h1. 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.

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h2. 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":https://github.com/theforeman/smart_proxy_example is a minimal example plugin that can be used as a skeleton

* "smart_proxy_dns_plugin_template":https://github.com/theforeman/smart_proxy_dns_plugin_template is a template for creating new DNS provider plugins

Also, "smart_proxy_pulp plugin":https://github.com/theforeman/smart-proxy-pulp is an example for a fully functional, yet easy to understand Smart-Proxy plugin.

h2. Making your plugin official

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

h2. 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:

<pre><code class='ruby'>

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!', :important_path => '/must/exist'

    validate_readable :optional_path, :important_path

  end

end

</code></pre>

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. Setting any of the parameters in default_settings to nil will trigger a validation error.

 * validate_readable :optional_path, :important_path: *optional*. Verifies that settings listed here contain paths to files that exist and are readable. Optional settings (not listed under default_settings) will be skipped if left uninitialized. 

 * 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. 

h3. 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. No rackup_paths are used for providers, since they don't add any new REST API, they only add functionality to an existing module.

<pre>

module Proxy::Dns::PluginTemplate

  class Plugin < ::Proxy::Provider

    plugin :dns_plugin_template, ::Proxy::Dns::PluginTemplate::VERSION

    requires :dns, '>= 1.10'

    after_activation do

      require 'smart_proxy_dns_plugin_template/dns_plugin_template_main'

      require 'smart_proxy_dns_plugin_template/dns_plugin_template_dependencies'

    end

  end

end

</pre>

Additionally, each provider must specify which class implements interface expected by the main plugin. This is done by declaring an association for module's dependency injection container.

<pre>

require 'dns_common/dependency_injection/dependencies'

class Proxy::Dns::DependencyInjection::Dependencies

  dependency :dns_provider, Proxy::Dns::PluginTemplate::Record

end

</pre>

h2. API

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

<pre><code class='ruby'>

module Proxy::Example

 class Api < Sinatra::Base

  helpers ::Proxy::Helpers

  get "/hello" do

    Proxy::Example::Plugin.settings.hello_greeting

  end

end

</code></pre>

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":http://www.sinatrarb.com/intro.html on details about routing, template rendering, available helpers, etc.

h2. 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:

<pre><code class="ruby">

require 'example_plugin/example_api'

map "/example" do

  run Proxy::Example::Api

end

</code></pre>

The example above should be sufficient for the majority of plugins. Please refer to "Sinatra+Rack":http://www.sinatrarb.com/intro.html documentation for additional information. 

h2. 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. 

<pre>

---

:enabled: true

:hello_greeting: "O hai!"

</pre>

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. 

h2. 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:

<pre><code class="ruby">

  gem 'smart_proxy_example'

  group :example do

    gem 'json'

  end

</code></pre>

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.

h2. Adding a DNS provider

*Requires Smart Proxy 1.10 or higher.*

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":https://github.com/theforeman/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.

<pre>

plugin :dns_plugin_template, ::Proxy::Dns::PluginTemplate::VERSION,

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

</pre>

And then in the main file of the plugin:

<pre>

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

</pre>

h2. Testing

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

<pre><code class="ruby">

group :development do

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

end

</code></pre>

Load 'smart_proxy_for_testing' in your tests:

<pre><code>

$: << 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

</code></pre>

To execute all tests <code><pre>bundle exec rake test</code></pre>.  To save time during development it is possible to execute tests in a single file: <code><pre>bundle exec rake test TEST=path/to/test/file</pre></code>

Please refer to "Sinatra documention":http://www.sinatrarb.com/testing.html for detailed information on testing of Sinatra applications.

Once you have tests, see "Jenkins":http://projects.theforeman.org/projects/foreman/wiki/Jenkins#Smart-proxy-plugin-testing for info on setting up tests under Jenkins.