com.bigdata.quorum

Class AbstractQuorumClient<S extends Remote>

java.lang.Object

com.bigdata.quorum.AbstractQuorumClient<S>

All Implemented Interfaces:

QuorumClient<S>, QuorumListener, ServiceLookup<S>

Direct Known Subclasses:

AbstractQuorumMember

public abstract class AbstractQuorumClient<S extends Remote>
extends Object
implements QuorumClient<S>

Base class for QuorumClients.

Version:

$Id$

Author:

Bryan Thompson

Field Summary

Fields

Modifier and Type	Field and Description
protected static org.apache.log4j.Logger	log

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractQuorumClient(String logicalServiceZPath)

Method Summary

Methods

Modifier and Type	Method and Description
void	disconnected() The client has become disconnected from the quorum (for zookeeper this is only generated if the session has expired rather than if there is a transient disconnect that can be cured).
S	getLeader(long token) Return the remote interface used to perform HA operations on the quorum leader.
String	getLogicalServiceZPath() The fully qualified identifier of the logical service whose quorum state will be monitored (for zookeeper, this is the logicalServiceZPath).
Quorum<?,?>	getQuorum() The quorum that is being monitored.
abstract S	getService(UUID serviceId) Return the remote interface used to perform HA operations on a member of quorum.
void	notify(QuorumEvent e) Notify the client of a quorum event.
void	start(Quorum<?,?> quorum) Life cycle message sent when the client will begin to receive messages from the Quorum.
void	terminate() Life cycle message send when the client will no longer receive messages from the Quorum.

Methods inherited from class java.lang.Object

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

Field Detail

log

protected static final transient org.apache.log4j.Logger log

Constructor Detail

AbstractQuorumClient

protected AbstractQuorumClient(String logicalServiceZPath)

Parameters:

logicalServiceZPath - the fully qualified logical service identifier (for zookeeper, this is the logicalServiceZPath).

Method Detail

getLogicalServiceZPath

public final String getLogicalServiceZPath()

Description copied from interface: QuorumClient

The fully qualified identifier of the logical service whose quorum state will be monitored (for zookeeper, this is the logicalServiceZPath). A highly available service is comprised of multiple physical services which are instances of the same logical service.

Note: The method was renamed from getLogicalServiceId() to QuorumClient.getLogicalServiceZPath() to avoid confusion with the zookeeper integration which has both a logicalServiceId (just the last component of the zpath) and a logicalServiceZPath. The Quorum and QuorumClient interfaces only understand a single logical service identifier - this is what corresponds to the for the zookeeper integration.

Specified by:

getLogicalServiceZPath in interface QuorumClient<S extends Remote>

See Also:

QuorumMember.getServiceId()

getQuorum

public Quorum<?,?> getQuorum()

The quorum that is being monitored.

Specified by:

getQuorum in interface QuorumClient<S extends Remote>

Returns:

The reference from an atomic variable that will be cleared if the quorum terminates.

See Also:

QuorumClient.start(Quorum)

start

public void start(Quorum<?,?> quorum)

Description copied from interface: QuorumClient

Life cycle message sent when the client will begin to receive messages from the Quorum. At a minimum, the client should save a reference to the Quorum.

Specified by:

start in interface QuorumClient<S extends Remote>

Parameters:

quorum - The quorum.

See Also:

AbstractQuorum.start(QuorumClient)

terminate

public void terminate()

Description copied from interface: QuorumClient

Life cycle message send when the client will no longer receive messages from the Quorum.

Specified by:

terminate in interface QuorumClient<S extends Remote>

See Also:

AbstractQuorum.terminate()

disconnected

public void disconnected()

The client has become disconnected from the quorum (for zookeeper this is only generated if the session has expired rather than if there is a transient disconnect that can be cured). This callback provides a hook to take any local actions that are required when the client can not longer rely on its role in the quorum state (if the client is disconnected from the quorum, then it is no longer part of the quorum, can not be a joined service, quorum member, etc).

The default implementation is a NOP.

Specified by:

disconnected in interface QuorumClient<S extends Remote>

getLeader

public S getLeader(long token)

Description copied from interface: QuorumClient

Return the remote interface used to perform HA operations on the quorum leader.

Specified by:

getLeader in interface QuorumClient<S extends Remote>

Parameters:

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

Returns:

The remote interface for the leader.

getService

public abstract S getService(UUID serviceId)

Description copied from interface: QuorumClient

Return the remote interface used to perform HA operations on a member of quorum.

Specified by:

getService in interface QuorumClient<S extends Remote>

Specified by:

getService in interface ServiceLookup<S extends Remote>

Parameters:

serviceId - The UUID associated with the service.

Returns:

The remote interface for that quorum member.

notify

public void notify(QuorumEvent e)

Description copied from interface: QuorumListener

Notify the client of a quorum event.

The listener MUST NOT take any event that could block. In particular, it MUST NOT wait on another thread that will access the Quorum as that will cause a deadlock around the internal lock maintained by the Quorum.

Specified by:

notify in interface QuorumListener