DevOps Classroom Series – 02/Sept/2020

Chef Resources

Common Functionality

* [Refer Here](https://docs.chef.io/resources/) for official docs
* Common Functionalities are available for all resources

• Actions: The action :nothing

service 'apache2' do
    action :nothing
end

• Properties:
  • ignore_failure: If this property is set to true chef will not stop executing on failure
  • retries: The number of attempts to catch exceptions and retry
  • retry_delay: The retry delay in seconds
  • sensitive:
• Example with common properties

apt_update 'ubuntu packages' do
  ignore_failure true
  action :update
end

• Guards: Every chef resource supports two blocks
  • only_if: The resource with this will be executed only if the condition matches

  apt_update 'ubuntu packages' do
      action :update
      only_if platform?('ubuntu')
  end
  

  • not_if: Executes the resource when the condition doesn’t match
• Lets experiment this with lamp stack
• Create a cookbook lampstack

chef generate -b lampstack

• Now make changes to kitchen.yaml file to create two platforms
  • ubuntu 18.04
  • Redhat 8
• Now execute

berks install
kitchen create
kitchen list

• Now lets create a recipe for apache & php packages call this as lamp

chef generate recipe . lamp

• Now add an attribute file default

chef generate attribute . default

• Make changes to attributes\default.rb with

if platform?('ubuntu')
    default['lampstack']['apache']['package'] = 'apache2'
    default['lampstack']['apache']['php_package'] = %w(php libapache2-mod-php php-mysql php-cli)
elsif platform?('redhat')
    default['lampstack']['apache']['package'] = 'httpd'    
    default['lampstack']['apache']['php_package'] = %w(php php-mysqlnd php-fpm)
end

• Make changes to recipes\lamp.rb

#
# Cookbook:: .
# Recipe:: lamp
#
# Copyright:: 2020, The Authors, All Rights Reserved.

apache_package = node['lampstack']['apache']['package']

php_packages = node['lampstack']['apache']['php_package']

apt_update 'ubuntu package update' do
    ignore_failure true
    action :update
    only_if { platform?('ubuntu') }
end


package apache_package do
    action :install
end

service apache_package do
    action :enable
end


package php_packages do
    action :install
end

service 'restart apache' do
    service_name  apache_package
    action :restart
end

• Now make changes to recipes\default.rb

if platform?('ubuntu') || platform?('redhat')
    include_recipe 'lampstack::lamp'
else
   Chef::Application.fatal!('This cookbook supports redhat and ubuntu platforms')
end

• Now lets converge our resources using kitchen

kitchen converge

• Now execute kitchen list
• Now the problem in the current recipe is we are writing the same resource service twice
• Chef has a concept of Notifications.

Chef Notifications

• Notification is a property on resource that listens to other resources in resource collection & takes action based on notification type.
• Two kinds of notifications
  • notifies
  • subscribes
• Refer Here
• Now implementing notifications in lamp.rb will help to reuse service resource

#
# Cookbook:: .
# Recipe:: lamp
#
# Copyright:: 2020, The Authors, All Rights Reserved.

apache_package = node['lampstack']['apache']['package']

php_packages = node['lampstack']['apache']['php_package']

apt_update 'ubuntu package update' do
    ignore_failure true
    action :update
    only_if  { platform?('ubuntu') }
end


package apache_package do
    action :install
    notifies :enable, "service[#{apache_package}]"
end

service apache_package do
    action :nothing
end


package php_packages do
    action :install
    notifies :restart, "service[#{apache_package}]", :immediately
end

• Lets add the last step of creating a file with below content in /var/www/html/info.php

<?php
phpinfo();
?>

• Now the recipe will look like

#
# Cookbook:: .
# Recipe:: lamp
#
# Copyright:: 2020, The Authors, All Rights Reserved.

apache_package = node['lampstack']['apache']['package']

php_packages = node['lampstack']['apache']['php_package']

apt_update 'ubuntu package update' do
    ignore_failure true
    action :update
    only_if  { platform?('ubuntu') }
end


package apache_package do
    action :install
    notifies :enable, "service[#{apache_package}]"
end

service apache_package do
    action :nothing
end


package php_packages do
    action :install
    notifies :restart, "service[#{apache_package}]"
end

file '/var/www/html/info.php' do
    content '<?php phpinfo(); ?>'
    action :create
    notifies :restart, "service[#{apache_package}]", :immediately
end

• Now converge and verify info.php at http://public-ip/info.php
• Since cookbook is working now upload cookbook to chef server

berks upload

• Destroy the test kitchen instances

kitchen destroy