Open Stack

I'm wondering which possibilities I have to do group/host specific
config file overrides. After reading [1], I'm still a little clueless.
To be specific, I have this setup (expressed as Ansible inventory file):

    [z_compute_nodes]
    compute1
    # more nodes
    [x_compute_nodes]
    compute2
    # more nodes
    [computes:children]
    z_compute_nodes
    x_compute_nodes

As an example, I want to set Nova's config option
`reserved_host_memory_mb` of the `DEFAULT` config file section:

    ### nova.conf
    [DEFAULT]
    reserved_host_memory_mb=$VALUE

My goal is this:

             | reserved_host_memory_mb
    ----------------------------------
    compute1 |         256
    compute2 |         512

I know there are overrides like `nova_nova_conf_overrides`.
So I tried to set a default override in `user_variables.yml`:

    ### /etc/openstack_deploy/user_variables.yml --------

    nova_nova_conf_overrides:
      DEFAULT:
        reserved_host_memory_mb: 512

But I wanted to override this depending on the host in
`openstack_user_config.yml`:

    ### /etc/openstack_deploy/openstack_user_config.yml --------
    # [...]
    # nova hypervisors
    compute_hosts:
      compute1:
        ip: 192.168.100.12
        host_vars:
          nova_nova_conf_overrides:
            DEFAULT:
              reserved_host_memory_mb: 256
      compute2:
        ip: 192.168.100.10

After testing this locally, it turned out that *both* hosts will
have 512 for $VALUE. which was not my intended configuration.

Please note that I only used 2 hosts here as an example but I'm looking
for a solution which scales with much more hosts. I'm also applying
those settings in a templated way like this:

    ### /etc/openstack_deploy/openstack_user_config.yml --------
    # [...]
    # nova hypervisors
    compute_hosts:
    {% for host in groups['computes'] %}
      {{ hostvars[host]['inventory_hostname'] }}:
        ip: {{ hostvars[host]['ansible_host'] }}
    {% endfor %}

The reason is, that I use the same steps for different environments
(dev, test, prod) with a different amount of nodes.

Any tips how to do this properly?

References:
[1]
https://docs.openstack.org/project-deploy-guide/openstack-ansible/draft/app-advanced-config-override.html


-- 
Regards, Markus Zoeller (markus_z)