Loops within loops - ansible

Question

I've set up some application information in my Ansible group_vars like this:
applications:
- name: app1
- name: app2
- name: app3
- name: app4
settings:
log_dir: /var/logs/app4
associated_files:
- auth/key.json
- name: app5
settings:
log_dir: /var/logs/app5
repo_path: new_apps/app5
I'm struggling to get my head around how I can use these "sub loops".
My tasks for each application are:
Create some folders based purely on the name value
Create a log folder if a settings/log_dir value exists
Copy associated files over, if specified
The syntax for these tasks isn't the problem here, I'm comfortable with those - I just need to know how to access the information from this applications variable. Number 3 in particular seems troublesome to me - I need to loop within a loop.
To debug this, I've been trying to run the following task:
- debug:
msg: "{{ item }}"
with_subelements:
- "{{ applications }}"
- settings
Here's the output:
with_items: I get the error with_items expects a list or a set
with_nested: I can see the top level information (e.g. msg: {{ item }} outputs an array of app1, app2 etc)
with_subelements: I get the error subelements lookup expects a dictionary, got 'None'
It's possible/probable that the way I've set the variable up in the first instance is wrong. If there's a better way to do this, it's not a problem to change it.

Answer 1

You can't use with_subelements because settings is a dictionary, not a list. If you were to restructure your data so that settings is a list, like this:
applications:
- name: app1
- name: app2
- name: app3
- name: app4
settings:
- name: log_dir
value: /var/logs/app4
- name: associated_files
value:
- auth/key.json
- name: app5
settings:
- name: log_dir
value: /var/logs/app5
- name: repo_path
value: new_apps/app5
You could then write something like the following to iterate over each setting for each application:
---
- hosts: localhost
gather_facts: false
vars_files:
- applications.yml
tasks:
- debug:
msg: "set {{ item.1.name }} to {{ item.1.value }} for {{ item.0.name }}"
loop: "{{ applications|subelements('settings', skip_missing=true) }}"
loop_control:
label: "{{ item.0.name }}.{{ item.1.name }} = {{ item.1.value }}"
(I'm using loop_control here just to make the output nicer.)
Using the sample data you posted in applications.yml, this will produce as output:
PLAY [localhost] *********************************************************************
TASK [debug] *************************************************************************
ok: [localhost] => (item=app4.log_dir = /var/logs/app4) => {
"msg": "set log_dir to /var/logs/app4 for app4"
}
ok: [localhost] => (item=app4.associated_files = ['auth/key.json']) => {
"msg": "set associated_files to ['auth/key.json'] for app4"
}
ok: [localhost] => (item=app5.log_dir = /var/logs/app5) => {
"msg": "set log_dir to /var/logs/app5 for app5"
}
ok: [localhost] => (item=app5.repo_path = new_apps/app5) => {
"msg": "set repo_path to new_apps/app5 for app5"
}
PLAY RECAP ***************************************************************************
localhost : ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0