K8s Service无法关联Pod端口问题求助

问题现象 #

• NextJS前端调用http://gateway-api:8000/...时，DNS可解析到正确的Service IP，但返回连接被拒绝
• Postman等工具可正常访问该API，前端始终无法建立连接

配置与查询信息 #

Pod配置 #

apiVersion: v1
kind: Pod
metadata:
  name: gateway-api
spec:
  selector:
    name: gateway-api
  template:
    metadata:
      labels:
        run: gateway-api
  containers:
    - name: gateway-api
      image: something/gateway-api:latest
      ports:
        - containerPort: 8000

Service配置 #

apiVersion: v1
kind: Service
metadata:
  name: gateway-api
  labels:
    run: gateway-api
spec:
  ports:
    - port: 8000
      protocol: "TCP"
      targetPort: 8000
  selector:
    app: gateway-api

查询结果 #

Service详情

kubectl describe service gateway-api
Name:              gateway-api
Namespace:         default
Labels:            app.kubernetes.io/managed-by=tilt
                   run=gateway-api
Annotations:       <none>
Selector:          app=gateway-api
Type:              ClusterIP
IP Family Policy:  SingleStack
IP Families:       IPv4
IP:                10.103.9.152
IPs:               10.103.9.152
Port:              <unset>  8000/TCP
TargetPort:        8000/TCP
Endpoints:         <none>
Session Affinity:  None
Events:            <none>

Pod列表

kubectl get pod -o wide             
NAME          READY   STATUS    RESTARTS      AGE   IP           NODE             NOMINATED NODE   READINESS GATES
gateway-api   1/1     Running   0             12m   10.1.1.161   docker-desktop   <none>           <none>
gateway-web   1/1     Running   0             12m   10.1.1.160   docker-desktop   <none>           <none>
mysql-0       1/1     Running   7 (19h ago)   75d   10.1.1.140   docker-desktop   <none>           <none>

Service列表

kubectl get service -o wide
NAME             TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE   SELECTOR
gateway-api      ClusterIP   10.103.9.152    <none>        8000/TCP   11m   app=gateway-api

问题根因 #

从配置和查询结果可直接定位：

• Service的selector设置为app=gateway-api，但Pod的labels仅包含run=gateway-api，标签完全不匹配
• kubectl describe service gateway-api显示Endpoints: <none>，说明Service未关联到任何Pod，这是连接被拒绝的核心原因

解决方案 #

方案1：修改Service的Selector匹配Pod标签 #

调整Service配置中的selector字段，使其与Pod的labels一致：

apiVersion: v1
kind: Service
metadata:
  name: gateway-api
  labels:
    run: gateway-api
spec:
  ports:
    - port: 8000
      protocol: "TCP"
      targetPort: 8000
  selector:
    run: gateway-api  # 修改为与Pod一致的标签

方案2：修改Pod的Labels匹配Service Selector #

在Pod配置的labels中添加Service期望的标签：

apiVersion: v1
kind: Pod
metadata:
  name: gateway-api
spec:
  selector:
    name: gateway-api
  template:
    metadata:
      labels:
        run: gateway-api
        app: gateway-api  # 添加匹配Service的标签
  containers:
    - name: gateway-api
      image: something/gateway-api:latest
      ports:
        - containerPort: 8000

修改后执行kubectl apply -f <配置文件路径>重新部署，再通过kubectl describe service gateway-api确认Endpoints已显示Pod的IP地址，此时前端即可正常连接服务。

注：因使用NextJS服务器，无法通过localhost:xxxx访问，只能通过命名Pod/Service路径调用。

内容的提问来源于stack exchange，提问作者NoGall