How to Create a Smart-Proxy Plugin¶

This guide outlines main components of a plugin, but assumes some degree of familiarity with ruby gems, bundler, rack, and Sinatra. You'll find links to useful documentation in each of the sections below.

• Table of contents
• How to Create a Smart-Proxy Plugin
  • Plugin Organization
  • Making your plugin official
  • Plugin definition
    • Provider definition
  • API
  • Rackup Configuration
  • Plugin Settings
  • Bundler Configuration
  • Adding a DNS provider
  • Testing

Plugin Organization¶

Smart-Proxy plugins are normal ruby gems, please follow documentation at http://guides.rubygems.org/make-your-own-gem/ for guidance on gem creation and packaging. It is strongly recommended to follow smart_proxy_<your plugin name here> naming convention for your plugin.

We have some templates for creating your plugin:

• smart_proxy_example plugin is a minimal example plugin that can be used as a skeleton
• smart_proxy_dns_plugin_template is a template for creating new DNS provider plugins

Also, smart_proxy_pulp plugin is an example for a fully functional, yet easy to understand Smart-Proxy plugin.

Making your plugin official¶

Once you're ready to release the first version, please see How_to_Create_a_Plugin for info on making your plugin part of the Foreman project.

Plugin definition¶

A plugin definition is used to define plugin's name, version, location of rackup configuration, and other parameters. At a minimum, Plugin Descriptor must define plugin name and version. Note the base class of the descriptor is ::Proxy::Plugin:

module Proxy::Example
  class Plugin < ::Proxy::Plugin
    plugin :example, "0.0.1" 
    http_rackup_path File.expand_path("http_config.ru", File.expand_path("../", __FILE__))
    https_rackup_path File.expand_path("https_config.ru", File.expand_path("../", __FILE__))
    default_settings :hello_greeting => 'Hello there!'
  end
end

Here we defined a plugin called "example", with version "0.0.1", that is going to listen on both http and https ports. Following is the full list of parameters that can be defined by the Plugin Descriptor.

• plugin :example, "1.2.3": required. Sets plugin name to "example" and version to "0.0.1".
• http_rackup_path "path/to/http_config.ru": optional. Sets path to http rackup configuration. If omitted, the plugin is not going to listen on the http port. Please see below for information on rackup configuration.
• https_rackup_path "path/to/https_config.ru": optional. Sets path to https rackup configuration. If omitted, the plugin is not going to listen on the https port. Please see below for information on rackup configuration.
• requires :another_plugin, '~> 1.2.0': optional. Specifies plugin dependencies, where ":another_plugin" is another plugin name, and '~> 1.2.0' is version specification (pls. see http://guides.rubygems.org/patterns/#pessimistic_version_constraint for details on version specification).
• default_settings :first => 'my first setting', :another => 'my other setting': optional. Defines default values for plugin parameters. These parameters can be overridden in plugin settings file.
• after_activation { do_something }: optional. Supplied block is going to be executed after the plugin has been loaded and enabled. Note that the block is going to be executed in the context of the Plugin Descriptor class.
• bundler_group :my_plugin_group: optional. Sets the name of the bundler group for plugin dependencies. If omitted the plugin name is used.

Provider definition¶

Some plugins are providers for an existing plugin or module in the Smart Proxy, e.g. a DNS provider.

These are registered almost identically, but use Proxy::Provider instead of Proxy::Plugin and additionally define a factory for initialization by the main module. No rackup_paths are used for providers, since they don't add any new REST API, they only add to an existing module.

module Proxy::Dns::PluginTemplate
  class Plugin < ::Proxy::Provider
    plugin :dns_plugin_template, ::Proxy::Dns::PluginTemplate::VERSION,
           :factory => proc { |attrs| ::Proxy::Dns::PluginTemplate::Record.record(attrs) }

    requires :dns, '>= 1.10'

    after_activation do
      require 'smart_proxy_dns_plugin_template/dns_plugin_template_main'
    end
  end
end

API¶

Modular Sinatra app is used to define plugin API. Note the base class Sinatra::Base and inclusion of ::Proxy::Helpers:

module Proxy::Example
 class Api < Sinatra::Base
  helpers ::Proxy::Helpers

  get "/hello" do
    Proxy::Example::Plugin.settings.hello_greeting
  end
end

Here we return a string defined in 'hello_greeting' parameter (see Plugin Descriptor above and settings file below) when a client performs a GET /hello. Please refer to Sinatra documentation on details about routing, template rendering, available helpers, etc.

Rackup Configuration¶

During startup Smart-Proxy assembles web applications listening on http and https ports using rackup files of enabled plugins. Plugin rackup files define mounting points of plugin API:

require 'example_plugin/example_api'

map "/example" do
  run Proxy::Example::Api
end

The example above should be sufficient for the majority of plugins. Please refer to Sinatra+Rack documentation for additional information.

Plugin Settings¶

On startup Smart-Proxy will load and parse plugin configuration files located in its settings.d/ directory. Each plugin config file is named after the plugin and is a yaml-encoded collection of key-value pairs and used to override default values of plugin parameters.

---
:enabled: true
:hello_greeting: "O hai!" 

This settings file enables the plugin (by default all plugins are disabled), and overrides :hello_greeting parameter. Plugin settings can be accessed through .settings method of the Plugin class, for example: ExamplePlugin.settings.hello_greeting. Global Smart-Proxy parameters are accessible through Proxy::SETTINGS, for example Proxy::SETTINGS.foreman_url returns Foreman url configured for this Smart-Proxy.

Bundler Configuration¶

Smart-Proxy relies on bundler to load its dependencies and plugins. We recommend to create a dedicated bundler config file for your plugin, and name it after the plugin. For example:

  gem 'smart_proxy_example'
  group :example do
    gem 'json'
  end

You'll need to create a dedicated bundler group for additional dependencies of your plugin. By default the group shares the name with the plugin, but you can override it using bundler_group parameter in Plugin Descriptor. Please refer to How_to_Install_a_Smart-Proxy_Plugin for additional details on "from source" plugin installations.

Adding a DNS provider¶

When extending the 'dns' smart proxy module, the plugin needs to create a new Proxy::Dns::Record class with create and remove methods for adding and removing the DNS record.

The easiest way to do this is using the Smart Proxy DNS plugin template which can get you up and running with a new DNS provider plugin in minutes.

New record classes are instantiated from the :factory proc in the plugin definition.

plugin :dns_plugin_template, ::Proxy::Dns::PluginTemplate::VERSION,
       :factory => proc { |attrs| ::Proxy::Dns::PluginTemplate::Record.record(attrs) }

And then in the main file of the plugin:

module Proxy::Dns::PluginTemplate
  class Record < ::Proxy::Dns::Record
    include Proxy::Log
    include Proxy::Util

    def self.record(attrs = {})
      new(attrs)
    end

    def create
      # use @fqdn, @value, @ttl, @type
    end

    def remove
      # use @fqdn, @value, @ttl, @type
    end
  end
end

Testing¶

Make sure that Gemfile includes "smart-proxy" gem as a development dependency:

group :development do
  gem 'smart_proxy', :git => "https://github.com/theforeman/smart-proxy.git" 
end

Load 'smart_proxy_for_testing' in your tests:

$: << File.join(File.dirname(__FILE__), '..', 'lib')

require 'smart_proxy_for_testing'
require 'test/unit'
require 'webmock/test_unit'
require 'mocha/test_unit'
require "rack/test" 

require 'smart_proxy_pulp_plugin/pulp_plugin'
require 'smart_proxy_pulp_plugin/pulp_api'

class PulpApiTest < Test::Unit::TestCase
  include Rack::Test::Methods

  def app
    PulpProxy::Api.new
  end

  def test_returns_pulp_status_on_200
    stub_request(:get, "#{::PulpProxy::Plugin.settings.pulp_url.to_s}/api/v2/status/").to_return(:body => "{\"api_version\":\"2\"}")
    get '/status'

    assert last_response.ok?, "Last response was not ok: #{last_response.body}" 
    assert_equal("{\"api_version\":\"2\"}", last_response.body)
  end
end

To execute all tests

bundle exec rake test

bundle exec rake test TEST=path/to/test/file

Please refer to Sinatra documention for detailed information on testing of Sinatra applications.

Once you have tests, see Jenkins for info on setting up tests under Jenkins.