
+
+ @Override
+ short getLeaderPayloadVersion() {
+ return -1;
+ }
+
+ @Override
+ String getLastLeaderId() {
+ return null;
+ }
+ };
+
+ private String lastValidLeaderId;
+ private String lastLeaderId;
+
+ BehaviorState capture(final RaftActorBehavior behavior) {
+ if (behavior == null) {
+ verify(lastValidLeaderId == null, "Null behavior with non-null last leader");
+ return NULL_BEHAVIOR_STATE;
+ }
+
+ lastLeaderId = behavior.getLeaderId();
+ if (lastLeaderId != null) {
+ lastValidLeaderId = lastLeaderId;
+ }
+
+ return new SimpleBehaviorState(lastValidLeaderId, lastLeaderId, behavior);
}
}
}