Package 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
    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 Details

    • 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