How to reference the label value in k8s yaml file - kubernetes

Question

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

Answer 1

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.

Answer 2

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