Ansible inventory patterns and limit argument

Question

I have the following inventory file called hosts-local:

host-1   ansible_host=minio-1.localdomain
host-2   ansible_host=minio-2.localdomain
host-3   ansible_host=minio-3.localdomain
host-4   ansible_host=minio-4.localdomain

[minio_cluster_members]
host-1
host-2
host-3
host-4

[nginx_reverse_proxies]
host-1
host-3

[all:vars]
ansible_connection=ssh

and a playbook that references the groups:

- name: "Install and configure Minio"
  hosts: minio_cluster_members
  become: yes
  remote_user: ansible
  roles:
    - minio

- name: "Install and configure nginx reverse proxy"
  hosts: nginx_reverse_proxies
  become: yes
  remote_user: ansible
  roles:
    - nginx

And I invoke ansible like this $ ansible-playbook -i hosts-local playbook.yml

My original thought was that I'd have hosts-local, hosts-test and hosts-prod files so that host-1, host-2 etc could be defined on a deployment environment basis (albeit with the duplication of the rest of the groups).

But then someone suggested I look at ansible patterns and specifically the --limit argument, referencing the ansible docs. This looks particularly relevant:

Finally, you can use --limit to read the list of hosts from a file by prefixing the file name with @:

ansible-playbook site.yml --limit @retry_hosts.txt

The way I've read this is that I'd have a single inventory file like this:

[minio_cluster_members]
host-1
host-2
host-3
host-4

[nginx_reverse_proxies]
host-1
host-3

[all:vars]
ansible_connection=ssh

and then a series of files that define host-1, host-2 etc for each environment:

# local dev hosts
host-1   ansible_host=minio-1.localdomain
host-2   ansible_host=minio-2.localdomain
host-3   ansible_host=minio-3.localdomain
host-4   ansible_host=minio-4.localdomain

# test hosts
host-1   ansible_host=test-minio-1.test.domain.com
host-2   ansible_host=test-minio-2.test.domain.com
host-3   ansible_host=test-minio-3.test.domain.com
host-4   ansible_host=test-minio-4.test.domain.com

etc.
And then I'd invoke ansible like this: $ ansible-playbook -i inventory playbook.yml --limit 'all:@hosts-local'

But for the life of me I cannot get this working. It complains about every line in the limit file (including the comment):

[WARNING]: Could not match supplied host pattern, ignoring: # local dev hosts
[WARNING]: Could not match supplied host pattern, ignoring: host-1   ansible_host=minio-1.localdomain
[WARNING]: Could not match supplied host pattern, ignoring: host-2   ansible_host=minio-2.localdomain
[WARNING]: Could not match supplied host pattern, ignoring: host-3   ansible_host=minio-3.localdomain
[WARNING]: Could not match supplied host pattern, ignoring: host-4   ansible_host=minio-4.localdomain

What I am doing wrong? Have I misunderstood how patterns and specifically the --limit argument with a file work? What format/syntax should the file be? I cannot find any examples of this on the internet anywhere.

Nathan Russell Nathan Russell · Accepted Answer · 2020-06-19T16:04:58

I think the --limit argument was a red herring, and not what I wanted in order to solve the problem.
What I've discovered is that you can specify multiple inventory files. So I have the main inventory hosts:

[minio_cluster_members]
host-1
host-2
host-3
host-4

[nginx_reverse_proxies]
host-1
host-3

[all:vars]
ansible_connection=ssh

I have an inventory for local hosts called hosts-local:

[local]
host-1   ansible_host=minio-1.localdomain
host-2   ansible_host=minio-2.localdomain
host-3   ansible_host=minio-3.localdomain
host-4   ansible_host=minio-4.localdomain

and one for test called hosts-test:

[test]
host-1   ansible_host=test-minio-1.test.domain.com
host-2   ansible_host=test-minio-2.test.domain.com
host-3   ansible_host=test-minio-3.test.domain.com
host-4   ansible_host=test-minio-4.test.domain.com

And I can combine them with: $ ansible-playbook playbook.yml -i hosts -i hosts-local

That's it! That's all there is to it.
Plus I get the added benefit of having groups test, local etc, so I can set variables based on the group name.

Ansible inventory patterns and limit argument

1 Answers