I recently upgraded to Ansible 2.12 and a couple of my playbooks stopped working. This seems to be down to a change in python discovery and if you have made the same mistakes as me, you’ll hit a similar issue. I thought I would write up my findings in case it helps anyone else.
HINT you’ve probably got an entry for localhost in your inventory!!
Everything was working in Ansible 2.11
I was using Ansible 2.11 in an execution environment and my playbook was happily working. Here is one of the tasks in my playbook which gives us a nice simple example to reproduce the problem.
---
- hosts: localhost
connection: local
gather_facts: false
tasks:
- name: print ansible version
debug:
var: ansible_version.full
- name: find vmware datastore name
community.vmware.vmware_datastore_info:
cluster: rhatnode1
hostname: vcenter7.demolab.local
username: administrator@vsphere.local
password: Redhat123
validate_certs: no
register: datastore
In my case I had an inventory that contained a localhost entry. Why did my inventory have a localhost entry? Who knows, but i’ve been managing this infrastructure for about 4 years now and at some point it got added in there. For simple testing this is all we need to reproduce the error:
$ cat inventory
localhost
If we run the playbook with the Ansible 2.11 execution environment then it should work fine. Note that I am including the inventory file in my command.
$ ansible-navigator run find_vmware_datastore.yml --eei registry.redhat.io/ansible-automation-platform-20-early-access/ee-supported-rhel8:latest -m stdout -i inventory
PLAY [localhost] ************************************************************************************************************************************************************
TASK [print ansible version] ************************************************************************************************************************************************
ok: [localhost] => {
"ansible_version.full": "2.11.6"
}
TASK [find vmware datastore name] *******************************************************************************************************************************************
[DEPRECATION WARNING]: Distribution rhel 8.5 on host localhost should use /usr/libexec/platform-python, but is using /usr/bin/python for backward compatibility with prior
Ansible releases. A future Ansible release will default to using the discovered platform python for this host. See https://docs.ansible.com/ansible-
core/2.11/reference_appendices/interpreter_discovery.html for more information. This feature will be removed in version 2.12. Deprecation warnings can be disabled by
setting deprecation_warnings=False in ansible.cfg.
ok: [localhost]
PLAY RECAP ******************************************************************************************************************************************************************
localhost : ok=2 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
Something changed in Ansible 2.12
I know! It was warning me all along - if only I took notice of it. Anyway, I decided to switch up to Ansible 2.12 and started hitting some issues with the same task:
Note the change of EE container image in the below command. This newer container image contains ansible-core 2.12.
ansible-navigator run find_vmware_datastore.yml --eei registry.redhat.io/ansible-automation-platform-21/ee-supported-rhel8:latest -m stdout -i inventory
PLAY [localhost] ************************************************************************************************************************************************************
TASK [print ansible version] ************************************************************************************************************************************************
ok: [localhost] => {
"ansible_version.full": "2.12.1"
}
TASK [find vmware datastore name] *******************************************************************************************************************************************
An exception occurred during task execution. To see the full traceback, use -vvv. The error was: ModuleNotFoundError: No module named 'requests'
fatal: [localhost]: FAILED! => {"ansible_facts": {"discovered_interpreter_python": "/usr/libexec/platform-python"}, "changed": false, "msg": "Failed to import the required Python library (requests) on 6f19163abcf6's Python /usr/libexec/platform-python. Please read the module documentation and install it in the appropriate location. If the required library is installed, but Ansible is using the wrong Python interpreter, please consult the documentation on ansible_python_interpreter"}
PLAY RECAP ******************************************************************************************************************************************************************
localhost : ok=1 changed=0 unreachable=0 failed=1 skipped=0 rescued=0 ignored=0
The playbook stopped working!
What changed?
As per the warning in Ansible 2.11 and the docs, Ansible 2.12 changed the default python discovery to auto:
“Detects the target OS platform, distribution, and version, then consults a table listing the correct Python interpreter and path for each platform/distribution/version. If an entry is found, uses the discovered interpreter.”
So something has messed up the way that I am discovering python within my execution environment and this is causing me to locate the wrong python interpreter. In this instance it is finding /usr/libexec/platform-python and then fails to import the necessary python libraries to execute the VMware modules - Failed to import the required Python library (requests) on 6f19163abcf6’s Python /usr/libexec/platform-python.
The previous discovery method used auto_legacy - let’s see if that works with Ansible 2.12:
ansible-navigator run find_vmware_datastore.yml --eei registry.redhat.io/ansible-automation-platform-21/ee-supported-rhel8:latest -m stdout -i inventory -e "ansible_python_interpreter=auto_legacy"
PLAY [localhost] ************************************************************************************************************************************************************
TASK [print ansible version] ************************************************************************************************************************************************
ok: [localhost] => {
"ansible_version.full": "2.12.1"
}
TASK [find vmware datastore name] *******************************************************************************************************************************************
[WARNING]: Distribution rhel 8.5 on host localhost should use /usr/libexec/platform-python, but is using /usr/bin/python for backward compatibility with prior Ansible
releases. See https://docs.ansible.com/ansible-core/2.12/reference_appendices/interpreter_discovery.html for more information
ok: [localhost]
PLAY RECAP ******************************************************************************************************************************************************************
localhost : ok=2 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
It does. But why do I need to make these changes?
Implicit localhost
I next stumbled upon the implicit localhost documentation. I’ve been using Ansible for a number of years now and this has completely bypassed me. From the docs - “When you try to reference a localhost and you don’t have it defined in inventory, Ansible will create an implicit one for you”.
Again from the docs, it will create a host entry which is equivalent to this:
...
hosts:
localhost:
vars:
ansible_connection: local
ansible_python_interpreter: "{{ansible_playbook_python}}"
Importantly, this is setting the correct ansible_python_interpreter for us.
Back to they key point for me (again from the docs) - “You can override the built-in implicit version by creating a localhost host entry in your inventory. At that point, all implicit behaviors are ignored”.
Once again, why did I have a localhost entry in my inventory? Absolutely no idea! But, this was what was causing my issues.
Running the playbook without localhost in the inventory
Now re-running the playbook without specifying the inventory gives the correct behaviour. Ansible is now creating the correct implicit localhost entry and the playbook completes as expected.
ansible-navigator run find_vmware_datastore.yml --eei registry.redhat.io/ansible-automation-platform-21/ee-supported-rhel8:latest -m stdout
[WARNING]: provided hosts list is empty, only localhost is available. Note that the implicit localhost does not match 'all'
PLAY [localhost] ************************************************************************************************************************************************************
TASK [print ansible version] ************************************************************************************************************************************************
ok: [localhost] => {
"ansible_version.full": "2.12.1"
}
TASK [find vmware datastore name] *******************************************************************************************************************************************
ok: [localhost]
PLAY RECAP ******************************************************************************************************************************************************************
localhost : ok=2 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
One more example to highlight the issue
Just a final point to try to highlight what was happening here. This playbook will just print the hostvars for my localhost.
---
- hosts: localhost
gather_facts: false
tasks:
- name: print ansible version
debug:
var: ansible_version.full
- name: print localhost hostvars
debug:
msg: "{{ hostvars['localhost'] }}"
With an inventory file containing a localhost entry:
ansible-navigator run show_localhost_vars.yml --eei registry.redhat.io/ansible-automation-platform-21/ee-supported-rhel8:latest -m stdout -i inventory
PLAY [localhost] ************************************************************************************************************************************************************
TASK [print ansible version] ************************************************************************************************************************************************
ok: [localhost] => {
"ansible_version.full": "2.12.1"
}
TASK [print localhost hostvars] *********************************************************************************************************************************************
ok: [localhost] => {
"msg": {
"ansible_check_mode": false,
"ansible_config_file": "/etc/ansible/ansible.cfg",
"ansible_diff_mode": false,
"ansible_facts": {},
"ansible_forks": 5,
"ansible_inventory_sources": [
"/tmp/inventory"
],
"ansible_playbook_python": "/usr/bin/python3.8",
< Output Truncated>
Note that we don’t have a variable set for ansible_python_interpreter.
Running it again without an inventory containing localhost allows Ansible to create the entry for us:
ansible-navigator run show_localhost_vars.yml --eei registry.redhat.io/ansible-automation-platform-21/ee-supported-rhel8:latest -m stdout
PLAY [localhost] ************************************************************************************************************************************************************
TASK [print ansible version] ************************************************************************************************************************************************
ok: [localhost] => {
"ansible_version.full": "2.12.1"
}
TASK [print localhost hostvars] *********************************************************************************************************************************************
ok: [localhost] => {
"msg": {
"ansible_check_mode": false,
"ansible_config_file": "/etc/ansible/ansible.cfg",
"ansible_connection": "local",
"ansible_diff_mode": false,
"ansible_facts": {},
"ansible_forks": 5,
"ansible_inventory_sources": [
"/etc/ansible/hosts"
],
"ansible_playbook_python": "/usr/bin/python3.8",
"ansible_python_interpreter": "/usr/bin/python3.8",
Now we have the correct ansible_python_interpreter set.
Summary
A combination of things caused a change in behaviour in my ansible playbook:
- Ansible 2.12 now uses auto as the default discovery method for python interpreter.
- I had a localhost entry in my inventory.
In my case, I just removed localhost from my inventory file. In Automation Controller I removed it from the inventory there. If for some reason you need a localhost entry in your inventory, be prepared to set some additional variables to mimic the behaviour of implicit localhost.