Скачать или смотреть How to Iterate Over a Dictionary in Ansible to Calculate CPU Usage

Discover a simple method to iterate over dictionaries in Ansible and calculate CPU usage percentages effectively using Prometheus data in an OpenShift environment.
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Understanding the Problem

When working with Ansible in an OpenShift environment, you might encounter various scenarios where you need to process and analyze data from external sources like Prometheus. For instance, you may want to calculate CPU usage percentages based on your gathered metrics.

In this guide, we’ll tackle the challenge of iterating over a dictionary to compute these percentages and ensure that the data is represented effectively for further use.

The Data Structure

Imagine you have a dictionary with machine names as keys and each machine having its own dictionary containing cpu_total and cpu_used metrics. Here’s an example of how that data structure looks:

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

The main requirement here is to calculate CPU usage percentage using the formula:
CPU Usage (%) = (CPU Used * 100) / CPU Total

The Solution

To achieve the task, you can use Ansible's capabilities to iterate over the dictionary and calculate the CPU usage percentage for each machine. Below is a step-by-step breakdown of the solution.

Step 1: Define Your Variables

Start by defining your original data structure. You can use a lookup to get data from a JSON file or define it directly in your playbook:

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

Step 2: Iterate Over the Dictionary

Next, you will employ Ansible's set_fact module to create a new dictionary that combines the original data with the newly calculated CPU percentages. Here’s how:

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

This block of code does the following:

Iterates over each item in the original dictionary (data).

Calculates the CPU percentage for each machine using the specified formula.

Combines these newly calculated percentages into the percents dictionary.

Step 3: Merge the Results

Once you have the percentages, you can merge them back into your original dictionary:

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

Step 4: Output the Result

Finally, use the debug module to display the updated data structure:

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

Final Output

After running the above tasks, your output will include the CPU percentage along with the original metrics:

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

Conclusion

By leveraging Ansible's powerful features, you can effectively iterate over complex data structures like dictionaries and perform necessary calculations. This method not only allows for quick data manipulation but also provides a clear output structure, making further analysis a breeze.

Now you have a solid understanding of how to calculate CPU usage percentages from dictionary data in Ansible, which can be extremely useful for monitoring and managing resources in an OpenShift environment.