k8s-service

最新推荐文章于 2025-11-23 12:47:13 发布

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#kubernetes #负载均衡 #docker

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本文介绍了Kubernetes Service，它是集群内的服务注册和负载均衡机制，提供统一访问入口，解决Pod动态变化问题。Service通过标签选择Pod并进行负载均衡。讨论了ClusterIP、NodePort和LoadBalancer三种类型的Service，以及如何进行操作练习，包括Deployment滚动更新、扩容、创建多容器Pod及Service。

Service对外暴露应用

Service是什么

其实就是k8s中的服务注册与负载均衡
最终能够实现，提供一个唯一的地址，供我们来访问地址，而不需要具体的去了解，这个服务起的Pod的ip是什么

Service存在的意义
Service引入主要是解决Pod的动态变化,提供统一访问入口

防止Pod失联，准备找到提供同一个服务的Pod(服务发现)
定义一组Pod的访问策略(负载均衡)

Pod与Service的关系
Service通过标签关联一组Pod
Service使用iptables或者ipvs为一组Pod提供负载均衡能力

service三种类型
ClusterlP
默认类型，分配一个稳定的IP地址，即VIP，只能在集群内部访问

一个简单的service清单文件

---
apiVersion: v1
kind: Service
metadata:
  name: test
  namespace: default
spec:
  ports:
  - port: 80		#Service端口
    protocol: TCP	#协议
    targetPort: 80	#容器端口
  selector:
    app: httpd		#指定关联Pod的标签
  type: ClusterIP	#服务类型，如果不指定类型，默认类型为ClusterIP
...					#文件结束用...

NodePort
在每个节点上启用一个端口来暴露服务，可以在集群外部访问。也会分配一个稳定内部集群IP地址。
访问地址：<任意NodelP> :<NodePort> 加上NodelP以防有多个IP
端口范围：30000-32767
LoadBalancer
与NodePort类似，在每个节点上启用一个端口来暴露服务。
除此之外，Kubernetes会请求底层云平台（例如阿里云、腾讯云、AWS等)上的负载均衡器，将每个Node ([NodelP]:[NodePort])作为后端添加进去。

操作练习

创建一个deployment副本数3，然后滚动更新镜像版本，并记录这个更新记录，最后再回滚到上一个版本

//清单文件
[root@master manifest]# cat test.yml 
---
apiVersion: apps/v1
kind: Deployment 
metadata: 
  name: test
  namespace: default 
spec:
  replicas: 3    //三个副本
  selector: 
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: web 
        image: soumnswa/httpd:v1.0   //1.01版本镜像
        imagePullPolicy: IfNotPresent

//运行pod
[root@master manifest]# kubectl apply -f test.yml 
deployment.apps/test created
[root@master manifest]# kubectl get pods
NAME                    READY   STATUS              RESTARTS   AGE
test-7746d6b875-8wqfw   1/1     Running             0          49s
test-7746d6b875-rtnbv   1/1     Running             0          49s
test-7746d6b875-tphkd   0/1     ContainerCreating   0          49s

//更换镜像，升级版本
[root@master manifest]# cat test.yml 
---
apiVersion: apps/v1
kind: Deployment 
metadata: 
  name: test
  namespace: default 
spec:
  replicas: 3
  selector: 
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: web
        image: soumnswa/httpd:v1.1    //1.1版本镜像
        imagePullPolicy: IfNotPresent

//升级应用
[root@master manifest]# kubectl apply -f test.yml 
deployment.apps/test configured
[root@master manifest]# kubectl get pods
NAME                    READY   STATUS    RESTARTS   AGE
test-6f778f5576-6ljqz   1/1     Running   0          12s
test-6f778f5576-bq7bz   1/1     Running   0          49s
test-6f778f5576-hgf5c   1/1     Running   0          14s

//查看历史发布版本
[root@master manifest]# kubectl rollout history deployment/test
deployment.apps/test 
REVISION  CHANGE-CAUSE
1         <none>
2         <none>

//查看指定版本详细信息
[root@master manifest]# kubectl rollout history deployment/test --revision=2
deployment.apps/test with revision #2
Pod Template:
  Labels:	app=web
	pod-template-hash=6f778f5576
  Containers:
   web:
    Image:	soumnswa/httpd:v1.1    #1.1镜像版本
    Port:	<none>
    Host Port:	<none>
    Environment:	<none>
    Mounts:	<none>
  Volumes:	<none>

//回滚到上一版本
[root@master manifest]# kubectl rollout undo deployment/test --to-revision=1 
deployment.apps/test rolled back

给一个应用扩容副本数为5

[root@master manifest]# kubectl scale deploy/test --replicas=5
deployment.apps/test scaled
[root@master manifest]# kubectl get pods
NAME                    READY   STATUS    RESTARTS   AGE
test-7746d6b875-6msxw   1/1     Running   0          7s
test-7746d6b875-6v9cr   1/1     Running   0          3m39s
test-7746d6b875-dlv92   1/1     Running   0          3m37s
test-7746d6b875-nwlcx   1/1     Running   0          3m38s
test-7746d6b875-qhr52   1/1     Running   0          7s

创建一个pod，其中运行着nginx、redis、memcached 3个容器

//清单文件
[root@master manifest]# cat test.yml 
---
apiVersion: apps/v1
kind: Deployment 
metadata: 
  name: test
  namespace: default 
spec:
  selector: 
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: nginx
        image: nginx
        imagePullPolicy: IfNotPresent
      - name: redis
        image: redis
        imagePullPolicy: IfNotPresent
      - name: memcached
        image: memcached
        imagePullPolicy: IfNotPresent

//查看pod
[root@master manifest]# kubectl apply -f test.yml 
deployment.apps/test created
[root@master manifest]# kubectl get pods
NAME                    READY   STATUS    RESTARTS   AGE
test-77d687f47b-nr9pc   3/3     Running   0          3s

给一个pod创建service，并可以通过ClusterlP/NodePort访问

//清单文件
[root@master manifest]# cat test.yml 
---
apiVersion: apps/v1
kind: Deployment 
metadata: 
  name: web
  namespace: default 
spec:
  replicas: 1
  selector: 
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: nginx
        image: nginx
        imagePullPolicy: IfNotPresent

---
apiVersion: v1
kind: Service
metadata:
  name: web
  namespace: default
spec:
  ports: 
  - port: 80
    protocol: TCP
    targetPort: 80
    nodePort: 30000
  selector:
    app: web
  type: NodePort

//运行pod
[root@master manifest]# kubectl apply -f test.yml 
deployment.apps/web created
service/web created
[root@master manifest]# kubectl get pod,svc
NAME                       READY   STATUS    RESTARTS   AGE
pod/web-59b9bb7664-ppnmh   1/1     Running   0          51s

NAME                 TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)        AGE
service/kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP        3d22h
service/web          NodePort    10.103.165.44   <none>        80:30000/TCP   51s

//NodePort访问测试
[root@master manifest]# curl 10.103.165.44
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
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>

//ClusterlP访问测试
[root@master manifest]# curl 192.168.218.133:30000
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
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>

创建deployment和service，使用busybox容器nslookup解析service

[root@master manifest]# kubectl get svc
NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)        AGE
kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP        3d22h
web          NodePort    10.103.165.44   <none>        80:30000/TCP   7m10s

[root@master manifest]# kubectl run -it b1 --image busybox -- /bin/sh
If you don't see a command prompt, try pressing enter.
/ # nslookup web.default.svc.cluster.local
Server:		10.96.0.10
Address:	10.96.0.10:53

Name:	web.default.svc.cluster.local
Address: 10.103.165.44

*** Can't find web.default.svc.cluster.local: No answer