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Service在Kubernetes中提供了一种抽象的方式来公开应用程序的网络访问#xff0c;并提供了负载均衡和服务发现等功能#xff0c;使得应用程序在集群内外都能够可靠地进行访问。
每个Service都会自动关联一个对应的Endpoint。当创建一个Service时#xff0c;Ku…Service概述
Service在Kubernetes中提供了一种抽象的方式来公开应用程序的网络访问并提供了负载均衡和服务发现等功能使得应用程序在集群内外都能够可靠地进行访问。
每个Service都会自动关联一个对应的Endpoint。当创建一个Service时Kubernetes会根据Service的选择器selector来找到匹配的Pod并将这些Pod的IP地址和端口信息作为Endpoint的一部分。当Service接收到来自外部或内部的请求时它会将请求转发到与之关联的Endpoint。Endpoint中包含了后端Pod的IP地址和端口信息Service会根据负载均衡算法将请求转发到一个或多个后端Pod上。并且Service会自动关联到防火墙规则 将pod的地址和端口保存在防火墙规则内
以上内容由gtp生成
举个例子以前我访问pod资源要一个一个访问现在我把一堆具有相同特征如标签的pod绑定一个service然后在service内侧与pod端口绑定service外侧映射一个端口到宿主机service还能改dns改防火墙规则。这样直接访问宿主机的端口就能访问到一组pod的特定端口。跟nginx做反向代理负载均衡差不多
#查看帮助
kubectl explain Service
apiVersion string
kind string
metadata Object
spec Object
status Objectkubectl explain Service.spec
allocateLoadBalancerNodePorts boolean#是否是默认映射端口nodeports
#如果是则会默认分配到30000-32767随机一个
clusterIP string #service的虚拟ip地址
externalIPs []string #公开到集群外的ip
externalName string #指定外部dns名称
externalTrafficPolicy string #定义外部流量策略可选cluster或local
healthCheckNodePort integer #用于健康检查的端口
sessionAffinity string #会话策略可选ClientIP或者None
type string #类型有四种ExternalName, ClusterIP, NodePort, LoadBalancer
ports []Objectkubectl explain service.spec.ports
name string
nodePort integer #对外映射的端口
port integer -required- #service的端口
protocol string #可选SCTP、TCP、UDP#在node上下载旧版本的nginx
ctr images pull docker.io/library/nginx:1.21
#创建被管理的pod的yaml文件
#
mkdir service
cd service
cat pod.yaml EOF
apiVersion: apps/v1
kind: Deployment
metadata:name: pods
spec:replicas: 2selector:matchLabels:nginx: 1.21template:metadata:labels:nginx: 1.21spec:containers:- name: test1image: docker.io/library/nginx:1.21imagePullPolicy: IfNotPresentports:- containerPort: 80startupProbe:periodSeconds: 5initialDelaySeconds: 20timeoutSeconds: 5httpGet:scheme: HTTPport: 80path: /livenessProbe:periodSeconds: 5initialDelaySeconds: 20timeoutSeconds: 5httpGet:scheme: HTTPport: 80path: /readinessProbe:periodSeconds: 5initialDelaySeconds: 20timeoutSeconds: 5httpGet:scheme: HTTPport: 80path: /
EOF
kubectl apply -f pod.yaml
#成功运行就不去用curl验证了
kubectl get pods -w
NAME READY STATUS RESTARTS AGE
pods-8599b54cf-6tzrx 0/1 Running 0 12s
pods-8599b54cf-vhxd8 0/1 Running 0 12s
pods-8599b54cf-6tzrx 0/1 Running 0 25s
pods-8599b54cf-vhxd8 0/1 Running 0 25s
pods-8599b54cf-6tzrx 1/1 Running 0 25s
pods-8599b54cf-vhxd8 1/1 Running 0 25s
ClusterIP模式
### ClusterIP模式仅允许集群内部访问
#创建servicea-clusterip.yaml
cat service-clusterip.yaml EOF
apiVersion: v1
kind: Service
metadata:name: service
spec:type: ClusterIPports:- port: 80 #service内侧端口protocol: TCPtargetPort: 80 #对应的pod的端口selector: #筛选器匹配标签nginx1.21的podnginx: 1.21
EOF
kubectl apply -f service.yaml
kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 none 443/TCP 12d
service ClusterIP 10.107.178.176 none 80/TCP 31s
#查看Endpoint列表
#只有完成就绪探测的pod才会被service接管才会被加入endpoint列表中。未完成启动探测的pod也不会
kubectl describe service service | grep Endpoint
Endpoints: 10.10.179.1:80,10.10.234.86:80
kubectl get ep service #也可以
NAME ENDPOINTS AGE
service 10.10.179.1:80,10.10.234.86:80 2m54s
#测试
curl 10.10.179.1:80
#service自动生成域名仅在pod内可以进行访问
service.default.svc.cluster.local:80
#进入pod
kubectl exec pods-8599b54cf-6tzrx -it -- /bin/sh
curl service.default.svc.cluster.local:80
!DOCTYPE html
html
head
titleWelcome 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
h1Welcome to nginx!/h1
pIf you see this page, the nginx web server is successfully installed and
working. Further configuration is required./ppFor online documentation and support please refer to
a hrefhttp://nginx.org/nginx.org/a.br/
Commercial support is available at
a hrefhttp://nginx.com/nginx.com/a./ppemThank you for using nginx./em/p
/body
/html
#清理
kubectl delete -f service-clusterip.yamlnodeport模式
#nodeport允许将ServiceIp映射到宿主机外部
#创建service-nodeport.yaml
cat service-nodeport.yaml EOF
apiVersion: v1
kind: Service
metadata:name: service
spec:type: NodePortports:- port: 80protocol: TCPtargetPort: 80 #对应的pod的端口nodePort: 30080 #映射到物理机的端口如果不写会随机分配到30000-32767之间的一个selector: #筛选器匹配标签nginx1.21的podnginx: 1.21
EOF
kubectl apply -f service-nodeport.yaml
kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 none 443/TCP 12d
service NodePort 10.108.9.134 none 80:30080/TCP 11s
#通过宿主机直接请求如图
ipvsadm -Ln | grep 30080 -A 2
TCP 172.17.0.1:30080 rr- 10.10.179.1:80 Masq 1 0 0- 10.10.234.86:80 Masq 1 0 0
--
TCP 192.168.8.160:30080 rr- 10.10.179.1:80 Masq 1 0 1- 10.10.234.86:80 Masq 1 0 0
--
TCP 192.168.122.1:30080 rr- 10.10.179.1:80 Masq 1 0 0- 10.10.234.86:80 Masq 1 0 0
--
TCP 10.10.189.192:30080 rr- 10.10.179.1:80 Masq 1 0 0- 10.10.234.86:80 Masq 1 0 0
kubectl delete -f service-nodeport.yaml ExternalName模式
充当一个别名将服务映射到集群外部的一个外部域名。当使用该服务时Kubernetes会将服务的DNS解析为ExternalName指定的外部域名从而实现对外部服务的访问。这种模式适用于需要将服务与集群外部的现有服务进行关联的场景。
#用以跨namespace调用资源
#创建一个新的ns
kubectl create ns server
#创建server中的yaml文件
cat pod-in-server.yaml EOF
apiVersion: apps/v1
kind: Deployment
metadata:name: podsnamespace: server
spec:replicas: 2selector:matchLabels:nginx: 1.21template:metadata:labels:nginx: 1.21spec:containers:- name: test1image: docker.io/library/nginx:1.21imagePullPolicy: IfNotPresent
EOF
kubectl apply -f pod-in-server.yaml
#创建pod in server中的service四层代理
cat service-in-server.yaml EOF
apiVersion: v1
kind: Service
metadata:name: service-in-servernamespace: server
spec:selector:nginx: 1.21ports:- name: httpprotocol: TCPport: 80targetPort: 80
EOF
kubectl apply -f service-in-server.yaml
#创建default中的service设置为externalname
cat service-externalname.yaml EOF
apiVersion: v1
kind: Service
metadata:name: service
spec:type: ExternalNameexternalName: service-in-server.server.svc.cluster.local #设置要关联的service的域名ports:- port: 80selector: nginx: 1.21
EOF
kubectl apply -f service-externalname.yaml
kubectl get pods -n server
NAME READY STATUS RESTARTS AGE
pods-8649769f54-fs72b 1/1 Running 0 22s
#进入默认的ns的pod中通过域名访问server的ns中的pod资源
kubectl exec pods-8599b54cf-6tzrx -it -- /bin/sh
curl service-in-server.server.svc.cluster.local
#可以访问到
!DOCTYPE html
html
head
titleWelcome 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
h1Welcome to nginx!/h1
pIf you see this page, the nginx web server is successfully installed and
working. Further configuration is required./ppFor online documentation and support please refer to
a hrefhttp://nginx.org/nginx.org/a.br/
Commercial support is available at
a hrefhttp://nginx.com/nginx.com/a./ppemThank you for using nginx./em/p
/body
/html#清理
kubectl delete -f service-externalname.yaml
kubectl delete -f service-in-server.yaml
kubectl delete -f pod-in-server.yaml
