Ansible: Conditionally define variables in vars file if a certain condition is met

Question

Depending on the value(True/False) of a variable defined into the group_vars I am trying to define some variables in a vars file. Their value depends on the group var's value.

My current var file looks like this:

{% if my_group_var %}
test:
   var1: value
   var2: value
   ...
   varn: value
{% else %}
test:
   var1: other_value
   var2: other_value
   ...
   varn: other_value
{% endif %}

For each one of my roles I'm using a variable defined into this file.

My test playbook looks like below:

- name: blabla
  hosts: blabla
  vars_files:
     - <path>/test_vars.yml
  roles: blabla 

The error I'm receiving after running the playbook is:

{% if my_group_var %}
 ^ here

exception type: <class 'yaml.scanner.ScannerError'>
exception: while scanning for the next token
found character that cannot start any token
  in "<unicode string>"

Am I doing something stupid here or this is not even supported? I've tried to find another way for defining these vars(I have a lot of them) but I didn't managed to get something functional here. Any suggestions?

Solution 1

What I did in the end was to create 2 separate var files - let's call them type_a.yml and type_b.yml - and I defined a group variable that indicates what file to use - something like type_of_file: a. This is how my playbook looks now:

- name: blabla
  hosts: blabla
  vars_files:
     - <path>/type_{{ type_of_file }}.yml
  roles: blabla

Thanks for all the answers. I find them really helpful.

Solution 2

Ansible allows one of following forms to define variable conditionally:

    test:
      var1: "{% if my_group_var %}value{% else %}other_value{% endif %}"
      var2: "{{'value' if (my_group_var) else 'other_value'}}"

Combining above syntax with vars lookup we can load complex vars (map in this case):

test_value_when_my_group_var_is_true:
   var1: value
   var2: value

test_value_when_my_group_var_is_false:
   var1: other_value
   var2: other_value

test: "{{ lookup('vars','test_value_when_my_group_var_is_true') if (my_group_var) else lookup('vars','test_value_when_my_group_var_is_false')}}"

There is another way of doing conditional tree loading with vars lookup. This way is handy when you need implement case logic (i.e. condition variable has more than two possible values):

test_value_when_my_group_var_is_foo:
   var1: value
   var2: value

test_value_when_my_group_var_is_bar:
   var1: other_value
   var2: other_value

test_value_when_my_group_var_is_baz:
   var1: yet_another_value
   var2: yet_another_value

test: "{{ lookup('vars','test_value_when_my_group_var_is_' + my_group_var) }}"

Solution 3

I don't think you can, I usually create separate files to hold conditional variable collections and use a when clause to include them on a specific condition:

- include_vars: test_environment_vars.yml
  when: global_platform == "test"

- include_vars: staging_environment_vars.yml
  when: global_platform == "staging"

- include_vars: prod_environment_vars.yml
  when: 
    - global_platform != "test" 
    - global_platform != "staging" 

Solution 4

Despite it would be nice, I'm afraid that your way isn't possible (or I'm not aware right way).

I'd suggest to first prepare vars file from jinja template and then include it with include_vars. See the example playbook:

---
- name: -Test-
  hosts: local
  vars:
    my_group_var: False
#    my_group_var: True

  tasks:

  - name: Prepare vars file from template.
    template: src=/tmp/vars.yaml.j2
              dest=/tmp/vars.yaml

  - name: Include vars
    include_vars: "/tmp/vars.yaml"

The content of example jinja template /tmp/vars.yaml.j2 is:

{% if my_group_var %}                                                                                                                                                                                             
test:                                                                                                                                                                                                             
   var1: value                                                                                                                                                                                                    
   var2: value                                                                                                                                                                                                    
{% else %}                                                                                                                                                                                                        
test:                                                                                                                                                                                                             
   var1: other_value                                                                                                                                                                                              
   var2: other_value                                                                                                                                                                                              
{% endif %}

Solution 5

Why no one mentions this?

_dist: "{{ ansible_lsb.id|lower if ansible_lsb.id == 'Raspbian' else ansible_distribution|lower }}"

View more solutions

Comments

[84104]

Where do these vars end up being used? This might be unnecessary if all you're going to use them for is part of a template module call.

[Konstantin Suvorov]

If test is group dependent, it should be placed into group_vars.

[pandoJohn]

Unfortunately, test is not group dependent. As mentioned in the description, test is depending on the value of a group_var variable.

[pandoJohn]

This is something I was trying to avoid. I don't want to use include vars or to define 2 additional var files for my tasks.

[pandoJohn]

I like this but the problem is that after generating the .yml file from the jinja template this is not available for the subsequent tasks from my playbook.

[Jaroslav Kucera]

Why? When I tried to extend the test playbook with debug task - debug: var=test I can see, that there are defined both test.var1 and test.var2 with expected values. So you should be able to use these variables in other tasks of the playbook.

[GP92]

I don't get it..when it's possible to use include_vars with condition, why not variable can be defined with condition?

[TRW]

this is in my eyes the best solution: divide and conquer.

[Rajnish Kumar Soni]

I am new to ansible and this ans save lot of my effort. Thanks

[Stan]

That last method of conditional logic worked perfectly for me. Thanks for the solution!