Kubernetes之Service
- Service的概念
- Service的类型
- Service演示案例
- 环境准备
- ClusterIP(集群内部访问)
- Iptables
- IPVS
- Endpoint
- NodePort(对外暴露应用)
- LoadBalancer(对外暴露应用,适用于公有云)
- Ingress
- 搭建Ingress环境
- 演示案例环境准备
- 配置http代理
Service的概念
Kubernetes Pod是有生命周期的,它们可以被创建,也可以被销毁,然而一旦被销毁生命就永远结束,每个Pod都会获取它自己的IP地址,可Pod一旦销毁并重新创建后,IP地址就会发生改变。这时候我们需要通过k8s中的Service访问整个Pod集群,只要Service不被销毁,Pod就算不断发生变化,入口访问的IP总是固定的。
Service资源用于为Pod对象提供一个固定、统一的访问入口及负载均衡的能力,并借助新一代DNS系统的服务发现功能,解决客户端发现并访问容器化应用的问题。
Kubernetes中的Service是一种逻辑概念。它定义了一个Pod逻辑集合以及访问它们的策略,Service与Pod的关联同样是通过Label完成的。Service的目标是提供一种桥梁,它会为访问者提供一个固定的访问IP地址,用于在访问时重定向到相应的后端。
Service的类型
- ClusterIP:默认值,K8S系统给Service自动分配的虚拟IP,只能在集群内部访问。一个Service可能对应多个EndPoint(Pod),Client访问的是Cluster IP,通过iptables规则转到Real Server,从而达到负载均衡的效果;
- NodePort:将Service通过指定的Node上的端口暴露给外部,访问任意一个;
- LoadBalancer:在NodePort的基础上,借助Cloud Provider创建一个外部的负载均衡器,并将请求转发到:NodePort,此模式只能在云服务器上使用;
- ExternalName:将服务通过DNS CNAME记录方式转发到指定的域名(通过spec.externlName设定);
Service演示案例
环境准备
在同一个Namespace下启动三个不同的pod
apiVersion: apps/v1
kind: Deployment
metadata:name: pc-deploymentnamespace: bubble-dev
spec:replicas: 3selector:matchLabels:app: nginx-podtemplate:metadata:labels:app: nginx-podspec:containers: - name: nginximage: nginx:1.17.9ports:- containerPort: 80
kubectl delete ns bubble-dev
kubectl create ns bubble-dev
vi pc-deployment.yaml
cat pc-deployment.yaml
kubectl create -f pc-deployment.yaml
修改每个Pod里面的Nginx容器信息
kubectl get pod -n bubble-dev -o wide --show-labels
为了方便测试查看的效果,修改每个Nginx中的index.html页面为对应的IP地址
kubectl exec -it pc-deployment-97b5dbd78-66k25 -n bubble-dev /bin/sh
echo "node1节点 172.17.0.3" > /usr/share/nginx/html/index.html
exit
kubectl exec -it pc-deployment-97b5dbd78-lwws7 -n bubble-dev /bin/sh
echo "node1节点 172.17.0.2" > /usr/share/nginx/html/index.html
exit
kubectl exec -it pc-deployment-97b5dbd78-sm8q5 -n bubble-dev /bin/sh
echo "node2节点 172.17.0.4" > /usr/share/nginx/html/index.html
exit
ClusterIP(集群内部访问)
apiVersion: v1
kind: Service
metadata:name: svc-clusteripnamespace: bubble-dev
spec:selector:app: nginx-podclusterIP: # Service的ip地址,如果不写默认会生成一个随机的IPtype: ClusterIPports:- port: 80 # Service端口targetPort: 80 # Pod端口
vi svc-clusterip.yaml
cat svc-clusterip.yaml
kubectl create -f svc-clusterip.yaml
kubectl describe svc svc-clusterip -n bubble-dev
在node1节点上执行
curl 10.96.26.149
每隔1s访问Nginx集群的IP
while true ;do curl 10.96.26.149 ; sleep 1;done;
分发策略:默认是随机或者轮询,自定义改成固定IP访问,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
apiVersion: v1
kind: Service
metadata:name: svc-clusteripnamespace: bubble-dev
spec:selector:app: nginx-podclusterIP: # Service的ip地址,如果不写默认会生成一个随机的IPtype: ClusterIPports:- port: 80 # Service端口targetPort: 80 # pod端口sessionAffinity: ClientIP
kubectl delete -f svc-clusterip.yaml
rm -rf svc-clusterip.yaml
vi svc-clusterip.yaml
cat svc-clusterip.yaml
kubectl create -f svc-clusterip.yaml
kubectl describe svc svc-clusterip -n bubble-dev
每隔1s访问Nginx集群的IP
while true ;do curl 10.96.213.94 ; sleep 1;done;
Iptables
查看iptables的规则
iptables -t nat -nL |grep 80
Iptables使用NAT等技术将virtualIP的流量转至endpoint中,容器内暴露的端口是80。kube-proxy 通过iptables处理Service的过程,需要在宿主机上设置相当多的iptables规则,如果宿主机有大量的Pod,不断刷新iptables规则,会消耗大量的CPU资源。
IPVS
IPVS模式的Service,可以使K8S集群支持更多量级的Pod。Pod和Service通信:通过iptables或ipvs实现通信,ipvs取代不了iptables,因为ipvs只能做负载均衡,而做不了NAT转换。
Endpoint
Endpoint是Kubernetes中的一个资源对象,存储在etcd中,用于记录一个Service对应的所有Pod的访问地址,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。
kubectl get endpoints -n bubble-dev -o wide
NodePort(对外暴露应用)
在每个节点启用一个端口来暴露服务,可以在集群外部访问,通过NodeIP:NodePort访问。
apiVersion: v1
kind: Service
metadata:name: svc-nodeportnamespace: bubble-dev
spec:selector:app: nginx-podtype: NodePort # Service类型ports:- port: 80nodePort: 30008 # 指定绑定的node端口(默认的取值范围是: 30000-32767),如果不指定,则会默认分配targetPort: 80
kubectl delete -f svc-clusterip.yaml
vi svc-nodeport.yaml
cat svc-nodeport.yaml
kubectl create -f svc-nodeport.yaml
kubectl describe svc svc-nodeport -n bubble-dev
使用NodeIP:NodePort从外部访问 http://192.168.102.160:30008/
LoadBalancer(对外暴露应用,适用于公有云)
与NodePort类似,在每个节点启用一个端口来暴露服务。除此之外,K8S请求底层云平台的负载均衡器,把每个NodeIP:NodePort作为后端添加进去。
Ingress
由于在Pod数量多的时候,NodePort性能会急剧下降,如果K8S集群有成百上千的服务需要管理成百上千个NodePort,非常不友好。Ingress和Service、Deployment一样,Ingress也是K8S的资源类型,Ingress实现用域名的方式访问K8S集群的内部应用,Ingress受命名空间隔离。
Ingress文档
搭建Ingress环境
mkdir -p /home/ingress-controller
cd /home/ingress-controller
下载文件
wget https://raw.githubusercontent.com/kubernetes/ingress-nginx/nginx-0.30.0/deploy/static/mandatory.yaml
wget https://raw.githubusercontent.com/kubernetes/ingress-nginx/nginx-0.30.0/deploy/static/provider/baremetal/service-nodeport.yaml
如果下载不了,可以自行使用翻墙工具下载该文件或者直接使用我下面贴出来的文件
mandatory.yaml
apiVersion: v1
kind: Namespace
metadata:name: ingress-nginxlabels:app.kubernetes.io/name: ingress-nginxapp.kubernetes.io/part-of: ingress-nginx---kind: ConfigMap
apiVersion: v1
metadata:name: nginx-configurationnamespace: ingress-nginxlabels:app.kubernetes.io/name: ingress-nginxapp.kubernetes.io/part-of: ingress-nginx---
kind: ConfigMap
apiVersion: v1
metadata:name: tcp-servicesnamespace: ingress-nginxlabels:app.kubernetes.io/name: ingress-nginxapp.kubernetes.io/part-of: ingress-nginx---
kind: ConfigMap
apiVersion: v1
metadata:name: udp-servicesnamespace: ingress-nginxlabels:app.kubernetes.io/name: ingress-nginxapp.kubernetes.io/part-of: ingress-nginx---
apiVersion: v1
kind: ServiceAccount
metadata:name: nginx-ingress-serviceaccountnamespace: ingress-nginxlabels:app.kubernetes.io/name: ingress-nginxapp.kubernetes.io/part-of: ingress-nginx---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:name: nginx-ingress-clusterrolelabels:app.kubernetes.io/name: ingress-nginxapp.kubernetes.io/part-of: ingress-nginx
rules:- apiGroups:- ""resources:- configmaps- endpoints- nodes- pods- secretsverbs:- list- watch- apiGroups:- ""resources:- nodesverbs:- get- apiGroups:- ""resources:- servicesverbs:- get- list- watch- apiGroups:- ""resources:- eventsverbs:- create- patch- apiGroups:- "extensions"- "networking.k8s.io"resources:- ingressesverbs:- get- list- watch- apiGroups:- "extensions"- "networking.k8s.io"resources:- ingresses/statusverbs:- update---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: Role
metadata:name: nginx-ingress-rolenamespace: ingress-nginxlabels:app.kubernetes.io/name: ingress-nginxapp.kubernetes.io/part-of: ingress-nginx
rules:- apiGroups:- ""resources:- configmaps- pods- secrets- namespacesverbs:- get- apiGroups:- ""resources:- configmapsresourceNames:# Defaults to "<election-id>-<ingress-class>"# Here: "<ingress-controller-leader>-<nginx>"# This has to be adapted if you change either parameter# when launching the nginx-ingress-controller.- "ingress-controller-leader-nginx"verbs:- get- update- apiGroups:- ""resources:- configmapsverbs:- create- apiGroups:- ""resources:- endpointsverbs:- get---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: RoleBinding
metadata:name: nginx-ingress-role-nisa-bindingnamespace: ingress-nginxlabels:app.kubernetes.io/name: ingress-nginxapp.kubernetes.io/part-of: ingress-nginx
roleRef:apiGroup: rbac.authorization.k8s.iokind: Rolename: nginx-ingress-role
subjects:- kind: ServiceAccountname: nginx-ingress-serviceaccountnamespace: ingress-nginx---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:name: nginx-ingress-clusterrole-nisa-bindinglabels:app.kubernetes.io/name: ingress-nginxapp.kubernetes.io/part-of: ingress-nginx
roleRef:apiGroup: rbac.authorization.k8s.iokind: ClusterRolename: nginx-ingress-clusterrole
subjects:- kind: ServiceAccountname: nginx-ingress-serviceaccountnamespace: ingress-nginx---apiVersion: apps/v1
kind: Deployment
metadata:name: nginx-ingress-controllernamespace: ingress-nginxlabels:app.kubernetes.io/name: ingress-nginxapp.kubernetes.io/part-of: ingress-nginx
spec:replicas: 1selector:matchLabels:app.kubernetes.io/name: ingress-nginxapp.kubernetes.io/part-of: ingress-nginxtemplate:metadata:labels:app.kubernetes.io/name: ingress-nginxapp.kubernetes.io/part-of: ingress-nginxannotations:prometheus.io/port: "10254"prometheus.io/scrape: "true"spec:# wait up to five minutes for the drain of connectionsterminationGracePeriodSeconds: 300serviceAccountName: nginx-ingress-serviceaccountnodeSelector:kubernetes.io/os: linuxcontainers:- name: nginx-ingress-controllerimage: quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.30.0args:- /nginx-ingress-controller- --configmap=$(POD_NAMESPACE)/nginx-configuration- --tcp-services-configmap=$(POD_NAMESPACE)/tcp-services- --udp-services-configmap=$(POD_NAMESPACE)/udp-services- --publish-service=$(POD_NAMESPACE)/ingress-nginx- --annotations-prefix=nginx.ingress.kubernetes.iosecurityContext:allowPrivilegeEscalation: truecapabilities:drop:- ALLadd:- NET_BIND_SERVICE# www-data -> 101runAsUser: 101env:- name: POD_NAMEvalueFrom:fieldRef:fieldPath: metadata.name- name: POD_NAMESPACEvalueFrom:fieldRef:fieldPath: metadata.namespaceports:- name: httpcontainerPort: 80protocol: TCP- name: httpscontainerPort: 443protocol: TCPlivenessProbe:failureThreshold: 3httpGet:path: /healthzport: 10254scheme: HTTPinitialDelaySeconds: 10periodSeconds: 10successThreshold: 1timeoutSeconds: 10readinessProbe:failureThreshold: 3httpGet:path: /healthzport: 10254scheme: HTTPperiodSeconds: 10successThreshold: 1timeoutSeconds: 10lifecycle:preStop:exec:command:- /wait-shutdown---apiVersion: v1
kind: LimitRange
metadata:name: ingress-nginxnamespace: ingress-nginxlabels:app.kubernetes.io/name: ingress-nginxapp.kubernetes.io/part-of: ingress-nginx
spec:limits:- min:memory: 90Micpu: 100mtype: Container
service-nodeport.yaml
apiVersion: v1
kind: Service
metadata:name: ingress-nginxnamespace: ingress-nginxlabels:app.kubernetes.io/name: ingress-nginxapp.kubernetes.io/part-of: ingress-nginx
spec:type: NodePortports:- name: httpport: 80targetPort: 80protocol: TCP- name: httpsport: 443targetPort: 443protocol: TCPselector:app.kubernetes.io/name: ingress-nginxapp.kubernetes.io/part-of: ingress-nginx---
执行yaml文件
kubectl apply -f ./
如果执行有问题,则删除命名空间
kubectl delete ns ingress-nginx
查看信息
kubectl get pod -n ingress-nginx
kubectl get svc -n ingress-nginx
其中30755是http协议端口,30176是为 https协议端口。
演示案例环境准备
apiVersion: apps/v1
kind: Deployment
metadata:name: nginx-deploymentnamespace: bubble-dev
spec:replicas: 3selector:matchLabels:app: nx-podtemplate:metadata:labels:app: nx-podspec:containers: - name: nginximage: nginx:1.17.9ports:- containerPort: 80---apiVersion: apps/v1
kind: Deployment
metadata:name: tomcat-deploymentnamespace: bubble-dev
spec:replicas: 3selector:matchLabels:app: tc-podtemplate:metadata:labels:app: tc-podspec:containers:- name: tomcatimage: tomcat:9ports:- containerPort: 8080---apiVersion: v1
kind: Service
metadata:name: nginx-servicenamespace: bubble-dev
spec:selector:app: nx-podclusterIP: Nonetype: ClusterIPports:- port: 80targetPort: 80---apiVersion: v1
kind: Service
metadata:name: tomcat-servicenamespace: bubble-dev
spec:selector:app: tc-podclusterIP: Nonetype: ClusterIPports:- port: 8080targetPort: 8080
kubectl create ns bubble-dev
vi ingress.yaml
cat ingress.yaml
kubectl create -f ingress.yaml
kubectl get svc -n bubble-dev
配置http代理
apiVersion: extensions/v1beta1
kind: Ingress
metadata:name: ingress-httpnamespace: bubble-dev
spec:rules:- host: nginx.bubble.comhttp:paths:- path: /backend:serviceName: nginx-serviceservicePort: 80- host: tomcat.bubble.comhttp:paths:- path: /backend:serviceName: tomcat-serviceservicePort: 8080
vi ingress-http.yaml
cat ingress-http.yaml
kubectl create -f ingress-http.yaml
kubectl describe ing ingress-http -n bubble-dev
为了能看到效果,在电脑上配置host文件
C:\Windows\System32\drivers\etc
192.168.102.160 nginx.bubble.com
192.168.102.160 tomcat.bubble.com
kubectl get svc -n ingress-nginx
分别访问:
http://nginx.bubble.com:30755/
http://tomcat.bubble.com:30755/