使用k8s来部署tomcat
1、创建一个部署，并指定镜像地址

kubectl create deployment tomcat6 --image=tomcat:6.0.53-jre8

2、查看部署pod状态

kubectl get pods # 获取default名称空间下的pods
kubectl get pods --all-namespaces # 获取所有名称空间下的pods
kubectl get pods -o wide # 获取pods详细信息

3、查看所有pods,deployment,service,replicaset信息

[root@k8s-master ~]# kubectl get all
NAME                           READY   STATUS    RESTARTS   AGE
pod/tomcat6-5f7ccf4cb9-8qjhm   1/1     Running   0          19m

NAME                 TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)        AGE
service/kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP        23h
service/tomcat6      NodePort    10.96.226.207   <none>        80:32383/TCP   3m16s

NAME                      READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/tomcat6   1/1     1            1           19m

NAME                                 DESIRED   CURRENT   READY   AGE
replicaset.apps/tomcat6-5f7ccf4cb9   1         1         1       19m

4、向外部暴露service服务

kubectl expose deployment tomcat6 --port=80 --target-port=8080 --type=NodePort

–port：pod的端口
–target-port：容器端口
–type=NodePort：指定暴露的方式

5、查看暴露的service

[root@k8s-master ~]# kubectl get svc
NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)        AGE
kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP        23h
tomcat6      NodePort    10.96.226.207   <none>        80:32383/TCP   12s

在上面我们可以看到k8s向外部暴露tomcat端口为32383
结合下面信息我们可以看到tomcat6是在node3上面的

[root@k8s-master ~]# kubectl get pods -o wide
NAME                       READY   STATUS    RESTARTS   AGE   IP           NODE        NOMINATED NODE   READINESS GATES
tomcat6-5f7ccf4cb9-8qjhm   1/1     Running   0          20m   10.244.2.2   k8s-node3   <none>           <none>

这里node3的地址是192.168.1.109，所以访问192.168.1.109:32383即可访问tomcat首页

6、动态扩容
扩容三个tomcat

kubectl scale --replicas=3 deployment tomcat6

查看pod信息

[root@k8s-master ~]# kubectl get pods -o wide
NAME                       READY   STATUS    RESTARTS   AGE     IP           NODE        NOMINATED NODE   READINESS GATES
tomcat6-5f7ccf4cb9-2bjhq   1/1     Running   0          5m56s   10.244.2.3   k8s-node3   <none>           <none>
tomcat6-5f7ccf4cb9-8qjhm   1/1     Running   0          33m     10.244.2.2   k8s-node3   <none>           <none>
tomcat6-5f7ccf4cb9-s42g5   1/1     Running   0          5m56s   10.244.1.4   k8s-node2   <none>           <none>

此时使用node2地址也能访问tomcat了（http://192.168.1.105:32383/）

7、故障转移和容量伸缩
假如node3节点挂点，会重新在node2节点上拉起两个pod，保持pod数量保持3个，
假如手动stop节点上的容器，也会自动重新拉起。
重新设置pod复制数量为1时（kubectl scale --replicas=1 deployment tomcat6），会选择停掉三个pod中的两个。

8、删除

[root@k8s-master ~]# kubectl get all
NAME                           READY   STATUS    RESTARTS   AGE
pod/tomcat6-5f7ccf4cb9-2bjhq   1/1     Running   0          9m50s
pod/tomcat6-5f7ccf4cb9-8qjhm   1/1     Running   0          37m
pod/tomcat6-5f7ccf4cb9-s42g5   1/1     Running   0          9m50s

NAME                 TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)        AGE
service/kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP        23h
service/tomcat6      NodePort    10.96.226.207   <none>        80:32383/TCP   21m

NAME                      READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/tomcat6   3/3     3            3           37m

NAME                                 DESIRED   CURRENT   READY   AGE
replicaset.apps/tomcat6-5f7ccf4cb9   3         3         3       37m

可以删除deployment,service,pod

kubectl delete pod/tomcat6-5f7ccf4cb9-2bjhq
kubectl delete service/tomcat6
kubectl delete deployment.apps/tomcat6