Скачать или смотреть Understanding Nested Loop in Helm Charts

Learn how to effectively manage `nested loops` in Helm charts, specifically for crafting `ingress` routes with proper syntax and structure.
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This video is based on the question https://stackoverflow.com/q/76219158/ asked by the user 'Venu Reddy' ( https://stackoverflow.com/u/6568885/ ) and on the answer https://stackoverflow.com/a/76222907/ provided by the user 'David Maze' ( https://stackoverflow.com/u/10008173/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding Nested Loop in Helm Charts: A Comprehensive Guide

If you're working with Kubernetes and Helm charts, you've likely encountered the complexity of nested loops, especially when it comes to ingress routing. In this guide, we'll look into a specific problem involving nested ingress values in a Helm chart and how to resolve it in a clear and effective manner.

The Problem with Nested Ingress in Helm Charts

Let's say you have the following nested ingress configuration in your values.yml file:

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You want to retrieve all the routes through a template (notes.txt) and your initial attempt yields a somewhat incorrect output. When you execute the following code:

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Expected Output vs Actual Output

You hoped to get the following output if TLS is enabled:

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However, the output you received was:

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As you can see, the host for the second set of paths (/api/v1/ppob and /api/v1/pgob) did not change as expected. This indicates an issue within your nested loop logic where the host is not being referenced correctly.

Solution: Correcting the Nested Loop Logic

Understanding the Loop Context

The root of the problem lies in how you're referencing the variables within the innermost range loop. Within that loop, the . (the current context) pertains to the item in the paths list, not the parent hosts list. To access the correct host, you should use the reference $host which points to the parent item in the hosts list.

Updating the Template Code

To fix this, change your references from .host to $host.host. Also, a more organized approach is to construct the URL parts at their respective levels within the loop. This change improves the clarity of your output generation. Here is how you can refactor the code:

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What Changed?

Here’s a breakdown of the improvements made:

Instead of directly accessing .host, we now leverage the $host variable which provides the correct context pertaining to the current host entry.

Utilizing the printf function for constructing the URL makes the code cleaner and reduces potential mistakes with string concatenation.

We clarified the connection between host and paths within the same level of the context, enhancing readability.

Conclusion

Navigating nested loops in Helm charts can be tricky, but understanding the context and being mindful of how you access different variables will help you craft correct and effective configuration files. By following the steps outlined above, you'll be better equipped to handle similar cases in your own Kubernetes projects, ensuring smoother deployments and reliable applications.

If you found this guide helpful or have any other questions related to Helm, Kubernetes, or anything else, feel free to comment below. Happy charting!