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	# Copyright 2001-2019 by Vinay Sajip. All Rights Reserved.
	#
	# Permission to use, copy, modify, and distribute this software and its
	# documentation for any purpose and without fee is hereby granted,
	# provided that the above copyright notice appear in all copies and that
	# both that copyright notice and this permission notice appear in
	# supporting documentation, and that the name of Vinay Sajip
	# not be used in advertising or publicity pertaining to distribution
	# of the software without specific, written prior permission.
	# VINAY SAJIP DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
	# ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
	# VINAY SAJIP BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
	# ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
	# IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
	# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

	"""
	Configuration functions for the logging package for Python. The core package
	is based on PEP 282 and comments thereto in comp.lang.python, and influenced
	by Apache's log4j system.

	Copyright (C) 2001-2019 Vinay Sajip. All Rights Reserved.

	To use, simply 'import logging' and log away!
	"""

	import errno
	import io
	import logging
	import logging.handlers
	import re
	import struct
	import sys
	import threading
	import traceback

	from socketserver import ThreadingTCPServer, StreamRequestHandler


	DEFAULT_LOGGING_CONFIG_PORT = 9030

	RESET_ERROR = errno.ECONNRESET

	#
	# The following code implements a socket listener for on-the-fly
	# reconfiguration of logging.
	#
	# _listener holds the server object doing the listening
	_listener = None

	def fileConfig(fname, defaults=None, disable_existing_loggers=True):
	"""
	Read the logging configuration from a ConfigParser-format file.

	This can be called several times from an application, allowing an end user
	the ability to select from various pre-canned configurations (if the
	developer provides a mechanism to present the choices and load the chosen
	configuration).
	"""
	import configparser

	if isinstance(fname, configparser.RawConfigParser):
	cp = fname
	else:
	cp = configparser.ConfigParser(defaults)
	if hasattr(fname, 'readline'):
	cp.read_file(fname)
	else:
	cp.read(fname)

	formatters = _create_formatters(cp)

	# critical section
	logging._acquireLock()
	try:
	_clearExistingHandlers()

	# Handlers add themselves to logging._handlers
	handlers = _install_handlers(cp, formatters)
	_install_loggers(cp, handlers, disable_existing_loggers)
	finally:
	logging._releaseLock()


	def _resolve(name):
	"""Resolve a dotted name to a global object."""
	name = name.split('.')
	used = name.pop(0)
	found = __import__(used)
	for n in name:
	used = used + '.' + n
	try:
	found = getattr(found, n)
	except AttributeError:
	__import__(used)
	found = getattr(found, n)
	return found

	def _strip_spaces(alist):
	return map(str.strip, alist)

	def _create_formatters(cp):
	"""Create and return formatters"""
	flist = cp["formatters"]["keys"]
	if not len(flist):
	return {}
	flist = flist.split(",")
	flist = _strip_spaces(flist)
	formatters = {}
	for form in flist:
	sectname = "formatter_%s" % form
	fs = cp.get(sectname, "format", raw=True, fallback=None)
	dfs = cp.get(sectname, "datefmt", raw=True, fallback=None)
	stl = cp.get(sectname, "style", raw=True, fallback='%')
	c = logging.Formatter
	class_name = cp[sectname].get("class")
	if class_name:
	c = _resolve(class_name)
	f = c(fs, dfs, stl)
	formatters[form] = f
	return formatters


	def _install_handlers(cp, formatters):
	"""Install and return handlers"""
	hlist = cp["handlers"]["keys"]
	if not len(hlist):
	return {}
	hlist = hlist.split(",")
	hlist = _strip_spaces(hlist)
	handlers = {}
	fixups = [] #for inter-handler references
	for hand in hlist:
	section = cp["handler_%s" % hand]
	klass = section["class"]
	fmt = section.get("formatter", "")
	try:
	klass = eval(klass, vars(logging))
	except (AttributeError, NameError):
	klass = _resolve(klass)
	args = section.get("args", '()')
	args = eval(args, vars(logging))
	kwargs = section.get("kwargs", '{}')
	kwargs = eval(kwargs, vars(logging))
	h = klass(args, *kwargs)
	h.name = hand
	if "level" in section:
	level = section["level"]
	h.setLevel(level)
	if len(fmt):
	h.setFormatter(formatters[fmt])
	if issubclass(klass, logging.handlers.MemoryHandler):
	target = section.get("target", "")
	if len(target): #the target handler may not be loaded yet, so keep for later...
	fixups.append((h, target))
	handlers[hand] = h
	#now all handlers are loaded, fixup inter-handler references...
	for h, t in fixups:
	h.setTarget(handlers[t])
	return handlers

	def _handle_existing_loggers(existing, child_loggers, disable_existing):
	"""
	When (re)configuring logging, handle loggers which were in the previous
	configuration but are not in the new configuration. There's no point
	deleting them as other threads may continue to hold references to them;
	and by disabling them, you stop them doing any logging.

	However, don't disable children of named loggers, as that's probably not
	what was intended by the user. Also, allow existing loggers to NOT be
	disabled if disable_existing is false.
	"""
	root = logging.root
	for log in existing:
	logger = root.manager.loggerDict[log]
	if log in child_loggers:
	if not isinstance(logger, logging.PlaceHolder):
	logger.setLevel(logging.NOTSET)
	logger.handlers = []
	logger.propagate = True
	else:
	logger.disabled = disable_existing

	def _install_loggers(cp, handlers, disable_existing):
	"""Create and install loggers"""

	# configure the root first
	llist = cp["loggers"]["keys"]
	llist = llist.split(",")
	llist = list(_strip_spaces(llist))
	llist.remove("root")
	section = cp["logger_root"]
	root = logging.root
	log = root
	if "level" in section:
	level = section["level"]
	log.setLevel(level)
	for h in root.handlers[:]:
	root.removeHandler(h)
	hlist = section["handlers"]
	if len(hlist):
	hlist = hlist.split(",")
	hlist = _strip_spaces(hlist)
	for hand in hlist:
	log.addHandler(handlers[hand])

	#and now the others...
	#we don't want to lose the existing loggers,
	#since other threads may have pointers to them.
	#existing is set to contain all existing loggers,
	#and as we go through the new configuration we
	#remove any which are configured. At the end,
	#what's left in existing is the set of loggers
	#which were in the previous configuration but
	#which are not in the new configuration.
	existing = list(root.manager.loggerDict.keys())
	#The list needs to be sorted so that we can
	#avoid disabling child loggers of explicitly
	#named loggers. With a sorted list it is easier
	#to find the child loggers.
	existing.sort()
	#We'll keep the list of existing loggers
	#which are children of named loggers here...
	child_loggers = []
	#now set up the new ones...
	for log in llist:
	section = cp["logger_%s" % log]
	qn = section["qualname"]
	propagate = section.getint("propagate", fallback=1)
	logger = logging.getLogger(qn)
	if qn in existing:
	i = existing.index(qn) + 1 # start with the entry after qn
	prefixed = qn + "."
	pflen = len(prefixed)
	num_existing = len(existing)
	while i < num_existing:
	if existing[i][:pflen] == prefixed:
	child_loggers.append(existing[i])
	i += 1
	existing.remove(qn)
	if "level" in section:
	level = section["level"]
	logger.setLevel(level)
	for h in logger.handlers[:]:
	logger.removeHandler(h)
	logger.propagate = propagate
	logger.disabled = 0
	hlist = section["handlers"]
	if len(hlist):
	hlist = hlist.split(",")
	hlist = _strip_spaces(hlist)
	for hand in hlist:
	logger.addHandler(handlers[hand])

	#Disable any old loggers. There's no point deleting
	#them as other threads may continue to hold references
	#and by disabling them, you stop them doing any logging.
	#However, don't disable children of named loggers, as that's
	#probably not what was intended by the user.
	#for log in existing:
	# logger = root.manager.loggerDict[log]
	# if log in child_loggers:
	# logger.level = logging.NOTSET
	# logger.handlers = []
	# logger.propagate = 1
	# elif disable_existing_loggers:
	# logger.disabled = 1
	_handle_existing_loggers(existing, child_loggers, disable_existing)


	def _clearExistingHandlers():
	"""Clear and close existing handlers"""
	logging._handlers.clear()
	logging.shutdown(logging._handlerList[:])
	del logging._handlerList[:]


	IDENTIFIER = re.compile('^[a-z_][a-z0-9_]*$', re.I)


	def valid_ident(s):
	m = IDENTIFIER.match(s)
	if not m:
	raise ValueError('Not a valid Python identifier: %r' % s)
	return True


	class ConvertingMixin(object):
	"""For ConvertingXXX's, this mixin class provides common functions"""

	def convert_with_key(self, key, value, replace=True):
	result = self.configurator.convert(value)
	#If the converted value is different, save for next time
	if value is not result:
	if replace:
	self[key] = result
	if type(result) in (ConvertingDict, ConvertingList,
	ConvertingTuple):
	result.parent = self
	result.key = key
	return result

	def convert(self, value):
	result = self.configurator.convert(value)
	if value is not result:
	if type(result) in (ConvertingDict, ConvertingList,
	ConvertingTuple):
	result.parent = self
	return result


	# The ConvertingXXX classes are wrappers around standard Python containers,
	# and they serve to convert any suitable values in the container. The
	# conversion converts base dicts, lists and tuples to their wrapped
	# equivalents, whereas strings which match a conversion format are converted
	# appropriately.
	#
	# Each wrapper should have a configurator attribute holding the actual
	# configurator to use for conversion.

	class ConvertingDict(dict, ConvertingMixin):
	"""A converting dictionary wrapper."""

	def __getitem__(self, key):
	value = dict.__getitem__(self, key)
	return self.convert_with_key(key, value)

	def get(self, key, default=None):
	value = dict.get(self, key, default)
	return self.convert_with_key(key, value)

	def pop(self, key, default=None):
	value = dict.pop(self, key, default)
	return self.convert_with_key(key, value, replace=False)

	class ConvertingList(list, ConvertingMixin):
	"""A converting list wrapper."""
	def __getitem__(self, key):
	value = list.__getitem__(self, key)
	return self.convert_with_key(key, value)

	def pop(self, idx=-1):
	value = list.pop(self, idx)
	return self.convert(value)

	class ConvertingTuple(tuple, ConvertingMixin):
	"""A converting tuple wrapper."""
	def __getitem__(self, key):
	value = tuple.__getitem__(self, key)
	# Can't replace a tuple entry.
	return self.convert_with_key(key, value, replace=False)

	class BaseConfigurator(object):
	"""
	The configurator base class which defines some useful defaults.
	"""

	CONVERT_PATTERN = re.compile(r'^(?P<prefix>[a-z]+)://(?P<suffix>.*)$')

	WORD_PATTERN = re.compile(r'^\s(\w+)\s')
	DOT_PATTERN = re.compile(r'^\.\s(\w+)\s')
	INDEX_PATTERN = re.compile(r'^\[\s(\w+)\s\]\s*')
	DIGIT_PATTERN = re.compile(r'^\d+$')

	value_converters = {
	'ext' : 'ext_convert',
	'cfg' : 'cfg_convert',
	}

	# We might want to use a different one, e.g. importlib
	importer = staticmethod(__import__)

	def __init__(self, config):
	self.config = ConvertingDict(config)
	self.config.configurator = self

	def resolve(self, s):
	"""
	Resolve strings to objects using standard import and attribute
	syntax.
	"""
	name = s.split('.')
	used = name.pop(0)
	try:
	found = self.importer(used)
	for frag in name:
	used += '.' + frag
	try:
	found = getattr(found, frag)
	except AttributeError:
	self.importer(used)
	found = getattr(found, frag)
	return found
	except ImportError:
	e, tb = sys.exc_info()[1:]
	v = ValueError('Cannot resolve %r: %s' % (s, e))
	v.__cause__, v.__traceback__ = e, tb
	raise v

	def ext_convert(self, value):
	"""Default converter for the ext:// protocol."""
	return self.resolve(value)

	def cfg_convert(self, value):
	"""Default converter for the cfg:// protocol."""
	rest = value
	m = self.WORD_PATTERN.match(rest)
	if m is None:
	raise ValueError("Unable to convert %r" % value)
	else:
	rest = rest[m.end():]
	d = self.config[m.groups()[0]]
	#print d, rest
	while rest:
	m = self.DOT_PATTERN.match(rest)
	if m:
	d = d[m.groups()[0]]
	else:
	m = self.INDEX_PATTERN.match(rest)
	if m:
	idx = m.groups()[0]
	if not self.DIGIT_PATTERN.match(idx):
	d = d[idx]
	else:
	try:
	n = int(idx) # try as number first (most likely)
	d = d[n]
	except TypeError:
	d = d[idx]
	if m:
	rest = rest[m.end():]
	else:
	raise ValueError('Unable to convert '
	'%r at %r' % (value, rest))
	#rest should be empty
	return d

	def convert(self, value):
	"""
	Convert values to an appropriate type. dicts, lists and tuples are
	replaced by their converting alternatives. Strings are checked to
	see if they have a conversion format and are converted if they do.
	"""
	if not isinstance(value, ConvertingDict) and isinstance(value, dict):
	value = ConvertingDict(value)
	value.configurator = self
	elif not isinstance(value, ConvertingList) and isinstance(value, list):
	value = ConvertingList(value)
	value.configurator = self
	elif not isinstance(value, ConvertingTuple) and\
	isinstance(value, tuple) and not hasattr(value, '_fields'):
	value = ConvertingTuple(value)
	value.configurator = self
	elif isinstance(value, str): # str for py3k
	m = self.CONVERT_PATTERN.match(value)
	if m:
	d = m.groupdict()
	prefix = d['prefix']
	converter = self.value_converters.get(prefix, None)
	if converter:
	suffix = d['suffix']
	converter = getattr(self, converter)
	value = converter(suffix)
	return value

	def configure_custom(self, config):
	"""Configure an object with a user-supplied factory."""
	c = config.pop('()')
	if not callable(c):
	c = self.resolve(c)
	props = config.pop('.', None)
	# Check for valid identifiers
	kwargs = {k: config[k] for k in config if valid_ident(k)}
	result = c(**kwargs)
	if props:
	for name, value in props.items():
	setattr(result, name, value)
	return result

	def as_tuple(self, value):
	"""Utility function which converts lists to tuples."""
	if isinstance(value, list):
	value = tuple(value)
	return value

	class DictConfigurator(BaseConfigurator):
	"""
	Configure logging using a dictionary-like object to describe the
	configuration.
	"""

	def configure(self):
	"""Do the configuration."""

	config = self.config
	if 'version' not in config:
	raise ValueError("dictionary doesn't specify a version")
	if config['version'] != 1:
	raise ValueError("Unsupported version: %s" % config['version'])
	incremental = config.pop('incremental', False)
	EMPTY_DICT = {}
	logging._acquireLock()
	try:
	if incremental:
	handlers = config.get('handlers', EMPTY_DICT)
	for name in handlers:
	if name not in logging._handlers:
	raise ValueError('No handler found with '
	'name %r' % name)
	else:
	try:
	handler = logging._handlers[name]
	handler_config = handlers[name]
	level = handler_config.get('level', None)
	if level:
	handler.setLevel(logging._checkLevel(level))
	except Exception as e:
	raise ValueError('Unable to configure handler '
	'%r' % name) from e
	loggers = config.get('loggers', EMPTY_DICT)
	for name in loggers:
	try:
	self.configure_logger(name, loggers[name], True)
	except Exception as e:
	raise ValueError('Unable to configure logger '
	'%r' % name) from e
	root = config.get('root', None)
	if root:
	try:
	self.configure_root(root, True)
	except Exception as e:
	raise ValueError('Unable to configure root '
	'logger') from e
	else:
	disable_existing = config.pop('disable_existing_loggers', True)

	_clearExistingHandlers()

	# Do formatters first - they don't refer to anything else
	formatters = config.get('formatters', EMPTY_DICT)
	for name in formatters:
	try:
	formatters[name] = self.configure_formatter(
	formatters[name])
	except Exception as e:
	raise ValueError('Unable to configure '
	'formatter %r' % name) from e
	# Next, do filters - they don't refer to anything else, either
	filters = config.get('filters', EMPTY_DICT)
	for name in filters:
	try:
	filters[name] = self.configure_filter(filters[name])
	except Exception as e:
	raise ValueError('Unable to configure '
	'filter %r' % name) from e

	# Next, do handlers - they refer to formatters and filters
	# As handlers can refer to other handlers, sort the keys
	# to allow a deterministic order of configuration
	handlers = config.get('handlers', EMPTY_DICT)
	deferred = []
	for name in sorted(handlers):
	try:
	handler = self.configure_handler(handlers[name])
	handler.name = name
	handlers[name] = handler
	except Exception as e:
	if 'target not configured yet' in str(e.__cause__):
	deferred.append(name)
	else:
	raise ValueError('Unable to configure handler '
	'%r' % name) from e

	# Now do any that were deferred
	for name in deferred:
	try:
	handler = self.configure_handler(handlers[name])
	handler.name = name
	handlers[name] = handler
	except Exception as e:
	raise ValueError('Unable to configure handler '
	'%r' % name) from e

	# Next, do loggers - they refer to handlers and filters

	#we don't want to lose the existing loggers,
	#since other threads may have pointers to them.
	#existing is set to contain all existing loggers,
	#and as we go through the new configuration we
	#remove any which are configured. At the end,
	#what's left in existing is the set of loggers
	#which were in the previous configuration but
	#which are not in the new configuration.
	root = logging.root
	existing = list(root.manager.loggerDict.keys())
	#The list needs to be sorted so that we can
	#avoid disabling child loggers of explicitly
	#named loggers. With a sorted list it is easier
	#to find the child loggers.
	existing.sort()
	#We'll keep the list of existing loggers
	#which are children of named loggers here...
	child_loggers = []
	#now set up the new ones...
	loggers = config.get('loggers', EMPTY_DICT)
	for name in loggers:
	if name in existing:
	i = existing.index(name) + 1 # look after name
	prefixed = name + "."
	pflen = len(prefixed)
	num_existing = len(existing)
	while i < num_existing:
	if existing[i][:pflen] == prefixed:
	child_loggers.append(existing[i])
	i += 1
	existing.remove(name)
	try:
	self.configure_logger(name, loggers[name])
	except Exception as e:
	raise ValueError('Unable to configure logger '
	'%r' % name) from e

	#Disable any old loggers. There's no point deleting
	#them as other threads may continue to hold references
	#and by disabling them, you stop them doing any logging.
	#However, don't disable children of named loggers, as that's
	#probably not what was intended by the user.
	#for log in existing:
	# logger = root.manager.loggerDict[log]
	# if log in child_loggers:
	# logger.level = logging.NOTSET
	# logger.handlers = []
	# logger.propagate = True
	# elif disable_existing:
	# logger.disabled = True
	_handle_existing_loggers(existing, child_loggers,
	disable_existing)

	# And finally, do the root logger
	root = config.get('root', None)
	if root:
	try:
	self.configure_root(root)
	except Exception as e:
	raise ValueError('Unable to configure root '
	'logger') from e
	finally:
	logging._releaseLock()

	def configure_formatter(self, config):
	"""Configure a formatter from a dictionary."""
	if '()' in config:
	factory = config['()'] # for use in exception handler
	try:
	result = self.configure_custom(config)
	except TypeError as te:
	if "'format'" not in str(te):
	raise
	#Name of parameter changed from fmt to format.
	#Retry with old name.
	#This is so that code can be used with older Python versions
	#(e.g. by Django)
	config['fmt'] = config.pop('format')
	config['()'] = factory
	result = self.configure_custom(config)
	else:
	fmt = config.get('format', None)
	dfmt = config.get('datefmt', None)
	style = config.get('style', '%')
	cname = config.get('class', None)

	if not cname:
	c = logging.Formatter
	else:
	c = _resolve(cname)

	# A TypeError would be raised if "validate" key is passed in with a formatter callable
	# that does not accept "validate" as a parameter
	if 'validate' in config: # if user hasn't mentioned it, the default will be fine
	result = c(fmt, dfmt, style, config['validate'])
	else:
	result = c(fmt, dfmt, style)

	return result

	def configure_filter(self, config):
	"""Configure a filter from a dictionary."""
	if '()' in config:
	result = self.configure_custom(config)
	else:
	name = config.get('name', '')
	result = logging.Filter(name)
	return result

	def add_filters(self, filterer, filters):
	"""Add filters to a filterer from a list of names."""
	for f in filters:
	try:
	filterer.addFilter(self.config['filters'][f])
	except Exception as e:
	raise ValueError('Unable to add filter %r' % f) from e

	def configure_handler(self, config):
	"""Configure a handler from a dictionary."""
	config_copy = dict(config) # for restoring in case of error
	formatter = config.pop('formatter', None)
	if formatter:
	try:
	formatter = self.config['formatters'][formatter]
	except Exception as e:
	raise ValueError('Unable to set formatter '
	'%r' % formatter) from e
	level = config.pop('level', None)
	filters = config.pop('filters', None)
	if '()' in config:
	c = config.pop('()')
	if not callable(c):
	c = self.resolve(c)
	factory = c
	else:
	cname = config.pop('class')
	klass = self.resolve(cname)
	#Special case for handler which refers to another handler
	if issubclass(klass, logging.handlers.MemoryHandler) and\
	'target' in config:
	try:
	th = self.config['handlers'][config['target']]
	if not isinstance(th, logging.Handler):
	config.update(config_copy) # restore for deferred cfg
	raise TypeError('target not configured yet')
	config['target'] = th
	except Exception as e:
	raise ValueError('Unable to set target handler '
	'%r' % config['target']) from e
	elif issubclass(klass, logging.handlers.SMTPHandler) and\
	'mailhost' in config:
	config['mailhost'] = self.as_tuple(config['mailhost'])
	elif issubclass(klass, logging.handlers.SysLogHandler) and\
	'address' in config:
	config['address'] = self.as_tuple(config['address'])
	factory = klass
	props = config.pop('.', None)
	kwargs = {k: config[k] for k in config if valid_ident(k)}
	try:
	result = factory(**kwargs)
	except TypeError as te:
	if "'stream'" not in str(te):
	raise
	#The argument name changed from strm to stream
	#Retry with old name.
	#This is so that code can be used with older Python versions
	#(e.g. by Django)
	kwargs['strm'] = kwargs.pop('stream')
	result = factory(**kwargs)
	if formatter:
	result.setFormatter(formatter)
	if level is not None:
	result.setLevel(logging._checkLevel(level))
	if filters:
	self.add_filters(result, filters)
	if props:
	for name, value in props.items():
	setattr(result, name, value)
	return result

	def add_handlers(self, logger, handlers):
	"""Add handlers to a logger from a list of names."""
	for h in handlers:
	try:
	logger.addHandler(self.config['handlers'][h])
	except Exception as e:
	raise ValueError('Unable to add handler %r' % h) from e

	def common_logger_config(self, logger, config, incremental=False):
	"""
	Perform configuration which is common to root and non-root loggers.
	"""
	level = config.get('level', None)
	if level is not None:
	logger.setLevel(logging._checkLevel(level))
	if not incremental:
	#Remove any existing handlers
	for h in logger.handlers[:]:
	logger.removeHandler(h)
	handlers = config.get('handlers', None)
	if handlers:
	self.add_handlers(logger, handlers)
	filters = config.get('filters', None)
	if filters:
	self.add_filters(logger, filters)

	def configure_logger(self, name, config, incremental=False):
	"""Configure a non-root logger from a dictionary."""
	logger = logging.getLogger(name)
	self.common_logger_config(logger, config, incremental)
	propagate = config.get('propagate', None)
	if propagate is not None:
	logger.propagate = propagate

	def configure_root(self, config, incremental=False):
	"""Configure a root logger from a dictionary."""
	root = logging.getLogger()
	self.common_logger_config(root, config, incremental)

	dictConfigClass = DictConfigurator

	def dictConfig(config):
	"""Configure logging using a dictionary."""
	dictConfigClass(config).configure()


	def listen(port=DEFAULT_LOGGING_CONFIG_PORT, verify=None):
	"""
	Start up a socket server on the specified port, and listen for new
	configurations.

	These will be sent as a file suitable for processing by fileConfig().
	Returns a Thread object on which you can call start() to start the server,
	and which you can join() when appropriate. To stop the server, call
	stopListening().

	Use the ``verify`` argument to verify any bytes received across the wire
	from a client. If specified, it should be a callable which receives a
	single argument - the bytes of configuration data received across the
	network - and it should return either ``None``, to indicate that the
	passed in bytes could not be verified and should be discarded, or a
	byte string which is then passed to the configuration machinery as
	normal. Note that you can return transformed bytes, e.g. by decrypting
	the bytes passed in.
	"""

	class ConfigStreamHandler(StreamRequestHandler):
	"""
	Handler for a logging configuration request.

	It expects a completely new logging configuration and uses fileConfig
	to install it.
	"""
	def handle(self):
	"""
	Handle a request.

	Each request is expected to be a 4-byte length, packed using
	struct.pack(">L", n), followed by the config file.
	Uses fileConfig() to do the grunt work.
	"""
	try:
	conn = self.connection
	chunk = conn.recv(4)
	if len(chunk) == 4:
	slen = struct.unpack(">L", chunk)[0]
	chunk = self.connection.recv(slen)
	while len(chunk) < slen:
	chunk = chunk + conn.recv(slen - len(chunk))
	if self.server.verify is not None:
	chunk = self.server.verify(chunk)
	if chunk is not None: # verified, can process
	chunk = chunk.decode("utf-8")
	try:
	import json
	d =json.loads(chunk)
	assert isinstance(d, dict)
	dictConfig(d)
	except Exception:
	#Apply new configuration.

	file = io.StringIO(chunk)
	try:
	fileConfig(file)
	except Exception:
	traceback.print_exc()
	if self.server.ready:
	self.server.ready.set()
	except OSError as e:
	if e.errno != RESET_ERROR:
	raise

	class ConfigSocketReceiver(ThreadingTCPServer):
	"""
	A simple TCP socket-based logging config receiver.
	"""

	allow_reuse_address = 1

	def __init__(self, host='localhost', port=DEFAULT_LOGGING_CONFIG_PORT,
	handler=None, ready=None, verify=None):
	ThreadingTCPServer.__init__(self, (host, port), handler)
	logging._acquireLock()
	self.abort = 0
	logging._releaseLock()
	self.timeout = 1
	self.ready = ready
	self.verify = verify

	def serve_until_stopped(self):
	import select
	abort = 0
	while not abort:
	rd, wr, ex = select.select([self.socket.fileno()],
	[], [],
	self.timeout)
	if rd:
	self.handle_request()
	logging._acquireLock()
	abort = self.abort
	logging._releaseLock()
	self.server_close()

	class Server(threading.Thread):

	def __init__(self, rcvr, hdlr, port, verify):
	super(Server, self).__init__()
	self.rcvr = rcvr
	self.hdlr = hdlr
	self.port = port
	self.verify = verify
	self.ready = threading.Event()

	def run(self):
	server = self.rcvr(port=self.port, handler=self.hdlr,
	ready=self.ready,
	verify=self.verify)
	if self.port == 0:
	self.port = server.server_address[1]
	self.ready.set()
	global _listener
	logging._acquireLock()
	_listener = server
	logging._releaseLock()
	server.serve_until_stopped()

	return Server(ConfigSocketReceiver, ConfigStreamHandler, port, verify)

	def stopListening():
	"""
	Stop the listening server which was created with a call to listen().
	"""
	global _listener
	logging._acquireLock()
	try:
	if _listener:
	_listener.abort = 1
	_listener = None
	finally:
	logging._releaseLock()