Redirect all logging (including errors) from Tornado web framework to stdout and use stderr for error logs only.

tornado_logging_to_stdout_and_stderr.py

"""Redirect all logging (including errors) from Tornado web framework to stdout
and use stderr for error logs only.

Can be usefull when you want to store separatelly all logs and error logs.
"""

import logging
import sys

import tornado.log
from tornado.options import options


def setup_logging_to_stream(stream, log_level):
    logger = logging.getLogger()

    channel = logging.StreamHandler(stream)
    channel.setLevel(log_level)
    channel.setFormatter(tornado.log.LogFormatter())
    logger.addHandler(channel)


def setup_logging(log_level=None):
    if log_level is None:
        log_level = getattr(logging, options.logging.upper())

    logger = logging.getLogger()
    logger.setLevel(log_level)

    setup_logging_to_stream(stream=sys.stdout, log_level=log_level)
    setup_logging_to_stream(stream=sys.stderr, log_level=logging.ERROR)