Python logging.lastResort() Examples

def callHandlers(self, record):
		# this is the same as Python 3.5's logging.Logger.callHandlers
		c = self
		found = 0
		while c:
			for hdlr in c.handlers:
				found = found + 1
				if record.levelno >= hdlr.level:
					hdlr.handle(record)
			if not c.propagate:
				c = None  # break out
			else:
				c = c.parent
		if (found == 0):
			if logging.lastResort:
				if record.levelno >= logging.lastResort.level:
					logging.lastResort.handle(record)
			elif logging.raiseExceptions and not self.manager.emittedNoHandlerWarning:
				sys.stderr.write("No handlers could be found for logger"
								 " \"%s\"\n" % self.name)
				self.manager.emittedNoHandlerWarning = True 

def test_last_resort(self):
        # Test the last resort handler
        root = self.root_logger
        root.removeHandler(self.root_hdlr)
        old_lastresort = logging.lastResort
        old_raise_exceptions = logging.raiseExceptions

        try:
            with support.captured_stderr() as stderr:
                root.debug('This should not appear')
                self.assertEqual(stderr.getvalue(), '')
                root.warning('Final chance!')
                self.assertEqual(stderr.getvalue(), 'Final chance!\n')

            # No handlers and no last resort, so 'No handlers' message
            logging.lastResort = None
            with support.captured_stderr() as stderr:
                root.warning('Final chance!')
                msg = 'No handlers could be found for logger "root"\n'
                self.assertEqual(stderr.getvalue(), msg)

            # 'No handlers' message only printed once
            with support.captured_stderr() as stderr:
                root.warning('Final chance!')
                self.assertEqual(stderr.getvalue(), '')

            # If raiseExceptions is False, no message is printed
            root.manager.emittedNoHandlerWarning = False
            logging.raiseExceptions = False
            with support.captured_stderr() as stderr:
                root.warning('Final chance!')
                self.assertEqual(stderr.getvalue(), '')
        finally:
            root.addHandler(self.root_hdlr)
            logging.lastResort = old_lastresort
            logging.raiseExceptions = old_raise_exceptions 

def test_last_resort(self):
        # Test the last resort handler
        root = self.root_logger
        root.removeHandler(self.root_hdlr)
        old_stderr = sys.stderr
        old_lastresort = logging.lastResort
        old_raise_exceptions = logging.raiseExceptions
        try:
            sys.stderr = sio = io.StringIO()
            root.debug('This should not appear')
            self.assertEqual(sio.getvalue(), '')
            root.warning('This is your final chance!')
            self.assertEqual(sio.getvalue(), 'This is your final chance!\n')
            #No handlers and no last resort, so 'No handlers' message
            logging.lastResort = None
            sys.stderr = sio = io.StringIO()
            root.warning('This is your final chance!')
            self.assertEqual(sio.getvalue(), 'No handlers could be found for logger "root"\n')
            # 'No handlers' message only printed once
            sys.stderr = sio = io.StringIO()
            root.warning('This is your final chance!')
            self.assertEqual(sio.getvalue(), '')
            root.manager.emittedNoHandlerWarning = False
            #If raiseExceptions is False, no message is printed
            logging.raiseExceptions = False
            sys.stderr = sio = io.StringIO()
            root.warning('This is your final chance!')
            self.assertEqual(sio.getvalue(), '')
        finally:
            sys.stderr = old_stderr
            root.addHandler(self.root_hdlr)
            logging.lastResort = old_lastresort
            logging.raiseExceptions = old_raise_exceptions 

def test_last_resort(self):
        # Test the last resort handler
        root = self.root_logger
        root.removeHandler(self.root_hdlr)
        old_lastresort = logging.lastResort
        old_raise_exceptions = logging.raiseExceptions

        try:
            with support.captured_stderr() as stderr:
                root.debug('This should not appear')
                self.assertEqual(stderr.getvalue(), '')
                root.warning('Final chance!')
                self.assertEqual(stderr.getvalue(), 'Final chance!\n')

            # No handlers and no last resort, so 'No handlers' message
            logging.lastResort = None
            with support.captured_stderr() as stderr:
                root.warning('Final chance!')
                msg = 'No handlers could be found for logger "root"\n'
                self.assertEqual(stderr.getvalue(), msg)

            # 'No handlers' message only printed once
            with support.captured_stderr() as stderr:
                root.warning('Final chance!')
                self.assertEqual(stderr.getvalue(), '')

            # If raiseExceptions is False, no message is printed
            root.manager.emittedNoHandlerWarning = False
            logging.raiseExceptions = False
            with support.captured_stderr() as stderr:
                root.warning('Final chance!')
                self.assertEqual(stderr.getvalue(), '')
        finally:
            root.addHandler(self.root_hdlr)
            logging.lastResort = old_lastresort
            logging.raiseExceptions = old_raise_exceptions 

def configure_standard_logging(verbosity: int, mode: LoggingMode):
    """Configure the standard library's `logging` module.

    Get `logging` working with options consistent with Twisted. NOTE CAREFULLY
    that `django.utils.log.DEFAULT_LOGGING` may have been applied (though only
    if installed and if configured in this environment). Those settings and
    the settings this function applies must be mentally combined to understand
    the resultant behaviour.

    :param verbosity: See `get_logging_level`.
    :param mode: The mode in which to configure logging. See `LoggingMode`.
    """
    set_standard_verbosity(verbosity)
    # Make sure that `logging` is not configured to capture warnings.
    logging.captureWarnings(False)
    # If a logger is ever configured `propagate=False` but without handlers
    # `logging.Logger.callHandlers` will employ the `lastResort` handler in
    # order that the log is not lost. This goes to standard error by default.
    # Here we arrange for these situations to be logged more distinctively so
    # that they're easier to diagnose.
    logging.lastResort = logging.StreamHandler(
        twistedModern.LoggingFile(
            logger=twistedModern.Logger("lost+found"),
            level=twistedModern.LogLevel.error,
        )
    ) 

def revision_call_handlers(self, record):  # 对logging标准模块打猴子补丁。主要是使父命名空间的handler不重复记录当前命名空间日志已有种类的handler。
    """
    重要。这可以使同名logger或父logger随意添加同种类型的handler，确保不会重复打印。

    :param self:
    :param record:
    :return:
    """

    """
    Pass a record to all relevant handlers.

    Loop through all handlers for this logger and its parents in the
    logger hierarchy. If no handler was found, output a one-off error
    message to sys.stderr. Stop searching up the hierarchy whenever a
    logger with the "propagate" attribute set to zero is found - that
    will be the last logger whose handlers are called.
    """
    c = self
    found = 0
    hdlr_type_set = set()

    while c:
        for hdlr in c.handlers:
            hdlr_type = type(hdlr)
            if hdlr_type == logging.StreamHandler:  # REMIND 因为很多handler都是继承自StreamHandler，包括filehandler，直接判断会逻辑出错。
                hdlr_type = ColorHandler
            found = found + 1
            if record.levelno >= hdlr.level:
                if hdlr_type not in hdlr_type_set:
                    hdlr.handle(record)
                hdlr_type_set.add(hdlr_type)
        if not c.propagate:
            c = None  # break out
        else:
            c = c.parent
    # noinspection PyRedundantParentheses
    if (found == 0):
        if logging.lastResort:
            if record.levelno >= logging.lastResort.level:
                logging.lastResort.handle(record)
        elif logging.raiseExceptions and not self.manager.emittedNoHandlerWarning:
            sys.stderr.write("No handlers could be found for logger"
                             " \"%s\"\n" % self.name)
            self.manager.emittedNoHandlerWarning = True


# noinspection PyProtectedMember