Custom inventory file failing to parse properly

Question

I've got the following production inventory file (playbooks/production.yaml) for Ansible:

all:
  children:
    control:
      moriarty.server.com
      toby.server.com
    managed:
      sherlock.server.com

Based on what I'm reading online, it looks like it should be correct, and I can't find any syntax errors in the file using a YAML linter. However, when I run ansible-playbook on my local machine, I get the following error:

$ ansible-playbook -i playbooks/production.yaml --extra-vars target=moriarty.server.com playbooks/create-server.yaml
[WARNING]: log file at /var/log/ansible.log is not writeable and we cannot create it, aborting

[WARNING]: Skipping 'control' as this is not a valid group definition

[WARNING]:  * Failed to parse /Users/username/infra/playbooks/production.yaml with auto plugin: no root 'plugin' key found,
'/Users/username/infra/playbooks/production.yaml' is not a valid YAML inventory plugin config file

[WARNING]:  * Failed to parse /Users/username/infra/playbooks/production.yaml with yaml plugin: control is not a known host nor group

[WARNING]:  * Failed to parse /Users/username/infra/playbooks/production.yaml with ini plugin: Invalid host pattern 'all:' supplied, ending in ':' is not allowed, this
character is reserved to provide a port.

[WARNING]: Unable to parse /Users/username/infra/playbooks/production.yaml as an inventory source

[WARNING]: No inventory was parsed, only implicit localhost is available

[WARNING]: provided hosts list is empty, only localhost is available. Note that the implicit localhost does not match 'all'

[WARNING]: Could not match supplied host pattern, ignoring: moriarty.server.com


PLAY [moriarty.server.com] ************************************************************************************************************************************************
skipping: no hosts matched

PLAY RECAP **************************************************************************************************************************************************************************

I'm at a loss, since it looks to be valid YAML. Do I need to format it some other way when I have groups in this manner?

Answer 1

The keyword hosts is missing. Also colons : are needed after the hostnames. Fix the syntax, for example

all:
  children:
    control:
      hosts:
        moriarty.server.com:
        toby.server.com:
    managed:
      hosts:
        sherlock.server.com:

See How to build your inventory.

Answer 2

Just add hosts before every block of hosts. I.e., under the group level, you should have hosts directive

See ansible source code example:

- Hosts must be specified in a group's hosts:

Working inventory.yml:

all:
  children:
    control:
      hosts:
        localhost
        127.0.0.1
    managed:
      hosts:
       localhost