Configuration Management

• Need:
  • As part of CI/CD we need to create various environments, To create environments we need servers
  • Once the servers are available we need to perform technology specific and application specific operations/commands to run the application.
  • sample techonology specifics:

#
java application
=> linux server (ubuntu/centos)
    => installing java
    => application server to be configured
    (tomcat/jboss/whatever)
    => copy the package into some location
    => restart the app server

    => database server changes if required


.net application
	=> windows server
        => configure IIS
        => copy the package built into some folder




python application

=> Linux Server
=> Python
=> install django/flask
=> configure apache/nginx server to run python code

* Application Specific configurations

# some app specific configurations
Create environment variables
create/Delete some folders

Add database urls in some file

• Possibilities:

  • Manual: Not an Option

  • Shell/Powershell Scripting:

    • Procedural
    • Pros: Stable technology & lot of knowledge around in existing teams
    • Cons:
      • Not Readable or Consistent among users.
      • Has assumptions and it is not guarnteed to give same results upon multiple executions.
    • Eg:

    # install tomcat
    # approach find and use commands
    sudo apt-get update && sudo apt-get install tomcat8 -y
    sudo systemctl enable tomcat8
    
    sudo yum update && sudo yum install tomcat8
    sudo systemctl enable tomcat8 
    sudo systemctl start tomcat8
    

  • Configuration Management:

    • Declarative
    • Simple to Learn
    • script should give same results upon multiple executions
    • Scripts should be Readable & Maintainable
    • Eg:

    # approach
    ensure packages are up to date
    enusure tomcat8 is installed
    enable and start tomcat8
    

Terms

• Idempotance: When you run the script n times and are expected to get the same result , then the script is idempotent.