Ansible: How to declare global variable within playbook?

Question

How can I declare global variable within Ansible playbook. I have searched in google and found the below solution, but its not working as expected.

- hosts: all
  vars:
    prod-servers:
     - x.x.x.x
     - x.x.x.x


- hosts: "{{prod-servers}}"
  tasks:
  - name: ping
    action: ping

When I'm trying the above code, it says variable prod-servers is undefined.

Answer 1

You cannot define a variable accessible on a playbook level (global variable) from within a play.

Variable Scopes

Ansible has 3 main scopes:

• Global: this is set by config, environment variables and the command line

• Play: each play and contained structures, vars entries (vars; vars_files; vars_prompt), role defaults and vars.

• Host: variables directly associated to a host, like inventory, include_vars, facts or registered task outputs

Anything you declare inside a play can thus only be either a play variable, or a (host) fact.

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To define a variable, which you can use in the hosts declaration:

• run ansible-playbook with --extra-vars option and pass the value in the argument;

or to achieve the same functionality (decide which hosts to run a play on, from within a preceding play):

• define an in-memory inventory and run the subsequent play against that inventory.