How to assign an array to a variable in an Ansible-Playbook

Question

In a playbook I got the following code:

--- - hosts: db   vars:     postgresql_ext_install_contrib: yes     postgresql_pg_hba_passwd_hosts: ['10.129.181.241/32'] ... 

I would like to replace the value of postgresql_pg_hba_passwd_hosts with all of my webservers private ips. I understand I can get the values like this in a template:

{% for host in groups['web'] %}    {{ hostvars[host]['ansible_eth1']['ipv4']['address'] }} {% endfor %} 

What is the simplest/easiest way to assign the result of this loop to a variable in a playbook? Or is there a better way to collect this information in the first place? Should I put this loop in a template?

Additional challenge: I'd have to add /32 to every entry.

Answer 1

You can assign a list to variable by set_fact and ansible filter plugin.

Put custom filter plugin to filter_plugins directory like this:

(ansible top directory) site.yml hosts filter_plugins/     to_group_vars.py 

to_group_vars.py convert hostvars into list that selected by group.

from ansible import errors, runner import json  def to_group_vars(host_vars, groups, target = 'all'):     if type(host_vars) != runner.HostVars:         raise errors.AnsibleFilterError("|failed expects a HostVars")      if type(groups) != dict:         raise errors.AnsibleFilterError("|failed expects a Dictionary")      data = []     for host in groups[target]:         data.append(host_vars[host])     return data  class FilterModule (object):     def filters(self):         return {"to_group_vars": to_group_vars} 

Use like this:

--- - hosts: all   tasks:   - set_fact:       web_ips: "{{hostvars|to_group_vars(groups, 'web')|map(attribute='ansible_eth0.ipv4.address')|list }}"   - debug:       msg: "web ip is {{item}}/32"     with_items: web_ips