DevOps Classroom Series – 03/Dec/2019

Scenario

• Important info:
  • By default chef always picks the latest version of cookbook
• All the nodes are deployed using
  • tomcat cookbook
    • version 1.0.0
    • java => 8
• Now you have been asked to change the following
  • JDK8 to JDK9
  • tomcat7 to tomcat8
• Ideally you should be making changes to QA Servers first and then to Production
• Now lets assume you have changed tomcat cookbook to install tomcat8 and jdk9 with version 1.1.0
• During next convergance all the servers will get update with 1.1.0 which can be a disaster
• For this in chef we have concept called as Environments
• Environment impose restrictions on cookbook versions.
• It is necessary that every node belongs to one environment. The default environment is _default.
• To solve the above problem
  • Create a new environment called as QA
    • tomcat = 1.1.0
  • Create a new environment called as Prod
    • tomcat = 1.0.0

Sample with Environments and Roles

• Create a simple cookbook with name envroledemo
• In the first version 1.0.0 write some resources. In this series i will be using file resource to create a file with some content
• Recipe => java in 1.0.0

file '/home/ubuntu/java' do
    content 'jdk8'
    action :create
end

• Recipe => java in 1.1.0

file '/home/ubuntu/java' do
    content 'jdk9'
    action :create
end

• Creating Roles: Roles can be created
  • On Chef Manage UI
  • From ruby or json files in Starter Kit.
• Refer Here for role formates
• In this series i prefer ruby files. I have create a tomcat.rb file in roles folder with following content

name "tomcat"
description "tomcat role"
run_list "recipe[envroledemo::java]"