Скачать или смотреть How to Loop Over a List with Multiple Items in Ansible Playbooks

Learn how to effectively loop over multiple items in Ansible playbooks for tasks like installing packages. This guide breaks down the solution with clear steps and helpful examples.
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Looping Over a List with Multiple Items in Ansible Playbooks

When writing Ansible playbooks, one common task is the need to loop over a list of items. For example, if you're managing PHP versions and want to install multiple packages for each version, you might encounter some challenges with looping correctly. In this guide, we will address how to loop over a list of PHP versions and install related packages efficiently.

The Problem

Suppose you have defined an array representing various PHP versions in your Ansible playbook, like this:

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

You want to use this list to install not just the PHP versions, but also their associated packages such as php-bcmath and php-bz2. A naive approach might involve using this like:

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

Unfortunately, this will not work due to incorrect looping syntax, leading to errors. It’s essential to know how to structure the loop correctly to achieve the desired outcome.

The Solution: Using the product Filter

The key to solving this issue lies in leveraging the product filter. This filter can combine multiple lists, allowing us to create permutations of the PHP versions and their corresponding packages. Here’s how you can implement it:

Step-by-Step Solution

Define Your PHP Versions: As you did, keep your list in a variable.

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

Use the product Filter: Instead of trying to manually combine items, use the filter to create a list of all combinations between your PHP versions and the suffixes ('', '-bcmath', and '-bz2').

Construct the Task: Set up your task to utilize this combined list.

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

Explanation of the Code

product Filter: This filter takes the first list (your PHP versions) and pairs each element with every item in the second list (the suffixes: '', '-bcmath', '-bz2').

item.0 and item.1: In the loop, item.0 represents the PHP version, and item.1 represents the suffix, allowing you to dynamically construct the complete package name needed for installation.

Expected Output

When executed, this task will lead to the installation of the following packages:

php71, php71-bcmath, php71-bz2

php72, php72-bcmath, php72-bz2

php73, php73-bcmath, php73-bz2

By structuring the loop this way, you efficiently iterate through all the required combinations without falling into common pitfalls encountered with simpler looping syntax.

Conclusion

Using Ansible effectively to manage complex operations like package installation requires mastery over looping constructs and filters. By employing the product filter, you can create elegant and powerful loops that make your playbooks not only functional but also easier to maintain. Now, the next time you need to loop through a list of items in your Ansible playbook, remember this solution to streamline your tasks!