Improving ansible facts documentation

[gundalow]

During CfgMgmtCamp & Contributors Summit 2025 in Ghent there was a lot of discussion around set_facts. One of the actions we took was to improve the documentation.

• using variable documentation
  • Detail the anti patterns (how not to use set_facts)
  • Some real world examples (not made up examples)
  • Link back to set_facts & ansible variable precedence page
  • Related URL: Controlling how Ansible behaves: precedence rules — Ansible Community Documentation

@felixfontein suggested

maybe we should add an action plugin ‘evaluate’ that evalutes an expression and allows you to register the result and use that, instead of returning ansible_facts (like set_facts). then you can add an evaluate task, evaluate all expressions there (optionally with run_once: true) to get the values evaluated at this point in time, register the result, and then use the result in vars:

@Thulium-Drake @kks Thanks for offering to help with this.

Related presentation

Sharing my presentation on applying SOLID principles when developing Ansible content

Recently I had a pleasure of presenting at DevConf.cz. Below is abstract you can find all talk materials at bit.ly/solid-ansible " Discover how the fundamental principles of SOLID—Single Responsibility, Open-Closed, Liskov Substitution, Interface Segregation, and Dependency Inversion—can significantly elevate your Ansible role and playbook development. Join us for a session that delves into the practical application of SOLID principles within the realm of Ansible content creation. Through in…

[Thulium-Drake (Jeffrey van Pelt)]

No worries! I’m going into this quite blank (I do know how to write roles etc), but I personally feel that the way I document my code could use a lot of improvements, and I think some of the questions I have will be related to the gaps we see now.

And who’s better suited to write a document on how to document

[smeeus (Sven Meeus)]

For a real life example, would the use case of where I used set_fact in a loop (and finally running out of physical memory) be a good example of how not to do it?

[kks (Kirill)]

That is a great example. There is always not enough content how not to do something.