Ansible way of replacing a line in config - ansible

Question

I have a json as follows:
{
"bootstrap": true,
"server": true,
"datacenter": "aws",
"data_dir": "/var/consul",
"log_level": "INFO",
"enable_syslog": true
}
This is on 3 servers which are in ansible inventory file as
[consul]
10.0.0.1
10.0.0.2
10.0.0.3
Now to make the nodes join the cluster i will have to actually add the following config line as well
"start_join": ["ip_of_other_node_1", "ip_of_other_node_2"]
and this will go on each of the 3 servers
So basically it means if 10.0.0.1 is one of those nodes in cluster, it's config will look like
{
"bootstrap": true,
"server": true,
"datacenter": "aws",
"data_dir": "/var/consul",
"log_level": "INFO",
"enable_syslog": true,
"start_join": ["10.0.0.2","10.0.0.3"]
}
I am trying to this via ansible as follows:
- name: Add the ip's of other servers to join cluster
lineinfile:
path: /etc/consul.d/server/config.json
regexp: '^"enable_syslog"'
insertafter: '^"enable_syslog"'
line: '"start_join": ["{{ groups['consul'][1] }}", "{{ groups['consul'][2] }}"]'
when: inventory_hostname == '{{ groups['consul'][0] }}'
Which is not really helping me out saying syntax error at line: , i am not sure what is the best way to achieve something like this via ansible and also what how to tackle the case when i increase the servers in inventory.

Answer 1

You can use the Template module to replace the config file on your servers, instead of changing it in place with the regex. This way you can add a task to generate a new config file with the start_join field containing the elements of your hosts file (or any other and more complex configuration) using regular jinja2 templates.