README.md

Log Library

The Log library provides a flexible and extensible logging system for Go applications in the EVO Framework. It supports multiple logging levels, customizable output formats, and various output destinations including console and files.

Installation

import "github.com/getevo/evo/v2/lib/log"

For file-based logging:

import "github.com/getevo/evo/v2/lib/log/file"

Features

Main Logging Features

• Multiple Logging Levels: Critical, Error, Warning, Notice, Info, Debug
• Customizable Writers: Add your own output destinations
• Structured Log Entries: Each entry includes timestamp, file, line number, and severity level
• Formatted Logging: Support for printf-style formatting
• Fatal and Panic Handling: Special functions for critical errors

File Logging Features

• Log Rotation: Automatic daily log rotation
• Configurable File Naming: Use date/time placeholders in file names
• Log Expiration: Automatic cleanup of old log files
• Custom Formatting: Define your own log entry format
• Thread-Safe: Mutex protection for concurrent logging

Usage Examples

Basic Logging

package main

import (
    "github.com/getevo/evo/v2/lib/log"
)

func main() {
    // Set the global log level
    log.SetLevel(log.DebugLevel)
    
    // Log messages at different levels
    log.Debug("This is a debug message")
    log.Info("This is an info message")
    log.Notice("This is a notice message")
    log.Warning("This is a warning message")
    log.Error("This is an error message")
    log.Critical("This is a critical message")
    
    // Formatted logging
    log.Infof("User %s logged in from %s", "john", "192.168.1.1")
    
    // Alternative format (uppercase 'F')
    log.InfoF("Processing item %d of %d", 1, 10)
}

Custom Log Writers

package main

import (
    "fmt"
    "github.com/getevo/evo/v2/lib/log"
)

func main() {
    // Create a custom writer
    customWriter := func(entry *log.Entry) {
        fmt.Printf("[%s] %s: %s\n", 
            entry.Level, 
            entry.Date.Format("2006-01-02 15:04:05"),
            entry.Message)
    }
    
    // Add the custom writer
    log.AddWriter(customWriter)
    
    // Or replace all writers
    log.SetWriters(customWriter)
    
    log.Info("This message will be formatted by the custom writer")
}

File Logging

package main

import (
    "github.com/getevo/evo/v2/lib/log"
    "github.com/getevo/evo/v2/lib/log/file"
    "time"
)

func main() {
    // Configure file logger
    fileLogger := file.NewFileLogger(file.Config{
        Path:       "/var/log/myapp",
        FileName:   "app_%y-%m-%d.log",  // Will create files like app_2025-08-03.log
        Expiration: 7 * 24 * time.Hour,  // Keep logs for 7 days
    })
    
    // Add file logger to writers
    log.AddWriter(fileLogger)
    
    log.Info("This message will be logged to both console and file")
}

Custom File Log Format

package main

import (
    "fmt"
    "github.com/getevo/evo/v2/lib/log"
    "github.com/getevo/evo/v2/lib/log/file"
    "time"
)

func main() {
    // Custom log format
    customFormat := func(entry *log.Entry) string {
        return fmt.Sprintf("[%s] %s - %s",
            entry.Level,
            entry.Date.Format("2006-01-02 15:04:05"),
            entry.Message)
    }
    
    // Configure file logger with custom format
    fileLogger := file.NewFileLogger(file.Config{
        Path:       "logs",
        FileName:   "app.log",
        LogFormat:  customFormat,
    })
    
    // Add file logger to writers
    log.AddWriter(fileLogger)
    
    log.Info("This message will use the custom format in the log file")
}

Log Levels

The library supports the following log levels, in order of increasing verbosity:

1. CriticalLevel: Severe errors that cause the application to abort
2. ErrorLevel: Error conditions that should be addressed
3. WarningLevel: Warning conditions that indicate potential issues
4. NoticeLevel: Normal but significant conditions
5. InfoLevel: Informational messages about normal operation
6. DebugLevel: Detailed information for debugging purposes

You can set the global log level using log.SetLevel(). Only messages at or above the set level will be logged.

Subdirectories

• file: Provides file-based logging capabilities with rotation and cleanup