4.1.k8s.svc(Service)

#Service

Service为Pod提供4层负载均衡, 访问 -> Service -> Pod组

#4种类型

• ClusterIP 默认，分配一个VIP,只能内部访问
• NodePort ClusterIP基础上，在每个节点绑定一个对外访问端口
• LoadBalancer 在NodePort基础上，外部负载均衡器转发到NodePort
• ExternalName 集群外部的服务引入到集群内部来,集群内部使用

#代理模式

• iptables 代理模式

• ipvs 代理模式

  #ips轮询模式
  rr      轮询调度
  lc      最小连接数
  dh      目标哈希
  sh      源哈希
  sed     最短期望延迟
  nq      不排队调度
  

#svc-demo.yaml

#Deployment
apiVersion: apps/v1
kind: Deployment
metadata:
 name: myapp-deploy
 namespace: default
spec:
 replicas: 3
 selector:
   matchLabels:
     app: myapp
     release: s1
 template:
   metadata:
     labels:
       app: myapp
       release: s1
       env: test
   spec:
     containers:
     - name: myapp
       image: alivv/nginx:node
       imagePullPolicy: IfNotPresent
       ports:
       - name: http
         containerPort: 80

---
#ClusterIP
apiVersion: v1
kind: Service
metadata:
 name: svc-ip
 namespace: default
spec:
 type: ClusterIP
 selector:
   app: myapp
   release: s1
 ports:
 - name: http
   port: 80
   targetPort: 80

---
#Headless Service
apiVersion: v1
kind: Service
metadata:
 name: svc-headless
 namespace: default
spec:
 selector:
   app: myapp
 clusterIP: "None"
 ports: 
 - port: 80
   targetPort: 80

---
#NodePort
   apiVersion: v1
   kind: Service
   metadata:
     name: svc-port
     namespace: default
   spec:
     type: NodePort
     selector:
       app: myapp
       release: s1
     ports:
     - name: http
       port: 80
       targetPort: 80
---
#ExternalName
kind: Service
apiVersion: v1
metadata:
 name: svc-cname
 namespace: default
spec:
 type: ExternalName
 externalName: hub.elven.vip

#创建
kubectl apply -f svc-demo.yaml

#查看
kubectl  get pod
kubectl  get deployment
kubectl  get svc

##ClusterIP
#curl访问svc-ip查看轮询效果
svc_ip=$(kubectl  get svc |awk '/svc-ip/{print $3}')
for((i=1;i<10;i++));do curl $svc_ip ;done

##Headless Service  #无头service 
#不分配Cluster IP ，service name直接解析为Pod ip
#查看kube-dns ip 默认是10.96.0.10
kubectl  get svc -A |grep  kube-dns
#指定dns解析svc
dig -t A @10.96.0.10 svc-headless.default.svc.cluster.local

##NodePort
#访问node-ip:port

##ExternalName
#DNS层CNAME别名方式绑定外部地址,访问Service实际访问外部地址
#指定dns解析svc-cname，查看到cname记录
dig -t A @10.96.0.10 svc-cname.default.svc.cluster.local

#删除
kubectl  delete -f svc-demo.yaml

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Blog地址 https://www.cnblogs.com/elvi/p/11755749.html
本文git地址 https://gitee.com/alivv/k8s/tree/master/notes