Solution 1: local facts
This solution is IMO the easiest one but requires to place a file on each target server.
let's imagine you put the following executable file in /etc/ansible/facts.d/kafka.fact. This is only a dummy example, adapt to your exact needs. I'm using jq to output a proper json string. You can echo directly if you trust the key content will not cause problems. You can also use any other executable you like (python, ruby, perl...) as long as you output a json structure
#!/bin/bash
# replace here with some logic to read the value you need.
# I'll use a static value for this example
PARSED_KEY="I'm a key that should be parsed dynamically"
# echo the json result using jq
echo $(
jq -n \
--arg pk "$PARSED_KEY" \
'{masterkey: $pk}'
)
Once this is done, you can see that the facts are available for the given host. I'll only demonstrate for localhost here but this will work with any host having this local facts script:
$ ansible localhost -m setup -a filter=ansible_local
localhost | SUCCESS => {
"ansible_facts": {
"ansible_local": {
"kafka": {
"masterkey": "I'm a key that should be parsed dynamically"
}
}
},
"changed": false
}
You are now ready to use this fact wherever you need it. Note that you must of course gather facts for this value to be available. In your case, we can test with the following playbook:
---
- hosts: localhost
environment:
CONFLUENT_KEY: "{{ ansible_local.kafka.masterkey | default ('empty') }}"
tasks:
- name: echo our env var
command: echo $CONFLUENT_KEY
register: echo
- name: show the result
debug:
msg: "Our env is: {{ echo.stdout }}"
which gives
PLAY [localhost] ***************************************************************************************************************************************************************
TASK [Gathering Facts] *********************************************************************************************************************************************************
ok: [localhost]
TASK [echo our env var] ********************************************************************************************************************************************************
changed: [localhost]
TASK [show the result] *********************************************************************************************************************************************************
ok: [localhost] => {
"msg": "Our env is: I'm a key that should be parsed dynamically"
}
PLAY RECAP *********************************************************************************************************************************************************************
localhost : ok=3 changed=1 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
Solution 2: custom facts module
This solution is a bit more complex but probably has better management capabilities on the long term and does not require to place files on the target server.
To be as straightforward as possible, I placed my demo facts module in a library folder adjacent to my playbook. Placing such a module inside a collection or a role is preferable for a production project but goes beyond this (already long) answer. To get more info on all these subjects you can read (non exhaustive list of references):
Create a library/kafka_facts.py file. You will have to adapt to your exact situation. In this case, I decided that the key would be placed on a single line in /tmp/keyfile.txt and I hardcoded this in my module. Note that the fact is not returned if the file does not exist. I added all document strings as advised in the examples in the above documentation link.
#!/usr/bin/python
from __future__ import (absolute_import, division, print_function)
__metaclass__ = type
DOCUMENTATION = r'''
---
module: kafka_facts
short_description: This is a test module for example
version_added: "1.0.0"
description: This is a test module for example to answer a question on StackOverflow.
author:
- Olivier Clavel (@zeitounator)
'''
EXAMPLES = r'''
- name: Return ansible_facts
kafka_facts:
'''
RETURN = r'''
ansible_facts:
description: Kafka facts to add to ansible_facts.
returned: always
type: dict
contains:
kafka_masterkey:
description: Masterkey present on server.
type: str
returned: when /tmp/keyfile.txt exists on server
sample: 'f18bba7f-caf6-4897-95be-c7d3cc66f98a'
'''
from ansible.module_utils.basic import AnsibleModule
def run_module():
module_args = dict()
# Initialize result dict
result = dict(
changed=False,
ansible_facts=dict(),
)
module = AnsibleModule(
argument_spec=module_args,
supports_check_mode=True
)
if module.check_mode:
module.exit_json(**result)
keyfile = "/tmp/keyfile.txt"
try:
with open(keyfile) as f:
result['ansible_facts'] = {
'kafka_masterkey': f.read(),
}
except FileNotFoundError:
pass
module.exit_json(**result)
def main():
run_module()
if __name__ == '__main__':
main()
As in my previous solution, the following demo will be done on localhost only but will work on any target server.
First we create a key in the expected file
echo $(uuidgen) > /tmp/keyfile.txt
And we can now use the module as demonstrated in the following playbook:
---
- name: Use custom facts
hosts: localhost
gather_facts: false
environment:
CONFLUENT_KEY: "{{ ansible_facts.kafka_masterkey | default('N/A') }}"
tasks:
- name: echo the env var
command: echo $CONFLUENT_KEY
register: echo_before
changed_when: false
- name: show our var is empty for now
debug:
msg: "CONFLUENT_KEY was returned as: {{ echo_before.stdout }}"
- name: Gather our custom facts related to kafka
kafka_facts:
- name: Echo the env var
command: echo $CONFLUENT_KEY
register: echo_after
changed_when: false
- name: show our var is empty for now
debug:
msg: "CONFLUENT_KEY was returned as: {{ echo_after.stdout }}"
which gives:
PLAY [Use custom facts] ****************************************************************************************************************************************************************************************************************
TASK [echo the env var] ****************************************************************************************************************************************************************************************************************
ok: [localhost]
TASK [show our var is empty for now] ***************************************************************************************************************************************************************************************************
ok: [localhost] => {
"msg": "CONFLUENT_KEY was returned as: N/A"
}
TASK [Gather our custom facts related to kafka] ****************************************************************************************************************************************************************************************
ok: [localhost]
TASK [Echo the env var] ****************************************************************************************************************************************************************************************************************
ok: [localhost]
TASK [show our var now has a value (if the file exists)] *******************************************************************************************************************************************************************************
ok: [localhost] => {
"msg": "CONFLUENT_KEY was returned as: d8fc525e-3fa9-4401-aca3-19ac915e5c0d"
}
PLAY RECAP *****************************************************************************************************************************************************************************************************************************
localhost : ok=5 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
