Searching for eficient way to check group of variables

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1

Hello,

I recently wrote role, that set up an openvz on centos host, including network configuration. For that purpose, I have variables ip, gateway, netmask, dns1 and dns2 in host_vars/.

Variables are mandatory, I cannot set up networking withnout them, so I`m checking them out. So far I have this code:

- fail: msg="You need to define ip, gateway, netmask, dns1 and dns2 in hosts_vars"
  when: ip is not defined

- fail: msg="You need to define ip, gateway, netmask, dns1 and dns2 in hosts_vars"

  when: gateway is not defined

- fail: msg="You need to define ip, gateway, netmask, dns1 and dns2 in hosts_vars"
  when: netmask is not defined

- fail: msg="You need to define ip, gateway, netmask, dns1 and dns2 in hosts_vars"
  when: dns1 is not defined

- fail: msg="You need to define ip, gateway, netmask, dns1 and dns2 in hosts_vars"

  when: dns2 is not defined

Somehow I think, Im pretty sure, Im missing some nicer way how to do it, is it possible to have it in one fail statement?

Regards
David Karban

2

In the latest 1.3, you can use the variable in a template like this:

{{ foo | mandatory }}

This will yell when you try to use the variable that is undefined.

You can also globally turn on “all variables must be defined” warnings in ansible.cfg
(see examples/ansible.cfg in the checkout)

3

Thanks, I will try it out!

Dne 5.7.2013 16:02 “Michael DeHaan” <michael@ansibleworks.com> napsal(a):

4

My approach:

(1) I use a single role variable that contains keys/value. E.g. for
the "webapp" role, I call it "webapp_args".

(2) Any globally defined variables (e.g. from host_vars), I copy into
a slot in webapp_args on each role invocation

(3) In the role, I check that webapp_args is defined

(4) In the role, I loop over mandatory items that must exist:

Example:

- name: Assert webapp_args
  fail: msg="required webapp_args parameters must be provided"
  when: webapp_args is not defined

- name: Assert required webapp_args parameters
  fail: msg="required webapp_args[{{item}}] must be provided"
  when: webapp_args[item] is not defined
  with_items:
    - app_name
    - app_path
    - app_port
    - ...

I hope someday there's a way to do that more automatically in the way
that roles work, but for now it's working fine for me.

You could probably do it with globals instead of a role argument
structure, but I personally dislike using globals in that way, so I
didn't do that myself.

-- David

5

Also:

  • fail: msg=variables not defined
    when: foo is not defined or bar is not defined or baz is not defined

should be valid.

6

Also:

- fail: msg=variables not defined
  when: foo is not defined or bar is not defined or baz is not defined

Hi Michael,

tested, works great, thanks !