org.opendaylight.controller.cluster.raft.behaviors

Class Leader

java.lang.Object

org.opendaylight.controller.cluster.raft.behaviors.AbstractRaftActorBehavior

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

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

All Implemented Interfaces:

AutoCloseable, RaftActorBehavior

public 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).

Field Summary

Fields inherited from class org.opendaylight.controller.cluster.raft.behaviors.AbstractRaftActorBehavior

context, log

Constructor Summary

Constructors

Constructor and Description
Leader(RaftActorContext context)

Method Summary

Modifier and Type	Method and Description
protected void	beforeSendHeartbeat()
void	close()
protected RaftActorBehavior	handleAppendEntriesReply(akka.actor.ActorRef sender, AppendEntriesReply appendEntriesReply) Derived classes should not directly handle AppendEntriesReply messages it should let the base class handle it first.
RaftActorBehavior	handleMessage(akka.actor.ActorRef sender, Object originalMessage) Handle a message.
void	transferLeadership(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, followerLogSize, getFollower, getFollowerIds, getLeaderId, getLeaderPayloadVersion, getMinIsolatedLeaderPeerCount, handleAppendEntries, handleRequestVoteReply, initiateCaptureSnapshot, isLeaderIsolated, printFollowerStates, removeClientRequestTracker, removeFollower, sendAppendEntries, updateMinReplicaCount

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

actor, appendEntries, applyLogToStateMachine, canGrantVote, canStartElection, createBehavior, currentTerm, electionDuration, getId, getLogEntryIndex, getLogEntryOrSnapshotTerm, getLogEntryTerm, getMajorityVoteCount, getReplicatedToAllIndex, internalSwitchBehavior, internalSwitchBehavior, lastIndex, lastTerm, logName, performSnapshotWithoutCapture, requestVote, scheduleElection, setReplicatedToAllIndex, state, stopElection, switchBehavior, votedFor

Methods inherited from class java.lang.Object

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

Constructor Detail

Leader

public Leader(RaftActorContext context)

Method Detail

handleMessage

public RaftActorBehavior handleMessage(akka.actor.ActorRef sender,
                                       Object originalMessage)

Description copied from interface: 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.

Specified by:

handleMessage in interface RaftActorBehavior

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.

beforeSendHeartbeat

protected void beforeSendHeartbeat()

Overrides:

beforeSendHeartbeat in class AbstractLeader

handleAppendEntriesReply

protected RaftActorBehavior handleAppendEntriesReply(akka.actor.ActorRef sender,
                                                     AppendEntriesReply appendEntriesReply)

Description copied from class: AbstractRaftActorBehavior

Derived classes should not directly handle AppendEntriesReply messages it should let the base class handle it first. Once the base class handles the AppendEntriesReply message and does the common actions that are applicable in all RaftState's it will delegate the handling of the AppendEntriesReply message to the derived class to do more state specific handling by calling this method

Overrides:

handleAppendEntriesReply in class AbstractLeader

Parameters:

sender - The actor that sent this message

appendEntriesReply - The AppendEntriesReply message

Returns:

a new behavior if it was changed or the current behavior

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 void close()

Specified by:

close in interface AutoCloseable

Specified by:

close in interface RaftActorBehavior

Overrides:

close in class AbstractLeader