util/logger.py

# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
import functools
import logging
import os
import sys
import colorlog


# so that calling setup_logger multiple times won't add many handlers
@functools.lru_cache()
def setup_logger(
    output=None, distributed_rank=0, *, color=True, name="imagenet", abbrev_name=None
):
    """
    Initialize the detectron2 logger and set its verbosity level to "INFO".

    Args:
        output (str): a file name or a directory to save log. If None, will not save log file.
            If ends with ".txt" or ".log", assumed to be a file name.
            Otherwise, logs will be saved to `output/log.txt`.
        name (str): the root module name of this logger

    Returns:
        logging.Logger: a logger
    """
    logger = logging.getLogger(name)
    logger.setLevel(logging.DEBUG)
    formatter = colorlog.ColoredFormatter(
            "%(log_color)s%(levelname)-8s%(reset)s %(log_color)s%(asctime)s | %(blue)s%(message)s",
        datefmt=None,
        reset=True,
        log_colors={
            'DEBUG':    'cyan', 
            'INFO':     'green',
            'WARNING':  'yellow',
            'ERROR':    'red',
            'CRITICAL': 'red,bg_white'
        }
    )
    logger.propagate = False

    if abbrev_name is None:
        abbrev_name = name

    # stdout logging: master only
    if distributed_rank == 0:
        ch = logging.StreamHandler(stream=sys.stdout)
        ch.setLevel(logging.DEBUG)
        ch.setFormatter(formatter)
        logger.addHandler(ch)

    # file logging: all workers
    if output is not None:
        if output.endswith(".txt") or output.endswith(".log"):
            filename = output
        else:
            filename = os.path.join(output, "log.txt")
        if distributed_rank > 0:
            filename = filename + f".rank{distributed_rank}"
        os.makedirs(os.path.dirname(filename), exist_ok=True)

        fh = logging.StreamHandler(_cached_log_stream(filename))
        fh.setLevel(logging.DEBUG)
        fh.setFormatter(formatter)
        logger.addHandler(fh)

    return logger


# cache the opened file object, so that different calls to `setup_logger`
# with the same file name can safely write to the same file.
@functools.lru_cache(maxsize=None)
def _cached_log_stream(filename):
    return open(filename, "a")