# 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)
 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):
 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()