io.permazen.kv.raft

Class LeaderRole

java.lang.Object

io.permazen.kv.raft.Role

io.permazen.kv.raft.LeaderRole

public class LeaderRole
extends Role

Raft leader role.

Method Summary

Modifier and Type	Method and Description
List<Follower>	getFollowers() Get this leader's known followers.
Timestamp	getLeaseTimeout() Get this leader's "lease timeout".
void	stepDown() Force this leader to step down.
String	toString()

Methods inherited from class io.permazen.kv.raft.Role

getKVDatabase, isLeaderLeaseActiveAt, isLeaderLeaseActiveNow

Methods inherited from class java.lang.Object

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

Method Detail

getFollowers

public List<Follower> getFollowers()

Get this leader's known followers.

The returned list is a copy; changes have no effect on this instance.

Returns:

this leader's followers

getLeaseTimeout

public Timestamp getLeaseTimeout()

Get this leader's "lease timeout".

This is the earliest possible time at which some other, new leader could be elected in a new term. Consequently, it is the earliest possible time at which any entry that this leader is unaware of could be appended to the Raft log, under the assumption that all nodes are configured with the same election timeout value.

Normally, if followers are responding to AppendRequests properly, this will be a value in the (near) future. This allows the leader to make the assumption, up until that point in time, that its log is fully up-to-date.

Until it hears from a majority of followers, a leader will not have a lease timeout established yet. This value is also not used or meaningful when this node is the only node in the cluster. In either case, this method returns null.

This method may also return null if a previous lease timeout has gotten very stale and in danger of rolling over (e.g., isolated leader).

Returns:

this leader's lease timeout, or null if none is established yet

stepDown

public void stepDown()

Force this leader to step down.

Throws:

IllegalStateException - if this role is no longer active or election timer is not running

toString

public String toString()

Specified by:

toString in class Role