Ansible: How to inherit variables?
I want to get variable inheritance in Ansible. Let's say I have:
group_vars / all
---
ifaces:
- name: eth0
adress: 10.107.13.236
netmask: 255.255.255.192
routes:
- {from: 10.108.100.34/31, via: 10.107.13.193}
- {from: 10.108.105.128/31, via: 10.107.13.193}
- name: eth1
adress: 10.112.13.236
netmask: 255.255.255.192
gateway: 10.112.13.193
routes:
- {from: 10.2.1.0/26, via: 10.112.13.254}
Now I want to extend eth0 routes like:
group_vars / webserver
--- ifaces:
- name: eth0
routes:
- {from: 1.2.3.34, via: 5.6.7.8}
- {from: 9.9.9.9/9, via: 5.6.7.8}
My desired output:
---
ifaces:
- name: eth0
adress: 10.107.13.236
netmask: 255.255.255.192
routes:
- {from: 10.108.100.34/31, via: 10.107.13.193}
- {from: 10.108.105.128/31, via: 10.107.13.193}
- {from: 1.2.3.34, via: 5.6.7.8}
- {from: 9.9.9.9/9, via: 5.6.7.8}
- name: eth1
adress: 10.112.13.236
netmask: 255.255.255.192
gateway: 10.112.13.193
routes:
- {from: 10.2.1.0/26, via: 10.112.13.254}
Thus, routes must be extended and not overwritten. I know about setting hash_behaviour: merge
in ansible.cfg
, but it doesn't suit my needs because I want to add values to the list stored in routes.
The background is that I need to be able to define some standard routes (note: this is not limited to routes, this is just an example) and improve those standards for certain groups instead of overriding them.
Is this possible in Ansible?
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I would suggest creating lookup_plugin
one that will do all the heavy ligation of merge / append variables.
eg:
lookup_plugins / myvars.py
import yaml
class LookupModule(object):
def __init__(self, basedir=None, **kwargs):
self.basedir = basedir
self.plugin_name = 'myvars'
def run(self, vars_file, variable=None, **kwargs):
all_routes = yaml.load(file('group_vars/all'))['ifaces'][0]['routes']
all_routes.extend(
yaml.load(file('group_vars/%s' % vars_file[0]))['ifaces'][0]['routes'])
return [all_routes]
playbook.yml
---
- hosts: webservers
gather_facts: no
connection: local
tasks:
- debug: msg=" Hey {{ item }}"
with_myvars:
- webservers
Of course, this doesn't completely solve your problem, and you still need to tweak it for it to work. But you should get an idea of how to achieve this from this example.
The result should look like this:
PLAY [webservers] *************************************************************
TASK: [debug msg=" Hey {{ item }}"] *******************************************
ok: [localhost] => (item=[{'via': '10.107.13.193', 'from': '10.108.100.34/31'}, {'via': '10.107.13.193', 'from': '10.108.105.128/31'}, {'via': '5.6.7.8', 'from': '1.2.3.34'}, {'via': '5.6.7.8', 'from': '9.9.9.9/9'}]) => {
"item": [
{
"from": "10.108.100.34/31",
"via": "10.107.13.193"
},
{
"from": "10.108.105.128/31",
"via": "10.107.13.193"
},
{
"from": "1.2.3.34",
"via": "5.6.7.8"
},
{
"from": "9.9.9.9/9",
"via": "5.6.7.8"
}
],
"msg": " Hey [{'via': '10.107.13.193', 'from': '10.108.100.34/31'}, {'via': '10.107.13.193', 'from': '10.108.105.128/31'}, {'via': '5.6.7.8', 'from': '1.2.3.34'}, {'via': '5.6.7.8', 'from': '9.9.9.9/9'}]"
}
PLAY RECAP ********************************************************************
localhost : ok=1 changed=0 unreachable=0 failed=0
So, you can see that it returns a list of routes, so you can easily fit {{ item }}
in whatever you need.
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