kubernets创建Service

一、开发一个测试的docker镜像

我先写一个go的web server项目，这个项目模块名称为mystarter，下面是关键的代码部分

启动类src/main.go

package main

import (
    "mystarter/src/controller"

    "github.com/gin-gonic/gin"
)

func main() {

    router := gin.Default()

    controllers := getControllers()
    for _, controller := range controllers {
        controller.Route(router)
    }

    router.Run(":8000")
}

func getControllers() []controller.Controller {

    controllers := []controller.Controller{}
    controllers = append(controllers, &controller.SwaggerController{})
    controllers = append(controllers, &controller.HomeController{})

    return controllers
}

在src/controller/home.go中写一个得到当前服务器名称的rest请求

package controller

import (
    "net/http"
    "os"

    "github.com/gin-gonic/gin"
)

type HomeController struct {
}

func (this *HomeController) Route(router *gin.Engine) {

    router.GET("/hostname", this.hostname)
}


func (this *HomeController) hostname(ctx *gin.Context) {
    hostname, _ := os.Hostname()
    ctx.String(http.StatusOK, hostname+"
")
}

src/Dockerfile

#!/bin/bash
FROM alpine:3.13.6
#ubuntu:latest
MAINTAINER kevin "kevin@hotmail.com"

WORKDIR /home/go
COPY ./gostarter /home/go
COPY ./static /home/go/static
COPY ./template /home/go/template

ENV TZ=Asia/Shanghai
RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone

CMD ["./gostarter"]

生成镜像的脚本src/dockerbuild.sh

app=gostarter
go build -o $app --ldflags "-extldflags -static"

docker stop $app
docker rm $app
docker image rm $app
docker build -t $app .
docker run --name $app -p 8000:8000 -d $app 

# # 阿里与云个人镜像：公网
# docker tag gostarter registry.cn-beijing.aliyuncs.com/xufangbo/gostarter:v1.0.0
# docker push registry.cn-beijing.aliyuncs.com/xufangbo/gostarter:v1.0.0

二、开发kubernets的配置文件

 编辑文件gostarter.yarml,参加下文

apiVersion: apps/v1
kind: Deployment
metadata:
  name: gostarter-dep
spec:
  selector:
    matchLabels:
      app: gostarter
  replicas: 5
  template:
    metadata:
      labels:
        app: gostarter
    spec:
      containers:
      - name: gostarter
        image: registry.cn-beijing.aliyuncs.com/xufangbo/gostarter:v1.0.0
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 8000
---
apiVersion: v1
kind: Service
metadata:
  name: gostarter-svc
spec:
  selector:
    app: gostarter
  ports:
  - name: "8000"
    protocol: TCP
    # service端口，即消费者调用的端口，Service只能在k8s集群内部调用，互联网调用需要使用Ingress
    port: 8000
    # 容器端口
    targetPort: 8000

三、发布到kubernetes集群中

 1.发布到kubernets集群中

$ kubectl apply -f gostarter.yaml
deployment.apps/gostarter-dep created
service/gostarter-svc created

2.查看pod

$ kubectl get pods
NAME                            READY   STATUS    RESTARTS   AGE
busybox                         1/1     Running   0          10h
gostarter-dep-df898587f-6rvg5   1/1     Running   0          55s
gostarter-dep-df898587f-hq7cz   1/1     Running   0          55s
gostarter-dep-df898587f-qjxrj   1/1     Running   0          55s
gostarter-dep-df898587f-x54lc   1/1     Running   0          55s
gostarter-dep-df898587f-xgbz7   1/1     Running   0          55s

3.查看Servcie

$ kubectl get svc
NAME            TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE
gostarter-svc   ClusterIP   10.109.68.204   <none>        8000/TCP   91s
kubernetes      ClusterIP   10.96.0.1       <none>        443/TCP    21d

4.使用脚本测试一下

$ for i in `seq 1 10`; do curl http://10.109.68.204:8000/hostname;done
gostarter-dep-df898587f-x54lc
gostarter-dep-df898587f-hq7cz
gostarter-dep-df898587f-qjxrj
gostarter-dep-df898587f-6rvg5
gostarter-dep-df898587f-x54lc
gostarter-dep-df898587f-6rvg5
gostarter-dep-df898587f-hq7cz
gostarter-dep-df898587f-6rvg5
gostarter-dep-df898587f-qjxrj
gostarter-dep-df898587f-qjxrj

可以看到每次请求server端的hostname都不是完全相同的，说明集群起作用了

四、测试DNS

 ClusterIP方式的IP可以在集群Node上进行访问，但是kubernets的dns不能在集群的node上访问

$ curl http://gostarter-svc:8000/hostname
curl: (6) Could not resolve host: gostarter-svc

kubernets的dns可以在pod中进行访问，所以我们要创建一个pod进行访问，busybox就是比较好的方式

$ kubectl run -it --rm --image=busybox /bin/sh
# busybox的pod一次创建下次还可以使用，下次进入方式：kubectl exec busybox -it  /bin/sh

/ # rm hostname
rm: can't remove 'hostname': No such file or directory

/ # wget http://10.109.68.204:8000/hostname
Connecting to 10.109.68.204:8000 (10.109.68.204:8000)
saving to 'hostname'
hostname             100% |************************************|    30  0:00:00 ETA
'hostname' saved

/ # rm hostname

/ # wget http://gostarter-svc:8000/hostname
Connecting to gostarter-svc:8000 (10.109.68.204:8000)
saving to 'hostname'
hostname             100% |************************************|    30  0:00:00 ETA
'hostname' saved

一切都很完美，只是busybox中不支持curl，wget可读性差一些

第一次使用busybox容器dns解析也不对，又换了infoblox/dnstools镜像就行，而且busybox后来的dns也支持了，没搞明白是什么原因，下面介绍infoblox/dnstools的例子(他也支持curl)

$ kubectl run -it --rm --image=infoblox/dnstools dns-clien
If you don't see a command prompt, try pressing enter.
dnstools# for i in `seq 1 10`; do curl http://gostarter-svc:8000/hostname;done
gostarter-dep-df898587f-x54lc
gostarter-dep-df898587f-qjxrj
gostarter-dep-df898587f-qjxrj
gostarter-dep-df898587f-xgbz7
gostarter-dep-df898587f-x54lc
gostarter-dep-df898587f-x54lc
gostarter-dep-df898587f-6rvg5
gostarter-dep-df898587f-qjxrj
gostarter-dep-df898587f-6rvg5
gostarter-dep-df898587f-xgbz7

至此，本文介绍的Service使用结束