log4rc

A log4j-like logging framework for Rust.

Overview

log4rc is a simple, extensible logging framework inspired by log4j. It provides different log levels and an easy-to-use API for Rust applications.

Features

• Multiple log levels (Trace, Debug, Info, Warn, Error)
• Simple API similar to log4j
• Thread-safe logging
• Timestamped log entries
• Configurable log levels
• File appender (append logs to disk)
• Cheap to disable: filtered-out levels skip formatting entirely

Installation

Add this to your Cargo.toml:

[dependencies]
log4rc = "0.1"

Example

use log4rc::{LogLevel, Logger};

fn main() {
    // Initialize the logger with Debug level
    Logger::init(LogLevel::Debug);
    
    // Test all log levels
    log4rc::trace!("This is a trace message - won't be printed");
    log4rc::debug!("This is a debug message - will be printed");
    log4rc::info!("This is an info message - will be printed");
    log4rc::warn!("This is a warning message - will be printed");
    log4rc::error!("This is an error message - will be printed");
}

Custom appenders

log4rc is extensible: implement the Appender trait (output target) and the Layout trait (message formatting), then build a logger with Logger::builder.

use log4rc::{Appender, LogEvent, LogLevel, Logger, SimpleLayout};

struct MyAppender;

impl Appender for MyAppender {
    fn append(&self, event: &LogEvent) {
        // Write `event.message` somewhere, e.g. a file or a network socket
    }
}

fn main() {
    Logger::builder(LogLevel::Debug)
        .appender(Box::new(MyAppender))
        .init();
}

You can add multiple appenders, and Logger::init remains a shortcut that installs a console appender with the default layout.

File appender

FileAppender appends formatted events to a file (creating it if needed) and flushes after every event. Size-based rotation is available via the builder — once the file reaches the limit, it is rolled over to a timestamped sibling (e.g. app.log.20260809-102530-1). max_files bounds how many rotated files are kept (the oldest are deleted once the count is exceeded), and .compressed() gzips rotated files:

use log4rc::{ConsoleAppender, FileAppender, LogLevel, Logger, SimpleLayout};

Logger::builder(LogLevel::Info)
    .appender(Box::new(ConsoleAppender::new(Box::new(SimpleLayout))))
    .appender(Box::new(
        FileAppender::builder("app.log", Box::new(SimpleLayout))
            .max_size(10 * 1024 * 1024) // roll at 10 MiB
            .max_files(5) // keep at most 5 rotated files
            .compressed() // gzip rotated files as app.log.<timestamp>.gz
            .build()
            .unwrap(),
    ))
    .init();

License

This project is licensed under the MIT License - see the LICENSE file for details.