DevOps Classroom Series – 22/Oct/2021

Templating using Jinja2

• Ansible uses Jinja2 templating to enable dynamic expressions and access to variables.
• First and foremost advantage of using Jinja2 is we can avoid static file copies.
• Couple of classes ago, we had problem with tomcat.service as the path of the java was different for centos and ubuntu systems. To solve this we created two service files and two tasks
• We can avoid this by using templates
• Lets create a new folder for templates and create a tomcat.service.j2 file
• Refer Here for the changeset containing the usage of jinja2 templates
• Refer Here for the official docs
• Refer Here for some example jinja2 filters
• Using map filter and list filter

- hosts: localhost 
  connection: local 
  gather_facts: no 
  vars: 
    names: 
     - first: Paul 
       last: Thompson 
     - first: Rod 
       last: Johnson
  tasks:
    - debug: 
        msg={{ names | map(attribute='first') | list }} 
    - debug: 
        msg={{ names | map(attribute='last') | list }} 
    - debug: 
        msg={{ names | map('upper') | list }} 
    - debug: 
        msg={{ names | map(attribute='last') | map('upper') | list }}

Ansible Behavioral Parameters

• The list of behavior parameters