yell

Yet another minimalist logging library

Programming language: Go

License: Mozilla Public License 2.0

Tags: Logging    

README

yell

yell is yet another minimalistic logging library. It comes with:

• four severity levels
• simple API
• io.Writer & sync.Locker support
• package-specific loggers
• customizations (severity names, time format, local or UTC time)
• easy, granular request location (file.go:line) logging
• semantic versioning

Example

mypkg.go:

package mypkg

import (
    "os"
    "github.com/jfcg/yell"
)

// log to stdout with warn or higher severity (for example).
var Logger = yell.New(": mypkg:", os.Stdout, yell.Swarn)

// Info tries to log message list with info severity
func Info(msg ...interface{}) error {
    return Logger.Log(yell.Sinfo, msg...)
}

// Warn tries to log message list with warn severity
func Warn(msg ...interface{}) error {
    return Logger.Log(yell.Swarn, msg...)
}

// Error tries to log message list with error severity
func Error(msg ...interface{}) (err error) {
    err = Logger.Log(yell.Serror, msg...)
    // extra stuff for error severity
    return
}

// Fatal tries to log message list with fatal severity and panics
func Fatal(msg ...interface{}) (err error) {
    err = Logger.Log(yell.Sfatal, msg...)
    pm := Logger.Name() + yell.Sname[yell.Sfatal]
    if err != nil {
        pm += err.Error()
    }
    // probably panic or os.Exit(1) in a fatal situation
    panic(pm)
}

myApp.go:

package main

import (
    "fmt"
    "mypkg"
    "github.com/jfcg/yell"
)

func log() {
    defer func() {
        fmt.Println("recovering:", recover())
    }()

    // uses mypkg.Logger. yell records calling line in file.go:line format
    mypkg.Info("some info:", 1, "more")

    // uses yell.Default Logger, minimum severity is warning by default
    yell.Warn("some warning:", "few details")

    // record log() caller instead of this line
    mypkg.Error(yell.Caller(1), "bad error", 3.5, "data")

    // Fatal() logs & panicks
    yell.Fatal("fatal mistake", 2, "hard to recover")
}

func main() {
    // minimum severity for mypkg.Logger is warning, so ignored
    mypkg.Info("some info:", 3, "more")

    // set min severity level to info
    mypkg.Logger.SetMinLevel(yell.Sinfo)
    log()

    // yell library uses local time by default, to get coordinated universal time
    yell.UTC = true
    log()

    // change time format
    yell.TimeFormat = yell.TimeFormat[:19]
    log()

    // customized severity names (increasing severity)
    yell.Sname = [...]string{"信息:", "警告:", "错误:", "致命的:"}
    yell.UTC = false
    log()

    // disable logging for yell.Default
    yell.Default.SetMinLevel(yell.Snolog)
    log()
}

output:

2021-03-28 21:48:53.591948: mypkg:info: myApp.go:15: some info: 1 more
2021-03-28 21:48:53.592051: myApp:warn: myApp.go:18: some warning: few details
2021-03-28 21:48:53.592063: mypkg:error: myApp.go:33: bad error 3.5 data
2021-03-28 21:48:53.592082: myApp:fatal: myApp.go:24: fatal mistake 2 hard to recover
recovering: myApp:fatal:
2021-03-28 18:48:53.592100: mypkg:info: myApp.go:15: some info: 1 more
2021-03-28 18:48:53.592110: myApp:warn: myApp.go:18: some warning: few details
2021-03-28 18:48:53.592118: mypkg:error: myApp.go:37: bad error 3.5 data
2021-03-28 18:48:53.592126: myApp:fatal: myApp.go:24: fatal mistake 2 hard to recover
recovering: myApp:fatal:
2021-03-28 18:48:53: mypkg:info: myApp.go:15: some info: 1 more
2021-03-28 18:48:53: myApp:warn: myApp.go:18: some warning: few details
2021-03-28 18:48:53: mypkg:error: myApp.go:41: bad error 3.5 data
2021-03-28 18:48:53: myApp:fatal: myApp.go:24: fatal mistake 2 hard to recover
recovering: myApp:fatal:
2021-03-28 21:48:53: mypkg:信息: myApp.go:15: some info: 1 more
2021-03-28 21:48:53: myApp:警告: myApp.go:18: some warning: few details
2021-03-28 21:48:53: mypkg:错误: myApp.go:46: bad error 3.5 data
2021-03-28 21:48:53: myApp:致命的: myApp.go:24: fatal mistake 2 hard to recover
recovering: myApp:致命的:
2021-03-28 21:48:53: mypkg:信息: myApp.go:15: some info: 1 more
2021-03-28 21:48:53: mypkg:错误: myApp.go:50: bad error 3.5 data
recovering: myApp:致命的:

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