How to organize Ansible inventory with datacenter and environment?

Question

If we have 2 data centers, East and West.

Then we have 3 environments DEV, QA, PROD.

Each data center and environment has a their own Consul cluster.

Now I want to reference the Consul cluster from inventory for example:

consul_servers: "{{ groups['consul'] | to_json }}"

How do I organize my inventory and group_vars to only result in the proper Consul cluster hosts for that data center and environment?

An idea I had would be to have an inventory file per data center and environment.

For example:

• west-dev.ini
• west-qa.ini
• west-prod.ini
• east-dev.ini
• east-qa.ini
• east-prod.ini

Which seems reasonable but now how do I address environment only or data center only variables in group_vars? Do I make them children groups?

Answer 1

One of approaches is to use symlinks. Define all your common environment and datacenter variables in separate files and then make all required combinations as subfolders with group_vars/all containing links to appropriate var files.

Here is example for two datacenters east/west and two environments dev/prod:

virt_inv/
├── dc_east.yml
├── dc_west.yml
├── east-prod
│   ├── group_vars
│   │   └── all
│   │       ├── dc.yml -> ../../../dc_east.yml
│   │       └── env.yml -> ../../../env_prod.yml
│   └── hosts
├── env_dev.yml
├── env_prod.yml
└── west-dev
    ├── group_vars
    │   └── all
    │       ├── dc.yml -> ../../../dc_west.yml
    │       └── env.yml -> ../../../env_dev.yml
    └── hosts

I've defined only east-prod and west-dev combinations here, but you can make others in similar way.

This is demo content:

$ find virt_inv -type f -print -exec cat {} \;
virt_inv/dc_east.yml
datacenter: east-02
virt_inv/dc_west.yml
datacenter: west-01
virt_inv/east-prod/hosts
[servers]
host4
host5
virt_inv/env_dev.yml
env: developer
virt_inv/env_prod.yml
env: production
virt_inv/west-dev/hosts
[servers]
host1
host2

And result:

$ ansible all -i virt_inv/east-prod/hosts -m debug -a 'msg={{datacenter}}-{{env}}'
host5 | SUCCESS => {
    "msg": "east-02-production"
}
host4 | SUCCESS => {
    "msg": "east-02-production"
}

$ ansible all -i virt_inv/west-dev/hosts -m debug -a 'msg={{datacenter}}-{{env}}'
host2 | SUCCESS => {
    "msg": "west-01-developer"
}
host1 | SUCCESS => {
    "msg": "west-01-developer"
}