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#!/usr/bin/env python
# Copyright 2012 Facebook
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""Logging support for Tornado.
Tornado uses three logger streams:
* ``tornado.access``: Per-request logging for Tornado's HTTP servers (and
potentially other servers in the future)
* ``tornado.application``: Logging of errors from application code (i.e.
uncaught exceptions from callbacks)
* ``tornado.general``: General-purpose logging, including any errors
or warnings from Tornado itself.
These streams may be configured independently using the standard library's
`logging` module. For example, you may wish to send ``tornado.access`` logs
to a separate file for analysis.
from __future__ import absolute_import, division, print_function, with_statement
import logging
import logging.handlers
import sys
import time
from tornado.escape import _unicode
from tornado.util import unicode_type, basestring_type
import curses
except ImportError:
curses = None
# Logger objects for internal tornado use
access_log = logging.getLogger("tornado.access")
app_log = logging.getLogger("tornado.application")
gen_log = logging.getLogger("tornado.general")
def _stderr_supports_color():
color = False
if curses and sys.stderr.isatty():
if curses.tigetnum("colors") > 0:
color = True
except Exception:
return color
class LogFormatter(logging.Formatter):
"""Log formatter used in Tornado.
Key features of this formatter are:
* Color support when logging to a terminal that supports it.
* Timestamps on every log line.
* Robust against str/bytes encoding problems.
This formatter is enabled automatically by
`tornado.options.parse_command_line` (unless ``--logging=none`` is
def __init__(self, color=True, *args, **kwargs):
logging.Formatter.__init__(self, *args, **kwargs)
self._color = color and _stderr_supports_color()
if self._color:
# The curses module has some str/bytes confusion in
# python3. Until version 3.2.3, most methods return
# bytes, but only accept strings. In addition, we want to
# output these strings with the logging module, which
# works with unicode strings. The explicit calls to
# unicode() below are harmless in python2 but will do the
# right conversion in python 3.
fg_color = (curses.tigetstr("setaf") or
curses.tigetstr("setf") or "")
if (3, 0) < sys.version_info < (3, 2, 3):
fg_color = unicode_type(fg_color, "ascii")
self._colors = {
logging.DEBUG: unicode_type(curses.tparm(fg_color, 4), # Blue
logging.INFO: unicode_type(curses.tparm(fg_color, 2), # Green
logging.WARNING: unicode_type(curses.tparm(fg_color, 3), # Yellow
logging.ERROR: unicode_type(curses.tparm(fg_color, 1), # Red
self._normal = unicode_type(curses.tigetstr("sgr0"), "ascii")
def format(self, record):
record.message = record.getMessage()
except Exception as e:
record.message = "Bad message (%r): %r" % (e, record.__dict__)
assert isinstance(record.message, basestring_type) # guaranteed by logging
record.asctime = time.strftime(
"%y%m%d %H:%M:%S", self.converter(record.created))
prefix = '[%(levelname)1.1s %(asctime)s %(module)s:%(lineno)d]' % \
if self._color:
prefix = (self._colors.get(record.levelno, self._normal) +
prefix + self._normal)
# Encoding notes: The logging module prefers to work with character
# strings, but only enforces that log messages are instances of
# basestring. In python 2, non-ascii bytestrings will make
# their way through the logging framework until they blow up with
# an unhelpful decoding error (with this formatter it happens
# when we attach the prefix, but there are other opportunities for
# exceptions further along in the framework).
# If a byte string makes it this far, convert it to unicode to
# ensure it will make it out to the logs. Use repr() as a fallback
# to ensure that all byte strings can be converted successfully,
# but don't do it by default so we don't add extra quotes to ascii
# bytestrings. This is a bit of a hacky place to do this, but
# it's worth it since the encoding errors that would otherwise
# result are so useless (and tornado is fond of using utf8-encoded
# byte strings whereever possible).
def safe_unicode(s):
return _unicode(s)
except UnicodeDecodeError:
return repr(s)
formatted = prefix + " " + safe_unicode(record.message)
if record.exc_info:
if not record.exc_text:
record.exc_text = self.formatException(record.exc_info)
if record.exc_text:
# exc_text contains multiple lines. We need to safe_unicode
# each line separately so that non-utf8 bytes don't cause
# all the newlines to turn into '\n'.
lines = [formatted.rstrip()]
lines.extend(safe_unicode(ln) for ln in record.exc_text.split('\n'))
formatted = '\n'.join(lines)
return formatted.replace("\n", "\n ")
def enable_pretty_logging(options=None, logger=None):
"""Turns on formatted logging output as configured.
This is called automaticaly by `tornado.options.parse_command_line`
and `tornado.options.parse_config_file`.
if options is None:
from tornado.options import options
if options.logging == 'none':
if logger is None:
logger = logging.getLogger()
logger.setLevel(getattr(logging, options.logging.upper()))
if options.log_file_prefix:
channel = logging.handlers.RotatingFileHandler(
if (options.log_to_stderr or
(options.log_to_stderr is None and not logger.handlers)):
# Set up color if we are in a tty and curses is installed
channel = logging.StreamHandler()
def define_logging_options(options=None):
if options is None:
# late import to prevent cycle
from tornado.options import options
options.define("logging", default="info",
help=("Set the Python log level. If 'none', tornado won't touch the "
"logging configuration."),
options.define("log_to_stderr", type=bool, default=None,
help=("Send log output to stderr (colorized if possible). "
"By default use stderr if --log_file_prefix is not set and "
"no other logging is configured."))
options.define("log_file_prefix", type=str, default=None, metavar="PATH",
help=("Path prefix for log files. "
"Note that if you are running multiple tornado processes, "
"log_file_prefix must be different for each of them (e.g. "
"include the port number)"))
options.define("log_file_max_size", type=int, default=100 * 1000 * 1000,
help="max size of log files before rollover")
options.define("log_file_num_backups", type=int, default=10,
help="number of log files to keep")
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