All credit for this snippet is due to Henrik Nyh.

Put this in application_controller.rb:

   1  alias_method :rescue_action_locally, :rescue_action_in_public if RAILS_ENV == 'development'
   2    
   3    def render_optional_error_file(status_code)
   4      if status_code == :not_found
   5        activate_authlogic
   6        render_404
   7      else
   8        super
   9      end
  10    end
  11  
  12    def render_404
  13      respond_to do |type| 
  14        type.html { render :template => "errors/error_404", :layout => 'application', :status => 404 } 
  15        type.all  { render :nothing => true, :status => 404 } 
  16      end
  17  
  18      true  # so we can do "render_404 and return"
  19    end

From the When to Tell Your Kids About Client Caching RailsConf presentation

   1  def fresh?(response)
   2  def stale?(:etag => @object, :last_modified => updated_at.utc)
   3  def not_modified?(modified_at)
   4  def etag_matches?(etag)

   1  class PeopleController < ApplicationController
   2  	def show
   3  		@person = Person.find(params[:id])
   4  		response.last_modified = @person.updated_at.utc
   5  		response.etag = @person	
   6  		return head(:not_modified) if request.fresh?(response)
   7  
   8  		respond_to do |wants|
   9  			#...
  10  		end
  11  	end
  12  end

   1  response.etag = @person # => “5cb44721b6ce18857ff6900486dc4aba”
   2  @person.cache_key # => "people/5-20071224150000"

   1  class PeopleController < ApplicationController
   2  	def show
   3  		@person = Person.find(params[:id])
   4  		if stale?(:etag => @person, :last_modified => @person.updated_at.utc)
   5  			respond_to do |wants|
   6  			#...
   7  			end
   8  		end
   9  	end
  10  end

Put this in ~/.bashrc:

   1  app () { cd "/var/www/$*/current"; }

Execute:

   1  . ~/.bashrc

Now you can change to another Rails app directory like this:

   1  app xxx.com

   1  script/plugin generate PluginTemplate

   1  module PluginTemplate
   2    def self.included(base)
   3      base.class_eval do
   4        include InstanceMethods
   5        extend ClassMethods
   6  
   7        alias_method_chain :rescue_action_in_public, :gulag
   8        alias_method_chain :rescue_action_locally, :gulag
   9      end
  10    end
  11  
  12    module ClassMethods
  13    end
  14  
  15    module InstanceMethods
  16    end
  17  end

init.rb:

   1  ActionController.send :include, PluginTemplate

Rails’ exception handling is defined in this file /usr/local/lib/ruby/gems/1.8/gems/actionpack-2.3.2/lib/action_controller/rescue.rb. To intercept all errors in your Rails app, you can do this:

   1  module GulagNotifier
   2    def self.included(base)
   3      if base.instance_methods.include?("rescue_action_in_public")
   4        base.module_eval { alias_method_chain :rescue_action_in_public, :gulag }
   5      end
   6      if base.instance_methods.include?("rescue_action_locally")
   7        base.module_eval { alias_method_chain :rescue_action_locally, :gulag }
   8      end
   9    end
  10  
  11    def rescue_action_locally_with_gulag(exception)
  12      send_to_gulag(exception)
  13      rescue_action_locally_without_gulag(exception)
  14    end
  15  
  16    def rescue_action_in_public_with_gulag(exception)
  17      send_to_gulag(exception)
  18      rescue_action_in_public_without_gulag(exception)
  19    end 
  20  
  21    def send_to_gulag(exception)
  22  # Do whatever you want with the exception
  23    end
  24    
  25  end