GO语言04（简单的RESTful API服务器，API 服务器健康状态自检）

目录

---

RESTful API服务器

1. REST Web 框架选择

    // 加载模块-处理函数模块化
    "apiserver/handler/sd"

    // 在Load函数中添加    
    //  -modify here- 添加健康检查的handler
    svcd := g.Group("/sd")
    {   
        svcd.GET("/health", sd.HealthCheck)
        svcd.GET("/disk", sd.DiskCheck)
        svcd.GET("/cpu", sd.CPUCheck)
        svcd.GET("/ram", sd.RAMCheck)
    }

/health/disk/cpu/ramsd.HealthChecksd.DiskChecksd.CPUChecksd.RAMCheckmain()router.Load

3. 服务器健康检查实现

apiserver/handler/sd/check.go

编写几个检查函数

package sd

import (
	"fmt"
	"net/http"

	"github.com/gin-gonic/gin"
	"github.com/shirou/gopsutil/cpu"
	"github.com/shirou/gopsutil/disk"
	"github.com/shirou/gopsutil/load"
	"github.com/shirou/gopsutil/mem"
)

// 定义常量
const (
	B  = 1
	KB = 1024 * B
	MB = 1024 * KB
	GB = 1024 * MB
)

// HealthCheck shows `OK` as the ping-pong result.
func HealthCheck(c *gin.Context) {
	message := "OK"
	// http.StatusOK => 所有HTTP状态码都对应到一个名字 （源码）
	c.String(http.StatusOK, "\n"+message)
}

// DiskCheck checks the disk usage.
func DiskCheck(c *gin.Context) {
    // 可查看disk.Usage的源代码，此处有2个返回值,*UsageStat, erro
	u, _ := disk.Usage("/")

	usedMB := int(u.Used) / MB
	usedGB := int(u.Used) / GB
	totalMB := int(u.Total) / MB
	totalGB := int(u.Total) / GB
	usedPercent := int(u.UsedPercent)

	status := http.StatusOK
	text := "OK"

	if usedPercent >= 95 {
		status = http.StatusInternalServerError
		text = "CRITICAL"
	} else if usedPercent >= 90 {
		status = http.StatusTooManyRequests
		text = "WARNING"
	}

	message := fmt.Sprintf("%s - Free space: %dMB (%dGB) / %dMB (%dGB) | Used: %d%%", text, usedMB, usedGB, totalMB, totalGB, usedPercent)
	c.String(status, "\n"+message)
}

// CPUCheck checks the cpu usage.
func CPUCheck(c *gin.Context) {
	cores, _ := cpu.Counts(false)

	a, _ := load.Avg()
	l1 := a.Load1
	l5 := a.Load5
	l15 := a.Load15

	status := http.StatusOK
	text := "OK"

	if l5 >= float64(cores-1) {
		status = http.StatusInternalServerError
		text = "CRITICAL"
	} else if l5 >= float64(cores-2) {
		status = http.StatusTooManyRequests
		text = "WARNING"
	}

	message := fmt.Sprintf("%s - Load average: %.2f, %.2f, %.2f | Cores: %d", text, l1, l5, l15, cores)
	c.String(status, "\n"+message)
}

// RAMCheck checks the disk usage.
func RAMCheck(c *gin.Context) {
	u, _ := mem.VirtualMemory()

	usedMB := int(u.Used) / MB
	usedGB := int(u.Used) / GB
	totalMB := int(u.Total) / MB
	totalGB := int(u.Total) / GB
	usedPercent := int(u.UsedPercent)

	status := http.StatusOK
	text := "OK"

	if usedPercent >= 95 {
		status = http.StatusInternalServerError
		text = "CRITICAL"
	} else if usedPercent >= 90 {
		status = http.StatusTooManyRequests
		text = "WARNING"
	}

	message := fmt.Sprintf("%s - Free space: %dMB (%dGB) / %dMB (%dGB) | Used: %d%%", text, usedMB, usedGB, totalMB, totalGB, usedPercent)
	c.String(status, "\n"+message)
}

4. 安装依赖并测试

mod tidy 会自动检查依赖并下载需要的内容，非常nice
```
go mod tidy 
```
这里主要是安装了：
```
go get github.com/shirou/gopsutil/cpu
go get github.com/shirou/gopsutil/disk
go get github.com/shirou/gopsutil/load
go get github.com/shirou/gopsutil/mem
```

5. 测试

命令行测试：

# curl http://localhost:8090/sd/health

OK

ApiPost测试：

6. 启动apiserver时自检

上面我们已经实现了几个接口用于获取服务器状态，但是，它需要我们主动访问才能获取状态，那么我们如何能在有问题时，直接收到提醒呢？定时任务/监控系统：编写监控脚本，有问题时提醒

启动服务时：主动检查，有问题直接停掉服务，提醒管理员

有时候 API 进程起来不代表 API 服务器正常，如API 进程存在，但是服务器却不能对外提供服务。因此在启动 API 服务器时，如果能够最后做一个自检会更好些。

在 apiserver 中添加了自检程序，通过自检可以最大程度地保证启动后的 API 服务器处于健康状态。

apiserver/main.go

定义pingServer用于检查/sd/health是否正常访问

// pingServer pings the http server to make sure the router is working.
func pingServer() error {
	for i := 0; i < 10; i++ {
		// 请求/sd/health => Get返回值有两个
		resp, err := http.Get("http://127.0.0.1:8090" + "/sd/health")
		log.Print("Waiting for the router, retry in 1 second.")
		// 如果返回200，则表示启动成功，直接返回nil
		if err == nil && resp.StatusCode == 200 {
			return nil
		}
		
		// 否则1秒后重试
		log.Print("Waiting for the router, retry in 1 second.")
		time.Sleep(time.Second)
	}
	// 尝试10次，均失败则返回一个错误
	return errors.New("Cannot connect to the router.")
}

pingServer()http.Gethttp://127.0.0.1:8080/sd/healthpingServer

apiserver/main.go 

调用pingServer检查服务是否正常

func main() {
	...

	// 调用协程函数，检查服务健康状态
	go func() {
		if err := pingServer(); err != nil {
			log.Fatal("The router has no response, or it might took too long to start up.", err)
		}
		log.Print("The router has been deployed successfully.")
	}()

	// 让应用运行在本地服务器上，默认监听端口是 8080
	g.Run(":8090") // listen and serve on 0.0.0.0:8090
}

pingServer/sd/health

7. 测试