Package org.opendaylight.controller.cluster.raft.behaviors

Class Leader

java.lang.Object

org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior

org.opendaylight.controller.cluster.raft.behaviors.AbstractLeader

org.opendaylight.controller.cluster.raft.behaviors.Leader

All Implemented Interfaces:

AutoCloseable

public non-sealed class Leader
extends AbstractLeader

The behavior of a RaftActor when it is in the Leader state.

Leaders:

• Upon election: send initial empty AppendEntries RPCs (heartbeat) to each server; repeat during idle periods to prevent election timeouts (§5.2)
• If command received from client: append entry to local log, respond after entry applied to state machine (§5.3)
• If last log index ≥ nextIndex for a follower: send AppendEntries RPC with log entries starting at nextIndex
• If successful: update nextIndex and matchIndex for follower (§5.3)
• If AppendEntries fails because of log inconsistency: decrement nextIndex and retry (§5.3)
• 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).

Nested Class Summary

Nested classes/interfaces inherited from class org.opendaylight.controller.cluster.raft.behaviors.AbstractLeader

AbstractLeader.SendHeartBeat

Constructor Summary

Constructors

Constructor	Description
Leader(RaftActorContext context)

Method Summary

Modifier and Type	Method	Description
final void	close()
RaftActorBehavior	handleMessage(org.apache.pekko.actor.ActorRef sender, Object originalMessage)	Handle a message.
void	transferLeadership(@NonNull RaftActorLeadershipTransferCohort leadershipTransferCohort)	Attempts to transfer leadership to a follower as per the raft paper (§3.10) as follows: Start a timer (Stopwatch). Send an initial AppendEntries heartbeat to all followers. On AppendEntriesReply, check if the follower's new match Index matches the leader's last index If it matches, Send an additional AppendEntries to ensure the follower has applied all its log entries to its state. Send an ElectionTimeout to the follower to immediately start an election. Notify RaftActorLeadershipTransferCohort.transferComplete(). Otherwise if the election time out period elapses, notify RaftActorLeadershipTransferCohort.abortTransfer().

Methods inherited from class org.opendaylight.controller.cluster.raft.behaviors.AbstractLeader

addFollower, checkConsensusReached, followerLogSize, getFollower, getFollowerIds, getLeaderId, getLeaderPayloadVersion, getMinIsolatedLeaderPeerCount, initiateCaptureSnapshot, isLeaderIsolated, printFollowerStates, removeFollower, sendAppendEntries, sendInstallSnapshot, updateMinReplicaCount

Methods inherited from class org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior

getReplicatedToAllIndex, raftRole, setReplicatedToAllIndex

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

Leader

public Leader(RaftActorContext context)

Method Details

handleMessage

public RaftActorBehavior handleMessage(org.apache.pekko.actor.ActorRef sender,
 Object originalMessage)

Description copied from class: RaftActorBehavior

Handle a message. If the processing of the message warrants a state change then a new behavior should be returned otherwise this method should return the current behavior.

Overrides:

handleMessage in class AbstractLeader

Parameters:

sender - The sender of the message

originalMessage - A message that needs to be processed

Returns:

The new behavior or current behavior, or null if the message was not handled.

transferLeadership

public void transferLeadership(@NonNull RaftActorLeadershipTransferCohort leadershipTransferCohort)

Attempts to transfer leadership to a follower as per the raft paper (§3.10) as follows:

• Start a timer (Stopwatch).
• Send an initial AppendEntries heartbeat to all followers.
• On AppendEntriesReply, check if the follower's new match Index matches the leader's last index
• If it matches,
  • Send an additional AppendEntries to ensure the follower has applied all its log entries to its state.
  • Send an ElectionTimeout to the follower to immediately start an election.
  • Notify RaftActorLeadershipTransferCohort.transferComplete().
• Otherwise if the election time out period elapses, notify RaftActorLeadershipTransferCohort.abortTransfer().

Parameters:

leadershipTransferCohort - the cohort participating in the leadership transfer

close

public final void close()

Specified by:

close in interface AutoCloseable

Overrides:

close in class AbstractLeader