Rust-Loguru

A flexible and efficient logging library for Rust inspired by Python's Loguru. Designed to provide an intuitive, powerful logging experience while maintaining Rust's performance characteristics.

Features

• Multiple log levels: TRACE, DEBUG, INFO, SUCCESS, WARNING, ERROR, CRITICAL
• Thread-safe global logger: Safe to use in multi-threaded applications
• Extensible handler system: Console, file, and custom handlers
• Configurable log formatting: Customize how log messages are displayed
• Support for metadata in log records: Add structured data to log messages
• Convenient logging macros: Easy to use macros for all log levels
• File rotation: Automatic file rotation based on size with retention policies
• Colorized output: Colorful console output for better readability
• Source location capture: Automatically capture file, line, and module information

Installation

Add this to your Cargo.toml:

[dependencies]
rust-loguru = "0.1.8" # Or Newer version

Quick Start

use rust_loguru::{info, debug, error, init, LogLevel, Logger};
use rust_loguru::handler::console::ConsoleHandler;
use std::sync::Arc;
use parking_lot::RwLock;

fn main() {
    // Initialize the global logger with a console handler
    let handler = Arc::new(RwLock::new(
        ConsoleHandler::stderr(LogLevel::Debug)
            .with_colors(true)
    ));
    
    let mut logger = Logger::new(LogLevel::Debug);
    logger.add_handler(handler);
    
    // Set the global logger (required for macros to work)
    init(logger);
    
    // Log messages at different levels
    debug!("This is a debug message");
    info!("This is an info message");
    error!("This is an error message: {}", "something went wrong");
    
    // Log with metadata
    use rust_loguru::log_with_metadata;
    log_with_metadata!(LogLevel::Info, "user_id" => "123", "session" => "abc123"; 
                       "User logged in: {}", "johndoe");
}

Core Concepts

Log Levels

Rust-Loguru supports the following log levels, in order of increasing severity:

• TRACE: Very detailed information, typically only useful for debugging specific issues
• DEBUG: Detailed information useful for debugging
• INFO: General information about the application's operation
• SUCCESS: Successful operations (similar to INFO but indicates success)
• WARNING: Potential issues that don't prevent the application from working
• ERROR: Errors that prevent specific operations from working
• CRITICAL: Critical errors that may lead to application failure

Handlers

Handlers determine where log messages are sent. Rust-Loguru comes with:

• ConsoleHandler: Outputs logs to stdout or stderr
• FileHandler: Writes logs to a file with optional rotation
• NullHandler: Discards all logs (useful for testing)

Creating a Console Handler

use rust_loguru::handler::console::ConsoleHandler;
use rust_loguru::LogLevel;

// Output to stderr with INFO level
let handler = ConsoleHandler::stderr(LogLevel::Info)
    .with_colors(true)
    .with_pattern("{time} {level} [{file}:{line}] {message}");

Creating a File Handler

use rust_loguru::handler::file::FileHandler;
use rust_loguru::LogLevel;
use std::path::Path;

// Write to a file with rotation at 10MB and keep 5 old files
let handler = FileHandler::new(Path::new("app.log")).unwrap()
    .with_rotation(10 * 1024 * 1024)
    .with_retention(5)
    .with_colors(false);

Logging with Metadata

You can add structured metadata to log records:

use rust_loguru::{Record, LogLevel, log};

// Using the Record API directly
let record = Record::new(
    LogLevel::Info,
    "User logged in",
    Some("auth_module".to_string()),
    Some("auth.rs".to_string()),
    Some(42),
)
.with_metadata("user_id", "123")
.with_metadata("ip_address", "192.168.1.1");

log(&record);

// Or using the macro
log_with_metadata!(LogLevel::Info, 
    "user_id" => "123", 
    "ip_address" => "192.168.1.1"; 
    "User logged in: {}", "johndoe"
);

Customizing Formatters

Customize how logs are formatted:

use rust_loguru::formatter::Formatter;

let formatter = Formatter::new()
    .with_colors(true)
    .with_timestamp(true)
    .with_level(true)
    .with_module(true)
    .with_location(true)
    .with_pattern("{time} {level} [{file}:{line}] {message}");

Configuration Presets

Use built-in configuration presets:

use rust_loguru::LoggerConfig;

// Development configuration with detailed logging
let config = LoggerConfig::development();

// Production configuration with minimal logging
let config = LoggerConfig::production();

Advanced Usage

Creating Custom Handlers

Implement the Handler trait to create custom handlers:

use rust_loguru::handler::Handler;
use rust_loguru::level::LogLevel;
use rust_loguru::record::Record;
use rust_loguru::formatter::Formatter;

#[derive(Debug)]
struct CustomHandler {
    level: LogLevel,
    enabled: bool,
    formatter: Formatter,
}

impl Handler for CustomHandler {
    fn level(&self) -> LogLevel {
        self.level
    }

    fn set_level(&mut self, level: LogLevel) {
        self.level = level;
    }

    fn enabled(&self) -> bool {
        self.enabled
    }

    fn set_enabled(&mut self, enabled: bool) {
        self.enabled = enabled;
    }

    fn formatter(&self) -> &Formatter {
        &self.formatter
    }

    fn set_formatter(&mut self, formatter: Formatter) {
        self.formatter = formatter;
    }

    fn handle(&mut self, record: &Record) -> bool {
        if !self.enabled || record.level() < self.level {
            return false;
        }
        
        let formatted = self.formatter.format(record);
        // Custom handling logic here
        println!("Custom handler: {}", formatted);
        true
    }
}

Structured Logging with JSON

Use the structured data capability:

use rust_loguru::{Record, LogLevel, log};
use serde_json::json;

let record = Record::new(
    LogLevel::Info,
    "API request completed",
    Some("api_module".to_string()),
    Some("api.rs".to_string()),
    Some(120),
)
.with_structured_data("request", &json!({
    "method": "GET",
    "path": "/users",
    "status": 200,
    "duration_ms": 42
}))
.unwrap();

log(&record);

Performance Considerations

• Log records below the configured level are filtered out early for minimal overhead
• File handlers use buffered I/O for efficient disk operations
• Consider using appropriate log levels in production to minimize overhead

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is licensed under MIT of:

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)