Rails - May 2014 - How to invoke cache sweeper from background jobs / models?

Hello list!

I need to expire fragment caches from a background job. The usual way to 
expire caches is to create a cache sweeper and put the observer hooks into 
the controller. That is fine as long as database is only modified through 
controller actions.

But in this case I have a background job importing data, and that needs to 
invalidate fragment caches for records it touches. The most elegant way 
would be to able to install the sweeping observer while the background job 
is running so it will expire all touched object's caches.

Thinking further, sometimes from the Rails console, I'm starting manual 
imports by invoking MyModel.import_all! on the model that's going to import 
data. Now, how would caches be expired here? Clearly, the MVC way cannot 
work here.

Time to break the rules. So, what would be the best approach to handle this? 
I'm seeing three ways with different downsides but only one that would solve
the problem:

1. Expire fragments through observers the MVC way
   Downside: Background importers won't purge caches because only
   controllers install sweepers/observers.
   Conclusion: This is no option.

2. Expire fragments through observers installed in controllers and
   background jobs
   Downside: No sweeping when running imports from console.
   Conclusion: Probably the cleanest solution but not a real option.

3. Expire fragments directly from the models
   Downside: Not the proposed MVC way, no support in Rails framework.
   Conclusion: The only solution that works in a DRY way for me.

Looking at these points, I question the whole design behind sweepers and 
their MVC voodoo. Trying to force cache sweeping into controllers only is 
somehow a failed design. I don't see why that is. In the end, it's the
data
that makes up the views. Why should a controller sweep its caches? Is it for 
performance reasons? Clearly it cannot be the choice about clearing its own 
views because other controllers could show results from the same models.

I often end up purging the caches from all controllers within the observer. 
While that is DRY it shows the misconception about making sweepers available 
to controllers only.

-- 
Replies to list only preferred.

-- 
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To view this discussion on the web visit
https://groups.google.com/d/msgid/rubyonrails-talk/32j75b-8bk.ln1%40hurikhan77.spdns.de.
For more options, visit https://groups.google.com/d/optout.