= lacquer

Rails drop in for Varnish support. This version is adapted from Russ Smith's gem and is in production use on posterous.com.

== Install
Basic installation

  sudo gem install posterous-lacquer

config/initializers/lacquer.rb

  Lacquer.configure do |config|
    # Globally enable/disable cache
    config.enable_cache = true

    # Unless overridden in a controller or action, the default will be used
    config.default_ttl = 1.week

    # Can be :none, :delayed_job, :resque
    config.job_backend = :none

    # Array of Varnish servers to manage
    config.varnish_servers << { 
      :host => '0.0.0.0', :port => 6082
    }

    # Number of retries
    config.retries = 5

    # config handler (optional, if you use Hoptoad or another error tracking service)
    config.command_error_handler = lambda {|s| HoptoadNotifier.notify(s) }
  end

app/controllers/application_controller.rb

  class ApplicationController < ActionController::Base
    include Lacquer::CacheUtils
  end

== Usage

To set a custom ttl for a controller:

  before_filter { |controller| controller.set_cache_ttl(15.minutes) }

Clearing the cache:

  class Posts < ApplicationController
    after_filter :clear_cache, :only => [ :create, :update, :destroy ]

  private

    def clear_cache
      clear_cache_for(
        root_path,
        posts_path,
        post_path(@post))
    end
  end

== Gotchas

The default TTL for most actions is set to 0, since for most cases you'll probably want to be fairly explicit about what pages do get cached by varnish. The default cache header is typically

  Cache-Control: max-age=0, no-cache, private

This is good for normal controller actions, since you won't want to cache them. If TTL for an action is set to 0, it won't mess with the default header. 

The key gotcha here is that cached pages strip cookies, so if your application relies on sessions and uses authenticity tokens, the user will need a session cookie set before form actions will work. Setting default TTL to 0 here will make sure these session cookies won't break.

As a result, all you have to do to set a cacheable action is the before filter above. 

== Note on Patches/Pull Requests

* Fork the project.
* Make your feature addition or bug fix.
* Add tests for it. This is important so I don't break it in a
  future version unintentionally.
* Commit, do not mess with rakefile, version, or history.
  (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
* Send me a pull request. Bonus points for topic branches.

== Copyright

Copyright (c) 2010 Russ Smith. See LICENSE for details.