go语言编程之旅笔记6

第六章： Go中的大杀器

1. 简介

   介绍了PProf，trace，godebug，gops，metrrics，prometheus等等库来进行性能监控等等的功能

2. PProf

   1. 使用net/http/pprof可以能方便的采集web服务在运行时的数据，直接import十分简单

   import (
       _ "net/http/pprof"
   )
   
   // 看看pprof的init发现注入了很多handler
   func init() {
   	http.HandleFunc("/debug/pprof/", Index)
   	http.HandleFunc("/debug/pprof/cmdline", Cmdline)
   	http.HandleFunc("/debug/pprof/profile", Profile)
   	http.HandleFunc("/debug/pprof/symbol", Symbol)
   	http.HandleFunc("/debug/pprof/trace", Trace)
   }
   
   

   可以通过浏览器或是交互式终端进行访问，我选择浏览器。-> IP地址/debug/pprof

   浏览器有时效性，真要查问题还是用终端

   go tool pprof ip/debug/pprof/profile?seconds=60
   

   不同的路由对应的项，比如cpu/heap/goroutine等等，这就不贴了。

   采集生成的profile文件也是可以用web方式查阅的，go tool pprof -http=:6000 profile，如果报graphviz的错说明要装组件。

   2. 通过Lookup进行采集,这种方式需要写code，支持6种类型，goroutine,threadcreate,heap,block,mutex
   这种方式需要写code，支持6种类型，goroutine,threadcreate,heap,block,mutex

   package main
   
   import (
   	"io"
   	"net/http"
   	_ "net/http/pprof"
   	"os"
   	"runtime"
   	"runtime/pprof"
   )
   
   //go tool pprof http://localhost:6060/debug/pprof/profile?seconds=60
   
   func main() {
   	http.HandleFunc("/lookup/heap", func(w http.ResponseWriter, r *http.Request) {
   		_ = pprofLookup(LookupHeap, os.Stdout)
   	})
   
   	http.HandleFunc("/lookup/threadcreate", func(w http.ResponseWriter, r *http.Request) {
   		_ = pprofLookup(LookupThreadcreate, os.Stdout)
   	})
   
   	http.HandleFunc("/lookup/block", func(w http.ResponseWriter, r *http.Request) {
   		_ = pprofLookup(LookupBlock, os.Stdout)
   	})
   
   	http.HandleFunc("/lookup/goroutine", func(w http.ResponseWriter, r *http.Request) {
   		_ = pprofLookup(LookupGoroutine, os.Stdout)
   	})
   
   	_ = http.ListenAndServe("0.0.0.0:6060", nil)
   }
   
   type LookupType int8
   
   const (
   	LookupGoroutine LookupType = iota
   	LookupThreadcreate
   	LookupHeap
   	LookupAllocs
   	LookupBlock
   	LookupMutex
   )
   
   func pprofLookup(lookupType LookupType, w io.Writer) error {
   	var err error
   	switch lookupType {
   	case LookupGoroutine:
   		p := pprof.Lookup("goroutine")
   		err = p.WriteTo(w, 2)
   	case LookupThreadcreate:
   		p := pprof.Lookup("threadcreate")
   		err = p.WriteTo(w, 2)
   	case LookupHeap:
   		p := pprof.Lookup("heap")
   		err = p.WriteTo(w, 2)
   	case LookupAllocs:
   		p := pprof.Lookup("allocs")
   		err = p.WriteTo(w, 2)
   	case LookupBlock:
   		p := pprof.Lookup("block")
   		err = p.WriteTo(w, 2)
   	case LookupMutex:
   		p := pprof.Lookup("mutex")
   		err = p.WriteTo(w, 2)
   	}
   	return err
   }
   
   func init() {
   	runtime.SetMutexProfileFraction(1)
   	runtime.SetBlockProfileRate(1)
   }
   
   

3. trace

   详细的使用方式/指标之类还是看书吧，字太多。

   package main
   
   // --go run .\cmd\trace\main.go 2> trace.out
   
   // go build .\cmd\trace\main.go
   //  .\main.exe
   // go tool trace trace.dat
   
   import (
   	"context"
   	"fmt"
   	"os"
   	"runtime"
   	"runtime/trace"
   	"sync"
   )
   
   func main() {
   	// 为了看协程抢占，这里设置了一个cpu 跑
   	runtime.GOMAXPROCS(1)
   
   	f, _ := os.Create("trace.dat")
   	defer f.Close()
   
   	_ = trace.Start(f)
   	defer trace.Stop()
   
   	ctx, task := trace.NewTask(context.Background(), "sumTask")
   	defer task.End()
   
   	var wg sync.WaitGroup
   	wg.Add(10)
   	for i := 0; i < 10; i++ {
   		// 启动10个协程，只是做一个累加运算
   		go func(region string) {
   			defer wg.Done()
   
   			// 标记region
   			trace.WithRegion(ctx, region, func() {
   				var sum, k int64
   				for ; k < 1000000000; k++ {
   					sum += k
   				}
   				fmt.Println(region, sum)
   			})
   		}(fmt.Sprintf("region_%02d", i))
   	}
   	wg.Wait()
   }
   
   

4. godebug

   这个同样太长不写了。环境变量可以通过vscode写入launch.json文件中，比如

     "env": {
               "GODEBUG":"scheddetail=1,schedtrace=1000"
           } 
   

5. 进程诊断工具 gops

   go get -u github.com/google/gops 
   
   package main
   
   import (
   	"log"
   	"net/http"
   
   	"github.com/google/gops/agent"
   )
   
   func main() {
   	if err := agent.Listen(agent.Options{}); err != nil {
   		log.Fatal("agent listen err : %v", err)
   	}
   	http.HandleFunc("/hello", func(w http.ResponseWriter, r *http.Request) {
   		_, _ = w.Write([]byte("golang projecct"))
   	})
   	_ = http.ListenAndServe(":6060", http.DefaultServeMux)
   }
   
   

   gops help查看命令，也是有很多，不细写

6. metrics 使用expvar标准库

   code中自定义了类型，并且封装成了gin中间件，可以和gin联动了

   package main
   
   import (
   	"expvar"
   	_ "expvar"
   	"fmt"
   	"net/http"
   	"runtime"
   	"time"
   
   	"github.com/gin-gonic/gin"
   )
   
   //http://localhost:6060/debug/vars
   func main() {
   	router := NewRouter()
   	http.HandleFunc("/hello", func(w http.ResponseWriter, r *http.Request) {
   		appleCounter.Add(1)
   		_, _ = w.Write([]byte("go project"))
   	})
   
   	_ = http.ListenAndServe(":6060", router)
   }
   
   var (
   	appleCounter      *expvar.Int
   	GOMAXPROCSMetrics *expvar.Int
   	upTimeMetrice     *upTimeVar
   )
   
   type upTimeVar struct {
   	value time.Time
   }
   
   func (v *upTimeVar) Set(date time.Time) {
   	v.value = date
   }
   
   func (v *upTimeVar) Add(duration time.Duration) {
   	v.value = v.value.Add(duration)
   }
   
   func (v *upTimeVar) String() string {
   	return v.value.Format(time.UnixDate)
   }
   
   func init() {
   	upTimeMetrice = &upTimeVar{value: time.Now().Local()}
   	expvar.Publish("uptime", upTimeMetrice)
   	appleCounter = expvar.NewInt("apple")
   	GOMAXPROCSMetrics = expvar.NewInt("GOMAXPROCS")
   	GOMAXPROCSMetrics.Set(int64(runtime.NumCPU()))
   }
   
   func Expvar(c *gin.Context) {
   	c.Writer.Header().Set("content-type", "application/json; charset=utf-8")
   	first := true
   	report := func(key string, value interface{}) {
   		if !first {
   			fmt.Fprintf(c.Writer, ",\n")
   		}
   		first = false
   		if str, ok := value.(string); ok {
   			fmt.Fprintf(c.Writer, "%q: %q", key, str)
   		} else {
   			fmt.Fprintf(c.Writer, "%q: %v", key, value)
   		}
   	}
   
   	fmt.Fprintf(c.Writer, "{\n")
   	expvar.Do(func(kv expvar.KeyValue) {
   		report(kv.Key, kv.Value)
   	})
   	fmt.Fprintf(c.Writer, "\n}\n")
   }
   
   func NewRouter() *gin.Engine {
   	r := gin.New()
   	r.Use(gin.Logger())
   	r.Use(gin.Recovery())
   	r.GET("/debug/vars", Expvar)
   	return r
   }
   

7. Pronmetheus

   Pronmetheus还是很出名的。四大指标类型Counter累计指标，Histogram一定时间范围内采样，Gauge可任意变化的指标，Summary也是一定时间内采样，他有仨指标，分位数分布/样本值大小总和/样本总数。

   go get -u github.com/prometheus/client_golang
   
   package main
   
   import (
   	"net/http"
   
   	"github.com/prometheus/client_golang/prometheus/promhttp"
   )
   
   func main() {
   	http.Handle("/metrics", promhttp.Handler())
   	http.HandleFunc("/hello", func(w http.ResponseWriter, r *http.Request) {
   		_, _ = w.Write([]byte("go project"))
   	})
   	_ = http.ListenAndServe(":6060", http.DefaultServeMux)
   }
   
   

   启动后访问 :6060/metrics

8. 其他 包括附录

   1. 逃逸分析，有很多情况会造成逃逸，这个还是要经验的，初学者的我还是用命令最直接。

   // 用-gcflags查看逃逸分析过程
   go build -gcflags '-m -l' main.go
   
   // 反编译命令查看
   go tool compile -S main.go
   

   2. Go modules
      去年刚开始学时用过gopath，那玩意儿能坑死，还是modules适合老子。

   // go get后的模块会缓存在gopath/pkg/mod 和gopath/pkg/sumdb中，如果需要清理可以执行
   go clean -modcache
   

   3. 为什么defer才能recover

   panic结构是一个链表，defer结构中包含了一个对panic结构的引用，在gopanic(interface{})方法中，会触发defer，如果没有defer则会直接跳出，就不会进行接来下的recover了。

   还有一些defer了也无法recover的方法，比如fatalthrow,fatalpanic等，比如并发写入map时就会引起fatalthrow。

   10种panic方法：数组切片越界，空指针调用，过早关闭HTTP响应体(resp.body.calose())，除零，向关闭的chan发送消息，重复关闭chan，关闭未初始化的的chan，使用未初始化的map，跨goroutine处理panic，sync计数负数。

   4. 让golang更适应docker

   // 这个库可以根据cgroup的挂载信息来修改GOMAXPROCS核数
   import _ "go.uber.org/automaxprocs"
   

完！