jdbm.helper

Class ActionVersioning

java.lang.Object

jdbm.helper.ActionVersioning

public class ActionVersioning
extends java.lang.Object

This is a helper class to keep track of versions assigned to actions. As client begin read only and read write actions, they call into this class and get the version they can use. As the clients end their actions, minimum read version any action is using is advanced and piggybacked to the client This class assumes that there is one readWrite action at a time.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ActionVersioning.Version

Field Summary

Fields

Modifier and Type	Field and Description
private java.util.concurrent.locks.Lock	listLock Lock to protect the list
private ActionVersioning.Version	nextVersion Current write version
private java.util.concurrent.atomic.AtomicReference<ActionVersioning.Version>	readReference Current read version reference
private ExplicitList<ActionVersioning.Version>	versions List to put versions on

Constructor Summary

Constructors

Constructor and Description
ActionVersioning()

Method Summary

Modifier and Type	Method and Description
ActionVersioning.Version	beginReadAction() Returns a version that can be used by the read only action
ActionVersioning.Version	beginWriteAction() Returns back the new version to be used with the read/write action.
ActionVersioning.Version	endReadAction(ActionVersioning.Version version) Called when the read action with the given action is ended.
ActionVersioning.Version	endWriteAction() Called when the read/write action completes.

Methods inherited from class java.lang.Object

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

Field Detail

nextVersion

private ActionVersioning.Version nextVersion

Current write version

readReference

private java.util.concurrent.atomic.AtomicReference<ActionVersioning.Version> readReference

Current read version reference

versions

private ExplicitList<ActionVersioning.Version> versions

List to put versions on

listLock

private java.util.concurrent.locks.Lock listLock

Lock to protect the list

Constructor Detail

ActionVersioning

public ActionVersioning()

Method Detail

beginWriteAction

public ActionVersioning.Version beginWriteAction()

Returns back the new version to be used with the read/write action. Assume one read/write action at a time.

Returns:

new version for the action system

endWriteAction

public ActionVersioning.Version endWriteAction()

Called when the read/write action completes. Advances the version of action subsystem and publishes a new version for the readers. Assume one read/write action at a time.

Returns:

minimum read version for the action subsystem

beginReadAction

public ActionVersioning.Version beginReadAction()

Returns a version that can be used by the read only action

Returns:

version to be used by the action

endReadAction

public ActionVersioning.Version endReadAction(ActionVersioning.Version version)

Called when the read action with the given action is ended. Checks whether the minimum read version advanced

Parameters:

version - version of the read only action

Returns:

returns the miminum read version. Might return null if read version did not advance for sure.