surveillance_authority

Introduction

This gem provides a dsl to easily write observers in one or more centralized files.

Installation

Install surveillance_authority by adding

gem 'surveillance_authority'

to your Gemfile or install it using

gem install surveillance_authority

Integration into your project

config/initializers

create one or more ruby files in which you can define your surveillance rules. For example:

SurveillanceAuthority.observe do # Do something after a new movie was created after "Movie#create" do |movie| # ... do stuff end


   # Do something before a User gets updated
   before "User#update" do |user|
     # ... do stuff
   end
 end

Uhm ...so what?

surveillance_authority is meant to be used together with some plugins. One of those is varnish_sweeper, which invalidates certain routes.

Writing plugins for surveillance_authority

Making methods available to surveillance_authority

In order to write a plugin for surveillance_authority, simply create a class that inherits from

SurveillanceAuthority::Sanctions

all public methods of that class will be available in the blocks. E.g.


 class VarnishSweeper < SurveillanceAuthority::Sanctions
   def sweep(url, options = {})
     options.reverse_merge(
       :method => :invalidate
     }

     options[:method] == :purge ? purge_url(url) : invalidate(url)
   end

   private
   def purge_url(url)
     ...
   end

   def invalidate(url)
     ...
   end
 end

will make the sweep method available:


 SurveillanceAuthority.observe do
   # Do something after a new movie was updated
   after "Movie#update" do |movie|
      sweep movie_path(movie), :method => :invalidate
   end
 end

Configuration for plugins

Configuring plugins should be made with the central config method provided by surveillance_authority. If we again use a plugin called VarnishSweeper, configuring this plugin should happen like this:

SurveillanceAuthority.config(VarnishSweeper, <hash with options>)

Withing your plugin, you will be able to access your options simply by calling config.

Example: `VarnishSweep` needs to be configured with a base url to varnish


 class VarnishSweeper < SurveillanceAuthority::Sanctions
   def sweep(url, options = {})
     options.reverse_merge(
       :method => :invalidate
     }

     options[:method] == :purge ? purge_url(url) : invalidate(url)
   end

   private
   def varnish_base_url
     config[:base_url]
   end

   def purge_url(url)
     ...
   end

   def invalidate(url)
     ...
   end
 end

In the project using this plugin:


  SurveillanceAuthority.config(VarnishSweeper, :base_url => "http://varnish.example.com")

  ...

If you want to access the config of other plugins, use:

  `SurveillanceAuthority.config_for(<plugin>)`