AnsibleModule

AnsibleModule is a Ruby class that provides basic functionalities as an Ansible module.

It is distributed as a gem package under the MIT-LICENSE.

Installation

Manual Installation

Install Ruby (2.0 or later) and ansible_module gem on your remote hosts.

The following is a typical procedure on Ubuntu Server 14.04:

$ sudo add-apt-repository -y ppa:brightbox/ruby-ng
$ sudo apt-get update
$ sudo apt-get -y install ruby2.1 ruby2.1-dev
$ sudo gem install ansible_module

Installation with Ansible

Create an Ansible playbook to install Ruby and ansible_module gem.

The following is an example for Ubuntu Server 14.04:

- hosts: servers
  sudo: yes
  tasks:
  - name: Add ppa for ruby
    apt_repository: repo='ppa:brightbox/ruby-ng' state=present
  - name: Install ruby 2.1
    apt: name=ruby2.1 state=present
  - name: Install ruby 2.1 headers
    apt: name=ruby2.1-dev state=present
  - name: Install ansible_module gem
    gem: name=ansible_module user_install=false state=present

If you named this file ruby_environment.yml, then run the following command on your local host:

$ ansible-playbook -i hosts ruby_environment.yml

In the above example, the hosts file is an inventory which lists up host names or IP addresses.

Example (1) -- Simple Calculation

Module

Create a file named calc on the library directory as follows:

#!/usr/bin/ruby

require 'ansible_module'

class Calc < AnsibleModule
  attribute :x, Integer
  attribute :y, Integer

  validates :x, :y, presence: true, numericality: { only_integer: true }

  def main
    sum = x + y

    exit_json(x: x, y: y, sum: sum, changed: true)
  end
end

Calc.instance.run

The values of attributes x and y are set during instantiation process by AnsibleModule.

Note that you can validate them with validates class method derived from ActiveModel.

The class method instance returns a singleton instance of Calc class, and its run method calls the main method if validations are successful.

So, the author of an Ansible module must implement the main method at least.

Playbook

Now, you can use the calc module in your playbook. For example, create a file named calc.yml as follows:

- hosts: servers
  tasks:
  - name: Make a calculation
    calc: x=50 y=50
    register: result
  - debug: msg="sum = {{ result['sum'] }}"

Then, run the following command on your local host:

$ ansible-playbook -i hosts calc.yml

Example (2) -- MySQL 5.6 Replication Management

Prerequisites

Install MySQL 5.6 Server, MySQL 5.6 Client, MySQL 5.6 development files and mysql2 gem.

The following is a typical procedure on Ubuntu Server 14.04:

$ sudo add-apt-repository -y ppa:ondrej/mysql-5.6
$ sudo apt-get update
$ sudo apt-get -y install mysql-server-5.6 mysql-client-5.6 libmysqlclient-dev
$ sudo gem install mysql2

You can also install them with the following playbook:

- hosts: servers
  sudo: yes
  tasks:
  - name: Add ppa for mysql 5.6
    apt_repository: repo='ppa:ondrej/mysql-5.6' state=present
  - name: Install mysql server 5.6
    apt: name=mysql-server-5.6 state=present
  - name: Install mysql client 5.6
    apt: name=mysql-client-5.6 state=present
  - name: Install libmysqlclient-dev
    apt: name=libmysqlclient-dev state=present
  - name: Install mysql2 gem
    gem: name=mysql2 user_install=false state=present

Module

Create a file named mysql_change_master on the library directory as follows:

#!/usr/bin/ruby

require 'ansible_module'
require 'mysql2'

class MysqlChangeMaster < AnsibleModule
  attribute :host, String
  attribute :port, Integer, default: 3306
  attribute :user, String
  attribute :password, String
  attribute :mysql_root_password, String

  validates :host, :user, :password, presence: true
  validates :port, inclusion: { in: 0..65535 }
  validates :password, maximum: 32

  def main
    done? && exit_json(changed: false)

    statement = %Q{
      CHANGE MASTER TO
        MASTER_HOST='#{host}',
        MASTER_PORT=#{port},
        MASTER_USER='#{user}',
        MASTER_PASSWORD='#{password}',
        MASTER_AUTO_POSITION=1
    }.squish

    mysql_client.query('STOP SLAVE')
    mysql_client.query(statement)
    mysql_client.query('START SLAVE')
    sleep(1)

    if done?
      exit_json(statement: statement, changed: true)
    else
      fail_json(msg: "Last Error: #{@last_error}")
    end
  end

  private

    def done?
      status = mysql_client.query('SHOW SLAVE STATUS').first || {}

      @last_error = [ status['Last_IO_Error'], status['Last_SQL_Error'] ]
        .compact.join(' ').squish

      status['Master_Host'] == host &&
        status['Master_User'] == user &&
        status['Master_Port'].to_i == port &&
        status['Auto_Position'].to_i == 1 &&
        status['Slave_IO_State'] != '' &&
        status['Last_IO_Error'] == '' &&
        status['Last_SQL_Error'] == ''
    end

    def mysql_client
      @client ||= Mysql2::Client.new(
        host: 'localhost',
        username: 'root',
        password: mysql_root_password,
        encoding: 'utf8'
      )
    end
end

MysqlChangeMaster.instance.run

Note that you can use methods added by ActiveSupport like String#squish.

Playbook

Then, create a file named replication.yml as follows:

- hosts: mysql-slave
  vars_files:
    - shared/secret.yml
  tasks:
  - name: Change master to the db1
    mysql: >
      host="db1"
      user="repl"
      password="{{ mysql_repl_password }}"
      mysql_root_password="{{ mysql_root_password }}"

Next, create a file named secret.yml on the shared directory as follows:

mysql_repl_password: p@ssw0rd
mysql_root_password: p@ssw0rd

Note that you should replace p@ssw0rd with real passwords.

And run the following command on your local host:

$ ansible-playbook -i hosts replication.yml

You might want to encrypt the secret.yml with ansible-vault. In that case, you must add --ask-vault-pass option to the above command:

$ ansible-playbook -i hosts --ask-vault-pass replication.yml

License

AnsibleModule is distributed under the MIT-LICENSE.