net.cnri.repository.layered

Class MigrationRepository

java.lang.Object

net.cnri.repository.AbstractRepository

net.cnri.repository.layered.LayeredRepository

net.cnri.repository.layered.MigrationRepository

All Implemented Interfaces:

DirectRepository, Repository

public class MigrationRepository
extends LayeredRepository

LayeredRepository for performing migration from top to bottom. Allows fast read-only access to objects in the bottom; all writes occur only in the top; a write causes migration of that object. Users may call migrate(String) on each handle of the bottom repository to ensure migration. Bottom objects which have been migrated will be deleted as they are garbage collected; calling cleanUp() periodically until getTotalReferenceCount() returns zero will complete that process.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	MigrationRepository.MigrationCallable Callable suitable for calling in a background thread to perform migration and delete bottom objects.

Constructor Summary

Constructors

Constructor and Description
MigrationRepository(Repository top, Repository bottom) Constructs a new repository allowing background migration from a bottom repository to a top repository.

Method Summary

Methods

Modifier and Type	Method and Description
void	cleanUp() Checks the reference counter queue for objects which may be deleted.
void	closeBottom() Close the bottom layer and stop using it.
int	getTotalReferenceCount() Returns the total number of references to bottom digital objects.
void	migrate(java.lang.String handle) Migrates an object from the bottom repository to the top repository.
boolean	migrationComplete() Checks whether all objects exist in the top.

Methods inherited from class net.cnri.repository.layered.LayeredRepository

close, copyDataOrSetAttributeForMissing, copyForLayeredRepo, createDataElement, createDigitalObject, deleteAttribute, deleteAttributes, deleteDataElement, deleteDigitalObject, getAttribute, getAttributes, getBottom, getDigitalObject, getFile, getSize, getTop, lift, listAttributes, listDataElementNames, listHandles, read, search, searchHandles, setAttribute, setAttributes, verifyDataElement, verifyDigitalObject, write

Methods inherited from class net.cnri.repository.AbstractRepository

getHandle, getOrCreateDigitalObject, listObjects, search, search, searchHandles, searchHandles, searchMapping

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.cnri.repository.Repository

getHandle, getOrCreateDigitalObject, listObjects, search, search, searchHandles, searchHandles, searchMapping

Constructor Detail

MigrationRepository

public MigrationRepository(Repository top,
                   Repository bottom)
                    throws RepositoryException

Constructs a new repository allowing background migration from a bottom repository to a top repository.

Parameters:

top - The top repository, to be migrated to.

bottom - The bottom repository, to be migrated from and made empty.

Throws:

RepositoryException

Method Detail

migrate

public void migrate(java.lang.String handle)
             throws RepositoryException,
                    java.io.IOException

Migrates an object from the bottom repository to the top repository. If it already exists in the top repository, it is deleted in the bottom. Otherwise it is queued for deletion when all references are garbage collected.

Parameters:

handle - The handle of the object in the bottom repository.

Throws:

RepositoryException

java.io.IOException

cleanUp

public void cleanUp()

Checks the reference counter queue for objects which may be deleted.

getTotalReferenceCount

public int getTotalReferenceCount()

Returns the total number of references to bottom digital objects. When this is zero, and all bottom objects have been migrated, the bottom repository should be empty.

Returns:

The total number of references to bottom digital objects.

migrationComplete

public boolean migrationComplete()

Checks whether all objects exist in the top. Does not ensure that all bottom objects have been deleted.

Returns:

Whether all objects exist in the top.

closeBottom

public void closeBottom()

Close the bottom layer and stop using it. Should only be called once migration is completed and getTotalReferenceCount() returns 0.