Create var based on list in dict - ansible

Question

Imagine this dict on 4 different hosts.
# on host 1
my_dict:
ip: 10.0.0.111
roles:
- name: something
observer: false
# on host 2
my_dict:
ip: 10.0.0.112
roles:
- name: something
observer: false
# on host 3
my_dict:
ip: 10.0.0.113
roles:
- name: something
observer: true
# on host 4
my_dict:
ip: 10.0.0.114
roles:
- name: whatever
When Ansible runs for all 4 hosts I want it to build a variable for each host having the roles name 'something'. The desired output is:
10.0.0.111 10.0.0.112 10.0.0.113:observer
There are 2 requirements:
when my_dict.roles.name == 'something' it must add the ip to the var
but when my_dict.roles.observer , it must add the ip + ':observer'
I eventually want to use the var in a Jinja template, so to me, the var can be either set via an Ansible task or as a jinja template.
This doesn't work:
- name: set fact for ip
debug:
msg: >-
{{ ansible_play_hosts |
map('extract', hostvars, ['my_dict', 'ip'] ) |
join(' ') }}
when: ???

Answer 1

You could create two lists:
one with what should be postfixed to the IPs with the condition based on the observer property
the other one with the IPs
And then zip them back together.
Given:
- debug:
msg: >-
{{
_ips | zip(_is_observer) | map('join') | join(' ')
}}
vars:
_hosts: >-
{{
hostvars
| dict2items
| selectattr('key', 'in', ansible_play_hosts)
| selectattr('value.my_dict.roles.0.name', '==', 'something')
}}
_is_observer: >-
{{
_hosts
| map(attribute='value.my_dict.roles.0.observer')
| map('replace', false, '')
| map('replace', true, ':observer')
}}
_ips: >-
{{
_hosts
| map(attribute='value.my_dict.ip')
}}
This yields:
TASK [debug] *************************************************************
ok: [localhost] =>
msg: 10.0.0.111 10.0.0.112 10.0.0.113:observer