logger.py

# Copyright (c) Facebook, Inc. and its affiliates.
# All rights reserved.
#
# This source code is licensed under the license found in the
# LICENSE file in the root directory of this source tree.
#

import logging
import time
from datetime import timedelta

class LogFormatter:
    def __init__(self):
        self.start_time = time.time()

    def format(self, record):
        elapsed_seconds = round(record.created - self.start_time)

        prefix = "%s - %s [%s]" % (
            time.strftime("%x %X"),
            timedelta(seconds=elapsed_seconds),
            record.levelname,
        )
        message = record.getMessage()
        message = message.replace("\n", "\n" + " " * (len(prefix) + 3))
        return "%s - %s" % (prefix, message) if message else ""


def create_logger(filepath=None):
    """
    Create a logger.
    Use a different log file for each process.
    """
    # create log formatter
    log_formatter = LogFormatter()

    # create file handler and set level to debug
    if filepath is not None:
        file_handler = logging.FileHandler(filepath, "a")
        file_handler.setLevel(logging.DEBUG)
        file_handler.setFormatter(log_formatter)

    # create console handler and set level to info
    console_handler = logging.StreamHandler()
    console_handler.setLevel(logging.INFO)
    console_handler.setFormatter(log_formatter)

    # create logger and set level to debug
    logger = logging.getLogger()
    logger.handlers = []
    logger.setLevel(logging.DEBUG)
    logger.propagate = False
    if filepath is not None:
        logger.addHandler(file_handler)
    logger.addHandler(console_handler)

    # reset logger elapsed time
    def reset_time():
        log_formatter.start_time = time.time()

    logger.reset_time = reset_time

    return logger