Example: Queue

Demonstrating the Queue API

The Queue API provides a traditional FIFO (first-in-first-out) queue, but also provides the concepts of:

• "Creating" a queued item, which means inserting it into a queue.
• "Claiming" a queued item, which essentially means requesting the next item from the queue and holding a lock on that item for a specified period of time.
• "Releasing" an item, which means giving up a claim but leaving the item in the queue.
• "Deleting" an item, which means finally removing it from the queue.

This example demonstrates only basic queue functionality, and will use the default queue implementation, which is SystemQueue, managed using persistent database storage.

Further resources include the limited Queue operations documentation. More:

Batch vs Queue Presentation slides by John VanDyk session video.

See also

system.queue.inc

Parent topics

File

modules/examples/queue_example/queue_example.module, line 8

Examples demonstrating the Backdrop Queue API.

Functions

Name	Location	Description
queue_example_add_remove_form	modules/examples/queue_example/queue_example.module	Form generator for managing the queue.
queue_example_add_remove_form_claim	modules/examples/queue_example/queue_example.module	Submit function for the "claim" button.
queue_example_add_remove_form_clear_queue	modules/examples/queue_example/queue_example.module	Submit handler for clearing/deleting the queue.
queue_example_add_remove_form_delete	modules/examples/queue_example/queue_example.module	Submit function for "Claim and delete" button.
queue_example_add_remove_form_insert	modules/examples/queue_example/queue_example.module	Submit function for the insert-into-queue button.
queue_example_add_remove_form_run_cron	modules/examples/queue_example/queue_example.module	Submit function for "run cron" button.
queue_example_menu	modules/examples/queue_example/queue_example.module	Implements hook_menu().
queue_example_retrieve_queue	modules/examples/queue_example/queue_example.module	Retrieves the queue from the database for display purposes only.
queue_example_show_queue	modules/examples/queue_example/queue_example.module	Submit function for the show-queue button.
queue_example_theme	modules/examples/queue_example/queue_example.module	Implements hook_theme().
theme_queue_items	modules/examples/queue_example/queue_example.module	Themes the queue display.

Classes

Name	Location	Description
QueueExampleTestCase	modules/examples/queue_example/queue_example.test	Functional tests for the Queue Example module.