K8S编排 之 Service

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本文的主线 引入 => 使用 => 特性

引入

  • Pod解决了容器的”超亲密关系”设计

  • Deployment解决了Pod水平扩展的问题

  • Service解决了Pod负载均衡的问题

使用

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vim deploy.yml
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apiVersion: apps/v1
kind: Deployment
metadata:
  name: hostnames
spec:
  selector:
    matchLabels:
      app: hostnames
  replicas: 3
  template:
    metadata:
      labels:
        app: hostnames
    spec:
      containers:
      - name: hostnames
        image: mirrorgooglecontainers/serve_hostname
        ports:
        - containerPort: 9376
          protocol: TCP
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kubectl apply -f deploy.yml

kubectl get pods
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NAME                         READY   STATUS    RESTARTS   AGE
hostnames-69cd56f6d5-cgmmk   1/1     Running   0          18m
hostnames-69cd56f6d5-nnjqp   1/1     Running   0          18m
hostnames-69cd56f6d5-vcp4s   1/1     Running   0          18m
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vim service-v1.yml
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apiVersion: v1
kind: Service
metadata:
  name: hostnames
spec:
  selector:
    app: hostnames
  ports:
  - name: default
    protocol: TCP
    port: 80
    targetPort: 9376
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kubectl apply -f service-v1.yml

kubectl get svc hostnames
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NAME        TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
hostnames   ClusterIP   10.109.68.71   <none>        80/TCP    118s

Service是通过selector来找到相应标签的Pod 解决了IP依赖的问题

特性

  • 上述ClusterIP类型的Service只能在集群内部访问
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curl 10.109.68.71:80
# curl: (7) Failed to connect to 10.109.68.71 port 80: Connection timed out
  • 想要在集群外部访问的一个方式是NodePort 既使用节点上的某个特定端口
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vim service-v2.yml
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apiVersion: v1
kind: Service
metadata:
  name: hostnames
spec:
  type: NodePort
  selector:
    app: hostnames
  ports:
  - name: default
    protocol: TCP
    port: 80
    targetPort: 9376
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kubectl apply -f service-v2.yml

kubectl get svc hostnames
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NAME        TYPE       CLUSTER-IP     EXTERNAL-IP   PORT(S)        AGE
hostnames   NodePort   10.109.68.71   <none>        80:32284/TCP   3m2s
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curl 172.10.66.201:32284
# hostnames-69cd56f6d5-vcp4s

curl 172.10.66.201:32714
# hostnames-69cd56f6d5-cgmmk

curl 172.10.66.201:32714
# hostnames-69cd56f6d5-nnjqp

Service同时解决了Pod水平扩展后的负载均衡问题