CentOS7.2如何基于Kubernetes部署简单的应用
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以下面的图来安装一个简单的静态内容的nginx应用：
首先，我们用复制器启动一个2个备份的nginx Pod。然后在前面挂Service，一个service只能被集群内部访问，一个能被集群外的节点访问。
1. 部署nginx pod 和复制器
#cat nginx-rc.yaml apiVersion: v1 kind: ReplicationController metadata: name: nginx-controller spec: replicas: 2 selector: name: nginx template: metadata: labels: name: nginx spec: containers: - name: nginx image: nginx ports: - containerPort: 80
我们定义了一个nginx pod复制器，复制份数为2，我们使用nginx docker镜像。
执行下面的操作创建nginx pod复制器:
[root@master test]# kubectl create -f nginx-rc.yaml replicationcontrollers/nginx-controller
记得先去下载gcr.io镜像，然后改名，否则会提示失败。由于还会下载nginx镜像，所以所创建的Pod需要等待一些时间才能处于running状态。
[root@master test]# kubectl get podsNAME READY STATUS RESTARTS AGEnginx 1/1 Running 0 1dnginx-controller-dkl3v 1/1 Running 0 14snginx-controller-hxcq8 1/1 Running 0 14s
我们可以使用describe 命令查看pod的相关信息:
[root@master test]# kubectl describe pod nginx-controller-dkl3vName: nginx-controller-dkl3vNamespace: defaultImage(s): nginxNode: 192.168.32.17/192.168.32.17Labels: name=nginxStatus: RunningReason: Message: IP: 172.17.67.2Replication Controllers: nginx-controller (2/2 replicas created)Containers: nginx: Image: nginx State: Running Started: Wed, 30 Dec 2015 02:03:19 -0500 Ready: True Restart Count: 0Conditions: Type Status Ready True Events: FirstSeen LastSeen Count From SubobjectPath Reason Message Wed, 30 Dec 2015 02:03:14 -0500 Wed, 30 Dec 2015 02:03:14 -0500 1 {scheduler } scheduled Successfully assigned nginx-controller-dkl3v to 192.168.32.17 Wed, 30 Dec 2015 02:03:15 -0500 Wed, 30 Dec 2015 02:03:15 -0500 1 {kubelet 192.168.32.17} implicitly required container POD pulled Pod container image "kubernetes/pause" already present on machine Wed, 30 Dec 2015 02:03:16 -0500 Wed, 30 Dec 2015 02:03:16 -0500 1 {kubelet 192.168.32.17} implicitly required container POD created Created with docker id e88dffe46a28 Wed, 30 Dec 2015 02:03:17 -0500 Wed, 30 Dec 2015 02:03:17 -0500 1 {kubelet 192.168.32.17} implicitly required container POD started Started with docker id e88dffe46a28 Wed, 30 Dec 2015 02:03:18 -0500 Wed, 30 Dec 2015 02:03:18 -0500 1 {kubelet 192.168.32.17} spec.containers{nginx} created Created with docker id 25fcb6b4ce09 Wed, 30 Dec 2015 02:03:19 -0500 Wed, 30 Dec 2015 02:03:19 -0500 1 {kubelet 192.168.32.17} spec.containers{nginx} started Started with docker id 25fcb6b4ce092. 部署节点内部可访问的nginx service
Service的type有ClusterIP和NodePort之分，缺省是ClusterIP，这种类型的Service只能在集群内部访问。配置文件如下：
#cat nginx-service-clusterip.yaml apiVersion: v1 kind: Service metadata: name: nginx-service-clusterip spec: ports: - port: 8001 targetPort: 80 protocol: TCP selector: name: nginx
执行下面的命令创建service:
[root@master test]# kubectl create -f ./nginx-service-clusterip.yaml services/nginx-service-clusterip
查看所创建的service：
[root@master test]# kubectl get serviceNAME LABELS SELECTOR IP(S) PORT(S)kubernetes component=apiserver,provider=kubernetes10.254.0.1 443/TCPnginx-service-clusterip name=nginx 10.254.234.255 8001/TCP
上面的输出告诉我们这个 Service的Cluster IP是10.254.234.255，端口是8001。下面我们验证这个PortalNet IP的工作情况：
在192.168.32.16上执行以下命令：
[root@minion1 ~]# curl -s 10.254.234.255:8001Welcome to nginx! Welcome to nginx!
If you see this page, the nginx web server is successfully installed andworking. Further configuration is required.
For online documentation and support please refer tonginx.org.
Commercial support is available atnginx.com.Thank you for using nginx.
从前面部署复制器的部分我们知道nginx Pod运行在17节点上。上面我们特意从16代理节点上访问我们的服务来体现Service Cluster IP在所有集群代理节点的可到达性。
3. 部署外部可访问的nginx service
下面我们创建NodePort类型的Service，这种类型的Service在集群外部是可以访问。配置文件如下：
cat nginx-service-nodeport.yaml apiVersion: v1 kind: Service metadata: name: nginx-service-nodeport spec: ports: - port: 8000 targetPort: 80 protocol: TCP type: NodePort selector: name: nginx
执行如下命令创建service并进行查看：
[root@master test]# kubectl create -f ./nginx-service-nodeport.yaml You have exposed your service on an external port on all nodes in yourcluster. If you want to expose this service to the external internet, you mayneed to set up firewall rules for the service port(s) (tcp:31000) to serve traffic.See http://releases.k8s.io/HEAD/docs/user-guide/services-firewalls.md for more details.services/nginx-service-nodeport[root@master test]# kubectl get serviceNAME LABELS SELECTOR IP(S) PORT(S)kubernetes component=apiserver,provider=kubernetes10.254.0.1 443/TCPnginx-service-clusterip name=nginx 10.254.234.255 8001/TCPnginx-service-nodeport name=nginx 10.254.210.68 8000/TCP
创建service时提示需要设置firewall rules，不用去管，不影响后续操作。
查看创建的service：
[root@master test]# kubectl describe service nginx-service-nodeportName: nginx-service-nodeportNamespace: defaultLabels:Selector: name=nginxType: NodePortIP: 10.254.210.68Port: 8000/TCPNodePort: 31000/TCPEndpoints: 172.17.67.2:80,172.17.67.3:80Session Affinity: NoneNo events.
这个 Service的节点级别端口是31000。下面我们验证这个 Service的工作情况：
[root@master test]# curl -s 192.168.32.16:31000Welcome to nginx! Welcome to nginx!
If you see this page, the nginx web server is successfully installed andworking. Further configuration is required.
For online documentation and support please refer tonginx.org.
Commercial support is available atnginx.com.Thank you for using nginx.
[root@master test]# curl -s 192.168.32.17:31000Welcome to nginx! Welcome to nginx!
If you see this page, the nginx web server is successfully installed andworking. Further configuration is required.
For online documentation and support please refer tonginx.org.
Commercial support is available atnginx.com.Thank you for using nginx.
不管是从16还是17，都能访问到我们的服务。
4. 总结
本文只是一个简单的应用，在应用部署时，了解Kubernetes的应用模型是非常重要的。还需要对Kubernetes进行更深入的研究。
到此，关于"CentOS7.2如何基于Kubernetes部署简单的应用"的学习就结束了，希望能够解决大家的疑惑。理论与实践的搭配能更好的帮助大家学习，快去试试吧！若想继续学习更多相关知识，请继续关注网站，小编会继续努力为大家带来更多实用的文章！
