Cache update task cancellation and pre-queue validation

Current Behavior

• There exist de-duplication mechanisms in the queue itself to protect duplicate tasks from appearing in the queue
• However, once the cache update task starts and has left the queue, there is no mechanism to prevent another update task from entering the queue.

Proposal

• When a cache update is triggered, the request will be validated before it enters the queue

• If a cache update is already in progress, then the update request will be ignored, and it will not enter the queue.

  • For single cache update request, Response will indicate cache update is already in progress.
  • For multiple cache update request, Response will indicate which cache updates have been queued, and which cache updates have been ignored as updates are already in progress.

• If a cache update is not already in progress, then the request will be processed as a task into the queue as normal

• Need task cancellation method to be triggered by executor (already implemented)

• Need task cancellation logic to allow process to be terminated (already implemented)

• Need task cancellation watcher to clean up processes during transformer reset operation (in progress)

Acceptance Criteria

• Ability to immediately cancel update operations
• Implement cancel-watcher
• Implement pre-queue validation for cache update requests
• Implement pre-queue validation responses for cache update requests