# -*- test-case-name: twisted.test.test_log -*- # Copyright (c) Twisted Matrix Laboratories. # See LICENSE for details. """ Logging and metrics infrastructure. """ from __future__ import division, absolute_import import sys import time import warnings from datetime import datetime import logging from zope.interface import Interface from twisted.python.compat import unicode, _PY3 from twisted.python import context from twisted.python import reflect from twisted.python import util from twisted.python import failure from twisted.python.threadable import synchronize class ILogContext: """ Actually, this interface is just a synonym for the dictionary interface, but it serves as a key for the default information in a log. I do not inherit from C{Interface} because the world is a cruel place. """ class ILogObserver(Interface): """ An observer which can do something with log events. Given that most log observers are actually bound methods, it's okay to not explicitly declare provision of this interface. """ def __call__(eventDict): """ Log an event. @type eventDict: C{dict} with C{str} keys. @param eventDict: A dictionary with arbitrary keys. However, these keys are often available: - C{message}: A C{tuple} of C{str} containing messages to be logged. - C{system}: A C{str} which indicates the "system" which is generating this event. - C{isError}: A C{bool} indicating whether this event represents an error. - C{failure}: A L{failure.Failure} instance - C{why}: Used as header of the traceback in case of errors. - C{format}: A string format used in place of C{message} to customize the event. The intent is for the observer to format a message by doing something like C{format % eventDict}. """ context.setDefault(ILogContext, {"isError": 0, "system": "-"}) def callWithContext(ctx, func, *args, **kw): newCtx = context.get(ILogContext).copy() newCtx.update(ctx) return context.call({ILogContext: newCtx}, func, *args, **kw) def callWithLogger(logger, func, *args, **kw): """ Utility method which wraps a function in a try:/except:, logs a failure if one occurrs, and uses the system's logPrefix. """ try: lp = logger.logPrefix() except KeyboardInterrupt: raise except: lp = '(buggy logPrefix method)' err(system=lp) try: return callWithContext({"system": lp}, func, *args, **kw) except KeyboardInterrupt: raise except: err(system=lp) def err(_stuff=None, _why=None, **kw): """ Write a failure to the log. The C{_stuff} and C{_why} parameters use an underscore prefix to lessen the chance of colliding with a keyword argument the application wishes to pass. It is intended that they be supplied with arguments passed positionally, not by keyword. @param _stuff: The failure to log. If C{_stuff} is C{None} a new L{Failure} will be created from the current exception state. If C{_stuff} is an C{Exception} instance it will be wrapped in a L{Failure}. @type _stuff: C{NoneType}, C{Exception}, or L{Failure}. @param _why: The source of this failure. This will be logged along with C{_stuff} and should describe the context in which the failure occurred. @type _why: C{str} """ if _stuff is None: _stuff = failure.Failure() if isinstance(_stuff, failure.Failure): msg(failure=_stuff, why=_why, isError=1, **kw) elif isinstance(_stuff, Exception): msg(failure=failure.Failure(_stuff), why=_why, isError=1, **kw) else: msg(repr(_stuff), why=_why, isError=1, **kw) deferr = err class Logger: """ This represents a class which may 'own' a log. Used by subclassing. """ def logPrefix(self): """ Override this method to insert custom logging behavior. Its return value will be inserted in front of every line. It may be called more times than the number of output lines. """ return '-' class LogPublisher: """ Class for singleton log message publishing. """ synchronized = ['msg'] def __init__(self): self.observers = [] def addObserver(self, other): """ Add a new observer. @type other: Provider of L{ILogObserver} @param other: A callable object that will be called with each new log message (a dict). """ assert callable(other) self.observers.append(other) def removeObserver(self, other): """ Remove an observer. """ self.observers.remove(other) def msg(self, *message, **kw): """ Log a new message. The message should be a native string, i.e. bytes on Python 2 and Unicode on Python 3. For compatibility with both use the native string syntax, for example:: >>> log.msg('Hello, world.') You MUST avoid passing in Unicode on Python 2, and the form:: >>> log.msg('Hello ', 'world.') This form only works (sometimes) by accident. Keyword arguments will be converted into items in the event dict that is passed to L{ILogObserver} implementations. Each implementation, in turn, can define keys that are used by it specifically, in addition to common keys listed at L{ILogObserver.__call__}. For example, to set the C{system} parameter while logging a message:: >>> log.msg('Started', system='Foo') """ actualEventDict = (context.get(ILogContext) or {}).copy() actualEventDict.update(kw) actualEventDict['message'] = message actualEventDict['time'] = time.time() for i in range(len(self.observers) - 1, -1, -1): try: self.observers[i](actualEventDict) except KeyboardInterrupt: # Don't swallow keyboard interrupt! raise except UnicodeEncodeError: raise except: observer = self.observers[i] self.observers[i] = lambda event: None try: self._err(failure.Failure(), "Log observer %s failed." % (observer,)) except: # Sometimes err() will throw an exception, # e.g. RuntimeError due to blowing the stack; if that # happens, there's not much we can do... pass self.observers[i] = observer def _err(self, failure, why): """ Log a failure. Similar in functionality to the global {err} function, but the failure gets published only to observers attached to this publisher. @param failure: The failure to log. @type failure: L{Failure}. @param why: The source of this failure. This will be logged along with the C{failure} and should describe the context in which the failure occurred. @type why: C{str} """ self.msg(failure=failure, why=why, isError=1) def showwarning(self, message, category, filename, lineno, file=None, line=None): """ Twisted-enabled wrapper around L{warnings.showwarning}. If C{file} is C{None}, the default behaviour is to emit the warning to the log system, otherwise the original L{warnings.showwarning} Python function is called. """ if file is None: self.msg(warning=message, category=reflect.qual(category), filename=filename, lineno=lineno, format="%(filename)s:%(lineno)s: %(category)s: %(warning)s") else: if sys.version_info < (2, 6): _oldshowwarning(message, category, filename, lineno, file) else: _oldshowwarning(message, category, filename, lineno, file, line) synchronize(LogPublisher) try: theLogPublisher except NameError: theLogPublisher = LogPublisher() addObserver = theLogPublisher.addObserver removeObserver = theLogPublisher.removeObserver msg = theLogPublisher.msg showwarning = theLogPublisher.showwarning def _safeFormat(fmtString, fmtDict): """ Try to format the string C{fmtString} using C{fmtDict} arguments, swallowing all errors to always return a string. """ # There's a way we could make this if not safer at least more # informative: perhaps some sort of str/repr wrapper objects # could be wrapped around the things inside of C{fmtDict}. That way # if the event dict contains an object with a bad __repr__, we # can only cry about that individual object instead of the # entire event dict. try: text = fmtString % fmtDict except KeyboardInterrupt: raise except: try: text = ('Invalid format string or unformattable object in log message: %r, %s' % (fmtString, fmtDict)) except: try: text = 'UNFORMATTABLE OBJECT WRITTEN TO LOG with fmt %r, MESSAGE LOST' % (fmtString,) except: text = 'PATHOLOGICAL ERROR IN BOTH FORMAT STRING AND MESSAGE DETAILS, MESSAGE LOST' return text def textFromEventDict(eventDict): """ Extract text from an event dict passed to a log observer. If it cannot handle the dict, it returns None. The possible keys of eventDict are: - C{message}: by default, it holds the final text. It's required, but can be empty if either C{isError} or C{format} is provided (the first having the priority). - C{isError}: boolean indicating the nature of the event. - C{failure}: L{failure.Failure} instance, required if the event is an error. - C{why}: if defined, used as header of the traceback in case of errors. - C{format}: string format used in place of C{message} to customize the event. It uses all keys present in C{eventDict} to format the text. Other keys will be used when applying the C{format}, or ignored. """ edm = eventDict['message'] if not edm: if eventDict['isError'] and 'failure' in eventDict: text = ((eventDict.get('why') or 'Unhandled Error') + '\n' + eventDict['failure'].getTraceback()) elif 'format' in eventDict: text = _safeFormat(eventDict['format'], eventDict) else: # we don't know how to log this return else: text = ' '.join(map(reflect.safe_str, edm)) return text class FileLogObserver: """ Log observer that writes to a file-like object. @type timeFormat: C{str} or C{NoneType} @ivar timeFormat: If not C{None}, the format string passed to strftime(). """ timeFormat = None def __init__(self, f): self.write = f.write self.flush = f.flush def getTimezoneOffset(self, when): """ Return the current local timezone offset from UTC. @type when: C{int} @param when: POSIX (ie, UTC) timestamp for which to find the offset. @rtype: C{int} @return: The number of seconds offset from UTC. West is positive, east is negative. """ offset = datetime.utcfromtimestamp(when) - datetime.fromtimestamp(when) return offset.days * (60 * 60 * 24) + offset.seconds def formatTime(self, when): """ Format the given UTC value as a string representing that time in the local timezone. By default it's formatted as a ISO8601-like string (ISO8601 date and ISO8601 time separated by a space). It can be customized using the C{timeFormat} attribute, which will be used as input for the underlying L{datetime.datetime.strftime} call. @type when: C{int} @param when: POSIX (ie, UTC) timestamp for which to find the offset. @rtype: C{str} """ if self.timeFormat is not None: return datetime.fromtimestamp(when).strftime(self.timeFormat) tzOffset = -self.getTimezoneOffset(when) when = datetime.utcfromtimestamp(when + tzOffset) tzHour = abs(int(tzOffset / 60 / 60)) tzMin = abs(int(tzOffset / 60 % 60)) if tzOffset < 0: tzSign = '-' else: tzSign = '+' return '%d-%02d-%02d %02d:%02d:%02d%s%02d%02d' % ( when.year, when.month, when.day, when.hour, when.minute, when.second, tzSign, tzHour, tzMin) def emit(self, eventDict): text = textFromEventDict(eventDict) if text is None: return timeStr = self.formatTime(eventDict['time']) fmtDict = {'system': eventDict['system'], 'text': text.replace("\n", "\n\t")} msgStr = _safeFormat("[%(system)s] %(text)s\n", fmtDict) util.untilConcludes(self.write, timeStr + " " + msgStr) util.untilConcludes(self.flush) # Hoorj! def start(self): """ Start observing log events. """ addObserver(self.emit) def stop(self): """ Stop observing log events. """ removeObserver(self.emit) class PythonLoggingObserver(object): """ Output twisted messages to Python standard library L{logging} module. WARNING: specific logging configurations (example: network) can lead to a blocking system. Nothing is done here to prevent that, so be sure to not use this: code within Twisted, such as twisted.web, assumes that logging does not block. """ def __init__(self, loggerName="twisted"): """ @param loggerName: identifier used for getting logger. @type loggerName: C{str} """ self.logger = logging.getLogger(loggerName) def emit(self, eventDict): """ Receive a twisted log entry, format it and bridge it to python. By default the logging level used is info; log.err produces error level, and you can customize the level by using the C{logLevel} key:: >>> log.msg('debugging', logLevel=logging.DEBUG) """ if 'logLevel' in eventDict: level = eventDict['logLevel'] elif eventDict['isError']: level = logging.ERROR else: level = logging.INFO text = textFromEventDict(eventDict) if text is None: return self.logger.log(level, text) def start(self): """ Start observing log events. """ addObserver(self.emit) def stop(self): """ Stop observing log events. """ removeObserver(self.emit) class StdioOnnaStick: """ Class that pretends to be stdout/err, and turns writes into log messages. @ivar isError: boolean indicating whether this is stderr, in which cases log messages will be logged as errors. @ivar encoding: unicode encoding used to encode any unicode strings written to this object. """ closed = 0 softspace = 0 mode = 'wb' name = '' def __init__(self, isError=0, encoding=None): self.isError = isError if encoding is None: encoding = sys.getdefaultencoding() self.encoding = encoding self.buf = '' def close(self): pass def fileno(self): return -1 def flush(self): pass def read(self): raise IOError("can't read from the log!") readline = read readlines = read seek = read tell = read def write(self, data): if not _PY3 and isinstance(data, unicode): data = data.encode(self.encoding) d = (self.buf + data).split('\n') self.buf = d[-1] messages = d[0:-1] for message in messages: msg(message, printed=1, isError=self.isError) def writelines(self, lines): for line in lines: if not _PY3 and isinstance(line, unicode): line = line.encode(self.encoding) msg(line, printed=1, isError=self.isError) try: _oldshowwarning except NameError: _oldshowwarning = None def startLogging(file, *a, **kw): """ Initialize logging to a specified file. @return: A L{FileLogObserver} if a new observer is added, None otherwise. """ if isinstance(file, StdioOnnaStick): return flo = FileLogObserver(file) startLoggingWithObserver(flo.emit, *a, **kw) return flo def startLoggingWithObserver(observer, setStdout=1): """ Initialize logging to a specified observer. If setStdout is true (defaults to yes), also redirect sys.stdout and sys.stderr to the specified file. """ global defaultObserver, _oldshowwarning if not _oldshowwarning: _oldshowwarning = warnings.showwarning warnings.showwarning = showwarning if defaultObserver: defaultObserver.stop() defaultObserver = None addObserver(observer) msg("Log opened.") if setStdout: sys.stdout = logfile sys.stderr = logerr class NullFile: softspace = 0 def read(self): pass def write(self, bytes): pass def flush(self): pass def close(self): pass def discardLogs(): """ Throw away all logs. """ global logfile logfile = NullFile() # Prevent logfile from being erased on reload. This only works in cpython. try: logfile except NameError: logfile = StdioOnnaStick(0, getattr(sys.stdout, "encoding", None)) logerr = StdioOnnaStick(1, getattr(sys.stderr, "encoding", None)) class DefaultObserver: """ Default observer. Will ignore all non-error messages and send error messages to sys.stderr. Will be removed when startLogging() is called for the first time. """ stderr = sys.stderr def _emit(self, eventDict): if eventDict["isError"]: if 'failure' in eventDict: text = ((eventDict.get('why') or 'Unhandled Error') + '\n' + eventDict['failure'].getTraceback()) else: text = " ".join([str(m) for m in eventDict["message"]]) + "\n" self.stderr.write(text) self.stderr.flush() def start(self): addObserver(self._emit) def stop(self): removeObserver(self._emit) try: defaultObserver except NameError: defaultObserver = DefaultObserver() defaultObserver.start()