Is there any way to loop through Ansible list of dictionary registered variable in combination with Jinja2?

Question

In my inventory I have 3 servers in a group. I want to be able to increase that size in the future so I can add more nodes into the network and generate the template with Jinja2.

- name: Gathering API results
  shell: 
    cmd: "curl {{ groups['nodes'][node_index] }}/whatever/api/result "
  loop: "{{ groups['nodes'] }}"
  loop_control:
    index_var: node_index
  register: api_value

If I run some debug tasks hardcoding which list I want to use everyhing works fine

- debug: "msg={{ api_value.results.0.stdout }}"
- debug: "msg={{ api_value.results.1.stdout }}"
- debug: "msg={{ api_value.results.2.stdout }}"

output:

ok: [server-1] => {
        "msg": "random-value-a"
ok: [server-2] => {
        "msg": "random-value-b"    
ok: [server-3] => {
        "msg": "random-value-c"

The problem is when I try to increase the list number in Jinja template. I tried several for loops combination, nested for loops and many other things but nothing seems to be working.

For example I want my Jinja template look similar like this:

{% for vm in groups['nodes'] %}
NODE_{{ loop.index }}={{ api_value.results.{loop.index}.stdout }}
{% endfor %}

This way I want to achieve this output:

NODE_0=random-value-a
NODE_1=random-value-b
NODE_2=random-value-c

Is there any other way to workaround this? Or maybe is something I could do better in the "Gathering API results" task?

Answer 1

Given the inventory

shell> cat hosts
[nodes]
server-1
server-2
server-3

1. Either run it in the loop at a single host, e.g.

- hosts: localhost
  gather_facts: false
  vars:
    whatever_api_result:
      server-1: random-value-a
      server-2: random-value-b
      server-3: random-value-c
  tasks:
    - command: "echo {{ whatever_api_result[item] }}"
      register: api_value
      loop: "{{ groups.nodes }}"
    - debug:
        msg: "{{ api_value.results|json_query('[].[item, stdout]') }}"

gives

  msg:
  - - server-1
    - random-value-a
  - - server-2
    - random-value-b
  - - server-3
    - random-value-c

Then, in the Jinja template, fix the index variable

    - debug:
        msg: |-
          {% for vm in groups.nodes %}
          NODE_{{ loop.index0 }}={{ api_value.results[loop.index0].stdout }}
          {% endfor %}

gives what you want

  msg: |-
    NODE_0=random-value-a
    NODE_1=random-value-b
    NODE_2=random-value-c

Optionally, iterate api_value.results. This gives the same result

    - debug:
        msg: |-
          {% for v in api_value.results %}
          NODE_{{ loop.index0 }}={{ v.stdout }}
          {% endfor %}

---

2. Or run it in the group, e.g.

- hosts: nodes
  gather_facts: false
  vars:
    whatever_api_result:
      server-1: random-value-a
      server-2: random-value-b
      server-3: random-value-c
  tasks:
    - command: "echo {{ whatever_api_result[inventory_hostname] }}"
      register: api_value
      delegate_to: localhost
    - debug:
        msg: "{{ api_value.stdout }}"

^{(delegate to localhost for testing)}

gives

ok: [server-1] => 
  msg: random-value-a
ok: [server-2] => 
  msg: random-value-b
ok: [server-3] => 
  msg: random-value-c

Then, in the Jinja template, use hostvars

    - debug:
        msg: |-
          {% for vm in groups.nodes %}
          NODE_{{ loop.index0 }}={{ hostvars[vm].api_value.stdout }}
          {% endfor %}
      run_once: true

gives also what you want

  msg: |-
    NODE_0=random-value-a
    NODE_1=random-value-b
    NODE_2=random-value-c

Optionally, iterate hostvars. This gives the same result

    - debug:
        msg: |-
          {% for k,v in hostvars.items() %}
          NODE_{{ loop.index0 }}={{ v.api_value.stdout }}
          {% endfor %}
      run_once: true