Gunakan expvar untuk mendedahkan metrik berjalan program Go

Mendapatkan metrik berjalan aplikasi memberi kita gambaran yang lebih baik tentang prestasi aplikasi itu sebenarnya. Dengan menyambungkan penunjuk ini kepada sistem pemantauan seperti prometheus dan zabbix, aplikasi boleh dikesan secara berterusan, dan keabnormalan boleh dimaklumkan dan dikendalikan tepat pada masanya.

Tarik dan Tolak

Terdapat dua cara untuk antara muka dengan sistem pemantauan, satu Tarik dan satu lagi Tolak.

Ambil Prometheus sebagai contoh Aplikasi ini mendedahkan antara muka HTTP dan membolehkan Prometheus menangkap penunjuk secara berkala melalui antara muka This is Pull. Dalam Push, aplikasi secara aktif menolak penunjuk ke PushGateway, dan Prometheus pergi ke PushGateway untuk menangkap data.

Terdapat pakej yang dipanggil expvar dalam perpustakaan standard Go Namanya ialah gabungan exp dan var, yang bermaksud mengeksport pembolehubah.

expvar menyediakan antara muka piawai untuk pembolehubah awam dan mendedahkan pembolehubah ini dalam format Json melalui HTTP, yang sangat sesuai untuk menyambung dengan sistem pemantauan menggunakan Pull.

Menggunakan perpustakaan expvar

expvar ialah perpustakaan standard, yang bermaksud kami tidak memerlukan kebergantungan tambahan, dan ia juga menyediakan beberapa penunjuk di luar kotak. Mari belajar cara menggunakan perpustakaan ini.

Apabila perpustakaan expvar dirujuk (<code style="font-size: 14px;word-wrap: break-word;padding: 2px 4px;border-radius: 4px;margin: 0 2px;background-color: rgba(27,31,35,.05);font-family: Operator Mono, Consolas, Monaco, Menlo, monospace;word-break: break-all;color: #000000;background: rgba(14, 210, 247, 0.15);"><span style="font-size: 15px;">import "expvar"</span>），以下 init 函数将被自动调用。

func init() {
 http.HandleFunc("/debug/vars", expvarHandler)
 Publish("cmdline", Func(cmdline))
 Publish("memstats", Func(memstats))
}

该函数为我们注册了 /debug/vars 路径的 HTTP 服务，访问该路径将得到 Json 格式的指标。

因此，我们还需要调用 ListenAndServe 绑定端口，并开始服务 HTTP 请求。

http.ListenAndServe(":8080", nil)

完整代码如下

package main

import (
 _ "expvar"
 "net/http"
)

func main() {
 http.ListenAndServe(":8080", nil)
}

将程序运行起来后，通过 curl 请求，得到以下结果

$ curl localhost:8080/debug/vars
{
"cmdline": ["/var/folders/xk/gn46n46d503dsztbc6_9qb2h0000gn/T/go-build1657217338/b001/exe/main"],
"memstats": {"Alloc":278880,"TotalAlloc":278880,"Sys":8735760,"Lookups":0,"Mallocs":1169,"Frees":87,"HeapAlloc":278880,"HeapSys":3866624,"HeapIdle":2949120,"HeapInuse":917504,"HeapReleased":2899968,"HeapObjects":1082,"StackInuse":327680,"StackSys":327680,"MSpanInuse":28696,"MSpanSys":32640,"MCacheInuse":9600,"MCacheSys":15600,"BuckHashSys":3875,"GCSys":3826448,"OtherSys":662893,"NextGC":4194304,"LastGC":0,"PauseTotalNs":0,"PauseNs":[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],"PauseEnd":[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],"NumGC":0,"NumForcedGC":0,"GCCPUFraction":0,"EnableGC":true,"DebugGC":false,"BySize":[{"Size":0,"Mallocs":0,"Frees":0},{"Size":8,"Mallocs":41,"Frees":0},{"Size":16,"Mallocs":496,"Frees":0},{"Size":24,"Mallocs":63,"Frees":0},{"Size":32,"Mallocs":28,"Frees":0},{"Size":48,"Mallocs":134,"Frees":0},{"Size":64,"Mallocs":50,"Frees":0},{"Size":80,"Mallocs":17,"Frees":0},{"Size":96,"Mallocs":17,"Frees":0},{"Size":112,"Mallocs":6,"Frees":0},{"Size":128,"Mallocs":9,"Frees":0},{"Size":144,"Mallocs":9,"Frees":0},{"Size":160,"Mallocs":18,"Frees":0},{"Size":176,"Mallocs":6,"Frees":0},{"Size":192,"Mallocs":0,"Frees":0},{"Size":208,"Mallocs":37,"Frees":0},{"Size":224,"Mallocs":6,"Frees":0},{"Size":240,"Mallocs":0,"Frees":0},{"Size":256,"Mallocs":12,"Frees":0},{"Size":288,"Mallocs":7,"Frees":0},{"Size":320,"Mallocs":2,"Frees":0},{"Size":352,"Mallocs":13,"Frees":0},{"Size":384,"Mallocs":1,"Frees":0},{"Size":416,"Mallocs":30,"Frees":0},{"Size":448,"Mallocs":1,"Frees":0},{"Size":480,"Mallocs":2,"Frees":0},{"Size":512,"Mallocs":0,"Frees":0},{"Size":576,"Mallocs":5,"Frees":0},{"Size":640,"Mallocs":5,"Frees":0},{"Size":704,"Mallocs":3,"Frees":0},{"Size":768,"Mallocs":0,"Frees":0},{"Size":896,"Mallocs":6,"Frees":0},{"Size":1024,"Mallocs":8,"Frees":0},{"Size":1152,"Mallocs":10,"Frees":0},{"Size":1280,"Mallocs":3,"Frees":0},{"Size":1408,"Mallocs":1,"Frees":0},{"Size":1536,"Mallocs":0,"Frees":0},{"Size":1792,"Mallocs":7,"Frees":0},{"Size":2048,"Mallocs":2,"Frees":0},{"Size":2304,"Mallocs":3,"Frees":0},{"Size":2688,"Mallocs":2,"Frees":0},{"Size":3072,"Mallocs":0,"Frees":0},{"Size":3200,"Mallocs":0,"Frees":0},{"Size":3456,"Mallocs":0,"Frees":0},{"Size":4096,"Mallocs":8,"Frees":0},{"Size":4864,"Mallocs":1,"Frees":0},{"Size":5376,"Mallocs":1,"Frees":0},{"Size":6144,"Mallocs":2,"Frees":0},{"Size":6528,"Mallocs":0,"Frees":0},{"Size":6784,"Mallocs":0,"Frees":0},{"Size":6912,"Mallocs":0,"Frees":0},{"Size":8192,"Mallocs":2,"Frees":0},{"Size":9472,"Mallocs":8,"Frees":0},{"Size":9728,"Mallocs":0,"Frees":0},{"Size":10240,"Mallocs":0,"Frees":0},{"Size":10880,"Mallocs":0,"Frees":0},{"Size":12288,"Mallocs":0,"Frees":0},{"Size":13568,"Mallocs":0,"Frees":0},{"Size":14336,"Mallocs":0,"Frees":0},{"Size":16384,"Mallocs":0,"Frees":0},{"Size":18432,"Mallocs":0,"Frees":0}]}
}

可以看到，expvar 默认已提供了两项指标，分别是程序执行命令（os.Args）和运行时内存分配（runtime.Memstats）信息。

expvar 库重点内容

expvar 中最重要的是 Publish 函数和 Var 接口。

func Publish(name string, v Var) {}

Publish 函数签名中需要两个参数，name 是我们指定的指标名。例如在上文 expvar 的 init 函数下 <span style="font-size: 15px;">Publish("cmdline", Func(cmdline))</span>代码行，其中<span style="font-size: 15px;">cmdline</span>就是指标名，而<span style="font-size: 15px;">Func(cmdline)</span>import "expvar"), fungsi init berikut akan dipanggil secara automatik.

// Var is an abstract type for all exported variables.
type Var interface {
 // String returns a valid JSON value for the variable.
 // Types with String methods that do not return valid JSON
 // (such as time.Time) must not be used as a Var.
 String() string
}

Fungsi ini mendaftarkan perkhidmatan HTTP laluan /debug/vars untuk kita Mengakses laluan ini akan mendapat penunjuk dalam format Json.

🎜🎜🎜 Oleh itu, kami juga perlu memanggil ListenAndServe untuk mengikat port dan mula melayani permintaan HTTP. 🎜🎜

type Int struct {
 i int64
}

type Float struct {
 f uint64
}

type Map struct {
 m      sync.Map // map[string]Var
 keysMu sync.RWMutex
 keys   []string // sorted
}

type String struct {
 s atomic.Value // string
}

type Func func() any

🎜🎜Kod lengkap adalah seperti berikut🎜🎜

intVar = expvar.NewInt(“metricName”)
floatVar = expvar.NewFloat(“metricName”)
mapVar = expvar.NewMap(“metricName”)
stringVar = expvar.NewString(“metricName”)

🎜🎜Selepas menjalankan program, melalui permintaan curl, hasil berikut diperoleh🎜🎜

func NewInt(name string) *Int {
 v := new(Int)
 Publish(name, v)
 return v
}

🎜🎜Seperti yang anda lihat, expvar telah menyediakan dua penunjuk secara lalai, iaitu arahan pelaksanaan program ( os.Args) dan maklumat peruntukan memori masa jalan (runtime.Memstats). 🎜🎜

Kandungan utama perpustakaan expvar🎜

🎜🎜Perkara paling penting dalam expvar ialah fungsi Terbitkan dan antara muka Var. 🎜🎜

type MyStruct struct {
 Field1 string
 Field2 int
 Field3 float64
}

🎜🎜Tandatangan fungsi penerbitan memerlukan dua parameter, nama ialah nama penunjuk yang kami nyatakan. Contohnya, di bawah fungsi init expvar di atas 🎜🎜Publish("cmdline", Func(cmdline))🎜🎜baris kod, di mana🎜🎜cmdline🎜🎜 ialah nama penunjuk dan 🎜🎜Func(cmdline)🎜🎜 ialah expvar.Func yang melaksanakan Pembolehubah jenis antara muka Var. 🎜🎜🎜🎜Antara muka Var, yang hanya mentakrifkan kaedah Rentetan. Perlu diingatkan bahawa kaedah ini mesti mengembalikan rentetan Json yang sah. 🎜🎜

// Var is an abstract type for all exported variables.
type Var interface {
 // String returns a valid JSON value for the variable.
 // Types with String methods that do not return valid JSON
 // (such as time.Time) must not be used as a Var.
 String() string
}

为了方便使用，expvar 库中提供了五种导出变量类型，它们均实现了 Var 接口。

type Int struct {
 i int64
}

type Float struct {
 f uint64
}

type Map struct {
 m      sync.Map // map[string]Var
 keysMu sync.RWMutex
 keys   []string // sorted
}

type String struct {
 s atomic.Value // string
}

type Func func() any

我们分别通过调用 expvar.NewXXX 函数即可完成前四种类型的变量创建与指标注册。

intVar = expvar.NewInt(“metricName”)
floatVar = expvar.NewFloat(“metricName”)
mapVar = expvar.NewMap(“metricName”)
stringVar = expvar.NewString(“metricName”)

例如 expvar.NewInt 函数，它会内部调用 Publish 方法完成指标名与 expvar.Int 类型变量的绑定。

func NewInt(name string) *Int {
 v := new(Int)
 Publish(name, v)
 return v
}

而 expvar.Func 类型，其实是为了让我们可以自定义导出类型。

例如，假如我们想要暴露以下定义的结构体

type MyStruct struct {
 Field1 string
 Field2 int
 Field3 float64
}

首先需要创建一个数据生成函数。它用于在每次调用 HTTP 服务路径时，通过该函数导出这里面的数据。

func MyStructData() interface{} {
 return MyStruct{
  Field1: "Gopher",
  Field2: 22,
  Field3: 19.99,
 }
}

最后，通过 Publish 函数注册指标名即可。

expvar.Publish("metricName", expvar.Func(MyStructData))

完整示例

下面，我们给出一个覆盖五种导出变量类型的完整示例。

package main

import (
 "expvar"
 "github.com/shirou/gopsutil/v3/host"
 "github.com/shirou/gopsutil/v3/load"
 "github.com/shirou/gopsutil/v3/mem"
 "net/http"
 "time"
)

type Load struct {
 Load1  float64
 Load5  float64
 Load15 float64
}

func AllLoadAvg() interface{} {
 return Load{
  Load1:  LoadAvg(1),
  Load5:  LoadAvg(5),
  Load15: LoadAvg(15),
 }
}

func LoadAvg(loadNumber int) float64 {
 avg, _ := load.Avg()
 switch loadNumber {
 case 5:
  return avg.Load5
 case 15:
  return avg.Load15
 default:
  return avg.Load1
 }
}

func main() {
 var (
  aliveOfSeconds = expvar.NewInt("aliveOfSeconds")
  hostID         = expvar.NewString("hostID")
  lastLoad       = expvar.NewFloat("lastLoad")
  virtualMemory  = expvar.NewMap("virtualMemory")
 )
 expvar.Publish("allLoadAvg", expvar.Func(AllLoadAvg))
 h, _ := host.HostID()
 hostID.Set(h)

 go http.ListenAndServe(":8080", nil)

 for {
  aliveOfSeconds.Add(1)
  vm, _ := mem.VirtualMemory()
  lastLoad.Set(LoadAvg(1))
  virtualMemory.Add("active", int64(vm.Active))
  virtualMemory.Add("buffer", int64(vm.Buffers))
  time.Sleep(1 * time.Second)
 }
}

在上述示例中，我们通过 gopsutil 库（介绍可见还在自己写 Go 系统监控函数吗一文）获取了一些系统信息，并展示了如何通过 expvar 中的各种变量类型将这些信息进行导出。

curl 访问 localhost:8080/debug/vars 结果如下

$ curl localhost:8080/debug/vars
{
"aliveOfSeconds": 1,
"allLoadAvg": {"Load1":1.69580078125,"Load5":1.97412109375,"Load15":1.90283203125},
"cmdline": ["/var/folders/xk/gn46n46d503dsztbc6_9qb2h0000gn/T/go-build3566019824/b001/exe/main"],
"hostID": "7a1a74f2-30fc-5bc1-b439-6b7aef22e58d",
"lastLoad": 1.69580078125,
"memstats": {"Alloc":256208,"TotalAlloc":256208,"Sys":8735760,"Lookups":0,"Mallocs":1089,"Frees":48,"HeapAlloc":256208,"HeapSys":3866624,"HeapIdle":2891776,"HeapInuse":974848,"HeapReleased":2859008,"HeapObjects":1041,"StackInuse":327680,"StackSys":327680,"MSpanInuse":19992,"MSpanSys":32640,"MCacheInuse":9600,"MCacheSys":15600,"BuckHashSys":3905,"GCSys":3851120,"OtherSys":638191,"NextGC":4194304,"LastGC":0,"PauseTotalNs":0,"PauseNs":[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],"PauseEnd":[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],"NumGC":0,"NumForcedGC":0,"GCCPUFraction":0,"EnableGC":true,"DebugGC":false,"BySize":[{"Size":0,"Mallocs":0,"Frees":0},{"Size":8,"Mallocs":35,"Frees":0},{"Size":16,"Mallocs":415,"Frees":0},{"Size":24,"Mallocs":71,"Frees":0},{"Size":32,"Mallocs":37,"Frees":0},{"Size":48,"Mallocs":141,"Frees":0},{"Size":64,"Mallocs":52,"Frees":0},{"Size":80,"Mallocs":20,"Frees":0},{"Size":96,"Mallocs":23,"Frees":0},{"Size":112,"Mallocs":14,"Frees":0},{"Size":128,"Mallocs":7,"Frees":0},{"Size":144,"Mallocs":7,"Frees":0},{"Size":160,"Mallocs":18,"Frees":0},{"Size":176,"Mallocs":6,"Frees":0},{"Size":192,"Mallocs":1,"Frees":0},{"Size":208,"Mallocs":42,"Frees":0},{"Size":224,"Mallocs":3,"Frees":0},{"Size":240,"Mallocs":0,"Frees":0},{"Size":256,"Mallocs":9,"Frees":0},{"Size":288,"Mallocs":8,"Frees":0},{"Size":320,"Mallocs":5,"Frees":0},{"Size":352,"Mallocs":13,"Frees":0},{"Size":384,"Mallocs":3,"Frees":0},{"Size":416,"Mallocs":33,"Frees":0},{"Size":448,"Mallocs":0,"Frees":0},{"Size":480,"Mallocs":2,"Frees":0},{"Size":512,"Mallocs":1,"Frees":0},{"Size":576,"Mallocs":4,"Frees":0},{"Size":640,"Mallocs":8,"Frees":0},{"Size":704,"Mallocs":3,"Frees":0},{"Size":768,"Mallocs":1,"Frees":0},{"Size":896,"Mallocs":6,"Frees":0},{"Size":1024,"Mallocs":8,"Frees":0},{"Size":1152,"Mallocs":9,"Frees":0},{"Size":1280,"Mallocs":3,"Frees":0},{"Size":1408,"Mallocs":1,"Frees":0},{"Size":1536,"Mallocs":1,"Frees":0},{"Size":1792,"Mallocs":9,"Frees":0},{"Size":2048,"Mallocs":1,"Frees":0},{"Size":2304,"Mallocs":2,"Frees":0},{"Size":2688,"Mallocs":2,"Frees":0},{"Size":3072,"Mallocs":0,"Frees":0},{"Size":3200,"Mallocs":1,"Frees":0},{"Size":3456,"Mallocs":0,"Frees":0},{"Size":4096,"Mallocs":5,"Frees":0},{"Size":4864,"Mallocs":0,"Frees":0},{"Size":5376,"Mallocs":1,"Frees":0},{"Size":6144,"Mallocs":1,"Frees":0},{"Size":6528,"Mallocs":0,"Frees":0},{"Size":6784,"Mallocs":0,"Frees":0},{"Size":6912,"Mallocs":0,"Frees":0},{"Size":8192,"Mallocs":1,"Frees":0},{"Size":9472,"Mallocs":8,"Frees":0},{"Size":9728,"Mallocs":0,"Frees":0},{"Size":10240,"Mallocs":0,"Frees":0},{"Size":10880,"Mallocs":0,"Frees":0},{"Size":12288,"Mallocs":0,"Frees":0},{"Size":13568,"Mallocs":0,"Frees":0},{"Size":14336,"Mallocs":0,"Frees":0},{"Size":16384,"Mallocs":0,"Frees":0},{"Size":18432,"Mallocs":0,"Frees":0}]},
"virtualMemory": {"active": 1957449728, "buffer": 0}
}

总结

标准库 expvar 为需要导出的公共变量提供了一个标准化的接口，使用比较简单。

expvar 包内部定义的几种基础类型都相应给出了并发安全的操作方法，我们不需要去重复实现一遍，能够开箱即用。

Namun, mengikut statistik projek awam di https://go.dev/, bilangan import perpustakaan ini adalah kurang daripada 10,000.

Berbanding dengan bilangan import dalam perpustakaan standard lain, kehadiran expvar terlalu rendah.

Atas ialah kandungan terperinci Gunakan expvar untuk mendedahkan metrik berjalan program Go. Untuk maklumat lanjut, sila ikut artikel berkaitan lain di laman web China PHP!