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# -*- test-case-name: twisted.test.test_log -*-
# Copyright (c) 2001-2009 Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Logging and metrics infrastructure.
"""
from __future__ import division
import sys
import time
import warnings
from datetime import datetime
import logging
from zope.interface import Interface
from twisted.python import util, context, reflect
class ILogContext:
"""
Actually, this interface is just a synoym for the dictionary interface,
but it serves as a key for the default information in a log.
I do not inherit from 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)
_keepErrors = 0
_keptErrors = []
_ignoreErrors = []
def startKeepingErrors():
"""
DEPRECATED in Twisted 2.5.
Support function for testing frameworks.
Start keeping errors in a buffer which can be retrieved (and emptied) with
flushErrors.
"""
warnings.warn("log.startKeepingErrors is deprecated since Twisted 2.5",
category=DeprecationWarning, stacklevel=2)
global _keepErrors
_keepErrors = 1
def flushErrors(*errorTypes):
"""
DEPRECATED in Twisted 2.5. See L{TestCase.flushLoggedErrors}.
Support function for testing frameworks.
Return a list of errors that occurred since the last call to flushErrors().
(This will return None unless startKeepingErrors has been called.)
"""
warnings.warn("log.flushErrors is deprecated since Twisted 2.5. "
"If you need to flush errors from within a unittest, "
"use TestCase.flushLoggedErrors instead.",
category=DeprecationWarning, stacklevel=2)
return _flushErrors(*errorTypes)
def _flushErrors(*errorTypes):
"""
PRIVATE. DEPRECATED. DON'T USE.
"""
global _keptErrors
k = _keptErrors
_keptErrors = []
if errorTypes:
for erk in k:
shouldReLog = 1
for errT in errorTypes:
if erk.check(errT):
shouldReLog = 0
if shouldReLog:
err(erk)
return k
def ignoreErrors(*types):
"""
DEPRECATED
"""
warnings.warn("log.ignoreErrors is deprecated since Twisted 2.5",
category=DeprecationWarning, stacklevel=2)
_ignore(*types)
def _ignore(*types):
"""
PRIVATE. DEPRECATED. DON'T USE.
"""
for type in types:
_ignoreErrors.append(type)
def clearIgnores():
"""
DEPRECATED
"""
warnings.warn("log.clearIgnores is deprecated since Twisted 2.5",
category=DeprecationWarning, stacklevel=2)
_clearIgnores()
def _clearIgnores():
"""
PRIVATE. DEPRECATED. DON'T USE.
"""
global _ignoreErrors
_ignoreErrors = []
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):
if _keepErrors:
if _ignoreErrors:
keep = 0
for err in _ignoreErrors:
r = _stuff.check(err)
if r:
keep = 0
break
else:
keep = 1
if keep:
_keptErrors.append(_stuff)
else:
_keptErrors.append(_stuff)
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.
For example::
>>> log.msg('Hello, world.')
In particular, you MUST avoid the forms::
>>> log.msg(u'Hello, world.')
>>> log.msg('Hello ', 'world.')
These forms work (sometimes) by accident and will be disabled
entirely in the future.
"""
actualEventDict = (context.get(ILogContext) or {}).copy()
actualEventDict.update(kw)
actualEventDict['message'] = message
actualEventDict['time'] = time.time()
for i in xrange(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
err(failure.Failure(),
"Log observer %s failed." % (observer,))
self.observers[i] = observer
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)
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
C{time.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 time.strftime(self.timeFormat, time.localtime(when))
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 stout/err.
"""
closed = 0
softspace = 0
mode = 'wb'
name = '<stdio (log)>'
def __init__(self, isError=0):
self.isError = isError
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):
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:
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)
logerr = StdioOnnaStick(1)
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.
"""
def _emit(self, eventDict):
if eventDict["isError"]:
if 'failure' in eventDict:
text = eventDict['failure'].getTraceback()
else:
text = " ".join([str(m) for m in eventDict["message"]]) + "\n"
sys.stderr.write(text)
sys.stderr.flush()
def start(self):
addObserver(self._emit)
def stop(self):
removeObserver(self._emit)
# Some more sibling imports, at the bottom and unqualified to avoid
# unresolvable circularity
import threadable, failure
threadable.synchronize(LogPublisher)
try:
defaultObserver
except NameError:
defaultObserver = DefaultObserver()
defaultObserver.start()
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