How to Use Wildcards for Dynamic Service Routing in Kubernetes Ingress

Описание: Learn how to configure Kubernetes ingress with wildcards to dynamically route services based on path or subdomain, allowing for easy service management.
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This video is based on the question https://stackoverflow.com/q/66561250/ asked by the user 'Colin FAY' ( https://stackoverflow.com/u/8236642/ ) and on the answer https://stackoverflow.com/a/66561397/ provided by the user 'coderanger' ( https://stackoverflow.com/u/78722/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Wildcards in Kubernetes Ingress: A Dynamic Routing Solution

Managing a Kubernetes cluster can be a complex task, especially when you have multiple services that need to be exposed to the outside world. One common requirement is to route traffic dynamically to different services based on the request URL path or subdomain. If you've found yourself wondering how to effectively implement this routing with wildcards in Kubernetes ingress, you're not alone. Today, we'll explore how to achieve this goal, and clarify the limitations you may encounter along the way.

The Challenge: Dynamic Service Routing

In a typical Kubernetes setup, you may have a series of services, each that you want to expose using different endpoints. For example:

http://yourdomain.com/xx should route to the service xx

http://yourdomain.com/yy should route to the service yy

The requirement is clear: as you add new services to your cluster, they should be accessible seamlessly at their unique endpoints without needing additional complex configurations each time.

In seeking a solution, Colin posed an idea of using wildcards in the ingress settings, representing service names dynamically based on the incoming path. Here’s a simplified version of the proposed YAML configuration:

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

While the intention is spot on, it leads us to an important discussion about the limitations of the current Kubernetes ingress system.

Understanding Kubernetes Ingress Limitations

Unfortunately, the Kubernetes ingress system does not natively support wildcards in the manner described. This means your proposed configuration will not work as intended. Ingress is designed for a more static route definition, defining specific paths and linking them to services explicitly.

Why Are Wildcards Not Supported?

Security Concerns: Allowing dynamic service resolution from paths could lead to potential security issues, as it may inadvertently expose services that should remain private.

Complexity in Management: Handling dynamic routing in a way that does not confuse or disrupt existing traffic would complicate the management of ingress rules significantly.

Alternative Solutions for Dynamic Service Management

Although Kubernetes ingress doesn't provide a straightforward method for wildcard-based routing, there are alternatives worth considering. Here are a couple of solutions that could achieve a similar result:

Solution 1: Static Nginx Configuration

For more flexibility, you might find it beneficial to use a static Nginx configuration outside of Kubernetes ingress. This allows you to have complete control over routing logic and can make use of regex for matching paths. Here’s a basic example:

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

Solution 2: Nginx Ingress Controller Customization

If you're using an Nginx ingress controller, you can leverage the customization capabilities of the ingress controller to route requests dynamically based on the request's hostname or path. Consider implementing your application logic on the server level (for example, with Lua scripting) to route requests as desired.

Consideration of Service Mesh

In more advanced scenarios, consider implementing a service mesh like Istio or Linkerd, which can provide rich routing capabilities, including dynamic service discovery and automatic updates to traffic routes without modifying ingress configurations.

Conclusion

While dynamic routing with wildcards in Kubernetes ingress isn't directly supported, alternative methods such as using a static Nginx configuration or customizing the Nginx Ingress Controller can help you achieve a similar result. As you design your Kubernetes architecture, it’s es