Pagination and page cache sweepers in Rails 3

This is how I handle page cache sweeping in Ruby on Rails 3.1 with pagination. This should work with earlier versions of Ruby on Rails.

First of all, I’m using the gem 'will_paginate', '~> 3.0' and have my routes setup to match the url and replace the ?page= with /page/2.

In routes.rb:

match '/articles/page/:page' => 'articles#index'

So now you want to do page caching on your site, but the problem is you can’t sweep the folder and the page numbers inside of them normally within the sweeper.

For example, you have your index action which uses pagination:

def index
  @articles = Article.paginate(:page => params[:page], :per_page => 5, :conditions => {:published => true}, :order => ('created_at DESC'))
end

and have it properly cached and watched by the sweeper:

caches_page :index
cache_sweeper :article_sweeper

When the pages get cached, they’ll be placed in /public/articles/page/1.html and so forth. The problem is getting the sweeper to delete the pages when there’s a change to the Article model.

Solution: Manually remove each page on the sweep.

class ArticleSweeper < ActionController::Caching::Sweeper
  observe Article # This sweeper is going to keep an eye on the article model

  # If our sweeper detects that a article was created call this
  def after_create(article)
    expire_cache_for(article)
  end

  # If our sweeper detects that a article was updated call this
  def after_update(article)
    expire_cache_for(article)
    expire_cache_for_single(article)
  end

  # If our sweeper detects that a article was deleted call this
  def after_destroy(article)
    expire_cache_for(article)
    expire_cache_for_single(article)
  end

  private
  def expire_cache_for_single(article)
    expire_page(:controller => 'articles', :action => 'show')
  end

  def expire_cache_for(article)
    # Expire the index page now that we added or modified an article
    expire_page(:controller => 'articles', :action => 'index')
    # expire the index.html which is created by root_path
    expire_page '/index.html'

    # manually remove pages(1.html, 2.html, etc)
    if File.exist?("#{Rails.root}/public/articles/page") # check to make sure directory exists
      Dir.foreach("#{Rails.root}/public/articles/page") do |entry|
        unless entry == "." || entry == ".." || entry == ".gitignore" # ignore dot files
          File.delete("#{Rails.root}/public/articles/page/#{entry}")
        end
      end
    end
  end
end

Published 15 Oct 2011

Software developer working with Ruby, Go, and JavaScript. Hobbyist street photographer and climber.

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