Provide an alternative and simple callback mechanism based on Rails controller actions rather than model by creating an application generic around filter. For each controller/action the filter publishes an event. No data from our database is sent along the event, subscribers are expected to use our standard API to find relevant records. Key features:

• Before callbacks send all request parameters along with an event.
• After callbacks send database record primary ID along with an event (but not more).
• Callback API available through the application for ad-hoc callback points when necessary.
• Subscribers are running outside of Rails application on purpose.
• Core feature with tests, not a plugin.