= lacquer
Rails drop in for Varnish support.
== Install
Basic installation
sudo gem install lacquer
rails generate lacquer:install
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 # if you have authentication enabled, add :secret => "your secret"
}
# 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
config/varnishd.yml
development:
listen: localhost:3001
telnet: localhost:6082
sbin_path: /usr/local/sbin
storage: "file,#{Rails.root}/log/varnishd.#{Rails.env}.cache,100MB"
test:
listen: localhost:3002
telnet: localhost:6083
sbin_path: /usr/local/sbin
storage: "file,#{Rails.root}/log/varnishd.#{Rails.env}.cache,100MB"
production:
listen: :80
telnet: localhost:6082
sbin_path: /usr/local/sbin
storage: "file,#{Rails.root}/log/varnishd.#{Rails.env}.cache,100MB"
params:
overflow_max: 2000
thread_pool_add_delay: 2
thread_pools: 4 # <Number of cpu cores>
thread_pool_min: 200 # <800/number of cpu cores>
thread_pool_max: 4000
If only some urls of the application should be cached by varnish, Lacquer::CacheControl will be helpful.
config/initializers/caches.rb
require "lacquer/cache_control"
Lacquer.cache_control.configure do |config|
config.register :static, :url => "^/images",
:expires_in => "365d"
config.register :static, :url => "^/stylesheets",
:expires_in => "365d"
config.register :static, :url => "^/javascripts",
:expires_in => "365d"
config.register :class_section, :url => "^(/[a-z]{2})?/(info_screens|class_sections)/%s.*$",
:args => "[0-9]+",
:expires_in => "1m"
config.register :open_scoring, :url => "^(/[a-z]{2})?/class_sections/%s/open_scoring.*$",
:args => "[0-9]+",
:expires_in => "1m"
end
In the sweeper we can do something like this
class_section = ClassSection.find(1)
Lacquer.cache_control.purge(:open_scoring, class_section)
This will purge "^(/[a-z]{2})?/class_sections/1/open_scoring.*$" (/sv/class_sections/1/open_scoring.js, /sv/class_sections/1/open_scoring.html)
The varnish.vcl is preprocssed when starting varnishd with the rake tasks
rake varnishd:start
config/varnish.vcl.erb
sub vcl_recv {
# Lookup requests that we know should be cached
if (<%= Lacquer.cache_control.to_vcl_conditions %>) {
# Clear cookie and authorization headers, set grace time, lookup in the cache
unset req.http.Cookie;
unset req.http.Authorization;
return(lookup);
}
# Generates
#
# if(req.url ~ "^/images" ||
# req.url ~ "^/stylesheets" ||
# req.url ~ "^/javascripts" ||
# req.url ~ "^(/[a-z]{2})?/(info_screens|class_sections)/[0-9]+.*$" ||
# req.url ~ "^(/[a-z]{2})?/class_sections/[0-9]+/open_scoring.*$") {
# unset req.http.Cookie;
# unset req.http.Authorization;
# return(lookup);
# }
}
sub vcl_fetch {
<%= Lacquer.cache_control.to_vcl_override_ttl_urls %>
# Generates
#
# if(req.url ~ "^/images" || req.url ~ "^/stylesheets" || req.url ~ "^/javascripts") {
# unset beresp.http.Set-Cookie;
# set beresp.ttl = 365d;
# return(deliver);
# }
#
# if(req.url ~ "^(/[a-z]{2})?/(info_screens|class_sections)/[0-9]+.*$" ||
# req.url ~ "^(/[a-z]{2})?/class_sections/[0-9]+/open_scoring.*$") {
# unset beresp.http.Set-Cookie;
# set beresp.ttl = 1m;
# return(deliver);
# }
}
This makes it much simpler to perform cacheing, it's only setuped in one place, purge it or just let it expire.
== 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
Control varnishd with the following rake tasks
rake varnishd:start
rake varnishd:stop
rake varnishd:restart
rake varnishd:status
rake varnishd:global_purge
== 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.