How to destroy/delete/unset a variable value in Ansible

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Is there a way to destroy the variable in Ansible?

Actually, I have a {{version}} variable being used in my all roles for respective packages. When I run multiple roles, the version value of one role is passed to another – this is due to for some role I am not giving version value so that it can install the default version of that package available for respective m/c like ubuntu/redhat etc.

Here is my role template. The value of {{version}} from mysql is being passed to rabbitmq.

    roles:
- { role: mysql }
- { role: rabbitmq}

If I can destory/delete the value of version in every role, it should solve the problem, I believe.

Best Answer

As already pointed out it is not possible to unset a variable in Ansible.

Avoid this situation by adding a prefix to your variable names like rabbitmq_version and so on. IMHO this a best practice.

Beside avoiding the situation you ran into, this will add clarity to your host_vars and group_vars.

Related Solutions

Ansible – Appending to Lists or Adding Keys to Dictionaries

You can merge two lists in a variable with +. Say you have a group_vars file with this content:

---
# group_vars/all
pgsql_extensions:
  - ext1
  - ext2
  - ext3

And it's used in a template pgsql.conf.j2 like:

# {{ ansible_managed }}
pgsql_extensions={% for item in pgsql_extensions %}{{ item }}, {% endfor %}

You can then append extensions to the testing database servers like this:

---
# group_vars/testing_db
append_exts:
  - ext4
  - ext5
pgsql_extensions: "{{ pgsql_extensions + append_exts }}"

When the role is run in any of the testing servers, the aditional extensions will be added.

I'm not sure this works for dictionaries as well, and also be careful with spaces and leaving a dangling comma at the end of the line.

How to check the JSON response from a uri request with Ansible

You need to use a jinja2 filter (http://docs.ansible.com/ansible/playbooks_filters.html). In this case, the name of the filter is from_json. In the following example I'll take an action when the key is found and other action when the could not be found:

 ---                                                                                                            

 - hosts: somehost                                                                                               
   sudo: yes                                                                                                    

   tasks:                                                                                                       

   - name: Get JSON from the Interwebs                                                                          
     uri: url="https://raw.githubusercontent.com/ljharb/node-json-file/master/package.json" return_content=yes  
     register: json_response                                                                                    

   - debug: msg="Error - undefined tag"                                                                         
     when: json_response["non_existent_tag"] is not defined                                                     

   - debug: msg="Success - tag defined =>{{  (json_response.content|from_json)['scripts']['test'] }}<="  
     when:  (json_response.content|from_json)['scripts']['test']  is defined

Now replace the debug for the appropriate to take the desired action.

Hope it helps,

Best Answer

Related Solutions

Ansible – Appending to Lists or Adding Keys to Dictionaries

How to check the JSON response from a uri request with Ansible

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