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Learn how to configure Ansible dynamic inventories with ServiceNow, ensuring your host variables are properly set, and troubleshoot common issues that arise in the process.
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This video is based on the question https://stackoverflow.com/q/73977134/ asked by the user 'Hoguss' ( https://stackoverflow.com/u/18495394/ ) and on the answer https://stackoverflow.com/a/73979881/ provided by the user 'mdaniel' ( https://stackoverflow.com/u/225016/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Setting Host Variables for Ansible Dynamic Inventories Using ServiceNow

When working with Ansible's dynamic inventories, especially using the ServiceNow integration, you may encounter challenges in setting up host variables correctly. One common question that arises is how to utilize the Jinja2 templating engine to set strings for various connection details, particularly when using Kerberos as your authentication method. In this guide, we will delve into the underlying issues and provide a straightforward solution to overcome these obstacles.

Understanding the Problem

As you attempt to set the host variables in your dynamic inventory configuration, you may notice that only certain variables, like ansible_password, are being correctly recognized while others, especially those containing mixed strings, seem to be ignored or misinterpreted.

The Setup

You have a configuration similar to this:

[[See Video to Reveal this Text or Code Snippet]]

In this configuration, you might be wondering why only the password variable is set correctly, while others fail to parse as expected.

The Solution: Proper Use of Jinja2

The root of the issue lies in how the Ansible dynamic inventory framework handles variable parsing. By default, each key in the compose section is implicitly treated as a Jinja2 expression. This means your setup requires you to format those keys in a manner that explicitly produces the desired string literals.

Correcting the Formatting

Instead of just writing the values as plain strings, you need to use Jinja2 syntax to ensure Ansible recognizes them correctly. Here’s how to fix your compose section:

[[See Video to Reveal this Text or Code Snippet]]

Key Takeaways

Implicit Jinja2 Parsing: When you define your compose values, understand that they are interpreted as Jinja2 expressions. Escaping the values correctly ensures they are recognized as string literals rather than variable names.

Avoid Errors: If a Jinja2 expression doesn’t resolve to a defined variable, it will throw an error. Using quotes around your strings allows them to be treated as literal values instead.

Testing Configurations: Always test your configurations after making adjustments to ensure that all variables are recognized as intended.

Future Considerations: Group Variables

While this post focuses on using the compose option, it’s important to note that if a variable's value is constant across all hosts, it’s often better to define them in group_vars. This way you can create a file, say group_vars/all.yaml, for common configurations that apply universally, simplifying your dynamic inventory management.

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Navigating Ansible dynamic inventories through ServiceNow can be tricky, especially regarding variable parsing with Jinja2. By correctly formatting your compose section to reflect Jinja2 expressions, you can successfully set all necessary host variables, leading to smoother automation processes. Happy automating!