How can i load a vars file in inventory which "prepares" a large number of variables via jinja2 expressions ?

[ishan jain]

For some servers in an inventory, i assign a range of ports. I want to use these ports in my playbooks while keeping them portable and compatible with any configuration. I am thinking of using variable for ports whose values are resolved via some script in inventory. Something like this:

--In Playbooks--

portValueUser: p1
hostName: localhost:p2
someURL: http://hostname:p3

--For first inventory, values of p1, p2, p3....---

p1: 5101
p2: 5102
p3 5103
...
...
p100:  5200

--For seconds inventory, values of p1, p2, p3....---

p1: 6201
p2: 6202
p3 6203
...
...
p100:  6300

This way, i can use a series of port values in my playbook which are defined by inventory(host vars). I am trying to figure out a way to really apply some logic in constructing these vars

Something like, in inventory/group_vars/all/load.yaml.j2

(please ignore the syntax errors, this is for illustration)

{% if a > b %}

{% for i = 1 to 100 and val = 5101 to 5200 %}

p{{i}} = val

{% endfor %}

{% else %}

{% for i = 1 to 100 and val = 6201 to 6300 %}

p{{i}} = val

{% endfor %}

{% endif %}

Remember the 2 main questions here:

1 - Can i really construct a large number of variables with loop like this ?

2 - How can i load or rather resolve a vars file like above via the inventory ?

[Cev Ing]

I do something similar in a role by generating a YML file, which gets included later on by include_vars.

This are the includes in the main.yml of the role:

- include: generate_vars.yml

- include_vars: generated_vars.yml

And this is the task in generate_vars.yml:

shell: |-

  exec >generated_vars.yml

  echo ---

  output_some_data

run_once: true

check_mode: false

I do the generation just once and disable check_mode to avoid errors by undefined variables during checks, because in check mode shell scripts are not executed.