Introduction

The assert module in Ansible is a powerful tool for validating conditions and ensuring the correctness of your automation workflows. By halting execution when a condition isn't met, it prevents cascading failures and provides valuable feedback to the user. In this article, we'll explore the quiet, fail_msg, and success_msg parameters, which enhance the flexibility and usability of assertions in playbooks.

What is the assert Module?

The assert module evaluates one or more conditions and ensures they are true. If any condition fails, the module raises an error and stops execution. It's particularly useful for debugging, validation, and ensuring preconditions in complex playbooks.

Basic Syntax

``yaml

  • name: Validate a condition

assert:

that:

- some_variable == "expected_value"

`

If some_variable doesn't equal expected_value, the playbook will fail at this step.

Enhancing Assertions with quiet, fail_msg, and success_msg

1. quiet: Suppress Output for Passed Assertions

By default, the assert module outputs all evaluated conditions. However, in scenarios where you only want feedback on failures, quiet: true suppresses success messages.

#### Example:

`yaml

  • name: Ensure a directory exists

assert:

that:

- ansible_facts['os_family'] == "RedHat"

quiet: true

`

Use Case:

  • Keeps playbook output clean and focused, especially when numerous assertions are involved.

---

2. fail_msg: Custom Error Messages for Failures

The fail_msg parameter allows you to define a custom error message displayed when the assertion fails. This is invaluable for providing context or instructions for resolving issues.

#### Example:

`yaml

  • name: Validate OS family

assert:

that:

- ansible_facts['os_family'] == "Debian"

fail_msg: "The target system is not running a Debian-based OS."

`

#### Output on Failure:

`plaintext

fatal: [localhost]: FAILED! =>

msg: "The target system is not running a Debian-based OS."

`

Use Case:

  • Improves debugging by clarifying the cause of failure and suggesting corrective actions.

---

3. success_msg: Provide Feedback on Success

The success_msg parameter lets you display a custom message when the assertion passes. This is useful for confirming critical preconditions or providing reassurance to the user.

#### Example:

`yaml

  • name: Ensure disk space is sufficient

assert:

that:

- available_disk_space > 1024

success_msg: "Sufficient disk space available for the deployment."

`

#### Output on Success:

`plaintext

ok: [localhost] =>

msg: "Sufficient disk space available for the deployment."

`

Use Case:

  • Provides positive feedback during playbook execution, boosting confidence in critical tasks.

---

Combining All Parameters: A Comprehensive Example

Here's how to use quiet, fail_msg, and success_msg together in a real-world scenario:

``yaml

  • name: Vali