com.bigdata.quorum

Interface QuorumMember<S extends Remote>

All Superinterfaces:

QuorumClient<S>, QuorumListener, QuorumStateChangeListener, ServiceLookup<S>

All Known Subinterfaces:

QuorumService<S>

All Known Implementing Classes:

AbstractQuorumMember, QuorumServiceBase

public interface QuorumMember<S extends Remote>
extends QuorumClient<S>, QuorumStateChangeListener

A non-remote interface for a service which will participate in a quorum as a member service (as opposed to a client service that merely watches the quorum). The methods on this interface are aware of the service UUID of the member service and can report on its role and relationships in the Quorum. In order to act on the distributed quorum state, the QuorumMember will issue various commands to its QuorumActor.

This interface defines a collection of messages which are used to inform the QuorumMember of significant changes in the distributed quorum state as it pertains to this quorum member. See QuorumStateChangeListener.

Version:

$Id$

Author:

Bryan Thompson

Method Summary

Methods

Modifier and Type	Method and Description
void	assertLeader(long token) Assert that this is the quorum leader.
QuorumActor<S,QuorumMember<S>>	getActor() Return the actor for this QuorumMember.
UUID	getDownstreamServiceId() Return the UUID of the service (if any) downstream from this service in the write pipeline.
ExecutorService	getExecutor() An ExecutorService which may be used by the QuorumMember to run various asynchronous tasks.
S	getService() Return the local service implementation object (NOT the RMI proxy for that object).
UUID	getServiceId() The identifier for this service (the quorum member).
boolean	isFollower(long token) Return true iff this node is a quorum follower.
boolean	isJoinedMember(long token) Return true if the service is joined with the quorum.
boolean	isLastInChain(long token) Return true iff the quorum is highly available and this node is last one in the write pipeline (it will not return true for a singleton quorum where the only node is the master).
boolean	isLeader(long token) Return true iff this node is the quorum leader.
boolean	isMember() Return trueif the quorum recognizes the service as a member of that quorum.
boolean	isPipelineMember() Return true if quorum recognizes the service is part of the write pipeline.

Methods inherited from interface com.bigdata.quorum.QuorumClient

disconnected, getLeader, getLogicalServiceZPath, getQuorum, getService, start, terminate

Methods inherited from interface com.bigdata.quorum.QuorumListener

notify

Methods inherited from interface com.bigdata.quorum.QuorumStateChangeListener

consensus, lostConsensus, memberAdd, memberRemove, pipelineAdd, pipelineChange, pipelineElectedLeader, pipelineRemove, pipelineUpstreamChange, quorumBreak, quorumMeet, serviceJoin, serviceLeave

Method Detail

getServiceId

UUID getServiceId()

The identifier for this service (the quorum member). Each quorum member is a physical service instance of some highly available logical service.

See Also:

QuorumClient.getLogicalServiceZPath()

getService

S getService()

Return the local service implementation object (NOT the RMI proxy for that object).

A service operating as a QuorumMember has both Remote interface and a non-remote interface. These interfaces typically define similar methods (for example, compare HACommitGlue, which is Remote, with QuorumCommit, which is non-remote). The Remote interface in turn will have a local implementation object inside of the JVM and an exported proxy for that Remote interface. This method returns the local implementation object for the Remote interface and is intended to facilitate operations which the QuorumMember executes against its own Remote interface. While the Remote interface will be exposed to other services using a proxy, how that happens is outside of the scope of this method.

getExecutor

ExecutorService getExecutor()

An ExecutorService which may be used by the QuorumMember to run various asynchronous tasks.

getActor

QuorumActor<S,QuorumMember<S>> getActor()

Return the actor for this QuorumMember.

isMember

boolean isMember()

Return trueif the quorum recognizes the service as a member of that quorum. The quorum token is not required for this method because membership status does not change with a quorum meet or break.

isPipelineMember

boolean isPipelineMember()

Return true if quorum recognizes the service is part of the write pipeline. The quorum token is not required for this method because pipeline status does not change with a quorum meet or break. Once a service is receiving synchronous messages from a Quorum it will notice when it enters and leaves the pipeline and when the downstream service for this service changes in the quorum.

isLastInChain

boolean isLastInChain(long token)

Return true iff the quorum is highly available and this node is last one in the write pipeline (it will not return true for a singleton quorum where the only node is the master).

Parameters:

token - The quorum token for which the request was made.

isJoinedMember

boolean isJoinedMember(long token)

Return true if the service is joined with the quorum.

Note: This method DOES NOT throw an exception if the quorum is not met, but it will not return true unless the quorum is met.

Parameters:

token - The quorum token for which the request was made.

isLeader

boolean isLeader(long token)

Return true iff this node is the quorum leader. The quorum leader is the only node which will accept writes. Note that is always true when the #replicationFactor() is ONE (1).

Parameters:

token - The quorum token for which the request was made.

isFollower

boolean isFollower(long token)

Return true iff this node is a quorum follower. This is true of all nodes in a Q except for the leader.

Parameters:

token - The quorum token for which the request was made.

assertLeader

void assertLeader(long token)

Assert that this is the quorum leader.

Parameters:

token - The quorum token for which the request was made.

Throws:

QuorumException - if the quorum is not met

QuorumException - if the caller's token is not the current quorum token.

QuorumException - if this is not the quorum leader.

getDownstreamServiceId

UUID getDownstreamServiceId()

Return the UUID of the service (if any) downstream from this service in the write pipeline.

Returns:

The UUID of the downstream service in the write pipeline. This will return null for services which are not part of the write pipeline, for the leader, and for the last service in the write pipeline.

Throws:

QuorumException - if the quorum token is no longer valid.