Advanced HTTPRoute Filters in Kubernetes Gateway API¶

This document provides a detailed reference on how to use HTTPRoute with advanced filters in the Gateway API. It includes real-world use cases and complete YAML examples.

📌 Prerequisites¶

Ensure you have the following deployed:

A Gateway controller (e.g., NGINX Gateway)
A Gateway resource named my-nginx-gateway in namespace nginx-gateway

Each HTTPRoute will reference this Gateway using:

parentRefs:
- name: my-nginx-gateway
  namespace: nginx-gateway
  sectionName: http

🔀 Filter Use Cases¶

1. 🚦 Request Redirection (HTTP → HTTPS)¶

rules:
- filters:
  - type: RequestRedirect
    requestRedirect:
      scheme: https
      statusCode: 301

Redirects all incoming HTTP requests to HTTPS.

2. 🔄 URL Rewrite (`/old` → `/new`)¶

rules:
- matches:
  - path:
      type: PathPrefix
      value: /old
  filters:
  - type: URLRewrite
    urlRewrite:
      path:
        replacePrefixMatch: /new
  backendRefs:
  - name: my-app
    port: 80

Rewrites /old paths to /new before forwarding to backend.

3. 🧠 Request Header Modification¶

rules:
- filters:
  - type: RequestHeaderModifier
    requestHeaderModifier:
      add:
        x-env: staging
      set:
        x-country: PK
      remove:
      - x-remove-this
  backendRefs:
  - name: my-app
    port: 80

Adds, sets, and removes headers in the request before it hits the backend.

4. 🪞 Request Mirroring¶

rules:
- filters:
  - type: RequestMirror
    requestMirror:
      backendRef:
        name: mirror-service
        port: 80
  backendRefs:
  - name: my-app
    port: 80

Sends a copy of the request to mirror-service without affecting the original flow.

5. 🧰 Combined Filters¶

rules:
- matches:
  - path:
      type: PathPrefix
      value: /products
  filters:
  - type: URLRewrite
    urlRewrite:
      path:
        replacePrefixMatch: /items
  - type: RequestHeaderModifier
    requestHeaderModifier:
      add:
        x-service-version: v2
  backendRefs:
  - name: product-service
    port: 8080

Chains rewrite and header modification for advanced routing.

6. 🧪 Default Basic Match¶

rules:
- matches:
  - path:
      type: PathPrefix
      value: /
  backendRefs:
  - name: frontend-svc
    port: 80

Acts as a fallback catch-all route.

🧱 Filter Summary¶

Filter Type	Description
`RequestRedirect`	Redirects requests (e.g., HTTP → HTTPS)
`URLRewrite`	Rewrites the path before sending to backend
`RequestHeaderModifier`	Add/Set/Remove headers on incoming requests
`RequestMirror`	Mirrors request to another backend silently
`ExtensionRef`	Custom filters (defined by controller vendors)

🧠 Tip¶

You can define multiple rules in one HTTPRoute, each with different matches and filters for microservices routing, A/B testing, canary deployments, and more.