werkzeug: disable bash colors when logging to file

Question

In a Flask application, I use a RotatingFileLogger to log werkzeug access logs to a file like shown in this question:

file_handler_access_log = RotatingFileHandler("access.log",
                                              backupCount=5,
                                              encoding='utf-8')
formatter = logging.Formatter('%(asctime)s %(module)s %(levelname)s: %(message)s', datefmt='%Y-%m-%d %H:%M:%S')
file_handler_access_log.setFormatter(formatter)
werkzeug_logger.addHandler(file_handler_access_log)
werkzeug_logger.setLevel(logging.DEBUG)

In the access.log file, the request looks like this:

2020-10-07 09:43:51 _internal INFO: 127.0.0.1 - - [07/Oct/2020 09:43:51] "[37mGET /api/foo HTTP/1.1[0m" 200 -

I want to get rid of the color codes like [37m in the log file.

The werkzeug documentation states:

The development server can optionally highlight the request logs in
different colors based on the status code. Install Click to enable
this feature.

Click is a Flask dependency, so I cannot uninstall it. How can I disable the colored logging?

Asked By: Suzana

||

Source

Answer 1

OK, so what you are hitting is

if click:
    color = click.style

    if code[0] == "1":  # 1xx - Informational
        msg = color(msg, bold=True)
    ...
self.log("info", '"%s" %s %s', msg, code, size)

Source: https://github.com/pallets/werkzeug/blob/ef545f0d0bf28cbad02066b4cb7471bea50a93ee/src/werkzeug/serving.py

Not easy to prevent the behavior. The second option is to remove color codes from messages. I would try to use log Filter to update the message, something like

import logging

import click
    

class RemoveColorFilter(logging.Filter):
    def filter(self, record):
        if record and record.msg and isinstance(record.msg, str):
            record.msg = click.unstyle(record.msg) 
        return True

remove_color_filter = RemoveColorFilter()
file_handler_access_log.addFilter(remove_color_filter)

The above suggestion was inspired by the following answer https://stackoverflow.com/a/60692906/4183498.

I didn’t test the proposed solution.

Answered By: Dušan Maďar

Answer 2

I went with what i think is a more straightforward solution, which is to simply throw away all the styling arguments – something like this in your application startup


    old_color = click.style

    def new_color(text, fg=None, bg=None, bold=None, dim=None, underline=None, blink=None, reverse=None, reset=True):
        return old_color(text)

    # replace flask styling with non-colorized styling
    click.style = new_color

Answered By: jhodges

Answer 3

This is a similar idea to @jhodges, but even simpler – it just removes all of the "click" module’s styling altogether.

import click
click.style = lambda text, *args, **kwargs: text

EDIT: In the end, I wound up going with a filter to remove escape sequences from log messages headed for a file handler. Because werkzeug puts escape sequences in the args list for the log message, those need to be stripped as well. This is the basic outline:

class NoEscape(logging.Filter):
    def __init__(self):
        self.regex = re.compile(r'(x9B|x1B[)[0-?]*[ -/]*[@-~]')
    def strip_esc(self, s):
        try: # string-like 
            return self.regex.sub('',s)
        except: # non-string-like
            return s
    def filter(self, record: logging.LogRecord) -> int:
        record.msg = self.strip_esc(record.msg)
        if type(record.args) is tuple:
            record.args = tuple(map(self.strip_esc, record.args))
        return 1

Hope this helps!

Answered By: Ryan Hoffman

Answer 4

I came across this question myself, but the filter solutions presented in other answers modified the record for all cases it was emitted, whereas I wanted to only remove styling for file handlers and leave it for console handlers.

I ended up subclassing Formatter instead of Filter:

import logging
import click

class AntiColorFormatter(logging.Formatter):
    def format(self, record: logging.LogRecord) -> str:
        return click.unstyle(super().format(record))

which then lends itself to something like:

logger = logging.getLogger()
FMT = '{asctime} {levelname} {message}'

handler = logging.StreamHandler()
# regular console output gets normal styling
handler.setFormatter(logging.Formatter(FMT, style='{'))
logger.addHandler(handler)

handler = logging.FileHandler('log.log', encoding='utf8')
# file handler gets styling stripped
handler.setFormatter(AntiColorFormatter(FMT, style='{'))
logger.addHandler(handler)

Answered By: AbyxDev

Answer 5

Thanks to @jhodges answer, that worked for me with a minor change:

# workaround to suppress color logging in werkzeug
try:
    import click
    old_color = click.style

    def _color(text, fg=None, bg=None, bold=None, dim=None, underline=None, blink=None, reverse=None, reset=True):
        return click.unstyle(text)

    click.style = _color
except:
    pass

Calling click.style(text) still produces escape sequences in some cases which I would like to avoid completely, so I used unstyle that works perfectly here.

Answered By: Andrei Belov

werkzeug: disable bash colors when logging to file

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