Support Drupal 7.x Queue API class extensions

Problem/Motivation

Anyone who works with the Drupal 7.x Queue API, to implement the DrupalReliableQueueInterface for an external AMQP application (RabbitMQ or Beanstalk), finds that Queue UI just doesn't work out-of-the-box. It requires further implementation of custom Queue UI classes and hooks and makes some assumptions that aren't supported by AMQP.

Looking elsewhere in contributed modules I cannot find a UI to the underlying Drupal 7.x Queue API. So I want to help make this module fit that stated aim.

Proposed resolution

Queue UI could and should work out-of-the-box with any queue that was created using a standard Drupal 7.x Queue API implementation. That could and should include providing a basic UI to any queue that implements the DrupalReliableQueueInterface and hook_cron_queue_info implementation.

Basic functionality in Queue UI 7.x-2.x-rc1 that would need rework to achieve this includes anything relying on a custom Queue UI class or hook implementation in order to achieve:

• Listing queues
• Viewing a queued item
• Deleting, editing or requeuing a queued item

Missing basic functionality in Queue UI that should be provided includes:

• Listing queue class implementations
• Setting a queue class to be used for a queue name
• Listing queue class implementations that do not have any assigned queue names

Remaining tasks

1. Document all custom Queue UI hooks or classes that remain in an INSTALL.txt
2. Explain how and why to implement any remaining custom Queue UI hooks or classes in a README.txt
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User interface changes

The following user interface changes are suggested:

• Addition of a page where you can set a class for a queue by name
• Live updating of queued item counts without requiring page refresh (behaviours / ajax)

API changes

(Placeholder for API changes/additions that would affect module, install profile, and theme developers.)