In this blog we will explore how can we manage inventory file for the ansible playbook.

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Problem Statement:

• There is a clustered application ( 2 application nodes and 1 database node), now how will you run your different playbooks for different nodes. For ex- you will be having different task to be done like install java on application node but that same task is not required on the database node

Solution:

We need to maintain the inventory file as shown below:

• We have created a tag [all] and provide all the host values
• We have created two other tags, one for application and one for database
• We have created one more tag to exclude the second application node

[all]
application-0 ansible_host=1.1.1.1
application-1 ansible_host=1.2.2.3
database-0    ansile_host=3.3.2.1
[application-nodes]
application-0
application-1

[database-nodes]
database-0

[all-nodes-exclude-second]
application-0
database-0

How to call in main.yml file ?

• We will provide the tag name as per our inventory in the playbook where particular role needs to be executed

Scenarios

- hosts: all
  gather_facts: yes

• Install java on all the application nodes

- hosts: application-nodes[0:] 
  gather_facts: yes
  tasks:
    - include_role:
        name: install_java
       

• Install java only on first application nodes

- hosts: application-nodes[1]
  gather_facts: yes
  tasks:
    - include_role:
        name: install_java

• Install java only on first application node and database node, exclude the second application node

 - hosts: all-nodes-exclude-second[0:]
   gather_facts: no
   tasks:
     - include_role:
         name: install_java
         

Like this you can create your inventory file as per your project need. I have provided some sample scenario that can help you how to Manage inventory files for ansible playbook