org.dspace.curate

Interface TaskQueue

All Known Implementing Classes:

FileTaskQueue

public interface TaskQueue

TaskQueue objects manage access to named queues of task entries. Entries represent curation task requests that have been deferred. The queue supports concurrent non-blocking writers, but controls read access to a single reader possessing a ticket (first come, first serve). After the read, the queue remains locked until released by the reader, after which it is typically purged.

Author:

richardrodgers

Method Summary

Modifier and Type	Method and 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.
String[]	queueNames() Returns list of queue names.
void	release(String queueName, long ticket, boolean removeEntries) Releases the lock upon the named queue, deleting it if removeEntries is set to true.

Method Detail

queueNames

String[] queueNames()

Returns list of queue names.

Returns:

queues the list of names of active queues

enqueue

void enqueue(String queueName,
             TaskQueueEntry entry)
      throws IOException

Queues a single entry to a named queue.

Parameters:

queueName - the name of the queue on which to write

entry - the task entry

Throws:

IOException - if IO error

enqueue

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

Queues a set of task entries to a named queue.

Parameters:

queueName - the name of the queue on which to write

entrySet - the set of task entries

Throws:

IOException - if IO error

dequeue

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

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.

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

void release(String queueName,
             long ticket,
             boolean removeEntries)

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

Parameters:

queueName - the name of the queue to release

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

removeEntries - flag to indicate whether entries may be deleted