Rotation Logger

A simple async rotation logger library for Rust. It can be safely used across threads by passing a logger instance as an argument or via macros.

Example

1. Configure the Formatter

Define how log strings and timestamps are formatted:

let formatter = MessageFormatter::new(
    "::",
    "{timestamp:-6:30:right}{splitter}{modules:_:_:left}{splitter}{message}",
    "%Y-%m-%d %H:%M:%S.%f",
);

The configuration consists of three parts:

• Splitter symbol — a character used to separate fields in the log line.

• Format string — defines the layout of each log line using masks. Each mask (except splitter) is surrounded by curly braces and supports formatting options separated by :.

  Available masks:

  • timestamp — where the timestamp will be printed.
  • splitter — where the splitter character will be inserted.
  • modules — the source modules of the log entry (joined by the splitter).
  • message — the log message itself.

  Formatting syntax inside curly braces:

  {<mask>:<string_length>:<column_width>:<text_halign>}
  

  • string_length — limits string length. Positive value trims from the end; negative value trims from the start.
  • column_width — fixed column width. Content is sliced if it doesn't fit.
  • text_halign — horizontal alignment: left, right, or center.

  Any formatting option can be omitted using _:

  {<mask>:_:<column_width>:_}
  

• Timestamp format — a chrono-compatible format string used for the timestamp mask.

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2. Configure the Output Channel

Choose where logs are written: file, console, or auto (console in debug mode, file in release mode).

let output = OutputChannel::file(
    "./".into(),
    10,
    FileSize::from_megabytes(5),
    "new_logger".into(),
    "log".into(),
);

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3. Create Settings

The first argument enables or disables the logger. When disabled, all log methods remain available but do nothing internally.

let settings = Settings::new(true, 5, output, formatter);

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4. Create a Logger Instance

A logger instance can be safely .clone()d and passed to other threads.

let logger = Logger::new(settings);
let logger_01 = logger.clone();
let logger_02 = logger.clone();

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5. Run the Logger

Start the async logger. You can join on its handle or keep another long-lived thread alive.

let joiner = logger.run_async();

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6. Use the Logger in Other Threads

Pass cloned instances into spawned threads:

let _ = thread::spawn(move || {
    logger_02.log(&vec!["THREAD2".into(), "MAIN".into()], "Starting...");
    let mut counter = 0;
    loop {
        logger_02.log(
            &vec!["THREAD2".into(), "WORKER".into()],
            format!("Processing Job: {counter}").as_str(),
        );
        counter += 2;
        sleep(Duration::from_millis(400));
    }
});

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For a complete example, see Demo.