My first encounter with Ansible release 12 wasn’t exactly encouraging. We were using a few Ansible Jinja2 filters (ipaddr and hwaddr) in internal netlab templates, and all of a sudden those templates started crashing due to some weird behavior of attributes starting with underscore.

We implemented don’t use Ansible release 12 as a quick workaround, but postponing painful things is never a good solution(see also: visiting a dentist), so I decided to try to make netlab work with Ansible release 12. What a mistake to make.

Here’s what I found before I hit a major showstopper:

When Conditions

The Ansible module/block when conditions were evaluated as Python boolean expressions, which means that a non-empty string (for example) would be True. Ansible release 12 expects them to produce a True/False result.

To make matters worse, due to the way Python evaluates boolean expressions, a and b results in value of b, not in True/False value, which means that most when expressions, even when they include boolean operators like and or or, might result in non-boolean results (not is the only exception).

Rubbing some salt into this open wound: according to Ansible documentation, the first_found lookup could return the file name, or an empty list or None when the file is not found.

I could use the truthy test on every when expression, but decided to go for a more verbose x is string and x != ''.

There is an Ansible environment variable that you can set to revert to the old behavior, but that just prolongs the pain.

Macro Results

In older Ansible releases, a Jinja2 macro that resulted in no text returned an empty string. With release 12, the same macro returns None. I have no idea whose fault that is, but it sucks.

This is how we were using Jinja2 macros with indent filters to generate configuration blocks that could be used in various places in the device configuration hierarchy (for example, you could have the redistribute command under router or router/address-family sections):

{{ some_config()|indent(2,first=True) }}

That no longer works in Ansible release 12. You have to check the results of the macro and use indent only if they are truthy, for example:

{% set redist_cfg = some_config() %}
{% if redist_cfg %}
{{   redist_cfg|indent(2,first=True) }}
{% endif %}

Whoever caused this change, thank you for the roses (I guess).

Tests of Undefined Variables

In the previous Ansible releases, x is string would be False if x was not defined. Now, the same test throws an error; you have to use something along the lines of x is defined and x is string.

I’m not blaming anyone for this change (after all, throwing an error is the correct response), but imagine how many hard-to-find errors this will trigger.

Some Built-In Filters Must Use FQDN Names

For whatever reason, using the ipaddr filter throws an error. You have to use ansible.utils.ipaddr. OTOH, you can still use ios_config instead of cisco.ios.ios_config module.

For extra fun, the change (if it was intentional) is not mentioned in the Ansible 12 Porting Guide (or maybe I missed it, I only searched that page for .utils).

The Showstopper: Using Templates in Device Configuration Modules

Since days immemorial, device configuration modules (for example, ios_config or eos_config) have accepted a Jinja2 template in the src parameter and rendered the template before pushing the configuration to the device (that’s also what the documentation claims).

It looks like at least ios_config and eos_config modules (in short- and FQDN form) no longer render the template but try to push Jinja2 code to the device. The device is not amused.

Of course, I could work around that. I could render the template into a local temporary file and push that file to the device, but I decided I would rather wait to see if someone gets annoyed enough to have the error fixed.

I also installed the ansible.netcommon (8.1.0) and arista.eos (12.0.0) collections (the versions packaged with Ansible release 12.0) on top of Ansible release 11.10, and they work (modulo the ipaddr quirk). The problem is thus deeper in the Ansible core and affects numerous network device modules; I can’t fathom how this could escape the integration tests.

Long Story Short

I understand why the Ansible team decided to bite the bullet and have their own Windows Longhorn/Vista moment1, but the many changes in behavior they introduced will be as popular as Vista’s endless security popups.

Just the things I discovered so far turn all your Ansible playbooks into ticking time bombs. Can you be sure you found all instances of the non-bool when conditions? I was… and was already proven wrong.

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If you’re too young to know what I’m talking about and care about the early history of IT, I can highly recommend the episodes the Acquired podcast did on Microsoft (part 1, part 2, the Steve Ballmer interview) ↩︎