Ansible fails to execute a playbook when the value for 'hosts' is defined somewhere in inventory

[ishan jain]

I want to define the target hosts for my playbooks somewhere in the inventory itself. But apparently, Ansible is resolving target hosts before it is finished loading the inventory. When i 'include' the file with these vars, it works just fine.

inventoryFile.yaml

[machines]
one ansible_host=000
two ansible_host=000
three ansible_host=000

group_vars/all/targets.yaml

hostList1:
   - one
   - two
hostList2:
   - two
   - three

playbook.yaml

---

- hosts: "{{hostList1}}"

  tasks:

     - debug: msg="works"

Error:

ERROR! the field 'hosts' has an invalid value, which appears to include a variable that is undefined. The error was: 'hostList1' is undefined

The error appears to have been in '/home/ishan/playbook.yaml': line 2, column 3, but may

be elsewhere in the file depending on the exact syntax problem.

The offending line appears to be:

---

- name: Executing playbook

  ^ here

But if i explicitly load the same file, it works just fine:

playbook.yaml

---

- name: Executing playbook

  hosts: "{{hostList1}}"

  vars_files:

        - "{{ inventory_dir ~ '/group_vars/all/targets.yaml'}}"

  tasks:

     - debug: msg="works"

Clearly, Ansible is loading/resolving host list too fast. I really don't want to explicitly load the vars file. I need that to be in inventory and loading it again is not a good thing. How can i make sure that some vars are loaded with the inventory first thing when i execute a playbook ? 

Please note that there might be some typos when i am specifying files and code above, but this is really not a problem of typos.

[Brian Coca]

The 'hostList1' inventory variable is not available until AFTER the
hosts: is processed, this is a chicken/egg issue.

Inventory variables are flattened per host, so only once you have a
host can you query the value of the variable.

`hosts:` defines which hosts are available, as such it cannot depend
on a host nor a variable associated to a host.


----------
Brian Coca

[ishan jain]

So is there no way to define something like 'global' variables along with the inventory ? I thought the implicit 'all' group can be treated like global variables.

[Brian Coca]

No, inventory vars are always flattened to the host, 'all' is a way to
assign a variable to all hosts, but it is still 'host level'.

Use vars/vars_files or extra_vars instead.

----------
Brian Coca

[chafik bel]

Why don't you simply use the power of the inventory file itself:
[group:children]
child1
child2

[child1]
host1
host2

[child2]
host3
host4

and use global vars or per host vars in the appropriate files?

N.B: the inventory is an "ini" file not a "yaml" one [inventoryFile.yaml].

[Brian Coca]

>N.B: the inventory is an "ini" file not a "yaml" one [inventoryFile.yaml].

it can be either, Ansible support YAML format for inventory also

----------
Brian Coca