使用errors.Wrapf()代替log.Error()

介绍不同语言的错误处理机制:
Error handling patterns

Musings about error handling mechanisms in programming languages

项目中 main调func1，func1调取func2...

这样就会出现很多的 if err != nil { log.Printf()} , 在Kibana上查看时会搜到多条日志, 需要逐级定位, 确定错误抛出的点

希望只有一条, 能清晰看到整个堆栈调用信息

使用log.xxxx方法:

package main

import (
    "fmt"
    "log"
    "strconv"
    "time"
)

func init() {
    log.SetFlags(log.Lshortfile | log.LstdFlags)
}

func main() {

    str := "123a"
    rs, err := func1(str)

    if err != nil {
        log.Printf("err is (%+v)\n", err)
        return
    }

    fmt.Println("最终结果为:", rs)

}

func func1(str string) (int, error) {

    b, err := func2()

    if err != nil {
        log.Printf("There is func11111,  func2 err(%+v)\n", err)
    }

    if b == false {
        strInt, err := strconv.Atoi(str)

        if err != nil {
            log.Printf("There is func11111, err(%+v)\n", err)
        }
        return strInt, err
    }
    return 0, nil
}

func func2() (bool, error) {

    now := time.Now().Unix()

    endTimeStr := "2021-08-06 20:00:0000"

    endtime, err := time.ParseInLocation("2006-01-02 15:04:05", endTimeStr, time.Local)

    if err != nil {
        log.Printf("There is func22222, err(%+v)\n", err)
        return false, err
    }

    if endtime.Unix() > now {
        return true, nil
    }

    return false, nil

}

执行结果:

2021/06/07 21:52:56 vs.go:56: There is func22222, err(parsing time "2021-08-06 20:00:0000": extra text: "00")
2021/06/07 21:52:56 vs.go:33: There is func11111,  func2 err(parsing time "2021-08-06 20:00:0000": extra text: "00")
2021/06/07 21:52:56 vs.go:40: There is func11111, err(strconv.Atoi: parsing "123a": invalid syntax)
2021/06/07 21:52:56 vs.go:20: err is (strconv.Atoi: parsing "123a": invalid syntax)

使用errors.Wrapf方法:

package main

import (
    "fmt"
    "github.com/pkg/errors"
    "strconv"
    "time"
)

func main() {

    str := "123a"
    rs, err := func1(str)

    if err != nil {

        fmt.Printf("err: %+v\n", err)
        //fmt.Println("err:", lastErr) //必须%+v才会打印完整堆栈信息,否则只打印错误信息
        return
    }

    fmt.Println("最终结果为:", rs)

}

func func1(str string) (int, error) {

    b, err := func2()

    if err != nil {
        err = errors.Wrapf(err, "There is func11111, func2 err, b is(%b) \n", b)
    }

    if b == false {
        var strInt int
        strInt, err = strconv.Atoi(str)

        if err != nil {
            err = errors.Wrapf(err, "There is func11111,str is(%s)\n", str)
        }
        return strInt, err
    }
    return 0, nil
}

func func2() (bool, error) {

    now := time.Now().Unix()

    endTimeStr := "2021-08-06 20:00:0000"

    endtime, err := time.ParseInLocation("2006-01-02 15:04:05", endTimeStr, time.Local)

    if err != nil {
        err = errors.Wrapf(err, "There is func22222,endTimeStr is(%s)\n", endTimeStr)
        return false, err
    }

    if endtime.Unix() > now {
        return true, nil
    }

    return false, nil

}

执行:

err: strconv.Atoi: parsing "123a": invalid syntax
There is func11111,str is(123a)

main.func1
        /Users/fliter/go/src/shuang/llog/1.go:39
main.main
        /Users/fliter/go/src/shuang/llog/1.go:13
runtime.main
        /usr/local/Cellar/go/1.16.3/libexec/src/runtime/proc.go:225
runtime.goexit
        /usr/local/Cellar/go/1.16.3/libexec/src/runtime/asm_amd64.s:1371

注意赋值这步, 必不可少！

有一个问题, 即对于f1调f2,f2调f3这种, 如果f3发生error, 可以逐级将error抛出.
但如果一个方法里有两个error, 则第二条会覆盖掉第一条,如上 err = errors.Wrapf(err, "There is func11111, func2 err, b is(%b) \n", b)这一条就被覆盖了

// Wrapf returns an error annotating err with a stack trace
// at the point Wrapf is called, and the format specifier.
// If err is nil, Wrapf returns nil.
func Wrapf(err error, format string, args ...interface{}) error {
    if err == nil {
        return nil
    }
    err = &withMessage{
        cause: err,
        msg:   fmt.Sprintf(format, args...),
    }
    return &withStack{
        err,
        callers(),
    }
}

func callers() *stack {
    const depth = 32
    var pcs [depth]uintptr
    n := runtime.Callers(3, pcs[:])
    var st stack = pcs[0:n]
    return &st
}

// Callers fills the slice pc with the return program counters of function invocations
// on the calling goroutine's stack. The argument skip is the number of stack frames
// to skip before recording in pc, with 0 identifying the frame for Callers itself and
// 1 identifying the caller of Callers.
// It returns the number of entries written to pc.
//
// To translate these PCs into symbolic information such as function
// names and line numbers, use CallersFrames. CallersFrames accounts
// for inlined functions and adjusts the return program counters into
// call program counters. Iterating over the returned slice of PCs
// directly is discouraged, as is using FuncForPC on any of the
// returned PCs, since these cannot account for inlining or return
// program counter adjustment.
func Callers(skip int, pc []uintptr) int {
    // runtime.callers uses pc.array==nil as a signal
    // to print a stack trace. Pick off 0-length pc here
    // so that we don't let a nil pc slice get to it.
    if len(pc) == 0 {
        return 0
    }
    return callers(skip, pc)
}

func callers(skip int, pcbuf []uintptr) int {
    sp := getcallersp()
    pc := getcallerpc()
    gp := getg()
    var n int
    systemstack(func() {
        n = gentraceback(pc, sp, 0, gp, skip, &pcbuf[0], len(pcbuf), nil, nil, 0)
    })
    return n
}

---

参考:

golang 打印error的堆栈信息

Go错误处理最佳实践

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