Service

9. Service

  • 什么是Service概述
Service可以简单的理解为逻辑上的一组Pod。一种可以访问Pod策略，而且其它Pod可以通过这个Service访问到这个Service代理的Pod。相对于Pod而言，它会有一个固定的名称，一旦创建就固定不变
  • 前言-一会用到

Pod的IP地址每一次重启之后都是变化的 ,svc会通过标签的方式去关联对应的pod。无须关心Pod的IP地址的变化，如果有删除或者重启它的IP地址都会加入到这个ep资源 svc在进行关联

[root@master01 deployment]# kubectl apply -f nginx-deployment.yaml 
deployment.apps/nginx created
[root@master01 deployment]# kubectl get pods
NAME                     READY   STATUS    RESTARTS   AGE
nginx-66bbc9fdc5-wxwvd   1/1     Running   0          3s
nginx-66bbc9fdc5-xksz7   1/1     Running   0          3s
[root@master01 deployment]# kubectl get pods
NAME                     READY   STATUS    RESTARTS   AGE
nginx-66bbc9fdc5-wxwvd   1/1     Running   0          4s
nginx-66bbc9fdc5-xksz7   1/1     Running   0          4s
[root@master01 deployment]# kubectl get pods -o wide
NAME                     READY   STATUS    RESTARTS   AGE   IP               NODE     NOMINATED NODE   READINESS GATES
nginx-66bbc9fdc5-wxwvd   1/1     Running   0          12s   10.244.186.218   node03   <none>           <none>
nginx-66bbc9fdc5-xksz7   1/1     Running   0          12s   10.244.140.84    node02   <none>           <none>
[root@master01 deployment]# curl 10.244.140.84
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
 
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
 
<p><em>Thank you for using nginx.</em></p>
</body>
</html>

9.1 定义一个svc

[root@master01 svc]# cat nginx-svc.yaml 
apiVersion: v1
kind: Service
metadata:
  labels:
    app: nginx-svc
  name: nginx-svc
spec:
  ports:
  - name: http   #Service端口的名称
    port: 80     #Service自己的端口
    protocol: TCP #支持UDP TCP SCTP 默认TCP
    targetPort: 80 #后端应用的端口
  - name: https
    port: 443
    protocol: TCP
    targetPort: 443
  selector:
    app: nginx
  sessionAffinity: None
  type: ClusterIP
 
#可以看出curl一下Pod的IP地址是可以访问的
[root@master01 svc]# kubectl create -f nginx-svc.yaml 
service/nginx-svc created
[root@master01 svc]# kubectl get svc
NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
kubernetes   ClusterIP   10.254.0.1      <none>        443/TCP          20h
nginx-svc    ClusterIP   10.254.172.22   <none>        80/TCP,443/TCP   3s
[root@master01 svc]# kubectl get pods -o wide
NAME                     READY   STATUS    RESTARTS   AGE     IP               NODE     NOMINATED NODE   READINESS GATES
busybox                  1/1     Running   0          2m41s   10.244.186.226   node03   <none>           <none>
nginx-66bbc9fdc5-wxwvd   1/1     Running   1          51m     10.244.186.224   node03   <none>           <none>
nginx-66bbc9fdc5-xksz7   1/1     Running   1          51m     10.244.140.85    node02   <none>           <none>
[root@master01 svc]# curl 10.244.186.224
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
 
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
 
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
 
#curl 一下svc的IP地址 也是可以访问的
[root@master01 svc]# kubectl get svc -o wide --show-labels 
NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE    SELECTOR    LABELS
kubernetes   ClusterIP   10.254.0.1      <none>        443/TCP          20h    <none>      component=apiserver,provider
nginx-svc    ClusterIP   10.254.172.22   <none>        80/TCP,443/TCP   7m4s   app=nginx   app=nginx-svc
[root@master01 svc]# curl 10.254.172.22
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
 
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
 
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
 
#查看一下ep资源有没有对应的记录 可以看到有对应的IP
[root@master01 svc]# kubectl describe svc nginx-svc 
Name:              nginx-svc
Namespace:         default
Labels:            app=nginx-svc
Annotations:       <none>
Selector:          app=nginx
Type:              ClusterIP
IP:                10.254.172.22
Port:              http  80/TCP
TargetPort:        80/TCP
Endpoints:         10.244.140.85:80,10.244.186.224:80
Port:              https  443/TCP
TargetPort:        443/TCP
Endpoints:         10.244.140.85:443,10.244.186.224:443
Session Affinity:  None
Events:            <none>
  • 查看svc的名称是否能解析
#是看到可以访问的
 
[root@master01 svc]# kubectl exec -it busybox -- sh
#没有curl命令就使用wget
 
/ # wget http://nginx-svc
Connecting to nginx-svc (10.254.172.22:80)
index.html           100% |*********************************************************************|   612   0:00:00 ETA
/ # cat index.html 
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
 
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
 
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
 
#这个是跨namespace去访问
/ # wget http://nginx-svc.default
Connecting to nginx-svc.default (10.254.172.22:80)
wget: can't open 'index.html': File exists

9.2 使用Service代理k8s外部应用

希望在生产环境中使用某个固定的名称而非IP地址进行访问外部的中间件服务
希望Service指向另一个Namespace中或其它集群的服务，但是不推荐这样做（service代理到另一service）
某个项目正在迁移至k8s集群，但是一部分服务仍然在集群外部，此时可以使用service代理至k8s集群外部的服务
  • service代理外部的应用
#关闭标签选择器 他就不会自动的创建ep资源
#其实443端口可以删除掉 svc ep 我就没删除
 
[root@master01 svc]# cat nginx-svc-external.yaml 
apiVersion: v1
kind: Service
metadata:
  labels:
    app: nginx-svc-external
  name: nginx-svc-external
spec:
  ports:
  - name: http   #Service端口的名称
    port: 80     #Service自己的端口
    protocol: TCP #支持UDP TCP SCTP 默认TCP
    targetPort: 80 #后端应用的端口
  - name: https
    port: 443
    protocol: TCP
    targetPort: 443
#  selector:
#    app: nginx
  sessionAffinity: None
  type: ClusterIP
 
#自己创建一个ep资源 把IP地址换成了百度的地址了 然后需要注意的是下面的ports.name的名字都需要与svc的名字相关联 名字要一致
[root@master01 svc]# cat nginx-ep-external.yaml 
apiVersion: v1
kind: Endpoints
metadata:
  labels:
    app: nginx-svc-external
  name: nginx-svc-external
  namespace: default
subsets:
- addresses:
  - ip: 110.242.68.66
  ports:
  - name: https
    port: 443
    protocol: TCP
  - name: http
    port: 80
    protocol: TCP
 
#创建ep资源 可以看到ep资源已经加进去了
[root@master01 svc]# kubectl create -f nginx-ep-external.yaml 
endpoints/nginx-svc-external created
[root@master01 svc]# kubectl get ep
NAME                 ENDPOINTS                                                           AGE
kubernetes           10.0.0.151:6443                                                     20h
nginx-svc            10.244.140.85:443,10.244.186.224:443,10.244.140.85:80 + 1 more...   40m
nginx-svc-external   110.242.68.66:443,110.242.68.66:80                                  3s
 
#测试
[root@master01 svc]# kubectl get svc
NAME                 TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
kubernetes           ClusterIP   10.254.0.1      <none>        443/TCP          21h
nginx-svc            ClusterIP   10.254.172.22   <none>        80/TCP,443/TCP   43m
nginx-svc-external   ClusterIP   10.254.29.15    <none>        80/TCP,443/TCP   10m
 
#这里curl名字不通是因为没有配置coredns
[root@master01 svc]# curl nginx-svc-external
curl: (6) Could not resolve host: nginx-svc-external; Unknown error
 
#访问地址可以看到已经被代理到百度上面去了
[root@master01 svc]# curl 10.254.29.15 -I
HTTP/1.1 200 OK
Date: Sun, 06 Nov 2022 03:28:45 GMT
Server: Apache
Last-Modified: Tue, 12 Jan 2010 13:48:00 GMT
ETag: "51-47cf7e6ee8400"
Accept-Ranges: bytes
Content-Length: 81
Cache-Control: max-age=86400
Expires: Mon, 07 Nov 2022 03:28:45 GMT
Connection: Keep-Alive
Content-Type: text/html
 
#如果想代理到别的服务上面去只需要更改ep资源的IP地址

9.3 Service类型

  • ClusterIP
#ClusterIP: 默认的类型，用于k8s内部之间的服务访问，即通过内部的service ip实现服务间的访问，service ip 仅可以在内部访问，不能从外部访问
ClusterIP:在集群中内部使用，也是默认值
ExternalName:通过返回定义的CNAME别名			不常用
NodePort:在所有安装了kube-proxy的节点上打开一个端口，此端口代理至后端的Pod,集群外部可以使用节点的IP地址和NodePort的端口号访问到集群Pod的服务，NodePort端口范围默认是30000-32767
#kubeadm 更改NodePort地址 
[root@master01 svc]# cat /etc/kubernetes/manifests/kube-apiserver.yaml
 #增加一处
 - --service-node-port-range=10000-20000
  • NodePort
#NodePort: 在clusterIP的基础之上，通过在每个node节点监听一个可以指定宿主机端口nodePort来暴露服务，从而允许外部client访问k8s集群中的服务，nodePort把外部client的请求转发至service进行处理
 
#要更改类型nodeport 也可以指定一个nodeport端口 如果不指定它会随机生成端口 范围：30000-32767
#然后宿主机就可以通过IP加端口方式访问了 每一个节点都可以访问
spec:
  clusterIP: 10.254.172.22
  externalTrafficPolicy: Cluster
  ports:
  - name: http
    nodePort: 31000
    port: 80
    protocol: TCP
    targetPort: 80
  - name: https
    nodePort: 32141
    port: 443
    protocol: TCP
    targetPort: 443
  selector:
    app: nginx
  sessionAffinity: None
  type: NodePort
  • LoadBalancer
#LoadBalancer：主要在公有云如阿里云、AWS上使用，LoadBalancer构建在nodePort基础之上，通过公有云服务商提供的负载均衡器将k8s集群中的服务暴露给集群外部的client访问
LoadBalancer:使用云提供商的负载均衡器公开服务
 
root@k8s-master1:~/4.Ingress-cases# cat 0.1.loadbalancer-dashboard.yaml 
kind: Service
apiVersion: v1
metadata:
  namespace: kubernetes-dashboard 
  name: dashboard-lb
  labels:
    k8s-app: kubernetes-dashboard
spec:
  ports:
    - protocol: TCP
      port: 8443
      targetPort: 8443
      nodePort: 30063
  type: LoadBalancer
  selector:
     k8s-app: kubernetes-dashboard
  • ExtemalName 功能类似于302
ExtemalName：用于将k8s集群外部的服务映射至k8s集群内部访问，从而让集群内部的pod能够通过固定的service name 访问集群外部的服务，有时候也用于将不同namespace之间的pod通过ExtemalName进行访问
root@k8s-master1:~/4.Ingress-cases# cat 0.2.externalName.yaml 
apiVersion: v1
kind: Service
metadata:
  name: my-external-test-name
  namespace: default
spec:
  type: ExternalName  #service类型
  externalName: www.nbrhce.com   #外部域名
 
root@k8s-master1:~/4.Ingress-cases# kubectl get svc 
NAME                    TYPE           CLUSTER-IP       EXTERNAL-IP      PORT(S)        AGE
kubernetes              ClusterIP      10.100.0.1       <none>           443/TCP        23d
my-external-test-name   ExternalName   <none>           www.nbrhce.com   <none>         5s
nginx-service           NodePort       10.100.219.106   <none>           88:14729/TCP   17h
 
#找个在同一个名称空间下测试访问 ping这个svc名字是可以通的
[root@net-test /]# ping my-external-test-name
  • Endpoints
root@k8s-master1:~/4.Ingress-cases# cat 0.3.Endpoints.yaml 
apiVersion: v1
kind: Service
metadata:
  name: mysql-production-server-name
  namespace: default
spec:
  ports:
    - port: 3306
---
kind: Endpoints
apiVersion: v1
metadata:
  name: mysql-production-server-name
  namespace: default
subsets:
  - addresses:
      - ip: 172.31.7.106
    ports:
      - port: 3306
posted @   YIDADA-SRE  阅读(219)  评论(0)  编辑  收藏  举报
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