利用go-kit/kit/metrics向prometheus提供metrics数据

这里介绍如何利用github.com/go-kit/kit和github.com/prometheus客户端库向prometheus提供metrics数据。

package main

import (
    "fmt"
    "log"
    "time"
    "net/http"

                "github.com/gorilla/mux"
                "github.com/prometheus/client_golang/prometheus/promhttp"
  stdprometheus "github.com/prometheus/client_golang/prometheus"
  kitprometheus "github.com/go-kit/kit/metrics/prometheus"
)


func main() {
    address := fmt.Sprintf("%s:%d", "0.0.0.0", 8080)
    router  := mux.NewRouter().StrictSlash(true)

    router.Handle("/metrics", promhttp.Handler())
    go func() {
        err := http.ListenAndServe(address, router)
        if err != nil {
            log.Panic("ListenAndServe err:", err)
        }
    }()


    counter := kitprometheus.NewCounterFrom(
            stdprometheus.CounterOpts{
                Namespace: "mynamespace",
                Name     : "myname",
                Help     : "Sample of Counter metrics",
            },
            []string{"type", "group"})

    for {
        counter.With("type", "mytype", "group", "mygroup",).Add(10)
        time.Sleep(5 * time.Second)
    }

}

首先定义metrics的收集地址：0.0.0.0:8080/metrics，启动http server。
然后定义一个Counter类型的metrics，包含namespace, name, help，以及label。
每隔5秒钟，counter计数器加10

验证访问

$ curl localhost:8080/metrics | grep -i myname
# HELP mynamespace_myname Sample of Counter metrics
# TYPE mynamespace_myname counter
mynamespace_myname{group="mygroup",type="mytype"} 10

$ curl localhost:8080/metrics | grep -i myname
# HELP mynamespace_myname Sample of Counter metrics
# TYPE mynamespace_myname counter
mynamespace_myname{group="mygroup",type="mytype"} 30

对于Gauge类型的metrics，如果不想在程序内部自动周期性收集，而是希望在prometheus发起请求的时候收集一次数据，然后上报的话，可以修改router.Handle("/metrics", promhttp.Handler())，指定一个自定义Handler函数，然后在自定义函数里面收集完，再调用promhttp.Handler()完成收集。

package main

import (
    "fmt"
    "log"
    "time"
    "net/http"
    "math/rand"

                "github.com/gorilla/mux"
                "github.com/prometheus/client_golang/prometheus/promhttp"
  stdprometheus "github.com/prometheus/client_golang/prometheus"
  kitprometheus "github.com/go-kit/kit/metrics/prometheus"
)

var gauge * kitprometheus.Gauge

func main() {
    address := fmt.Sprintf("%s:%d", "0.0.0.0", 8080)
    router  := mux.NewRouter().StrictSlash(true)

    //router.Handle("/metrics", promhttp.Handler())
    router.HandleFunc("/metrics", metricsHandler)
    go func() {
        err := http.ListenAndServe(address, router)
        if err != nil {
            log.Panic("ListenAndServe err:", err)
        }
    }()

    gauge = kitprometheus.NewGaugeFrom(
            stdprometheus.GaugeOpts{
                Namespace: "mynamespace",
                Name     : "myname",
                Help     : "Sample of Gauge metrics",
            },
            []string{"type", "group"})

    for {
        time.Sleep(5 * time.Second)
    }
}

func metricsHandler(w http.ResponseWriter, r *http.Request) {
    // generate your gauge data
    gauge.With("type", "mytype", "group", "mygroup",).Set(rand.Float64()*100)
    // call prometheus internal handler
    promhttp.Handler().ServeHTTP(w, r)
}

验证：

$ curl localhost:8080/metrics | grep -i name
# HELP mynamespace_myname Sample of Gauge metrics
# TYPE mynamespace_myname gauge
mynamespace_myname{group="mygroup",type="mytype"} 60.466028797961954
$ curl localhost:8080/metrics | grep -i name
# HELP mynamespace_myname Sample of Gauge metrics
# TYPE mynamespace_myname gauge
mynamespace_myname{group="mygroup",type="mytype"} 94.05090880450125
$ curl localhost:8080/metrics | grep -i name
# HELP mynamespace_myname Sample of Gauge metrics
# TYPE mynamespace_myname gauge
mynamespace_myname{group="mygroup",type="mytype"} 66.45600532184905
$ curl localhost:8080/metrics | grep -i name
# HELP mynamespace_myname Sample of Gauge metrics
# TYPE mynamespace_myname gauge
mynamespace_myname{group="mygroup",type="mytype"} 43.771418718698015

附：原生HTTP方法为prometheus提供metrics数据

前面提到的是使用prometheus库来生成数据，其实prometheus客户端和服务端的协议是非常简单的，就是文本协议，我们可以使用原始的HTTP request/response来生成prometheus数据。

package main

import (
    "fmt"
    "log"
    "net/http"

    "github.com/gorilla/mux"
)

func main() {
    address := fmt.Sprintf("%s:%d", "0.0.0.0", 8080)
    router  := mux.NewRouter().StrictSlash(true)

    router.HandleFunc("/metrics", metrics)
    err := http.ListenAndServe(address, router)
    if err != nil {
        log.Panic("ListenAndServe err:", err)
    }
}

func metrics(w http.ResponseWriter, r *http.Request) {
    stat := getPrometheusStats()

    w.WriteHeader(http.StatusOK)
    w.Write([]byte(stat))
}


func getPrometheusStats() string {
    var stats string = ""
    stats += "# HELP mycounter Number of invocations.\n"
    stats += "# TYPE mycounter counter\n"
    stats += "# HELP mygauge Status of invocations.\n"
    stats += "# TYPE mygauge gauge\n"

    stats += "mycounter{label1=\"aaa\",label2=\"bbb\"}" +  " " + "120" + "\n"
    stats += "mygauge{label3=\"123\",label4=\"300\"}"   +  " " + "100" + "\n"
    return stats;
}

所有数据按行处理。