Ansible - Write variable to config file - ansible

Question

We have some redis configurations that only differs on port and maxmemory settings, so I'm looking for a way to write a 'base' config file for redis and then replace the port and maxmemory variables.
Can I do that with Ansible?

Answer 1

For such operations usually lineinfile module works best; for example:
- name: Ensure maxmemory is set to 2 MB
lineinfile:
dest: /path/to/redis.conf
regexp: maxmemory
line: maxmemory 2mb
Or change multiple lines in one task with with_items:
- name: Ensure Redis parameters are configured
lineinfile:
dest: /path/to/redis.conf
regexp: "{{ item.line_to_match }}"
line: "{{ item.line_to_configure }}"
with_items:
- { line_to_match: "line_to_match", line_to_configure: "maxmemory 2mb" }
- { line_to_match: "port", line_to_configure: "port 4096" }
Or if you want to create a base config, write it in Jinja2 and use a template module:
vars:
redis_maxmemory: 2mb
redis_port: 4096
tasks:
- name: Ensure Redis is configured
template:
src: redis.conf.j2
dest: /path/to/redis.conf
with redis.conf.j2 containing:
maxmemory {{ redis_maxmemory }}
port {{ redis_port }}

Answer 2

The best way i've found to do this (and i use the same technique everywhere)
is to create a role redis with a default vars file and then override the vars when you call the role.
So in roles/redis/default/main.yml :
redis_bind: 127.0.0.1
redis_memory: 2GB
redis_port: 1337
And in your playbook :
- name: Provision redis node
hosts: redis1
roles:
- redis:
redis_port: 9999
redis_memory: 4GB
- name: Provision redis node
hosts: redis2
roles:
- redis:
redis_port: 8888
redis_memory: 8GB