kitty_logger

Cross-process Python logger. The main process starts a dedicated log-server subprocess; every other process (forked or spawned) ships LogRecords to it via logging.handlers.SocketHandler, so all log lines end up in one place with no interleaving or file-locking issues.

Install

pip install .

Usage

# main.py
import multiprocessing as mp
import kitty_logger

def worker(i):
    log = kitty_logger.getLogger(f"worker.{i}")
    log.info("hello from worker %d", i)

if __name__ == "__main__":
    kitty_logger.setup_logging(log_file="app.log")
    log = kitty_logger.getLogger("main")
    log.info("starting")

    with mp.get_context("spawn").Pool(4) as pool:
        pool.map(worker, range(4))

setup_logging sets the env vars KITTY_LOGGER_HOST / KITTY_LOGGER_PORT, which child processes inherit and use to connect.

API

• setup_logging(log_file=None, level=logging.INFO, host="127.0.0.1", port=0, stream=True, console_fmt=..., file_fmt=..., datefmt=None, attach_main_logger=True) -> (host, port) Starts the log-server subprocess (always uses the spawn start method). Idempotent. Registered with atexit. port=0 lets the OS pick a free port; the actual (host, port) is returned.
• getLogger(name=None) -> logging.Logger Returns a logger with a SocketHandler pointing at the server.
• shutdown_logging() — stop the server subprocess explicitly.

Why spawn-only

Child processes started with fork inherit the parent's already-connected SocketHandler (and its TCP fd). Parent and child would then interleave pickled-record bytes on the same connection, which corrupts every record on the wire. fork is also unsafe in multi-threaded parents and unavailable on Windows. KittyLogger therefore only supports spawn. Use multiprocessing.get_context("spawn") (or just rely on Python's defaults under if __name__ == "__main__":).

Security

The server uses pickle to deserialize incoming LogRecords. Only ever bind to a loopback address (the default 127.0.0.1). Binding to 0.0.0.0 or any externally reachable interface exposes a remote-code-execution surface to anyone who can reach the port.

Caveats

• Do not call logging.basicConfig() (or otherwise attach a StreamHandler to the root logger) before setup_logging(attach_main_logger=True) — the main process would emit each record twice: once via the local root handler and once via the log-server. Either let kitty_logger be the only configurer, or pass attach_main_logger=False and manage main-process handlers yourself.
• After shutdown_logging(), kitty_logger removes its own SocketHandlers from this process's loggers and clears KITTY_LOGGER_* env vars, so the process state is symmetric with setup_logging. If you attach extra handlers yourself, you remain responsible for cleaning them up.