logger

package module
v0.1.13 Latest Latest
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 Go to latest Published: Jul 21, 2026 License: Apache-2.0 Imports: 4 Imported by: 0

README

📚 OTMC Logger

A simple, high-performance logging library for Go applications, designed for CLI, Desktop, API, and Server applications.

✨ Features

  • Simple API - Similar to fmt.Printf, easy to use
  • Beautiful Console Output - Automatic formatting with colors and alignment
  • File Logging - With automatic rotation support
  • Multiple Formatters - Pretty (default), Text, and JSON
  • Log Levels - TRACE, DEBUG, INFO, WARN, ERROR, CRIT
  • Caller Information - Automatically captures function, file, and line number
  • Runtime Configuration - Change settings at runtime without restart
  • Multiple Logger Instances - Create independent loggers with different configs
  • Thread-Safe - Safe for concurrent use
  • Production Ready - Default configuration optimized for production

📦 Installation

go get github.com/otmc-sw/logger@latest

🚀 Quick Start

package main

import (
    "github.com/otmc-sw/logger"
)

func main() {
    err := "OTMC Testing Message"

	logger.Trace("🚀 Starting application...")
	logger.Debug("📝 Configuration loaded from %s", "config.yaml")
	logger.Info("🌐 Server listening on %s:%d", "localhost", 8080)
	logger.Warn("⚠️ Memory usage is high: %.1f%%", 85.5)
	logger.Error("❌ Failed to connect to database: %s", "postgres")
    // Warning: This will close the application.
	logger.Crit("❌ Unable to initialize application: %v", err)
}

🖥️ Console Output

The logger automatically formats output with timestamps, caller information, and colors:

2026-07-06 08:57:34.208 +07:00     Initializer()      main.go:104   | INFO  | ✅ Database connection established.
2026-07-06 08:57:34.208 +07:00     Initializer()      main.go:106   | INFO  | 🧩 Loading settings...
2026-07-06 08:57:34.209 +07:00     Initializer()      main.go:112   | INFO  | 🤖 LLM Provider: groq
2026-07-06 08:57:34.209 +07:00     Initializer()      main.go:119   | INFO  | ✅ LLM client initialized.
2026-07-06 08:57:34.209 +07:00     Initializer()      main.go:149   | INFO  | 📁 Run directory: D:\SCM\GitHub\OTMC\Softwares\document-hub\backend
2026-07-06 08:57:34.209 +07:00     Initializer()      main.go:150   | INFO  | 📦 Frontend dist: D:\SCM\GitHub\OTMC\Softwares\document-hub\frontend\dist
2026-07-06 08:57:34.209 +07:00          Runner()      main.go:154   | INFO  | 🌿 Running application ...
2026-07-06 08:57:34.209 +07:00          Runner()      main.go:157   | INFO  | 🌐 Registering APIs ...
2026-07-06 08:57:34.210 +07:00           Start() scheduler.go:57    | INFO  | ✅ Backup scheduler engine started
2026-07-06 08:57:34.210 +07:00          reload() scheduler.go:142   | INFO  | 🔀 Backup scheduled with cron expression: 0 2 * * * (max backups: 10)

⚙️ Configuration

🛠️ Creating a Logger
// With no options — uses default config (console, InfoLevel, caller on)
log := logger.New()

// With one or more options
log := logger.New(
    logger.WithLevel(logger.DebugLevel),
    logger.WithConsole(),
    logger.WithFile("logs/app.log"),
    logger.WithJSON(),
    logger.WithCaller(false),
    logger.WithMaxSize(20),
    logger.WithMaxBackups(3),
    logger.WithMaxAge(30),
    logger.WithCompress(true),
    logger.WithTimeFormat(time.RFC3339),
)
🔄 Runtime Configuration

The logger supports runtime configuration changes. Most changes can be done through Configure() or dedicated methods:

Configure (batch update)

Apply one or more options at once. This is the recommended way to change settings that affect the formatter or writer (JSON toggle, file path, etc.).

log.Configure(
    logger.WithJSON(),
    logger.WithFile("logs/app.log"),
    logger.WithCaller(false),
)

// Global
logger.Configure(
    logger.WithLevel(logger.DebugLevel),
    logger.WithJSON(),
)
SetLevel (single update — no rebuild)

Changing the log level is the most frequent operation and does not require recreating the logger internals.

log.SetLevel(logger.DebugLevel)

// Global
logger.SetLevel(logger.WarnLevel)
Config / Update (round-trip)

Get a copy of the current config, modify it, and apply it back.

cfg := log.Config()
cfg.Level = logger.DebugLevel
cfg.JSON = true
cfg.Filename = "logs/app.log"
log.Update(cfg)

// Global
cfg := logger.GetConfig()
cfg.Console = true
logger.Update(cfg)
Available Options
Option Default Description
WithLevel(level) InfoLevel Minimum log level
WithConsole(enabled) true Enable/disable console output
WithFile(filename) "" Enable file output with rotation
WithJSON(enabled) false JSON format instead of pretty
WithCaller(enabled) true Include caller info (file:line)
WithStacktrace(enabled) false Include stack trace on errors
WithMaxSize(mb) 10 Max file size before rotation (MB)
WithMaxBackups(n) 3 Max rotated files to keep
WithMaxAge(days) 90 Max age of rotated files (days)
WithCompress(enabled) true Compress rotated files
WithTimeFormat(format) "2006-01-02 15:04:05.000 -07:00" Time format string

📊 Log Levels

logger.Trace("Detailed trace information")
logger.Debug("Debug information")
logger.Info("General informational messages")
logger.Warn("Warning messages")
logger.Error("Error messages")
logger.Crit("Critical errors — exits after logging")

🎨 Formatters

🎯 Pretty Formatter (Default)
log := logger.New(
    logger.WithConsole(),
)

Output:

2026-07-06 08:57:34.208 +07:00     Initializer()      main.go:106   | INFO  | 🧩 Loading settings...
2026-07-06 08:57:34.209 +07:00          Runner()      main.go:154   | INFO  | 🌿 Running application ...
📋 JSON Formatter
log := logger.New(
    logger.WithJSON(),
    logger.WithConsole(),
)

Output:

{
  "time": "2026-07-04T08:49:40.404+07:00",
  "level": "INFO",
  "message": "Application started",
  "function": "main",
  "file": "main.go",
  "line": 20
}

🌍 Global Logger

The library provides a global logger instance that mirrors the instance API:

// Logging
logger.Trace("...")
logger.Debug("...")
logger.Info("...")
logger.Warn("...")
logger.Error("...")
logger.Crit("...")

// Request logging
logger.Request("GET", "/api/users", 200, 150*time.Millisecond, "10.0.0.1")

// Configuration
logger.SetLevel(logger.DebugLevel)
logger.Configure(logger.WithJSON(), logger.WithFile("app.log"))
logger.Update(cfg)
cfg := logger.GetConfig()

🔧 Custom Logger Instances

Create independent logger instances with different configurations:

// Console logger — debug level, pretty format
consoleLog := logger.New(
    logger.WithConsole(),
    logger.WithLevel(logger.DebugLevel),
)
consoleLog.Info("This is a console log")
consoleLog.SetLevel(logger.TraceLevel)

// File logger — info level, rotated files
fileLog := logger.New(
    logger.WithFile("logs/app.log"),
    logger.WithLevel(logger.InfoLevel),
    logger.WithMaxSize(20),
)
fileLog.Info("This is a file log")

// JSON logger — for structured monitoring
jsonLog := logger.New(
    logger.WithFile("logs/metrics.json"),
    logger.WithJSON(),
    logger.WithCaller(false),
)
jsonLog.Info("This is a JSON log for metrics")

// Change settings at runtime
jsonLog.Configure(logger.WithCaller(true))

♻️ Log Rotation

Automatic log rotation using the built-in rotator package:

log := logger.New(
    logger.WithFile("logs/app.log"),
    logger.WithMaxSize(20),    // 20 MB per file
    logger.WithMaxBackups(3),  // keep 3 rotated files
    logger.WithMaxAge(30),     // keep for 30 days
    logger.WithCompress(true), // compress rotated files
)

The rotator package is lightweight, dependency-free, and supports:

  • Configurable naming strategies (index, date, timestamp, or custom)
  • Gzip compression
  • Automatic cleanup by count and age
  • Thread-safe concurrent writes

For advanced usage, see the rotator package documentation.

🎨 Color Output

Colors are automatically applied to console output:

  • TRACE - Gray
  • DEBUG - Cyan
  • INFO - Blue
  • WARN - Yellow
  • ERROR - Red
  • CRIT - Bright Red

Colors are automatically stripped when writing to files.

🏗️ Architecture

Application
    ↓
Logger API (Trace, Debug, Info, Warn, Error, Crit, Request)
    ↓
┌─────────────────────────────────────┐
│ Logger struct                       │
│   ┌─────────┐  ┌──────────────────┐ │
│   │ Config  │  │ Core             │ │
│   │ Level   │  │   → Formatter    │ │
│   │ JSON    │  │   → Writer       │ │
│   │ Console │  │   → Hooks        │ │
│   │ File    │  └──────────────────┘ │
│   │ Caller  │                       │
│   └─────────┘                       │
│                                     │
│   Configure()  SetLevel()           │
│   Config()     Update()             │
└─────────────────────────────────────┘
    ↓
├── Formatter (Pretty, Text, JSON)
├── Writer (Console, File, Multi)
└── Hooks (Webhook, Discord, Slack, etc.)

📄 License

  • Apache License 2.0
  • Copyright (c) 2026 OTMC Softwares.

✨ Contributors

  • 🌿 Nguyen Van Trung
  • 🌿 Nguyen Thi Hoai
  • 🌿 OTMC Contributors

Documentation

Overview

*

  • @License Apache License 2.0
  • @Copyright (c) 2026 OTMC Softwares. OTMC Golang Logger.
  • @Contributors Nguyen Van Trung, Nguyen Thi Hoai, OTMC Contributors.

*

*

  • @License Apache License 2.0
  • @Copyright (c) 2026 OTMC Softwares. OTMC Golang Logger.
  • @Contributors Nguyen Van Trung, Nguyen Thi Hoai, OTMC Contributors. *

*

  • @License Apache License 2.0
  • @Copyright (c) 2026 OTMC Softwares. OTMC Golang Logger.
  • @Contributors Nguyen Van Trung, Nguyen Thi Hoai, OTMC Contributors.

*

Index

Constants

View Source 
const (
	TraceLevel = core.TraceLevel
	DebugLevel = core.DebugLevel
	InfoLevel  = core.InfoLevel
	WarnLevel  = core.WarnLevel
	ErrorLevel = core.ErrorLevel
	CritLevel  = core.CritLevel
)

Variables

This section is empty.

Functions

func AddListener added in v0.1.8 

func AddListener() chan LogEntry

func Close added in v0.1.7 

func Close() error

func Configure added in v0.1.4 

func Configure(opts ...Option)

func Crit added in v0.1.1 

func Crit(format string, args ...any)

func Debug 

func Debug(format string, args ...any)

func Error 

func Error(format string, args ...any)

func Info 

func Info(format string, args ...any)

func Metadata added in v0.1.11 

func Metadata(metadata interface{}, level Level, format string, args ...any)

func RemoveListener added in v0.1.8 

func RemoveListener(ch chan LogEntry)

func Request added in v0.1.3 

func Request(method, path string, statusCode int, latency time.Duration, clientIP string)

func SetLevel 

func SetLevel(level Level)

func Sync 

func Sync() error

func Trace 

func Trace(format string, args ...any)

func Update added in v0.1.4 

func Update(cfg Config)

func Warn 

func Warn(format string, args ...any)

Types

type Config 

type Config struct {
	Level         Level
	Console       bool
	File          bool
	Filename      string
	JSON          bool
	Caller        bool
	Stacktrace    bool
	MaxSize       float64
	MaxBackups    int
	MaxAge        int
	Compress      bool
	TimeFormat    string
	MaxLogEntries int
}

func DefaultConfig 

func DefaultConfig() Config

func GetConfig added in v0.1.4 

func GetConfig() Config

type Formatter 

type Formatter = core.Formatter

type Hook 

type Hook = core.Hook

type Level 

type Level = core.Level

func ParseLevel 

func ParseLevel(level string) Level

type LogEntry added in v0.1.8 

type LogEntry = core.Entry

func GetRecentLogs added in v0.1.8 

func GetRecentLogs(limit int) []LogEntry

type Logger 

type Logger struct {
	// contains filtered or unexported fields
}

func New 

func New(opts ...Option) *Logger

func (*Logger) AddListener added in v0.1.8 

func (l *Logger) AddListener() chan LogEntry

func (*Logger) Close added in v0.1.7 

func (l *Logger) Close() error

func (*Logger) Config added in v0.1.4 

func (l *Logger) Config() Config

func (*Logger) Configure added in v0.1.4 

func (l *Logger) Configure(opts ...Option)

func (*Logger) Crit added in v0.1.1 

func (l *Logger) Crit(format string, args ...any)

func (*Logger) Debug 

func (l *Logger) Debug(format string, args ...any)

func (*Logger) Error 

func (l *Logger) Error(format string, args ...any)

func (*Logger) GetRecentLogs added in v0.1.8 

func (l *Logger) GetRecentLogs(limit int) []LogEntry

func (*Logger) Info 

func (l *Logger) Info(format string, args ...any)

func (*Logger) Metadata added in v0.1.11 

func (l *Logger) Metadata(metadata interface{}, level Level, format string, args ...any)

func (*Logger) RemoveListener added in v0.1.8 

func (l *Logger) RemoveListener(ch chan LogEntry)

func (*Logger) Request added in v0.1.3 

func (l *Logger) Request(method, path string, statusCode int, latency time.Duration, clientIP string)

func (*Logger) SetLevel added in v0.1.4 

func (l *Logger) SetLevel(level Level)

func (*Logger) Sync 

func (l *Logger) Sync() error

func (*Logger) Trace 

func (l *Logger) Trace(format string, args ...any)

func (*Logger) Update added in v0.1.4 

func (l *Logger) Update(cfg Config)

func (*Logger) Warn 

func (l *Logger) Warn(format string, args ...any)

type Option 

type Option func(*Config)

func WithCaller 

func WithCaller(enabled bool) Option

func WithCompress 

func WithCompress(enabled bool) Option

func WithConsole 

func WithConsole(enabled bool) Option

func WithFile 

func WithFile(filename string) Option

func WithJSON 

func WithJSON(enabled bool) Option

func WithLevel 

func WithLevel(level Level) Option

func WithMaxAge 

func WithMaxAge(maxAge int) Option

func WithMaxBackups 

func WithMaxBackups(maxBackups int) Option

func WithMaxLogEntries added in v0.1.8 

func WithMaxLogEntries(maxEntries int) Option

func WithMaxSize 

func WithMaxSize(maxSize float64) Option

func WithStacktrace 

func WithStacktrace(enabled bool) Option

func WithTimeFormat added in v0.1.4 

func WithTimeFormat(format string) Option

Source Files

View all Source files

Directories

Path Synopsis
*
 *
*
 *
*
 *
*
 *
tests
printer command
*
 *
rotator command
*
 *
*
 *

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