Joe Blog

背景

Kubernetes的service是一种抽象，它定义了在集群中运行的一组逻辑 Pod，由该组逻辑Pod提供相同的功能。创建时，每个服务都分配有一个唯一的 IP 地址（也称为 clusterIP）。此地址与服务的生命周期相关联，并且在服务存在期间不会更改。Pod可以配置为与Service 通信，此时Service的将自动负载平衡到属于Service成员的其中一个Pod。

由于service和pod之间通过labels selector 标签过滤器来做关联。

由于label标签的定义可以在metadata 和template等多个位置，此时需要我们定义在Pod的template模板中

您可以使用以下yaml创建billing-app和checkout-app以及billing-svc

apiVersion: apps/v1
kind: Deployment
metadata:
  name: billing-app
spec:
  selector:
    matchLabels:
      run: billing-app
  replicas: 2
  template:
    metadata:
      labels:
        run: billing-app
        component: backend
    spec:
      containers:
      - name: billing-app
        image: nginx
        ports:
        - containerPort: 80

apiVersion: apps/v1
kind: Deployment
metadata:
  name: checkout-app
spec:
  selector:
    matchLabels:
      run: checkout-app
  replicas: 2
  template:
    metadata:
      labels:
        run: checkout-app
        component: backend
    spec:
      containers:
      - name: checkout-app
        image: nginx
        ports:
        - containerPort: 80

apiVersion: v1
kind: Service
metadata:
  name: billing-service
spec:
  ports:
  - port: 80
    protocol: TCP
  selector:
    component: backend

可以看出svcbilling-svc 通过selector来筛选Pod，来实现多组Pod对应一个svc服务

...
selector:
  component: backend
...

验证

root@node1:~/muti-deplpoyment-a-service# kubectl  get svc
NAME              TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
billing-service   ClusterIP   10.233.2.143   <none>        80/TCP    9s
kubernetes        ClusterIP   10.233.0.1     <none>        443/TCP   195d
root@node1:~/muti-deplpoyment-a-service#
oot@node1:~/muti-deplpoyment-a-service# kubectl  get pod -owide
NAME                            READY   STATUS    RESTARTS   AGE     IP              NODE    NOMINATED NODE   READINESS GATES
billing-app-54c4cb6dc8-fr6tx    1/1     Running   0          2m46s   10.233.66.212   node3   <none>           <none>
billing-app-54c4cb6dc8-wr8lw    1/1     Running   0          2m46s   10.233.68.212   node6   <none>           <none>
checkout-app-66966dfc84-74hxv   1/1     Running   0          2m46s   10.233.67.60    node4   <none>           <none>
checkout-app-66966dfc84-w5689   1/1     Running   0          2m46s   10.233.66.51    node3   <none>           <none>
root@node1:~/muti-deplpoyment-a-service# kubectl  get ep
NAME              ENDPOINTS                                                      AGE
billing-service   10.233.66.212:80,10.233.66.51:80,10.233.67.60:80 + 1 more...   19s
kubernetes        192.168.2.101:6443,192.168.2.102:6443                          195d

以上svcbilling-svc对于的endpoints成员包含了4个Pod的ip

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