service¶

service可以简写为svc。

service是用于为pod提供固定访问端点的， service的网络是用于节点之间访问的。

expose用于创建一个service，将deployment管理的pod的端口给映射到service上。

service在被pod访问的时候，是可以用service的名称来访问的，因为service name 会被自动添加dns里，能够解析为这个service的IP地址。

service 使用ipvs规则，把所有访问service cluster-ip的请求全部调度至它用标签选择器关联到的各pod后端的。

通过kubectl describe svc $service_name

修改service中NodePort方式暴露的服务的二端口默认范围¶

K8S中NodePort方式暴露服务的端口的默认范围（30000-32767）的方法：

比如像把端口范围改成1-65535，则在apiserver的启动命令里面添加如下参数：

–service-node-port-range=1-65535

创建个deployment¶

这里我们先创建一个deployment

$ kubectl run nginx-deploy --image=nginx:1.14-alpine --port=80 --replicas=2

查看deployment的描述信息¶

名称为nginx-deploy， labels就是标签，这里的标签是run=nginx-deploy，默认将名字赋值给run作为标签。

[root@k8s1 ~]# kubectl describe deploy nginx-deploy
Name:                   nginx-deploy
Namespace:              default
CreationTimestamp:      Mon, 27 Aug 2018 17:18:41 +0800
Labels:                 run=nginx-deploy
Annotations:            deployment.kubernetes.io/revision=1
Selector:               run=nginx-deploy
Replicas:               2 desired | 2 updated | 2 total | 2 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  run=nginx-deploy
  Containers:
   nginx-deploy:
    Image:        nginx:1.14-alpine
    Port:         80/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Progressing    True    NewReplicaSetAvailable
  Available      True    MinimumReplicasAvailable
OldReplicaSets:  <none>
NewReplicaSet:   nginx-deploy-5b595999 (2/2 replicas created)
Events:          <none>

然后我们将这个名为nginx-deploy的deployment给暴露出来，放到service里。

以下命令中，–target-port=80 表示目标deployment里的pod提供服务的端口是80， –port=80 表示service这里提供服务的端口是80.

$ kubectl expose deployment nginx-deploy --name=nginx --port=80 --target-port=80 --protocol=TCP

然后我们查看一下，确认service创建完成，而且可以访问。

[root@k8s1 ~]# kubectl get service
NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE
kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP    5h
nginx        ClusterIP   10.110.69.178   <none>        8000/TCP   1m
[root@k8s1 ~]# curl 10.110.69.178:80
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

查看service的描述信息¶

service信息里有一行 Selector, 就是标签选择器，通过标签选择器来将请求调度到后端的pod

[root@k8s1 ~]# kubectl describe svc nginx
Name:              nginx
Namespace:         default
Labels:            run=nginx-deploy
Annotations:       <none>
Selector:          run=nginx-deploy
Type:              ClusterIP
IP:                10.110.69.178
Port:              <unset>  80/TCP
TargetPort:        80/TCP
Endpoints:         10.244.1.10:80,10.244.2.10:80
Session Affinity:  None
Events:            <none>
[root@k8s1 ~]#

通过yaml文件创建registry的service¶

$ vim registry-service.yaml
apiVersion: v1
kind: Service
metadata:
  name: registry-svc
  labels:
    run: registry-svc
spec:
  ports:
  - port: 5000
    protocol: TCP
  selector:
    run: registry
  type: NodePort
  ports:
  - port: 5000
    targetPort: 5000
    nodePort: 30001

$ kubectl create -f registry-service.yaml