Package org.dspace.curate

Class FileTaskQueue

java.lang.Object

org.dspace.curate.FileTaskQueue

All Implemented Interfaces:

TaskQueue

public class FileTaskQueue
extends Object
implements TaskQueue

FileTaskQueue provides a TaskQueue implementation based on flat files for the queues and semaphores.

Author:

richardrodgers

Field Summary

Fields

Modifier and Type	Field	Description
protected List<Integer>	readList
protected long	readTicket
protected String	tqDir

Constructor Summary

Constructors

Constructor	Description
FileTaskQueue()

Method Summary

Modifier and Type	Method	Description
Set<TaskQueueEntry>	dequeue(String queueName, long ticket)	Returns the set of task entries from the named queue.
void	enqueue(String queueName, Set<TaskQueueEntry> entrySet)	Queues a set of task entries to a named queue.
void	enqueue(String queueName, TaskQueueEntry entry)	Queues a single entry to a named queue.
protected File	ensureQueue(String queueName)
String[]	queueNames()	Returns list of queue names.
void	release(String queueName, long ticket, boolean remove)	Releases the lock upon the named queue, deleting it if removeEntries is set to true.

Methods inherited from class java.lang.Object

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

Field Detail

tqDir

protected String tqDir

readTicket

protected long readTicket

readList

protected List<Integer> readList

Constructor Detail

FileTaskQueue

public FileTaskQueue()

Method Detail

queueNames

public String[] queueNames()

Description copied from interface: TaskQueue

Returns list of queue names.

Specified by:

queueNames in interface TaskQueue

Returns:

queues the list of names of active queues

enqueue

public void enqueue(String queueName,
                    TaskQueueEntry entry)
             throws IOException

Description copied from interface: TaskQueue

Queues a single entry to a named queue.

Specified by:

enqueue in interface TaskQueue

Parameters:

queueName - the name of the queue on which to write

entry - the task entry

Throws:

IOException - if IO error

enqueue

public void enqueue(String queueName,
                    Set<TaskQueueEntry> entrySet)
             throws IOException

Description copied from interface: TaskQueue

Queues a set of task entries to a named queue.

Specified by:

enqueue in interface TaskQueue

Parameters:

queueName - the name of the queue on which to write

entrySet - the set of task entries

Throws:

IOException - if IO error

dequeue

public Set<TaskQueueEntry> dequeue(String queueName,
                                   long ticket)
                            throws IOException

Description copied from interface: TaskQueue

Returns the set of task entries from the named queue. The operation locks the queue from any further enqueue or dequeue operations until a release is called. The ticket may be any number, but a timestamp should guarantee sufficient uniqueness.

Specified by:

dequeue in interface TaskQueue

Parameters:

queueName - the name of the queue to read

ticket - a token which must be presented to release the queue

Returns:

set the current set of queued task entries

Throws:

IOException - if IO error

release

public void release(String queueName,
                    long ticket,
                    boolean remove)

Description copied from interface: TaskQueue

Releases the lock upon the named queue, deleting it if removeEntries is set to true.

Specified by:

release in interface TaskQueue

Parameters:

queueName - the name of the queue to release

ticket - a token that was presented when queue was dequeued.

remove - flag to indicate whether entries may be deleted

ensureQueue

protected File ensureQueue(String queueName)