How to split a string into a list with Ansible/Jinja2?

Question

I have the following variables:

domain_names:
  - app1.example.com
  - app2.example.com

customers:
  - name: customer1
  - name: customer2

And I'm trying to generate the following list of domain names:

- customer1.app1.example.com
- customer2.app1.example.com
- customer1.app2.example.com
- customer2.app2.example.com

By using the following Ansible/Jinja2 code:

- name: check which certificates exist
  stat:
    path: '/etc/nginx/{{item}}.crt'
  register: cert_file
  loop: '{% for d in domain_names %}{{ d }} {% for customer in customers %}{{ customer.name }}.{{ d }} {% endfor %}{% endfor %}'

However, I'm getting the following error:

failed | msg: Invalid data passed to 'loop', it requires a list, got this instead: customer1.app1.example.com customer2.app1.example.com customer1.app2.example.com customer2.app2.example.com. Hint: If you passed a list/dict of just one element, try adding wantlist=True to your lookup invocation or use q/query instead of lookup.

How can I fix this?

Answer 1

Simply use the right tools :). In this case your friends are:

• the map filter to extract the name attribute as a list from your customers variable
• the product filter to mix-up your two lists

e.g. test.yml playbook:

---
- name: product and map filters demo
  hosts: localhost
  gather_facts: false
  
  vars:
    domain_names:
      - app1.example.com
      - app2.example.com

    customers:
      - name: customer1
      - name: customer2

  tasks:
    - name: Demonstrate product and map filters use
      debug:
        msg: "{{ item.0 }}.{{ item.1 }}"
      loop: "{{ customers | map(attribute='name') | product(domain_names) | list }}"

Which gives:

$ ansible-playbook test.yml 

PLAY [product and map filters demo] *******************************************************************************************************************************************************************************

TASK [Demonstrate product and map filters use] ********************************************************************************************************************************************************************
ok: [localhost] => (item=['customer1', 'app1.example.com']) => {
    "msg": "customer1.app1.example.com"
}
ok: [localhost] => (item=['customer1', 'app2.example.com']) => {
    "msg": "customer1.app2.example.com"
}
ok: [localhost] => (item=['customer2', 'app1.example.com']) => {
    "msg": "customer2.app1.example.com"
}
ok: [localhost] => (item=['customer2', 'app2.example.com']) => {
    "msg": "customer2.app2.example.com"
}

PLAY RECAP ********************************************************************************************************************************************************************************************************
localhost                  : ok=1    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   

Applied to your task, this gives:

- name: Check which certificates exist
  stat:
    path: '/etc/nginx/{{ item.0 }}.{{ item.1 }}.crt'
  register: cert_file
  loop: "{{ customers | map(attribute='name') | product(domain_names) | list }}"

If you really want to re-use that list you can build it into an other var. One easy way to understand is to build it in a set_fact task, e.g.

- name: Create my application names list
  vars:
    current_name: "{{ item.0 }}.{{ item.1 }}"
  set_fact:
    application_names_list: "{{ application_names_list | default([]) + [current_name] }}"
  loop: "{{ customers | map(attribute='name') | product(domain_names) | list }}"

- name: Check which certificates exist
  stat:
    path: '/etc/nginx/{{ item }}.crt'
  register: cert_file
  loop: "{{ application_names_list }}"

But you can also declare it "statically" in your vars with a little more complex expression (see the map filter possibilities and the join filter)

---
- name: product and map filters demo
  hosts: localhost
  gather_facts: false

  vars:
    domain_names:
      - app1.example.com
      - app2.example.com

    customers:
      - name: customer1
      - name: customer2

    application_names_list: "{{ customers | map(attribute='name') | product(domain_names) | map('join', '.') | list }}"

  tasks:
    - name: Demonstrate product and map filters use
      debug:
        var: application_names_list

=>

PLAY [product and map filters demo] ****************************************************************************************************************************************************************************************************

TASK [Demonstrate product and map filters use] *****************************************************************************************************************************************************************************************
ok: [localhost] => {
    "all_domains": [
        "customer1.app1.example.com",
        "customer1.app2.example.com",
        "customer2.app1.example.com",
        "customer2.app2.example.com"
    ]
}

PLAY RECAP *****************************************************************************************************************************************************************************************************************************
localhost                  : ok=1    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0