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logger.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 
# Scenic
# Copyright (C) 2008 Société des arts technologiques (SAT)
# http://www.sat.qc.ca
# All rights reserved.
#
# This file is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 2 of the License, or
# (at your option) any later version.
#
# Scenic is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Scenic. If not, see <http://www.gnu.org/licenses/>.
"""
Python logging utility.

Wraps the logging module and Twisted's python.log module.
Now with non-blocking output
"""
import logging
import sys
import twisted # for its version 
import twisted.python.log as twisted_log
from twisted.internet import fdesc

# Deals with older version of twisted (in Ubuntu 8.04 and other)
# We need to add the class PythonLoggingObserver to the twisted.python.log module.
version = int(twisted.__version__.split('.')[0])
if version < 8:
    from scenic.twistedbackports import PythonLoggingObserver
    twisted_log.PythonLoggingObserver = PythonLoggingObserver

#TODO: Specify the level by output
ENABLE_NON_BLOCKING_OUTPUT = False
SYSTEMWIDE_LOG_FILE_NAME = None
SYSTEMWIDE_TO_FILE = False
SYSTEMWIDE_TO_STDOUT = True
SYSTEMWIDE_LEVEL = "warning"
#LoggerClass = logging.getLoggerClass()

# XXX: totally useless.
#class CoreLogger(LoggerClass):
#    """
#    Overrides the logger class in tyhe logging module.
#    """
#    def debug(self, msg=None, *args):
#        # if there is no msg get the name of method/function
#        if not msg:
#            msg = "def: %s" % sys._getframe(2).f_code.co_name
#        LoggerClass.debug(self, msg, *args)
#
#logging.setLoggerClass(CoreLogger)
#logging.setLoggerClass(LoggerClass)

def start(level=None, name="twisted", to_stdout=None, to_file=None, log_file_name=None):
    """
    Starts the logging for a single module.
    
    Each module should import this logging module and decide its level.
    
    The first time this is called, don't give any argument. It will log everything with the name "twisted".
    
    The programmer can choose the level from which to log, discarding any message with a lower level.
    Example : If level is INFO, the DEBUG messages (lower level) will not be displayed but the CRITICAL ones will.
    
    @param level: debug, info, error, warning or critical
    @type level: str
    @param to_stdout: Whether it should be printed to stdout. (False to disable)
    @param to_file: Whether it should be printed to file. (True to enable)
    @param name: What string to prefix with.
    @rtype: L{twisted.python.logging.PythonLoggingObserver}
    """
    global SYSTEMWIDE_TO_STDOUT
    global SYSTEMWIDE_TO_FILE 
    global SYSTEMWIDE_LOG_FILE_NAME
    global SYSTEMWIDE_LEVEL
    
    if log_file_name is not None:
        SYSTEMWIDE_LOG_FILE_NAME = log_file_name
    if to_file is True:
        SYSTEMWIDE_TO_FILE = True
    if level is not None:
        SYSTEMWIDE_LEVEL = level
    logger = logging.getLogger(name)
    formatter = logging.Formatter('%(asctime)s %(name)-13s %(levelname)-8s %(message)s')
    set_level(SYSTEMWIDE_LEVEL, name)
    if to_stdout is True or to_stdout is False:
        SYSTEMWIDE_TO_STDOUT = to_stdout
    if to_file is True or to_file is False:
        SYSTEMWIDE_TO_FILE = to_file
    
    if SYSTEMWIDE_TO_STDOUT:
        so_handler = logging.StreamHandler(sys.stdout)
        if ENABLE_NON_BLOCKING_OUTPUT: 
            fdesc.setNonBlocking(so_handler.stream) # NON-BLOCKING OUTPUT
        so_handler.setFormatter(formatter)
        logger.addHandler(so_handler)
    if SYSTEMWIDE_TO_FILE:
        if SYSTEMWIDE_LOG_FILE_NAME is None:
            raise RuntimeError("The log file name has not been set.")
        # file_handler = logging.FileHandler(log_file_name, mode='a', encoding='utf-8')
        file_handler = logging.FileHandler(SYSTEMWIDE_LOG_FILE_NAME) # FIXME: not catching IOError that could occur.
        if ENABLE_NON_BLOCKING_OUTPUT: 
            fdesc.setNonBlocking(file_handler.stream) # NON-BLOCKING OUTPUT
        file_handler.setFormatter(formatter)
        logger.addHandler(file_handler)
    if name == 'twisted':
        observer = twisted_log.PythonLoggingObserver(name)
        observer.start()
        return logging.getLogger(name)
    else:
        return logging.getLogger(name)

def stop():
    """
    Stops logging for a single module.
    """
    logging.shutdown()

def set_level(level, logger='twisted'):
    """
    Sets the logging level for a single file. 
    """
    # It is totally useless to be able to change dynamically the logging level.
    #TODO: Merge with start()
    levels = {
        'critical':logging.CRITICAL, # 50
        'error':logging.ERROR, # 40
        'warning':logging.WARNING, # 30
        'info':logging.INFO, # 20
        'debug':logging.DEBUG, # 10
        }        
    logger = logging.getLogger(logger)
    if level in levels:
        logger.setLevel(levels[level])
    else:
        raise RuntimeError("%s is not a valid log level." % (level)) #ERR ?

def critical(msg):
    """
    Logs a message with CRITICAL level. (highest)
    """
    twisted_log.msg(msg, logLevel=logging.CRITICAL)

def error(msg):
    """
    Logs a message with ERROR level. (2nd) 
    """
    twisted_log.msg(msg, logLevel=logging.ERROR)

def warning(msg):
    """
    Logs a message with WARNING level. (3rd)
    """
    twisted_log.msg(msg, logLevel=logging.WARNING)

def info(msg):
    """
    Logs a message with INFO level. (4th)
    """
    twisted_log.msg(msg)

def debug(msg): 
    """
    Logs a message with DEBUG level. (5th and last level)
    """
    twisted_log.msg(msg, logLevel=logging.DEBUG)
       
if __name__ == "__main__":
    # Here is a simple test:
    start('warning')
    critical('critical1é')
    error('error1')
    warning('warning1')
    info('info1')
    debug('debug1')
    set_level('debug')
    critical('critical2')
    error('error2')
    warning('warning2')
    info('info2')
    debug('debug2')
    try:
        set_level('asd')
    except RuntimeError, e:
        print e.message
    stop()


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