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

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

Answer 2

in playbook:
vars:
- arrayname:
- name: itemname
value1: itemvalue1
value2: itemvalue2
- name: otheritem
value1: itemvalue3
value2: itemvalue4
in template: (example is of type ini file, with sections, keys and values):
{% for item in arrayname %}
[{{ item.name }}]
key1 = {{ item.value1 }}
key2 = {{ item.value2 }}
{% endfor %}
This should render the template as:
[itemname]
key1 = itemvalue1
key2 = itemvalue2
[otheritem]
key1 = itemvalue3
key2 = itemvalue4

Answer 3

Variables can be represented as standard YAML structures so you can assign a list value to a key like this:
---
- hosts: db
vars:
postgresql_ext_install_contrib: yes
postgresql_pg_hba_passwd_hosts:
- '10.129.181.241/32'
- '1.2.3.0/8'

Answer 4

You can use jinja2 filters:
{{ groups['nodes']|map('extract', hostvars, ['ansible_eth1','ipv4', 'address']) |list }}
will return a list of ip addresses. i.e.
---
- hosts: db
vars:
postgresql_ext_install_contrib: yes
postgresql_pg_hba_passwd_hosts: {{ groups['nodes']|map('extract', hostvars, ['ansible_eth1','ipv4', 'address']) |list }}
...
Does not include the challange (appending /32). But it should also be possible somehow with jinja2 filters.
Reqiures ansible version >= 2.1

Answer 5

To add '/32' to the address, you can use the Ansible ipaddr filter (converting to CIDR notation).
{{ ip_addresses|ipaddr('host') }}