前言
- 本篇来学习Service使用
Service使用
实验准备
在使用service之前，首先利用Deployment创建出3个pod，注意要为pod设置app=nginx-pod的标签
创建deployment.yaml，内容如下：
apiVersion: apps/v1 kind: Deployment metadata: name: pc-deployment namespace: dev spec: replicas: 3 selector: matchLabels: app: nginx-pod template: metadata: labels: app: nginx-pod spec: containers: - name: nginx image: nginx:1.17.1 ports: - containerPort: 80
# 创建pod [root@master ~]# kubectl create -f deployment.yaml deployment.apps/pc-deployment created # 查看pod [root@master ~]# kubectl get pods -n dev -o wide --show-labels NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES LABELS pc-deployment-6696798b78-jhkpr 1/1 Running 0 7m58s 10.244.2.54 node3 <none> <none> app=nginx-pod,pod-template-hash=6696798b78 pc-deployment-6696798b78-k8snv 1/1 Running 0 7m58s 10.244.3.64 node2 <none> <none> app=nginx-pod,pod-template-hash=6696798b78 pc-deployment-6696798b78-kcc2h 1/1 Running 0 7m58s 10.244.3.63 node2 <none> <none> app=nginx-pod,pod-template-hash=6696798b78 # 为了方便后面的测试，修改下三台nginx的index.html页面（三台修改的IP地址不一致） # kubectl exec -it pc-deployment-6696798b78-jhkpr -n dev /bin/sh echo "10.244.2.54" > /usr/share/nginx/html/index.html # kubectl exec -it pc-deployment-6696798b78-k8snv -n dev /bin/sh echo "10.244.3.64" > /usr/share/nginx/html/index.html # kubectl exec -it pc-deployment-6696798b78-kcc2h -n dev /bin/sh echo "10.244.3.63" > /usr/share/nginx/html/index.html #修改完毕之后，访问测试 [root@master ~]# curl 10.244.2.54 10.244.2.54 [root@master ~]# curl 10.244.3.64 10.244.3.64 [root@master ~]# curl 10.244.3.63 10.244.3.63
ClusterIP类型的Service
- 创建service-clusterip.yaml文件
apiVersion: v1 kind: Service metadata: name: service-clusterip namespace: dev spec: selector: app: nginx-pod clusterIP: 10.97.97.97 # service的ip地址，如果不写，默认会生成一个 type: ClusterIP ports: - port: 80 # Service端口 targetPort: 80 # pod端口
# 创建service [root@master ~]# kubectl create -f service-clusterip.yaml service/service-clusterip created # 查看service [root@master ~]# kubectl get svc -n dev -o wide NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR service-clusterip ClusterIP 10.97.97.97 <none> 80/TCP 7s app=nginx-pod # 查看service的详细信息 # 在这里有一个Endpoints列表，里面就是当前service可以负载到的服务入口 [root@master ~]# kubectl describe svc service-clusterip -n dev Name: service-clusterip Namespace: dev Labels: <none> Annotations: <none> Selector: app=nginx-pod Type: ClusterIP IP: 10.97.97.97 Port: <unset> 80/TCP TargetPort: 80/TCP Endpoints: 10.244.2.54:80,10.244.3.63:80,10.244.3.64:80 Session Affinity: None Events: <none> # 查看ipvs的映射规则 [root@master ~]# ipvsadm -Ln IP Virtual Server version 1.2.1 (size=4096) Prot LocalAddress:Port Scheduler Flags -> RemoteAddress:Port Forward Weight ActiveConn InActConn TCP 10.97.97.97:80 rr -> 10.244.2.54:80 Masq 1 0 0 -> 10.244.3.63:80 Masq 1 0 0 -> 10.244.3.64:80 Masq 1 0 0 # 访问10.97.97.97:80观察效果 [root@master ~]# curl 10.97.97.97:80 10.244.3.64
Endpoint
Endpoint是kubernetes中的一个资源对象，存储在etcd中，用来记录一个service对应的所有pod的访问地址，它是根据service配置文件中selector描述产生的。
一个Service由一组Pod组成，这些Pod通过Endpoints暴露出来，Endpoints是实现实际服务的端点集合。换句话说，service和pod之间的联系是通过endpoints实现的。
负载分发策略
对Service的访问被分发到了后端的Pod上去，目前kubernetes提供了两种负载分发策略：
- 如果不定义，默认使用kube-proxy的策略，比如随机、轮询
- 基于客户端地址的会话保持模式，即来自同一个客户端发起的所有请求都会转发到固定的一个Pod上
此模式可以使在spec中添加sessionAffinity:ClientIP选项
NAME ENDPOINTS AGE nginx 10.244.3.62:80 12d service-clusterip 10.244.2.54:80,10.244.3.63:80,10.244.3.64:80 15m # 查看ipvs的映射规则（rr 轮询） [root@master ~]# ipvsadm -Ln IP Virtual Server version 1.2.1 (size=4096) Prot LocalAddress:Port Scheduler Flags -> RemoteAddress:Port Forward Weight ActiveConn InActConn TCP 10.97.97.97:80 rr -> 10.244.2.54:80 Masq 1 0 0 -> 10.244.3.63:80 Masq 1 0 0 -> 10.244.3.64:80 Masq 1 0 0 # 循环访问测试 [root@master ~]# while true;do curl 10.97.97.97:80; sleep 5; done; 10.244.3.63 10.244.2.54 10.244.3.64 10.244.3.63 10.244.2.54 10.244.3.64 10.244.3.63 # 删除service [root@master ~]# kubectl delete -f service-clusterip.yaml service "service-clusterip" deleted # 修改分发策略 添加 sessionAffinity:ClientIP [root@master ~]# vim service-clusterip.yaml # 重新创建 [root@master ~]# kubectl create -f service-clusterip.yaml service/service-clusterip created # 查看ipvs规则【persistent 代表持久】 [root@master ~]# ipvsadm -Ln IP Virtual Server version 1.2.1 (size=4096) Prot LocalAddress:Port Scheduler Flags -> RemoteAddress:Port Forward Weight ActiveConn InActConn TCP 10.97.97.97:80 rr persistent 10800 -> 10.244.2.54:80 Masq 1 0 0 -> 10.244.3.63:80 Masq 1 0 0 -> 10.244.3.64:80 Masq 1 0 0 # 循环访问测试 [root@master ~]# while true;do curl 10.97.97.97; sleep 5; done; 10.244.3.64 10.244.3.64 10.244.3.64 10.244.3.64 # 删除service [root@master ~]# kubectl delete -f service-clusterip.yaml service "service-clusterip" deleted
HeadLiness类型的Service
在某些场景中，开发人员可能不想使用Service提供的负载均衡功能，而希望自己来控制负载均衡策略，针对这种情况，kubernetes提供了HeadLiness Service，这类Service不会分配Cluster IP，如果想要访问service，只能通过service的域名进行查询。
- 创建service-headliness.yaml
apiVersion: v1 kind: Service metadata: name: service-headliness namespace: dev spec: selector: app: nginx-pod clusterIP: None # 将clusterIP设置为None，即可创建headliness Service type: ClusterIP ports: - port: 80 targetPort: 80
# 创建service [root@master ~]# kubectl create -f service-headliness.yaml service/service-headliness created # 获取service， 发现CLUSTER-IP未分配 [root@master ~]# kubectl get svc service-headliness -n dev -o wide NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR service-headliness ClusterIP None <none> 80/TCP 45m app=nginx-pod [root@master ~]# kubectl describe svc service-headliness -n dev Name: service-headliness Namespace: dev Labels: <none> Annotations: <none> Selector: app=nginx-pod Type: ClusterIP IP: None Port: <unset> 80/TCP TargetPort: 80/TCP Endpoints: 10.244.2.54:80,10.244.3.63:80,10.244.3.64:80 Session Affinity: None Events: <none> [root@master ~]# kubectl get pod -n dev NAME READY STATUS RESTARTS AGE pc-deployment-6696798b78-jhkpr 1/1 Running 0 112m pc-deployment-6696798b78-k8snv 1/1 Running 0 112m pc-deployment-6696798b78-kcc2h 1/1 Running 0 112m # 查看域名的解析情况 [root@master ~]# kubectl exec -it pc-deployment-6696798b78-jhkpr -n dev /bin/sh # cat /etc/resolv.conf nameserver 10.96.0.10 search dev.svc.cluster.local svc.cluster.local cluster.local options ndots:5 # exit [root@master ~]# dig @10.96.0.10 service-headliness.dev.svc.cluster.local service-headliness.dev.svc.cluster.local. 30 IN A 10.244.3.63 service-headliness.dev.svc.cluster.local. 30 IN A 10.244.2.54 service-headliness.dev.svc.cluster.local. 30 IN A 10.244.3.64
NodePort类型的Service
在之前的样例中，创建的Service的ip地址只有集群内部才可以访问，如果希望将Service暴露给集群外部使用，那么就要使用到另外一种类型的Service，称为NodePort类型。NodePort的工作原理其实就是将service的端口映射到Node的一个端口上，然后就可以通过NodeIp:NodePort来访问service了。
- 创建service-nodeport.yaml
apiVersion: v1 kind: Service metadata: name: service-nodeport namespace: dev spec: selector: app: nginx-pod type: NodePort # service类型 ports: - port: 80 nodePort: 30002 # 指定绑定的node的端口(默认的取值范围是：30000-32767), 如果不指定，会默认分配 targetPort: 80
# 创建service [root@master ~]# kubectl create -f service-nodeport.yaml service/service-nodeport created # 查看service [root@master ~]# kubectl get svc -n dev -o wide NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR service-nodeport NodePort 10.102.253.49 <none> 80:30002/TCP 7s app=nginx-pod # 接下来可以通过电脑主机的浏览器去访问集群中任意一个nodeip的30002端口，即可访问到pod http://192.168.96.100:30002/
LoadBalancer类型的Service
LoadBalancer和NodePort很相似，目的都是向外部暴露一个端口，区别在于LoadBalancer会在集群的外部再来做一个负载均衡设备，而这个设备需要外部环境支持的，外部服务发送到这个设备上的请求，会被设备负载之后转发到集群中。
ExternalName类型的Service
ExternalName类型的Service用于引入集群外部的服务，它通过externalName属性指定外部一个服务的地址，然后在集群内部访问此service就可以访问到外部的服务了。
- 创建service-externalname.yaml
apiVersion: v1 kind: Service metadata: name: service-externalname namespace: dev spec: type: ExternalName # service类型 externalName: www.baidu.com #改成ip地址也可以
# 创建service [root@master ~]# kubectl create -f service-externalname.yaml service/service-externalname created # 查看service [root@master ~]# kubectl get svc service-externalname -n dev NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE service-externalname ExternalName <none> www.baidu.com <none> 2m7s [root@master ~]# kubectl describe svc service-externalname -n dev Name: service-externalname Namespace: dev Labels: <none> Annotations: <none> Selector: <none> Type: ExternalName IP: External Name: www.baidu.com Session Affinity: None Events: <none> # 域名解析 [root@master ~]# dig @10.96.0.10 service-externalname.dev.svc.cluster.local service-externalname.dev.svc.cluster.local. 30 IN CNAME www.baidu.com. www.baidu.com. 30 IN CNAME www.a.shifen.com. www.a.shifen.com. 30 IN A 110.242.68.4 www.a.shifen.com. 30 IN A 110.242.68.3
