When working with Ansible inventories where a single host belongs to multiple groups with conflicting group variables, you might encounter unexpected behavior in variable precedence. The specific case involves:

[group1]
host1.mydomain

[maingroup:children]
group1

[group2]
host1.mydomain

Ansible loads group variables in a specific order, and subsequent runs may cache these values, leading to inconsistent behavior:

• First run: Correctly loads /service1/path for maingroup
• Second run: Correctly loads /service2/path for group2
• Subsequent runs: May incorrectly persist the group2 value

Instead of relying solely on group_vars, explicitly load variables in your playbook:

- name: Load service-specific variables
  include_vars: "{{ 'group_vars/' + group_names | first }}.yml"
  when: group_names | length == 1

Consider using host variables for service-specific configurations:

host_vars/host1.mydomain.yml:
---
services:
  group1:
    path: /service1/path
  group2: 
    path: /service2/path

Then reference them in tasks:

- name: Use correct service path
  debug:
    msg: "Using path {{ services[group_names | first].path }}"

To prevent variable caching issues:

ansible.cfg:
[defaults]
fact_caching = jsonfile
fact_caching_connection = /tmp/ansible_facts
fact_caching_timeout = 0

• Avoid duplicate host declarations when possible
• Use distinct variable names for different services
• Consider service-specific inventory files
• Implement clear naming conventions (service1_path, service2_path)

In complex Ansible environments, we often need to declare the same host in multiple inventory groups to manage different services. Consider this inventory structure:

[group1]
host1.mydomain

[maingroup:children]
group1

[group2]
host1.mydomain

With corresponding group variables:

# group_vars/maingroup
---
servicepath: /service1/path

# group_vars/group2
---
servicepath: /service2/path

When running playbooks sequentially:

1. First execution with hosts: maingroup correctly uses /service1/path
2. Second execution with hosts: group2 correctly uses /service2/path
3. Subsequent runs with maingroup incorrectly inherit /service2/path

This behavior stems from Ansible's variable caching mechanism. When host1.mydomain first appears in group2, Ansible caches its variables and subsequent inventory parsing doesn't properly reset them for maingroup context.

Solution 1: Use distinct variable names

# group_vars/maingroup
---
service1_path: /service1/path

# group_vars/group2
---
service2_path: /service2/path

Solution 2: Leverage group priorities

# inventory file
[group1]
host1.mydomain

[maingroup:children]
group1

[group2]
host1.mydomain ansible_group_priority=10

Solution 3: Use include_vars dynamically

- name: Load correct variables
  include_vars: 
    file: "group_vars/{{ ansible_play_hosts_all[0] }}.yml"
  when: ansible_play_hosts_all[0] in group_names

For complex multi-group scenarios, consider:

• Using host_vars for host-specific overrides
• Implementing custom facts via set_fact
• Creating wrapper roles with explicit variable definitions

Always debug variable precedence with:

- debug:
    msg: "{{ hostvars[inventory_hostname].servicepath }}"