Expiring cache from a rake task


I have a question on cache expiration only working from the web, and not from the console or from a rake task.

I have 2 models, Post e Comments. I have this page /archives where I list all old posts.

I created a controller ‘archives’, where I have a page cache (caches_page :index). I need to expire this page cache, every time a Post or Comment is created/updated/destroyed.

Using sweepers, this works 100%. (http://www.railsenvy.com/2007/2/28/rails-caching-tutorial#sweepers)

The problem is that, now, I implemented spam moderation by Akismet. So when a new comment is created in the database, it gets a ‘pending’ status. And there’s a rake task that runs every x minutes, in order to check all ‘pending’ comments against the Akismet database, and only then comments earn an ‘approved’ or ‘spam’ status. And it’s only then that I should expire the /archives page.

So I need to expire a cached page, from something that happens outsite a controller. And it seems the only situation a sweeper works is when the event is triggered by the web.

If I open the console, add a new comment to a post, nothing happens (ok!). And now I run the Akismet check, and assuming it gives the comment an ‘approved’ status, the cache is not expired, when it should be.

I tried to use Observers, from the Rails docs (http://www.railsbrain.com/api/rails-2.2.2/doc/index.html?a=M001871&name=observe).

In environment.rb I added the line: config.active_record.observers = :archives_observer I created the file app/models/archives_observer.rb with:

class ArchivesObserver < ActiveRecord::Observer observe :post, :comment

def after_save(record) expire_page(:controller => ‘archives’, :action => ‘index’)

end end

But I get an error: NoMethodError: undefined method `expire_page’ for #ArchivesObserver:0x247eddc

I tried this also:

class ArchivesObserver < ActionController::Caching::Sweeper


In this case, there’s no error, and it does nothing at all. The public/archives.html just stays there.

I’m trying my best to avoid hacking it, using a simple File.delete :slight_smile:

Like the code below:

# File rails/actionpack/lib/action_controller/caching/pages.rb, line 65
65: def expire_page(path)

66: return unless perform_caching
68: benchmark "Expired page: #{page_cache_file(path)}" do

69: File.delete(page_cache_path(path)) if File.exist?(page_cache_path(path))

70: end
71: end

Is there a way to expire pages without having to hack it?

Thanks a lot, Levy

I ran into a similar issue a few days ago. If I remember correctly, if you look at what Rails is doing under the covers, you'll see that ActionController::Caching::Sweeper subclasses will only work when called from inside a controller. Basically the "expire_page" message ends up getting intercepted by "method_missing", which tries to forward it on to a controller stored in the @controller instance variable. So if you invoke your Sweeper subclass from somewhere else (like a Rake task), that @controller variable will be nil and nothing will happen.

My workaround was just to fall back to File.delete and friends. Ugly, but it works.

Cheers, Wincent

Thanks, Vincent.

I just wanted to know if there was something better. I guess I’ll resort to the File.delete and friends as you mentioned :slight_smile:

Regards, Levy

Coming in late, but this might be helpful... I've used this from ./ script/runner... not quite rake, but...

... require 'lib/console_app' ... ActionController::Base.expire_page(app.user_profile_path(:id =>
user.username)) ...

(where 'user_profile' is a named route)