Log4j logging hierarchy order

I consider fatal errors to be when your application can't do any more useful work. Non-fatal errors are when there's a problem but your application can still continue to function, even at a reduced level of functionality or performance.

Examples of fatal errors include:

• Running out of disk space on the logging device and you're required to keep logging.
• Total loss of network connectivity in a client application.
• Missing configuration information if no default can be used.

Non-fatal errors would include:

• A server where a single session fails for some reason but you can still service other clients.
• An intermittent error, such as lost session, if a new session can be established.
• Missing configuration information if a default value can be used.

I already knew about the color escapes, I used them in my bash prompt a while ago. Thanks anyway.
What I wanted was to integrate it with the logging module, which I eventually did after a couple of tries and errors.
Here is what I end up with:

BLACK, RED, GREEN, YELLOW, BLUE, MAGENTA, CYAN, WHITE = range(8)

#The background is set with 40 plus the number of the color, and the foreground with 30

#These are the sequences need to get colored ouput
RESET_SEQ = "\033[0m"
COLOR_SEQ = "\033[1;%dm"
BOLD_SEQ = "\033[1m"

def formatter_message(message, use_color = True):
    if use_color:
        message = message.replace("$RESET", RESET_SEQ).replace("$BOLD", BOLD_SEQ)
    else:
        message = message.replace("$RESET", "").replace("$BOLD", "")
    return message

COLORS = {
    'WARNING': YELLOW,
    'INFO': WHITE,
    'DEBUG': BLUE,
    'CRITICAL': YELLOW,
    'ERROR': RED
}

class ColoredFormatter(logging.Formatter):
    def __init__(self, msg, use_color = True):
        logging.Formatter.__init__(self, msg)
        self.use_color = use_color

    def format(self, record):
        levelname = record.levelname
        if self.use_color and levelname in COLORS:
            levelname_color = COLOR_SEQ % (30 + COLORS[levelname]) + levelname + RESET_SEQ
            record.levelname = levelname_color
        return logging.Formatter.format(self, record)

And to use it, create your own Logger:

# Custom logger class with multiple destinations
class ColoredLogger(logging.Logger):
    FORMAT = "[$BOLD%(name)-20s$RESET][%(levelname)-18s]  %(message)s ($BOLD%(filename)s$RESET:%(lineno)d)"
    COLOR_FORMAT = formatter_message(FORMAT, True)
    def __init__(self, name):
        logging.Logger.__init__(self, name, logging.DEBUG)                

        color_formatter = ColoredFormatter(self.COLOR_FORMAT)

        console = logging.StreamHandler()
        console.setFormatter(color_formatter)

        self.addHandler(console)
        return


logging.setLoggerClass(ColoredLogger)

Just in case anyone else needs it.

Be careful if you're using more than one logger or handler: ColoredFormatter is changing the record object, which is passed further to other handlers or propagated to other loggers. If you have configured file loggers etc. you probably don't want to have the colors in the log files. To avoid that, it's probably best to simply create a copy of record with copy.copy() before manipulating the levelname attribute, or to reset the levelname to the previous value, before returning the formatted string (credit to Michael in the comments).