Render maintenance pages

Capistrano fancy maintenance page

# In spite of the proscription at the end of Recipe 69, "Upload Custom Maintenance
# Pages" in Mike Clark's excellent Advanced Rails Recipes, I wanted to generate my
# maintenance page with the full awesome power of Rails (ok, well, I wanted to use
# a real template, to avoid having to maintain the look of the maintenance page
# separately).
# 
# My solution was to render the page using this rake task, which goes in:
# lib/tasks/render_maintenance.rake
task :render_maintenance => :environment do
  # Render the maintenance page into tmp/maintenance.html,
  # where the Capistrano deploy:web:disable task (which calls this)
  # can find it. (Note: this runs locally, on the machine of the 
  # person doing the deployment!)
  view = ActionView::Base.new(Rails::Configuration.new.view_path)
  view.class_eval do
    include ApplicationHelper
  end
  page = view.render(:file => 'home/maintenance',
                     :layout => 'layouts/minimal',
                     :locals => { :reason => ENV['REASON'],
                                  :deadline => ENV['UNTIL']})
  File.open("#{RAILS_ROOT}/tmp/maintenance.html", 'w') {|f| f.write(page)}
end

# Then, I override Capistrano's built-in deploy:web:disable with this in:
# config/deploy.rb
task "deploy:web:disable", :roles => :web do
  # Put up a "Sorry, we're closed" page for now.
  # (There's a built-in 'deploy:web:enable' that undoes this; we're
  # overriding Capistrano's default recipe here.)
  local_maintenance_file = "tmp/maintenance.html"
  remote_maintenance_file = "#{shared_path}/system/maintenance.html"
  on_rollback { run "rm #{remote_maintenance_file}" } 

  # Render the maintenance page to a local temp file
  FileUtils.rm_f(local_maintenance_file)
  `rake render_maintenance`
  page = File.read(local_maintenance_file)
  FileUtils.rm_f(local_maintenance_file)
  abort "unable to generate maintenance page" \ 
    unless page.size > 900

  # Put it on the server where Apache will see it.
  put page, remote_maintenance_file, :mode => 0644
end