K8s——Service、代理模式演示(二)

news2025/1/11 9:13:36

Service

演示

SVC

创建svc-deployment.yaml

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

vim svc.yaml

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

注意：svc的selector的标签一定要全都包含在deployment的labels中
创建deploymen、svc

kubectl apply -f svc-deployment.yaml
kuebctl apply -f  svc.yaml

查看

[root@master ~]# kubectl get pod -o wide
NAME                           READY   STATUS    RESTARTS   AGE    IP               NODE    NOMINATED NODE   READINESS GATES
myapp-deploy-bfd7cc44f-qcnhw   1/1     Running   0          102m   10.244.166.177   node1   <none>           <none>
myapp-deploy-bfd7cc44f-txcxf   1/1     Running   0          102m   10.244.166.176   node1   <none>           <none>
myapp-deploy-bfd7cc44f-wbrhh   1/1     Running   0          102m   10.244.104.28    node2   <none>           <none>
8    node2   <none>           <none>

查看svc

[root@apiserver ~]# kubectl get svc
NAME         TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
myapp        ClusterIP   10.102.30.82   <none>        80/TCP    39s

访问验证
通过svc IP访问pod

curl 10.102.30.82

Headless Service

有时不需要或不想要负载均衡，以及单独的 Service IP 。遇到这种情况，可以通过指定 ClusterIP(spec.clusterIP) 的值为“None”来创建 Headless Service 。这类 Service 并不会分配 Cluster IP， kube-proxy 不会处理它们，而且平台也不会为它们进行负载均衡和路由

演示

示例
创建svc-none.yaml文件

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

创建Svc

kubectl apply -f svc-none.yaml

查看

[root@apiserver ~]# kubectl get svc
NAME             TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
myapp-headless   ClusterIP   None           <none>        80/TCP    8s

查看Headles Service代理IP

#使用dig需要
yum -y install bind-utils
dig -t A myapp-headless.default.svc.cluster.local. @192.168.137.141

#解释：
myapp-headless.：svc的名字
default：命名空间
svc.cluster.local. ：默认域名
@192.168.137.14 ：coredns的IP

查看coredns的方法：

kubectl get pod -n kube-system

 [root@apiserver ~]# kubectl get pod -n kube-system
NAME                                       READY   STATUS    RESTARTS   AGE
coredns-6967fb4995-5fg4q                   1/1     Running   4          3d10h
coredns-6967fb4995-8v5kb                   1/1     Running   4          3d10h

连接验证

[root@apiserver ~]# dig -t A myapp-headless.default.svc.cluster.local. @192.168.137.141

; <<>> DiG 9.11.4-P2-RedHat-9.11.4-9.P2.el7 <<>> -t A myapp-headless.default.svc.cluster.local. @192.168.137.141
;; global options: +cmd
;; Got answer:
;; WARNING: .local is reserved for Multicast DNS
;; You are currently testing what happens when an mDNS query is leaked to DNS
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 32737
;; flags: qr aa rd; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;myapp-headless.default.svc.cluster.local. IN A

;; ANSWER SECTION:
myapp-headless.default.svc.cluster.local. 30 IN	A 192.168.102.186
myapp-headless.default.svc.cluster.local. 30 IN	A 192.168.102.185
myapp-headless.default.svc.cluster.local. 30 IN	A 192.168.102.189

;; Query time: 1 msec
;; SERVER: 192.168.137.141#53(192.168.137.141)
;; WHEN: 三 1月 01 02:09:09 CST 2020
;; MSG SIZE  rcvd: 237

curl 192.168.102.189就能访问页面

NodePort

nodePort 的原理在于在 node 上开了一个端口，将向该端口的流量导入到 kube-proxy，然后由 kube-proxy 进
一步到给对应的 pod

演示

创建nodeport.yaml

apiVersion: v1
kind: Service
metadata:
  name: myapp
  namespace: default
spec:
  type: NodePort
  selector:
     app: myapp
     release: stabel
  ports:
   - name: http
     port: 80
     targetPort: 80

创建svc

kubectl apply -f nodeport.yaml

查看svc

[root@apiserver ~]# kubectl get  svc
NAME             TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)        AGE
myapp            NodePort    10.102.30.82   <none>        80:30250/TCP   83m

访问验证
在网页上输入master或者node节点的IP+30250就能访问
在这里插入图片描述

LoadBalancer

LoadBalancer和nodePort其实是同一种方式，区别在于loadBalancer比nodePort多了一步，就是可以调用cloud provider去创建LB来向节点导流。（收费服务）
在这里插入图片描述

类型ExternalName

类型为 ExternalName 的服务将服务映射到 DNS 名称，而不是典型的选择器，例如 my-service 或者 cassandra。您可以使用 spec.externalName 参数指定这些服务。

演示

例如，以下 Service 定义将 prod 名称空间中的 my-service 服务映射到 hub.kxq.com：
示例：
创建
vim external.yaml

apiVersion: v1
kind: Service
metadata:
  name: my-service
  namespace: prod
spec:
  type: ExternalName
  externalName: hub.kxq.com

注意：前提必须有prod的namespace没有的话，需要先创建：
创建svc

kubectl create namespace prod

检查是否有prod这个命名空间

kubectl get namespaces

kubectl apply -f external.yaml

查看
会发现EXTERNAL-IP 以变为我修改的名字

[root@apiserver ~]# kubectl get svc -n prod
NAME             TYPE           CLUSTER-IP     EXTERNAL-IP   PORT(S)        AGE
my-service-1     ExternalName   <none>         hub.kxq.com   <none>         10s

dig解析查看

[root@apiserver ~]# dig -t A my-service-1.prod.hub.kxq.com. @192.168.137.141

;; ANSWER SECTION:
my-service-1.default.svc.cluster.local.	30 IN CNAME hub.kxq.com.
hub.kxq.com.		30	IN	A	199.59.241.250