使用中间件统一记录 Prometheus 指标

概述 #

Go 程序使用 Prometheus 官方的 client_golang 来暴露指标，如果需要暴露作为客户端发送请求相关的指标，比如统计请求数，统计请求 P99 耗时等，可以利用 req 的中间件来统一记录，本文将给出代码实例。

使用 Response 中间件的示例 #

package main

import (
  "github.com/imroc/req/v3"
  "github.com/prometheus/client_golang/prometheus"
  "strconv"
  "time"
)

var (
  SendHTTPRequests = prometheus.NewCounterVec(
    prometheus.CounterOpts{
      Name: "send_http_requests_total",
      Help: "Number of the http requests sent since the server started",
    },
    []string{"method", "host", "path", "code"},
  )
  SendHTTPRequestsDuration = prometheus.NewHistogramVec(
    prometheus.HistogramOpts{
      Name:    "send_http_requests_duration_seconds",
      Help:    "Duration in seconds to send http requests",
      Buckets: prometheus.DefBuckets,
    },
    []string{"method", "host", "path", "code"},
  )
)

var client = req.C().
  OnAfterResponse(func(c *req.Client, resp *req.Response) error {
    req := resp.Request

    code := ""
    if resp.Response != nil {
      code = strconv.Itoa(resp.Response.StatusCode)
    }
    SendHTTPRequests.WithLabelValues(
      req.Method, req.URL.Host, req.URL.Path, code,
    ).Inc()

    duration := float64(resp.TotalTime()) / float64(time.Second)
    SendHTTPRequestsDuration.WithLabelValues(
      req.Method, req.URL.Host, req.URL.Path, code,
    ).Observe(duration)

    return nil
  })

func init() {
  prometheus.MustRegister(SendHTTPRequests, SendHTTPRequestsDuration)
}