Kubernetes中如何从ConfigMap的嵌套对象读取环境变量值？

当前ConfigMap的结构如下：

Name:         my-configmap
Namespace:    my-namespace
Labels:       <none>
Annotations:  alb.ingress.kubernetes.io/certificate-arn: arn:aws:acm:***

Data
====
payment-api-url:
----
dev: dev-url
qa: qa-url
prod: prod-url


BinaryData
====

Events:  <none>  

对应的ConfigMap和Deployment清单：

---
apiVersion: v1
kind: ConfigMap
metadata:
  name: my-configmap
data:
  payment-api-url: |
    dev: dev-url
    qa: qa-url
    prod: prod-url
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: my-pod
  replicas: 1
  template:
    metadata:
      labels:
        app.kubernetes.io/name: my-pod
    spec:
      containers:
        - image: my-image
          imagePullPolicy: Always
          name: my-container
          ports:
            - containerPort: 8080
          env:
            - name: PAYMENT_API_URL
              valueFrom:
                configMapKeyRef:
                  name: my-configmap
                  key: payment-api-url.dev
---

部署后Pod出现CreateContainerConfigError，错误信息：

Error: couldn't find key payment-api-url.dev in ConfigMap my-namespace/my-configmap

方法一：重构ConfigMap为独立键值对（推荐） #

当前ConfigMap中payment-api-url是一个多行文本值，并非Kubernetes可识别的嵌套对象，因此无法通过payment-api-url.dev的方式直接访问内部字段。最规范的做法是将每个环境的URL拆分为ConfigMap的独立键：

修改后的ConfigMap：

apiVersion: v1
kind: ConfigMap
metadata:
  name: my-configmap
data:
  payment-api-url-dev: dev-url
  payment-api-url-qa: qa-url
  payment-api-url-prod: prod-url

对应的Deployment配置，直接引用对应键：

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: my-pod
  replicas: 1
  template:
    metadata:
      labels:
        app.kubernetes.io/name: my-pod
    spec:
      containers:
        - image: my-image
          imagePullPolicy: Always
          name: my-container
          ports:
            - containerPort: 8080
          env:
            - name: PAYMENT_API_URL
              valueFrom:
                configMapKeyRef:
                  name: my-configmap
                  key: payment-api-url-dev # 根据环境选择对应键

方法二：通过脚本解析多行文本（不推荐） #

如果无法修改ConfigMap结构，可以在容器启动时通过脚本解析payment-api-url的多行内容，提取目标值并设置为环境变量。例如，在Deployment中修改容器启动命令：

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: my-pod
  replicas: 1
  template:
    metadata:
      labels:
        app.kubernetes.io/name: my-pod
    spec:
      containers:
        - image: my-image
          imagePullPolicy: Always
          name: my-container
          ports:
            - containerPort: 8080
          env:
            - name: PAYMENT_API_CONFIG
              valueFrom:
                configMapKeyRef:
                  name: my-configmap
                  key: payment-api-url
          # 用shell脚本解析配置并启动应用
          command: ["/bin/sh", "-c"]
          args:
            - export PAYMENT_API_URL=$(echo "$PAYMENT_API_CONFIG" | grep 'dev:' | awk '{print $2}') && exec <你的应用启动命令>

注意：这种方式依赖容器内有grep、awk等工具，且维护性不如方法一。

内容的提问来源于stack exchange，提问作者Shanika Ediriweera