Global Hooks Proposal

Background

DJ 2.1 introduced a callback mechanism, allowing jobs to receive notifications at various points in the lifecycle. While useful, this is limited in that the callback methods need to be implemented on a job class, can't be used by PerformableMethod, and have to be implemented/mixed in to each Job class individually.

Proposal

Global hooks would simplify most callback use cases and allow straightforward integration of third-party tools (Hoptoad, stats tracking, etc) while still providing custom behavior on a per-job basis.

Configuration

Global hooks are configured at the worker level using a block which receives the job. (I want them to be defined on Delayed::Job but the backend isn't likely to be set up by the time third-party plugins would need to be hooked up. Anyone have ideas?)

Delayed::Worker.hook :name, lambda {|job| ... }

Multiple blocks can be configured as a chain and will be executed in the order defined.

Delayed::Worker.hook :name, lambda{|job| puts "First"}

Delayed::Worker.hook :name, lambda{|job| puts "Second"}

Global hooks have the same names as the callback methods on the job class (before, success, after, error, etc).

Behavior Notes

• job-specific hooks should be invoked before global hooks.

Questions

• Should global hooks be cancelable by returning false from a job hook?
• Should global hook blocks in the chain be allowed to cancel execution like rails filter chains?

Comments

(Stephen V.T.) Implement named queues and allow global hooks to be applied to the queue. Then this would allow 3 levels of hooks: Individual job hooks, queue hooks and global hooks (applies to all queues).

(John H.) Want