Logger

A high-performance, configurable logging library for Go applications.

Features

• Multiple log levels (Debug, Info, Warn, Error, Fatal, Panic)
• Flexible output formatting (Plain text, JSON, LogFmt)
• Customizable log fields
• Color support for console output
• Log file rotation
• Zero allocation logging
• Context support
• Thread-safe

Installation

go get github.com/yc-alpha/logger

Quick Start

package main

import "github.com/yc-alpha/logger"

func main() {
    // Use default logger
    logger.Info("hello world")
    
    // Create custom logger
	log := logger.NewLogger(
		// Won't output logs below Info level
		logger.WithLevel(logger.InfoLevel),
		// Set the output to stdout for all log levels
		logger.WithBackends(logger.AnyLevel, backend.OSBackend().Build()),
		logger.WithFields(logger.AnyLevel,
			logger.DatetimeField(time.DateTime),
			logger.LevelField().Key("level").Upper(),
			logger.MessageField(),
		),
		// Set the encoder to LogFmtEncoder for all log levels
		logger.WithEncoders(logger.AnyLevel, logger.LogFmtEncoder),
	)
    
    log.Info("hello logger!")
}

Configuration

Log Levels

• DebugLevel
• InfoLevel (default)
• WarnLevel
• ErrorLevel
• FatalLevel
• PanicLevel

Backends

• Console output (OSBackend)
• File output with rotation (DefaultFileBackend)

Fields

Built-in fields:

• LevelField - Log level
• MessageField - Log message
• DatetimeField - Formated time
• TimeField - Timestamp
• CallerField - File and line number
• FuncNameField - Function name
• CustomField - User-defined field

Formatting

Supported encoders:

• PlainEncoder - Simple text format
• JSONEncoder - JSON format
• LogFmtEncoder - LogFmt format

Examples

Adding Custom Fields

log.Infos("hello",
    logger.Group("metadata",
        logger.String("user", "admin"),
        logger.Int("id", 123),
    ),
)

Using Colors

log := logger.NewLogger(
    logger.WithFields(logger.ErrorLevel,
        logger.LevelField().Color(logger.Red),
        logger.MessageField().Color(logger.Yellow),
    ),
)

Customize different fields for different log levels

• Add a group field "sys_info" to info and warn level logs
• Add file and func fields to warn level logs and above

log := NewLogger(
	WithLevel(InfoLevel),
	WithBackends(AnyLevel, backend.OSBackend().Build()),
	WithFields(AnyLevel,
		DatetimeField(time.DateTime).Key("datetime"),
		LevelField().Key("level").Upper().Prefix("[").Suffix("]"),
		MessageField().Key("msg"),
	),
	WithFields(InfoLevel|WarnLevel,
		Group("sys_info",
			CustomField(func(buf *buffer.Buffer) {
				buildInfo, _ := debug.ReadBuildInfo()
				buf.WriteString(buildInfo.GoVersion)
			}).Key("go_version"),
			Group("sys", CustomField(func(buf *buffer.Buffer) {
				buf.WriteInt(int64(os.Getpid()))
			}).Key("pid")),
		)),
	WithFields(ErrorLevel|FatalLevel|PanicLevel,
		CallerField(true, false).Key("file"),
		FuncNameField(true).Key("func"),
	),
	WithEncoders(AnyLevel, LogFmtEncoder),
)
log.Debug("hello debug")
log.Info("hello info")
log.Warn("hello warn")
log.Error("hello error")

File Rotation

log := logger.NewLogger(
    logger.WithBackends(logger.InfoLevel,
        backend.DefaultFileBackend().
            Filename("app.log").
            MaxSize(100).  // MB
            MaxBackups(5).
            Compress(true).
            Build(),
    ),
)

Performance

View test case Here

BenchmarkInfo-12			24850		58835 ns/op		0 B/op		0 allocs/op
BenchmarkInfos-12       	27985       51170 ns/op     0 B/op      0 allocs/op
BenchmarkDefaultLogger-12	26377		54866 ns/op		232 B/op	2 allocs/op

Reference Projects

• zap:Refer to the implementation of buffer
• lumberjack:Refer to lumberjack for file rotation implementation

License

MIT License - see LICENSE for details