CODEWITHSUNDEEP
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Jeffrey
Jeffrey

Reputation: 4506

How to reference the label value in k8s yaml file

I want to reference the label's value in VirtualService's spec section inside k8s yaml file. I use ${metadata.labels[component]} to indicate the positions below. Is there a way to implement my idea?

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: istio-ingress-version
  namespace: netops
  labels:
    component: version
spec:
  hosts:
  - "service.api.com" 
  gateways:
  - public-inbound-gateway 
  http:
  - match: 
    - uri:
        prefix: /${metadata.labels[component]}/
      headers: 
        referer:
          regex: ^https://[^\s/]*a.api.com[^\s]* 
    rewrite:
      uri: "/"
    route:
    - destination:
        host: ${metadata.labels[component]}.3da.svc.cluster.local  
  - match: 
    - uri:
        prefix: /${metadata.labels[component]}/
      headers: 
        referer:
          regex: ^https://[^\s/]*b.api.com[^\s]* 
    rewrite:
      uri: "/"
    route:
    - destination:
        host: ${metadata.labels[component]}.3db.svc.cluster.local  
  - match: 
    - uri:
        prefix: /${metadata.labels[component]}/
    rewrite:
      uri: "/"
    route:
    - destination:
        host: ${metadata.labels[component]}.3db.svc.cluster.local

Upvotes: 1

Views: 2186

Answers (2)

P Ekambaram
P Ekambaram

Reputation: 17689

Look at downwardAPI to inject pod metadata like labels and annotations to pods at runtime.

apiVersion: v1
kind: Pod
metadata:
  name: kubernetes-downwardapi-volume-example
  labels:
    zone: us-est-coast
    cluster: test-cluster1
    rack: rack-22
  annotations:
    build: two
    builder: john-doe
spec:
  containers:
    - name: client-container
      image: gcr.io/google_containers/busybox
      command: ["sh", "-c", "while true; do if [[ -e /etc/labels ]]; then cat /etc/labels; fi; if [[ -e /etc/annotations ]]; then cat /etc/annotations; fi; sleep 5; done"]
      volumeMounts:
        - name: podinfo
          mountPath: /etc
          readOnly: false
  volumes:
    - name: podinfo
      downwardAPI:
        items:
          - path: "labels"
            fieldRef:
              fieldPath: metadata.labels
          - path: "annotations"
            fieldRef:
              fieldPath: metadata.annotations

Upvotes: 1

Paul Annetts
Paul Annetts

Reputation: 9604

This isn't a capability of Kubernetes itself, however other tools exist that can help you with this scenario.

The main one of these is Helm. It allows you to create variables that can be shared across several different YAML files, allowing you to share values or even fully parameterise your deployment.

Upvotes: 2

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