org.apache.nifi.cluster.coordination.flow

Class PopularVoteFlowElection

java.lang.Object

org.apache.nifi.cluster.coordination.flow.PopularVoteFlowElection

All Implemented Interfaces:

FlowElection

public class PopularVoteFlowElection
extends java.lang.Object
implements FlowElection

An implementation of FlowElection that waits until either a maximum amount of time has elapsed or a maximum number of Data Flows have entered the running to be elected, and then elects the 'winner' based on the number of 'votes' that a particular DataFlow has received. This implementation considers two Flows with the same fingerprint to be the same Flow. If there is a tie in the number of votes for a particular DataFlow, one will be chosen in a non-deterministic manner. If multiple DataFlows are presented with the same fingerprint but different Flows (for instance, the position of a component has changed), one of the Flows with that fingerprint will be chosen in a non-deterministic manner.

Constructor Summary

Constructors

Constructor and Description
PopularVoteFlowElection(long maxWait, java.util.concurrent.TimeUnit maxWaitPeriod, java.lang.Integer maxNodes, FingerprintFactory fingerprintFactory)

Method Summary

Modifier and Type	Method and Description
DataFlow	castVote(DataFlow candidate, NodeIdentifier nodeId) If the election has not yet completed, adds the given DataFlow to the list of candidates (if it is not already in the running) and increments the number of votes for this DataFlow by 1.
DataFlow	getElectedDataFlow() Returns the DataFlow that has been elected as the "correct" version of the flow, or null if the election has not yet completed.
java.lang.String	getStatusDescription() Returns a human-readable description of the status of the election
boolean	isElectionComplete() Checks if the election has completed or not.
boolean	isVoteCounted(NodeIdentifier nodeIdentifier) Returns true if a vote has already been counted for the given Node Identifier, false otherwise.

Methods inherited from class java.lang.Object

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

Constructor Detail

PopularVoteFlowElection

public PopularVoteFlowElection(long maxWait,
                               java.util.concurrent.TimeUnit maxWaitPeriod,
                               java.lang.Integer maxNodes,
                               FingerprintFactory fingerprintFactory)

Method Detail

isElectionComplete

public boolean isElectionComplete()

Description copied from interface: FlowElection

Checks if the election has completed or not.

Specified by:

isElectionComplete in interface FlowElection

Returns:

true if the election has completed, false otherwise.

isVoteCounted

public boolean isVoteCounted(NodeIdentifier nodeIdentifier)

Description copied from interface: FlowElection

Returns true if a vote has already been counted for the given Node Identifier, false otherwise.

Specified by:

isVoteCounted in interface FlowElection

Parameters:

nodeIdentifier - the identifier of the node

Returns:

true if a vote has already been counted for the given Node Identifier, false otherwise.

castVote

public DataFlow castVote(DataFlow candidate,
                         NodeIdentifier nodeId)

Description copied from interface: FlowElection

If the election has not yet completed, adds the given DataFlow to the list of candidates (if it is not already in the running) and increments the number of votes for this DataFlow by 1. If the election has completed, the given candidate is ignored, and the already-elected DataFlow will be returned. If the election has not yet completed, a vote will be cast for the given candidate and null will be returned, signifying that no candidate has yet been chosen.

Specified by:

castVote in interface FlowElection

Parameters:

candidate - the DataFlow to vote for and add to the pool of candidates if not already present

nodeId - the identifier of the node casting the vote

Returns:

the elected DataFlow, or null if no DataFlow has yet been elected

getElectedDataFlow

public DataFlow getElectedDataFlow()

Description copied from interface: FlowElection

Returns the DataFlow that has been elected as the "correct" version of the flow, or null if the election has not yet completed.

Specified by:

getElectedDataFlow in interface FlowElection

Returns:

the DataFlow that has been elected as the "correct" version of the flow, or null if the election has not yet completed.

getStatusDescription

public java.lang.String getStatusDescription()

Description copied from interface: FlowElection

Returns a human-readable description of the status of the election

Specified by:

getStatusDescription in interface FlowElection

Returns:

a human-readable description of the status of the election