wordpress_app

Table of Contents

1. Description
2. Setup - The basics of getting started with wordpress_app
   • What [modulename] affects
     • Setup requirements
       • Beginning with [modulename]
       3. Usage - Configuration options and additional functionality
       4. Reference - An under-the-hood peek at what the module is doing and how
       5. Limitations - OS compatibility, etc.
       6. Development - Guide for contributing to the module

Description

The Puppet wordpress_app is a module that demonstrates an example application model. The module contains application components you can use to set up a WordPress database, a PHP application server, and an HAProxy load balancer. With these components, you can build two WordPress applications: a simple LAMP stack or a complex stack that uses load-balancing.

Setup Requirements

To use this module, you must enable application management on the Puppet master. Add app_management = true to the puppet.conf file on your Puppet master. You also need to enable plugin sync on any agents that will host application components.

If you use Puppet Enterprise, the Puppet orchestrator documentation provides commands and API endpoints you can use to deploy the wordpress_app.

In addition, see the application orchestration workflow docs for more conceptual information.

If you use r10k, this module includes a Puppetfile that will install the module and its dependencies.

Getting started with wordpress_app

The most basic use of the wordpress_app module is to install Wordpress on a single node. For example, you can add the following application declaration to your site.pp:

  # Example code to be added to the site.pp
  wordpress_app::simple { 'all_in_one':
    nodes => {
      Node['node1.example.com'] => [
        Wordpress_app::Database['all_in_one'],
        Wordpress_app::Web['all_in_one'],
      ]
    }
  }

After deploying this application, you can access it at http://node1.example.com.

SELinux

SELinux may prevent Apache from connecting to MySQL. Make sure it's properly configured or disabled if you run into database connection errors.

Patterns

wordpress_app::simple

This is a simple Wordpress application model. The three components are defined statically in the application definition with their names expected to match the name of the application. The database component produces a database resource. The web component consumes that database resource, and produces an HTTP resource. The load balancer component consumes the HTTP resource.

You should use this style of declaration if every instance of the application has the same components. Such declarations make it easier to assign components to a single node or to spread them across multiple nodes in different instances.

wordpress_app

This is a more complex application definition. It uses functions to dynamically discover what components have been declared, and then it validates and connects them. You should use this type of definition if you have a varying number of components, or if some components are optional. By discovering the component names dynamically, you don't have to worry about matching statically declared component names.

In the following example, the collect_component_titles function searches through the application's nodes and finds all resources matching a certain component type and returns a list of their titles. The function verifies that there is one database, and it then declares that resource. Since the name of the exported database capability resource is set for internal consumption, you shouldn't have to track the name.

  # Example code in wordpress_app/manifests/init.pp
  $db_components = collect_component_titles($nodes, Wordpress_app::Database)
  if (size($db_components) != 1){
    $db_size = size($db_components)
    fail("There must be one database component for wordpress_app. found: ${db_size}")
  }
  wordpress_app::database { $db_components[0]:
    database   => $database,
    user       => $db_user,
    password   => $db_pass,
    export     => Database["wdp-${name}"]
  }

For the web components, the function collects all resources assigned to nodes in the application. The map function loops over the resources and declares the components, and it then collects the HTTP resources they export for later consumption. This allows you to declare one or more web components to scale your application dynamically through the declaration.

For example:

  # Example code in wordpress_app/manifests/init.pp
  $web_components = collect_component_titles($nodes, Wordpress_app::Web)
  # Verify there is at least one Web.
  if (size($web_components) == 0) {
    fail("Found no web component for Wordpress_app[${name}]. At least one is required")
  }
  # For each of these, declare the component and create an array of the exported
  # Http resources from them for the load balancer.
  $web_https = $web_components.map |$comp_name| {
    # Compute the Http resource title for export and return.
    $http = Http["web-$comp_name"]
    # Declare the web component.
    wordpress_app::web { $comp_name:
      apache_port => $web_port,
      interface   => $web_int,
      consume     => Database["wdp-${name}"],
      export      => $http,
    }
    # Return the $http resource for the array.
    $http
  }

The load balancer component of the application is optional, and you may have any number of instances of it. In some cases, you may have no need for a load balancer, or you may require several in a high availability configuration. Each load balancer requires the web-https resources exported by the web components to ensure ordering. The web-https resources are also passed in via the balancermembers parameter. Passing this resource as a parameter instead of as 'consumes' allows the the load balancer to collect any number of Http capability resources.

For example:

  # Example code in wordpress_app/manifests/init.pp
  $lb_components = collect_component_titles($nodes, Wordpress_app::Lb)
  $lb_components.each |$comp_name| {
    wordpress_app::lb { $comp_name:
      balancermembers => $web_https,
      lb_options      => $lb_options,
      ipaddress       => $lb_listen_ip,
      port            => $lb_listen_port,
      balance_mode    => $lb_balance_mode,
      require         => $web_https,
      export          => Http["lb-${name}"],
    }
  }

The following example shows a declaration of an instance of the Wordpress application with two web nodes and a single load balancer. The resource titles used here are arbitrary, but they must be unique in this environment.

  # Example code to be added to the site.pp
  wordpress_app { 'tiered':
    nodes => {
      # The titles of these don't matter as long as they're unique per component.
      Node['node1.example.com'] => Wordpress_app::Database['wordpress-db'],
      Node['node2.example.com'] => Wordpress_app::Lb['tiered'],
      Node['node3.example.com'] => Wordpress_app::Web['tiered-web01'],
      Node['node4.example.com'] => Wordpress_app::Web['wordpress-web02'],
    }
  }

Components vs Profiles

If you're already organizing your code into roles and profiles, the application components are probably very similiar to your profiles. If all your nodes serve a single purpose, you may be able to just convert your profile classes into component defined types. However, if you need to put multiple components on a single node that share resources, this may result in conflicts. For example, if you have one database node that provides databases for multiple Wordpress application instances, MySQL resources may be shared. Or, if you have multiple HTTP components in your stack, Apache resources might be shared. If this is the case, you should turn the components into profile classes that can then be included in the component. Consider wordpress_app:database and workpress_app::database_profile: the underlying MySQL server and firewall rules are configured in the profile while the specific datbase, user, and permissions are managed in the component.

Reference

Applications

wordpress_app::simple

This is a simple WordPress application.

Components

• Wordpress_app::Database[$name]
• Wordpress_app::Web[$name]
  • consumes from Database
• Wordpress_app::Lb[$name]
  • consumes from Web

Parameters

• database: The database name (default 'wordpress').
• db_user: The database user for the application (default: 'wordpress').
• db_pass: The password for the database (default: wordpress).
• web_port: The port the webserver listens on (default: '8080').
• lb_port - The port HAProxy listens on when load balancing (default: '80').

wordpress_app

This is a more complex WordPress application. Using the collect_component_titles function means that the names of the components don't matter as long as they are unique per component throughout the environment.

Components

• Wordpress_app::Database[.*]
  • You must have only one of these
• Wordpress_app::Web[.*]
  • You can have one or more of these
  • consumes from Database
• Wordpress_app::Lb[.*]
  • You can have any number of Lb components
  • each consumes all Web components

Parameters

• database: The database name (default 'wordpress').
• db_user: The database user for the application (default: 'wordpress').
• db_pass: The password for the database (default: wordpress).
• web_int: The interface the webserver listens on.
• web_port: The port the webserver listens on (default: '80').
• lb_ipaddress: The IP address the load balancer listens on (default: '0.0.0.0').
• lb_port: The port the load balancer listens on (default: '8080').
• lb_balance_mode: The loadbalancer mode to use (default: 'roundrobin').
• lb_options: The HAProxy options to pass (default: ['forwardfor','http-server-close','httplog'] ).

Component Types

word_press_app::database

The application component to manage the WordPress database.

Capabilities

• Produces a Database capabality resource for the MySQL database

Parameters

• database: The database name for this application (default: 'wordpress').
• user: The application user that will connect to the database (default: 'wordpress').
• password: The password the application uses to connect to the database (default: 'wordpress').

wordpress_app::web

The application component to manage WordPress and Apache.

Capabilities

• Consumes the Database capability resource for the MySQL database
• Produces an Http capability resource for WordPress

Parameters

• db_host: The database host.
• db_port: The database port.
• db_name: The database name.
• db_user: The database user.
• db_password: The database password.
• apache_port: The Apache port WordPress listens on.
• interface: The interface Apache listens on.

wordpress::lb

The application component to manage HAProxy load balancing.

Capabilities

• Consumes an Array [Http] capability resource for WordPress nodes
• Produces an Http capability resource for HAProxy

Parameters

• balancermembers: An array of Http resources of WordPress nodes to load balance.
• lb_options: An array of options to pass to HaProxy (default: ['forwardfor', 'http-server-close', 'httplog']).
• balance_mode: The load balancing mode to use (default: 'roundrobin').
• ipaddress: The IP address HAProxy listens on (default: '0.0.0.0).
• port: The port HAProxy listens on (default: '80').

Classes

wordpress_app::ruby

The class that manages the ruby package for puppetlabs-concat.

Parameters

• manage: Whether to manage the ruby package (default is true). Set to false if you are managing the ruby package elsewhere.

wordpress_app::database_profile

The class that manages the MySQL server and firewall rules.

Parameters

• bind_address: The address MySQL listens on (default: '0.0.0.0').

wordpress_app::web_profile

The class that manages Apache, the MySQL client libraries, and wget for WordPress.

Parameters

none