Class: BackgroundQueueProcessingJob

• Inheritance
• Description
• Related information
• Instance protocol
  • adding & removing
  • initialization
  • private
  • processing
  • queries
  • start & stop
  • utilities
• Examples

Inheritance:

   Object
   |
   +--AbstractBackgroundJob
      |
      +--BackgroundQueueProcessingJob

Package:

stx:libbasic2

Category:

System-Support

Version:

rev: 1.22 date: 2017/08/09 12:15:27

user: cg

file: BackgroundQueueProcessingJob.st directory: libbasic2

module: stx stc-classLibrary: libbasic2

Author:

Jan Vrany <jan.vrany@fit.cvut.cz>

Description:

A BackgroundQueueProcessingJob is a specialized form
of a BackgroundJob for background processing of a queue.
Each item in the queue (added by sending #add: item) 
is processed (using the instance variable job).

Implementation notes:
The thread is running only if there is at least one item
to process. When the queue is empty, the thread teminates.
It is started again when a new item is added to the queue.


[instance variables:]
    queue       <OrderedCollection>     the queue of items to be procesed
    queueAccessLock<RecursionLock>      a lock used to synchronize
                                        access to the queue
    queueProcessedSema<Semaphore>       a semaphore signaled when the queue is
                                        processed (and therefore empty).
[class variables:]

Related information:

    BackgroundJob

Instance protocol:

 add: object

 add: object at: index

Modified (format): / 03-08-2011 / 16:43:01 / cg

 initialize

Invoked when a new instance is created.

 setupThread: t priority: p

Sets up worker thread

 process

(comment from inherited method)
Actually perform the job. This method is called from the background worker thread

 processItem: item

 numberOfItemsInQueue

Returns number of items waiting to be processed.
May not be accurate as there is no synchronization
(intentionally, for performance reasons)

 stopAndRemoveAll

Terminates queue processing and remove all pending
items in a queue

 waitUntilProcessed

Blocks the receiver until all items from the queue are processed.
NOTE, that it may block forever if another thread is filling queue
fast enough.

Examples: