A method of getting per-user logs in python logging. It turns out my original plan which is /var/log/myapp/user.<pk>.log isn't a very good idea from performance b/c you're basically sitting there with a bunch of open files and a bunch of logging handlers each with their own per-user id filter applied. After you get logs in this format, you can w…

gistfile1.py

class UserLog(object):
    """
    Simple log that will output specially formatted user id for logging
    purposes.

    -1 is used as a sentinal value to mean "no user". Otherwise, the user's `pk`
    attribute is logged instead.

    An explicit decision was made not to use a LoggerAdapter with a custom
    format string because if we attach it to something that isn't the logger
    adapter, it explodes.

    For more info, see:
    http://docs.python.org/2/howto/logging.html#using-arbitrary-objects-as-messages
    """
    def __init__(self, msg, user=None):
        self.msg = msg
        self.user = user

    def __repr__(self):
        return self.__str__()

    def __str__(self):
        return "-- user_pk:%s -- %s" % (
            self.user.pk if self.user is not None else -1,
            self.msg
        )


# Example Usage:
from thing_above import UserLog as _
from collections import namedtuple
import logging

logging.basicConfig(level=logging.DEBUG)
log = logging.getLogger('path.to.module')

user_t = namedtuple('user', 'pk')


log.debug("test")    # DEBUG:path.to.module:test
log.debug(_("test with _"))  # DEBUG:path.to.module:-- user_pk:-1 -- test with _
log.debug(_("test with _", user=user_t(pk=99)))  # DEBUG:path.to.module:-- user_pk:99 -- test with _

I don't understand why you can't use the extra parameter in that case:

FORMAT = '%(levelname)s:%(name)s -- user_pk:%(user)s -- %(message)s'
logging.basicConfig(format=FORMAT, level=logging.DEBUG)

log = logging.getLogger('path.to.module')
log.debug('test', extra={'user': 1})  # DEBUG:path.to.module -- user_pk:1 -- test

http://docs.python.org/2/library/logging.html#logging.Logger.debug