Configuring a Custom Header Forwarding Policy for a LoadBalancer Ingress

Dedicated load balancer ingresses support custom header forwarding policies. You can configure different header key-value pairs to determine the backend Service to which data is forwarded.

Prerequisites

A cluster meeting the following requirements is available:

v1.23: v1.23.16-r0 or later
v1.25: v1.25.11-r0 or later
v1.27: v1.27.8-r0 or later
v1.28: v1.28.6-r0 or later
v1.29: v1.29.2-r0 or later

Using kubectl

An example YAML file of an ingress created using an existing load balancer is as follows:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: test-header
  namespace: default
  annotations:
    kubernetes.io/elb.port: '80'
    kubernetes.io/elb.id: 08eab934-1636-4d90-a4cd-cb3fa4330411
    kubernetes.io/elb.class: performance  # A dedicated load balancer is required.
    # Path /a can be accessed only through Header key1=value1 or key1=value2. The accessed Service is svc-a:80.
    kubernetes.io/elb.headers.svc-a: | 
      {
          "key": "key1",
          "values": [
              "value1",
              "value2"
          ]
      }
    # Path /b can be accessed only through Header key2=value1 or key2=value2. The accessed Service is svc-b:81.
    kubernetes.io/elb.headers.svc-b: |  
      {
          "key": "key2",
          "values": [
              "value1",
              "value2"
          ]
      }
spec:
  rules:
    - host: ''
      http:
        paths:
          - path: /a
            backend:
              service:
                name: svc-a
                port:
                  number: 80
            property:
              ingress.beta.kubernetes.io/url-match-mode: STARTS_WITH
            pathType: ImplementationSpecific
          - path: /b
            backend:
              service:
                name: svc-b
                port:
                  number: 81
            property:
              ingress.beta.kubernetes.io/url-match-mode: STARTS_WITH
            pathType: ImplementationSpecific
  ingressClassName: cce

**Table 1** Annotations for configuring a custom header forwarding policy
Parameter	Type	Description
kubernetes.io/elb.headers.${svc_name}	String	Custom header of the Service associated with an ingress. ${svc_name} is the Service name. Format: a JSON string, for example, {"key": "test", "values": ["value1", "value2"]} key/value indicates the key-value pair of the custom header. A maximum of eight values can be configured. Enter 1 to 40 characters for a key. Only letters, digits, hyphens (-), and underscores (_) are allowed. Enter 1 to 128 characters for a value. Asterisks () and question marks (?) are allowed, but spaces and double quotation marks are not allowed. An asterisk can match zero or more characters, and a question mark can match one character. Either a custom header or grayscale release can be configured. Enter 1 to 51 characters for ${svc_name}*.