Prometheus 之 exporter模块源代码

编写一个exporter的流程

用go开发一个exporter的源代码及讲解

对于编写exporter的个人建议

1、编写一个exporter的流程

官网有介绍编写exporter的详细内容

首先不同于pushgateway，exporter是一个独立运行的采集程序

其中的功能需要有这三个部分

1）自身是HTTP服务器，可以响应从外发过来的HTTP GET请求
2）自身需要运行在后台，并可以定期触发、抓取本地的监控数据
3）返回给prometheus_server的内容是需要符合prometheus规定的metrics类型（Key-Value）
4)key-value ->prometheus(TS)values(float int)

2、用go开发一个exporter的源代码及讲解

package main 

import (  
 "fmt"   
_ "net/http/pprof"    
 "sync" 
//  "github.com/hpcloud/tail" 
 "github.com/prometheus/client_golang/prometheus"
 "github.com/prometheus/common/log"
 "github.com/prometheus/common/version"
//  //"net"
"net/http"
//  "net/url" 
//   "errors"   
"flag"   
"os"  
"os/exec"   
"io/ioutil" 
//  "regexp" 
//  "strconv" 
//  "strings"     
"time" 
) 


const (   
namespace = "my_exporter"  
 ) 


type Exporter struct { 

cmd               string 
mutex             sync.RWMutex 
up,freeRam,TotalRam   prometheus.Gauge 
Debug                 bool 
upstreamResponseTimes  *prometheus.HistogramVec

} 



func (e *Exporter) scrape() { 
log.Infoln("--------") 
e.up.Set(1)
     } 


func (e *Exporter) Describe(ch chan<- *prometheus.Desc) {
   e.upstreamResponseTimes.Describe(ch)
 } 


 func (e *Exporter) Collect(ch chan<- prometheus.Metric) { 

 e.mutex.Lock() // To protect metrics from concurrent collects  
  defer e.mutex.Unlock()

  e.scrape()   
  e.upstreamResponseTimes.Collect(ch)   
  e.up.Collect(ch)
 } 


func NewExporter(cmd string, timeout time.Duration) (*Exporter, error) {
   return &Exporter{
     cmd: cmd,
     up: prometheus.NewGauge(prometheus.GaugeOpts{
       Namespace: namespace,
       Name:      "up",
       Help:      "Was the last scrape of nginx exporter successful.",     
      }),
     upstreamResponseTimes: prometheus.NewHistogramVec(
       prometheus.HistogramOpts{
         Namespace: namespace,
         Name:      "http_upstream_request_times",
         Help:      "Response times from backends/upstreams",
       },       
       []string{"method", "endpoint", "response_code","client_type"},
     ),
   }, nil
 } 



func run() {

   cmd := exec.Command("/bin/sh", "-c", `free -m `)

   stdout , err := cmd.StdoutPipe()

   if err != nil {
     panic(err.Error())
   }

   if err != nil {
     fmt.Println("Stdoutpipe error", err.Error())
   }

     stderr , err := cmd.StderrPipe()

   if err != nil {
     fmt.Println("Stderrpipe error", err.Error())
   }

   if err := cmd.Start(); err != nil {
     fmt.Println("error start", err )

   }

   bytesErr, err := ioutil.ReadAll(stderr)
     if err != nil {
         fmt.Println("ReadAll stderr: ", err.Error())
         return
     }

     if len(bytesErr) != 0 {
         fmt.Printf("stderr is not nil: %s", bytesErr)
         return
     }

     bytes, err := ioutil.ReadAll(stdout)
     if err != nil {
         fmt.Println("ReadAll stdout: ", err.Error())
         return
     }

     if err := cmd.Wait(); err != nil {
         fmt.Println("Wait: ", err.Error())
         return
     }

     fmt.Printf("stdout: %s", string(bytes))


 } 

func main() {
   var (
       listenAddress = flag.String("web.listen-address", ":9101", "Address to listen on for web interface and telemetry.")
       metricsPath   = flag.String("web.telemetry-path", "/metrics", "Path under which to expose metrics.")
       cmd           = flag.String("free", "", "command to run")
       nginxTimeout  = flag.Duration("nginx.timeout", 5*time.Second, "Timeout for trying to get stats from HA.")
       showVersion   = flag.Bool("version", false, "Print version information.")
 //    debug         = flag.Bool("debug", false, "Print debug information.")
   )
   flag.Parse()

   if *showVersion {
     fmt.Println(os.Stdout, version.Print("shannon_exporter"))
     os.Exit(0)
   }

   log.Infoln("Starting shannon_exporter", version.Info())
   log.Infoln("Build context", version.BuildContext())

   run() 


   exporter, _ := NewExporter(*cmd, *nginxTimeout)  

 
  prometheus.MustRegister(exporter)
  prometheus.MustRegister(version.NewCollector("nginx_exporte r"))   http.Handle(*metricsPath, prometheus.Handler())
 


  http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
     w.Write([]byte(`<html>       
       <head><title>Haproxy Exporter</title></head>
       <body>
       <h1>Haproxy Exporter</h1>
       <p><a href='` + *metricsPath+`'>Metrics</a></p>
       </body> 
       </html>`))
    })             
  log.Fatal(http.ListenAndServe(*listenAddress, nil))

   }

//前⾯的 scrape describeCollect 是struct类型的成员函数，这⼏个函数并没有直接在这个go⾥被调⽤，⽽是 MustRegister注册进去了它们。
// http.Handle⾥的prometheus.Handler 将上⼀部2个Mustregister 的注册关联进⼊http.handle. 也就进⼀步注册进⼊了httpserverlisterner
// http.lister是组赛程序，只有启动后被curl的时候才会执⾏。并且由于之前经过2步的注册，跟exporter的成员函数建⽴了关联（其实是指针关联）所以，每次被curl的时候所有上⾯的成员函数都会被调⽤
//例如上⾯的up.set(1) 就是只有被curl的时候才会被调⽤，成员函数是作为⽣成metrics的⼊⼜注：本Go exporter 源代码是半年前写的了其中⼀些地⽅可能需要进⼀步修改才可以正常使⽤

exporter-prometheus 5s GET => exporter Handler-> handler-lister开发的过程中要特别注意各种⽂件句柄等等资源的完整回收因为⼀个⾮常被频繁调⽤的后台程序中⼀旦循环中出现资源泄漏那么后果是很严重的（之前其实就遇到过⼀次资源没有正确回收导致每⼀次promethue_server访问过来都造成僵⼫进程最终服务器被拖垮的窘境 …囧当然了如果是开发⾼⼿的话相信我的担⼼也就多余啦～～）所以如果企业中运维开发的实⼒不够过硬，我还是尽量建议⼤家使⽤现成的社区exporters, 配合⾃⾏开发pushgateway脚本