org.onosproject.cluster

Class Leadership

java.lang.Object

org.onosproject.cluster.Leadership

public class Leadership
extends Object

Abstract leadership concept. The information carried by this construct include the topic of contention, the NodeIds of Nodes that could become leader for the topic, the epoch when the term for a given leader began, and the system time when the term began. Note:

• The list of NodeIds may include the current leader at index 0, and the rest in decreasing preference order.
• The epoch is the logical age of a Leadership construct, and should be used for comparing two Leaderships, but only of the same topic.
• The leader may be null if its accuracy can't be guaranteed. This applies to CANDIDATES_CHANGED events and candidate board contents.

Constructor Summary

Constructors

Constructor and Description
Leadership(String topic, List<NodeId> candidates, long epoch, long electedTime)
Leadership(String topic, NodeId leader, List<NodeId> candidates, long epoch, long electedTime)
Leadership(String topic, NodeId leader, long epoch, long electedTime)

Method Summary

Modifier and Type	Method and Description
List<NodeId>	candidates() Returns an preference-ordered list of nodes that are in the leadership race for this topic.
long	electedTime() The system time when the term started.
long	epoch() The epoch when the leadership was assumed.
boolean	equals(Object obj)
int	hashCode()
NodeId	leader() The nodeId of leader for this topic.
String	topic() The topic for which this leadership applies.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

Leadership

public Leadership(String topic,
                  NodeId leader,
                  long epoch,
                  long electedTime)

Leadership

public Leadership(String topic,
                  NodeId leader,
                  List<NodeId> candidates,
                  long epoch,
                  long electedTime)

Leadership

public Leadership(String topic,
                  List<NodeId> candidates,
                  long epoch,
                  long electedTime)

Method Detail

topic

public String topic()

The topic for which this leadership applies.

Returns:

leadership topic.

leader

public NodeId leader()

The nodeId of leader for this topic.

Returns:

leader node.

candidates

public List<NodeId> candidates()

Returns an preference-ordered list of nodes that are in the leadership race for this topic.

Returns:

a list of NodeIds in priority-order, or an empty list.

epoch

public long epoch()

The epoch when the leadership was assumed.

Comparing epochs is only appropriate for leadership events for the same topic. The system guarantees that for any given topic the epoch for a new term is higher (not necessarily by 1) than the epoch for any previous term.

Returns:

leadership epoch

electedTime

public long electedTime()

The system time when the term started.

The elected time is initially set on the node coordinating the leader election using its local system time. Due to possible clock skew, relying on this value for determining event ordering is discouraged. Epoch is more appropriate for determining event ordering.

Returns:

elected time.

hashCode

public int hashCode()

Overrides:

hashCode in class Object

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

toString

public String toString()

Overrides:

toString in class Object