Create var based on list in dict

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: ???

Why would your variables and task give 10.0.0.111 10.0.0.112 10.0.0.113:observer with the provided example? Is observer the variable name and true or false the values, and you're trying to run a command on hosts that have that variable set? I'm admittedly confused as to what you're trying to accomplish. — Joe
– Joe, Commented Feb 18, 2022 at 22:08
I don't understand your question. But i'll edit my question to make it more clear. — Kevin C
– Kevin C, Commented Feb 18, 2022 at 22:12
It would be helpful to know what the variable is being constructed for as well. My guess is to template a configuration file for a cluster of some type where hosts take on some type of persona based upon the variable. — Joe
– Joe, Commented Feb 18, 2022 at 22:50
Benoit, that was a copy/paste mistake. And Joe, yes, your guess is correct. — Kevin C
– Kevin C, Commented Feb 18, 2022 at 23:06

β.εηοιτ.βε · Accepted Answer · 2022-02-18 23:30:17Z

2

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

edited Feb 18, 2022 at 23:30

answered Feb 18, 2022 at 23:17

β.εηοιτ.βε

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4 Comments

β.εηοιτ.βε Over a year ago

That should do, and it has been DRY'ed

Kevin C Over a year ago

I love these answers. I really have to learn how to do this stuff.

Kevin C Over a year ago

Simple question, can I also easily configure it, so that when 'observer: true' that IP omitted from the list, the result would then be: '10.0.0.111 10.0.0.112'

β.εηοιτ.βε Over a year ago

Sure, a list without the observer(s) would be "{{ _hosts | selectattr('value.my_dict.roles.0.observer') }}" which is a short version of "{{ _hosts | selectattr('value.my_dict.roles.0.observer', '==', true) }}"

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