OfflineSweeper

I have this problem. We use the Rails fragment cache a lot, and we use Sweepers to expire the cache when models are changed. We have a lot of cache invalidation logic in our sweepers. Sweepers work great when you use them the way they are expected to be used: inside controllers.

But over time we've added background jobs fired from cron or DJ or email (even a chat bot) that make changes to the same models that our sweepers are supposed to be sweeping. As some people have noticed, sweepers quietly don't work unless the model is changed inside a web request.

There appear to be these problems that prevent sweepers from expiring the fragment cache inside e.g. a cron job:

• If you use a hash as your fragment cache key, Rails wants to use the full URL of the incoming request (indirectly through url_for) as part of the generated key string. This is a problem because the background job doesn't have a request and because it doesn't necessarily know what hostname/port was used to create the fragment

• Sweepers aren't loaded and run automatically like other Observers outside of a controller request?

• Even if you call them explictly the sweeper will silently do nothing without a controller (the method_missing thing in sweeping.rb)

Action caching isn't really a problem for me so it isn't supported yet. There appears to be some handwringing in the code about formats that I don't want to dig into now.

Example

Example goes here.

Copyright (c) 2010 Matt Gleeson, released under the MIT license