Current File : //lib/python3/dist-packages/twisted/logger/_format.py
# -*- test-case-name: twisted.logger.test.test_format -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Tools for formatting logging events.
"""
from __future__ import annotations
from datetime import datetime as DateTime
from typing import Any, Callable, Iterator, Mapping, Optional, Union, cast
from constantly import NamedConstant
from twisted.python._tzhelper import FixedOffsetTimeZone
from twisted.python.failure import Failure
from twisted.python.reflect import safe_repr
from ._flatten import aFormatter, flatFormat
from ._interfaces import LogEvent
timeFormatRFC3339 = "%Y-%m-%dT%H:%M:%S%z"
def formatEvent(event: LogEvent) -> str:
"""
Formats an event as text, using the format in C{event["log_format"]}.
This implementation should never raise an exception; if the formatting
cannot be done, the returned string will describe the event generically so
that a useful message is emitted regardless.
@param event: A logging event.
@return: A formatted string.
"""
return eventAsText(
event,
includeTraceback=False,
includeTimestamp=False,
includeSystem=False,
)
def formatUnformattableEvent(event: LogEvent, error: BaseException) -> str:
"""
Formats an event as text that describes the event generically and a
formatting error.
@param event: A logging event.
@param error: The formatting error.
@return: A formatted string.
"""
try:
return "Unable to format event {event!r}: {error}".format(
event=event, error=error
)
except BaseException:
# Yikes, something really nasty happened.
#
# Try to recover as much formattable data as possible; hopefully at
# least the namespace is sane, which will help you find the offending
# logger.
failure = Failure()
text = ", ".join(
" = ".join((safe_repr(key), safe_repr(value)))
for key, value in event.items()
)
return (
"MESSAGE LOST: unformattable object logged: {error}\n"
"Recoverable data: {text}\n"
"Exception during formatting:\n{failure}".format(
error=safe_repr(error), failure=failure, text=text
)
)
def formatTime(
when: Optional[float],
timeFormat: Optional[str] = timeFormatRFC3339,
default: str = "-",
) -> str:
"""
Format a timestamp as text.
Example::
>>> from time import time
>>> from twisted.logger import formatTime
>>>
>>> t = time()
>>> formatTime(t)
u'2013-10-22T14:19:11-0700'
>>> formatTime(t, timeFormat="%Y/%W") # Year and week number
u'2013/42'
>>>
@param when: A timestamp.
@param timeFormat: A time format.
@param default: Text to return if C{when} or C{timeFormat} is L{None}.
@return: A formatted time.
"""
if timeFormat is None or when is None:
return default
else:
tz = FixedOffsetTimeZone.fromLocalTimeStamp(when)
datetime = DateTime.fromtimestamp(when, tz)
return str(datetime.strftime(timeFormat))
def formatEventAsClassicLogText(
event: LogEvent, formatTime: Callable[[Optional[float]], str] = formatTime
) -> Optional[str]:
"""
Format an event as a line of human-readable text for, e.g. traditional log
file output.
The output format is C{"{timeStamp} [{system}] {event}\\n"}, where:
- C{timeStamp} is computed by calling the given C{formatTime} callable
on the event's C{"log_time"} value
- C{system} is the event's C{"log_system"} value, if set, otherwise,
the C{"log_namespace"} and C{"log_level"}, joined by a C{"#"}. Each
defaults to C{"-"} is not set.
- C{event} is the event, as formatted by L{formatEvent}.
Example::
>>> from time import time
>>> from twisted.logger import formatEventAsClassicLogText
>>> from twisted.logger import LogLevel
>>>
>>> formatEventAsClassicLogText(dict()) # No format, returns None
>>> formatEventAsClassicLogText(dict(log_format="Hello!"))
u'- [-#-] Hello!\\n'
>>> formatEventAsClassicLogText(dict(
... log_format="Hello!",
... log_time=time(),
... log_namespace="my_namespace",
... log_level=LogLevel.info,
... ))
u'2013-10-22T17:30:02-0700 [my_namespace#info] Hello!\\n'
>>> formatEventAsClassicLogText(dict(
... log_format="Hello!",
... log_time=time(),
... log_system="my_system",
... ))
u'2013-11-11T17:22:06-0800 [my_system] Hello!\\n'
>>>
@param event: an event.
@param formatTime: A time formatter
@return: A formatted event, or L{None} if no output is appropriate.
"""
eventText = eventAsText(event, formatTime=formatTime)
if not eventText:
return None
eventText = eventText.replace("\n", "\n\t")
return eventText + "\n"
def keycall(key: str, getter: Callable[[str], Any]) -> PotentialCallWrapper:
"""
Check to see if C{key} ends with parentheses ("C{()}"); if not, wrap up the
result of C{get} in a L{PotentialCallWrapper}. Otherwise, call the result
of C{get} first, before wrapping it up.
@param key: The last dotted segment of a formatting key, as parsed by
L{Formatter.vformat}, which may end in C{()}.
@param getter: A function which takes a string and returns some other
object, to be formatted and stringified for a log.
@return: A L{PotentialCallWrapper} that will wrap up the result to allow
for subsequent usages of parens to defer execution to log-format time.
"""
callit = key.endswith("()")
realKey = key[:-2] if callit else key
value = getter(realKey)
if callit:
value = value()
return PotentialCallWrapper(value)
class PotentialCallWrapper(object):
"""
Object wrapper that wraps C{getattr()} so as to process call-parentheses
C{"()"} after a dotted attribute access.
"""
def __init__(self, wrapped: object) -> None:
self._wrapped = wrapped
def __getattr__(self, name: str) -> object:
return keycall(name, self._wrapped.__getattribute__)
def __getitem__(self, name: str) -> object:
# The sub-object may not be indexable, but if it isn't, that's the
# caller's problem.
value = self._wrapped[name] # type:ignore[index]
return PotentialCallWrapper(value)
def __format__(self, format_spec: str) -> str:
return self._wrapped.__format__(format_spec)
def __repr__(self) -> str:
return self._wrapped.__repr__()
def __str__(self) -> str:
return self._wrapped.__str__()
class CallMapping(Mapping[str, Any]):
"""
Read-only mapping that turns a C{()}-suffix in key names into an invocation
of the key rather than a lookup of the key.
Implementation support for L{formatWithCall}.
"""
def __init__(self, submapping: Mapping[str, Any]) -> None:
"""
@param submapping: Another read-only mapping which will be used to look
up items.
"""
self._submapping = submapping
def __iter__(self) -> Iterator[Any]:
return iter(self._submapping)
def __len__(self) -> int:
return len(self._submapping)
def __getitem__(self, key: str) -> Any:
"""
Look up an item in the submapping for this L{CallMapping}, calling it
if C{key} ends with C{"()"}.
"""
return keycall(key, self._submapping.__getitem__)
def formatWithCall(formatString: str, mapping: Mapping[str, Any]) -> str:
"""
Format a string like L{str.format}, but:
- taking only a name mapping; no positional arguments
- with the additional syntax that an empty set of parentheses
correspond to a formatting item that should be called, and its result
C{str}'d, rather than calling C{str} on the element directly as
normal.
For example::
>>> formatWithCall("{string}, {function()}.",
... dict(string="just a string",
... function=lambda: "a function"))
'just a string, a function.'
@param formatString: A PEP-3101 format string.
@param mapping: A L{dict}-like object to format.
@return: The string with formatted values interpolated.
"""
return str(aFormatter.vformat(formatString, (), CallMapping(mapping)))
def _formatEvent(event: LogEvent) -> str:
"""
Formats an event as a string, using the format in C{event["log_format"]}.
This implementation should never raise an exception; if the formatting
cannot be done, the returned string will describe the event generically so
that a useful message is emitted regardless.
@param event: A logging event.
@return: A formatted string.
"""
try:
if "log_flattened" in event:
return flatFormat(event)
format = cast(Optional[Union[str, bytes]], event.get("log_format", None))
if format is None:
return ""
# Make sure format is text.
if isinstance(format, str):
pass
elif isinstance(format, bytes):
format = format.decode("utf-8")
else:
raise TypeError(f"Log format must be str, not {format!r}")
return formatWithCall(format, event)
except BaseException as e:
return formatUnformattableEvent(event, e)
def _formatTraceback(failure: Failure) -> str:
"""
Format a failure traceback, assuming UTF-8 and using a replacement
strategy for errors. Every effort is made to provide a usable
traceback, but should not that not be possible, a message and the
captured exception are logged.
@param failure: The failure to retrieve a traceback from.
@return: The formatted traceback.
"""
try:
traceback = failure.getTraceback()
except BaseException as e:
traceback = "(UNABLE TO OBTAIN TRACEBACK FROM EVENT):" + str(e)
return traceback
def _formatSystem(event: LogEvent) -> str:
"""
Format the system specified in the event in the "log_system" key if set,
otherwise the C{"log_namespace"} and C{"log_level"}, joined by a C{"#"}.
Each defaults to C{"-"} is not set. If formatting fails completely,
"UNFORMATTABLE" is returned.
@param event: The event containing the system specification.
@return: A formatted string representing the "log_system" key.
"""
system = cast(Optional[str], event.get("log_system", None))
if system is None:
level = cast(Optional[NamedConstant], event.get("log_level", None))
if level is None:
levelName = "-"
else:
levelName = level.name
system = "{namespace}#{level}".format(
namespace=cast(str, event.get("log_namespace", "-")),
level=levelName,
)
else:
try:
system = str(system)
except Exception:
system = "UNFORMATTABLE"
return system
def eventAsText(
event: LogEvent,
includeTraceback: bool = True,
includeTimestamp: bool = True,
includeSystem: bool = True,
formatTime: Callable[[float], str] = formatTime,
) -> str:
r"""
Format an event as text. Optionally, attach timestamp, traceback, and
system information.
The full output format is:
C{"{timeStamp} [{system}] {event}\n{traceback}\n"} where:
- C{timeStamp} is the event's C{"log_time"} value formatted with
the provided C{formatTime} callable.
- C{system} is the event's C{"log_system"} value, if set, otherwise,
the C{"log_namespace"} and C{"log_level"}, joined by a C{"#"}. Each
defaults to C{"-"} is not set.
- C{event} is the event, as formatted by L{formatEvent}.
- C{traceback} is the traceback if the event contains a
C{"log_failure"} key. In the event the original traceback cannot
be formatted, a message indicating the failure will be substituted.
If the event cannot be formatted, and no traceback exists, an empty string
is returned, even if includeSystem or includeTimestamp are true.
@param event: A logging event.
@param includeTraceback: If true and a C{"log_failure"} key exists, append
a traceback.
@param includeTimestamp: If true include a formatted timestamp before the
event.
@param includeSystem: If true, include the event's C{"log_system"} value.
@param formatTime: A time formatter
@return: A formatted string with specified options.
@since: Twisted 18.9.0
"""
eventText = _formatEvent(event)
if includeTraceback and "log_failure" in event:
f = event["log_failure"]
traceback = _formatTraceback(f)
eventText = "\n".join((eventText, traceback))
if not eventText:
return eventText
timeStamp = ""
if includeTimestamp:
timeStamp = "".join([formatTime(cast(float, event.get("log_time", None))), " "])
system = ""
if includeSystem:
system = "".join(["[", _formatSystem(event), "]", " "])
return "{timeStamp}{system}{eventText}".format(
timeStamp=timeStamp,
system=system,
eventText=eventText,
)
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