456 lines
16 KiB
Python
456 lines
16 KiB
Python
# -*- test-case-name: twisted.logger.test.test_logger -*-
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# Copyright (c) Twisted Matrix Laboratories.
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# See LICENSE for details.
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"""
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Logger class.
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"""
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from __future__ import annotations
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from time import time
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from types import TracebackType
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from typing import Any, Callable, ContextManager, Optional, Protocol, cast
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from twisted.python.compat import currentframe
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from twisted.python.failure import Failure
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from ._interfaces import ILogObserver, LogTrace
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from ._levels import InvalidLogLevelError, LogLevel
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class Operation(Protocol):
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"""
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An L{Operation} represents the success (or lack thereof) of code performed
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within the body of the L{Logger.failureHandler} context manager.
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"""
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@property
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def succeeded(self) -> bool:
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"""
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Did the operation succeed? C{True} iff the code completed without
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raising an exception; C{False} while the code is running and C{False}
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if it raises an exception.
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"""
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@property
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def failure(self) -> Failure | None:
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"""
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Did the operation raise an exception? If so, this L{Failure} is that
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exception.
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"""
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@property
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def failed(self) -> bool:
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"""
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Did the operation fail? C{True} iff the code raised an exception;
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C{False} while the code is running and C{False} if it completed without
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error.
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"""
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class _FailCtxMgr:
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succeeded: bool = False
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failure: Failure | None = None
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def __init__(self, fail: Callable[[Failure], None]) -> None:
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self._fail = fail
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@property
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def failed(self) -> bool:
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return self.failure is not None
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def __enter__(self) -> Operation:
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return self
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def __exit__(
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self,
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exc_type: type[BaseException] | None,
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exc_value: BaseException | None,
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traceback: TracebackType | None,
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/,
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) -> bool:
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if exc_type is not None:
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failure = Failure()
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self.failure = failure
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self._fail(failure)
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else:
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self.succeeded = True
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return True
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class _FastFailCtxMgr:
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def __init__(self, fail: Callable[[Failure], None]) -> None:
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self._fail = fail
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def __enter__(self) -> None:
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pass
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def __exit__(
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self,
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exc_type: type[BaseException] | None,
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exc_value: BaseException | None,
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traceback: TracebackType | None,
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/,
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) -> bool:
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if exc_type is not None:
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failure = Failure()
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self.failure = failure
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self._fail(failure)
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return True
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class Logger:
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"""
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A L{Logger} emits log messages to an observer. You should instantiate it
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as a class or module attribute, as documented in L{this module's
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documentation <twisted.logger>}.
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@ivar namespace: the namespace for this logger
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@ivar source: The object which is emitting events via this logger
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@ivar observer: The observer that this logger will send events to.
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"""
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@staticmethod
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def _namespaceFromCallingContext() -> str:
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"""
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Derive a namespace from the module containing the caller's caller.
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@return: the fully qualified python name of a module.
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"""
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try:
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return cast(str, currentframe(2).f_globals["__name__"])
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except KeyError:
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return "<unknown>"
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def __init__(
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self,
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namespace: Optional[str] = None,
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source: Optional[object] = None,
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observer: Optional["ILogObserver"] = None,
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) -> None:
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"""
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@param namespace: The namespace for this logger. Uses a dotted
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notation, as used by python modules. If not L{None}, then the name
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of the module of the caller is used.
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@param source: The object which is emitting events via this
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logger; this is automatically set on instances of a class
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if this L{Logger} is an attribute of that class.
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@param observer: The observer that this logger will send events to.
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If L{None}, use the L{global log publisher <globalLogPublisher>}.
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"""
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if namespace is None:
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namespace = self._namespaceFromCallingContext()
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self.namespace = namespace
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self.source = source
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if observer is None:
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from ._global import globalLogPublisher
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self.observer: ILogObserver = globalLogPublisher
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else:
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self.observer = observer
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def __get__(self, instance: object, owner: Optional[type] = None) -> "Logger":
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"""
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When used as a descriptor, i.e.::
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# File: athing.py
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class Something:
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log = Logger()
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def hello(self):
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self.log.info("Hello")
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a L{Logger}'s namespace will be set to the name of the class it is
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declared on. In the above example, the namespace would be
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C{athing.Something}.
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Additionally, its source will be set to the actual object referring to
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the L{Logger}. In the above example, C{Something.log.source} would be
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C{Something}, and C{Something().log.source} would be an instance of
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C{Something}.
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"""
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assert owner is not None
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if instance is None:
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source: Any = owner
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else:
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source = instance
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return self.__class__(
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".".join([owner.__module__, owner.__name__]),
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source,
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observer=self.observer,
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)
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def __repr__(self) -> str:
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return f"<{self.__class__.__name__} {self.namespace!r}>"
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def emit(
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self, level: LogLevel, format: Optional[str] = None, **kwargs: object
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) -> None:
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"""
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Emit a log event to all log observers at the given level.
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@param level: a L{LogLevel}
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@param format: a message format using new-style (PEP 3101)
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formatting. The logging event (which is a L{dict}) is
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used to render this format string.
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@param kwargs: additional key/value pairs to include in the event.
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Note that values which are later mutated may result in
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non-deterministic behavior from observers that schedule work for
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later execution.
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"""
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if level not in LogLevel.iterconstants():
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self.failure(
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"Got invalid log level {invalidLevel!r} in {logger}.emit().",
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Failure(InvalidLogLevelError(level)),
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invalidLevel=level,
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logger=self,
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)
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return
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event = kwargs
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event.update(
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log_logger=self,
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log_level=level,
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log_namespace=self.namespace,
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log_source=self.source,
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log_format=format,
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log_time=time(),
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)
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if "log_trace" in event:
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cast(LogTrace, event["log_trace"]).append((self, self.observer))
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self.observer(event)
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def failure(
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self,
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format: str,
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failure: Optional[Failure] = None,
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level: LogLevel = LogLevel.critical,
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**kwargs: object,
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) -> None:
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"""
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Log a failure and emit a traceback.
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For example::
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try:
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frob(knob)
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except Exception:
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log.failure("While frobbing {knob}", knob=knob)
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or::
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d = deferredFrob(knob)
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d.addErrback(lambda f: log.failure("While frobbing {knob}",
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f, knob=knob))
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This method is meant to capture unexpected exceptions in code; an
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exception that is caught and handled somehow should be logged, if
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appropriate, via L{Logger.error} instead. If some unknown exception
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occurs and your code doesn't know how to handle it, as in the above
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example, then this method provides a means to describe the failure.
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This is done at L{LogLevel.critical} by default, since no corrective
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guidance can be offered to an user/administrator, and the impact of the
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condition is unknown.
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@param format: a message format using new-style (PEP 3101) formatting.
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The logging event (which is a L{dict}) is used to render this
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format string.
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@param failure: a L{Failure} to log. If L{None}, a L{Failure} is
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created from the exception in flight.
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@param level: a L{LogLevel} to use.
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@param kwargs: additional key/value pairs to include in the event.
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Note that values which are later mutated may result in
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non-deterministic behavior from observers that schedule work for
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later execution.
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@see: L{Logger.failureHandler}
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@see: L{Logger.failuresHandled}
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"""
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if failure is None:
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failure = Failure()
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self.emit(level, format, log_failure=failure, **kwargs)
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def debug(self, format: Optional[str] = None, **kwargs: object) -> None:
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"""
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Emit a log event at log level L{LogLevel.debug}.
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@param format: a message format using new-style (PEP 3101) formatting.
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The logging event (which is a L{dict}) is used to render this
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format string.
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@param kwargs: additional key/value pairs to include in the event.
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Note that values which are later mutated may result in
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non-deterministic behavior from observers that schedule work for
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later execution.
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"""
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self.emit(LogLevel.debug, format, **kwargs)
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def info(self, format: Optional[str] = None, **kwargs: object) -> None:
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"""
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Emit a log event at log level L{LogLevel.info}.
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@param format: a message format using new-style (PEP 3101) formatting.
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The logging event (which is a L{dict}) is used to render this
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format string.
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@param kwargs: additional key/value pairs to include in the event.
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Note that values which are later mutated may result in
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non-deterministic behavior from observers that schedule work for
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later execution.
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"""
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self.emit(LogLevel.info, format, **kwargs)
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def warn(self, format: Optional[str] = None, **kwargs: object) -> None:
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"""
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Emit a log event at log level L{LogLevel.warn}.
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@param format: a message format using new-style (PEP 3101) formatting.
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The logging event (which is a L{dict}) is used to render this
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format string.
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@param kwargs: additional key/value pairs to include in the event.
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Note that values which are later mutated may result in
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non-deterministic behavior from observers that schedule work for
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later execution.
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"""
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self.emit(LogLevel.warn, format, **kwargs)
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def error(self, format: Optional[str] = None, **kwargs: object) -> None:
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"""
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Emit a log event at log level L{LogLevel.error}.
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@param format: a message format using new-style (PEP 3101) formatting.
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The logging event (which is a L{dict}) is used to render this
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format string.
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@param kwargs: additional key/value pairs to include in the event.
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Note that values which are later mutated may result in
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non-deterministic behavior from observers that schedule work for
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later execution.
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"""
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self.emit(LogLevel.error, format, **kwargs)
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def critical(self, format: Optional[str] = None, **kwargs: object) -> None:
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"""
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Emit a log event at log level L{LogLevel.critical}.
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@param format: a message format using new-style (PEP 3101) formatting.
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The logging event (which is a L{dict}) is used to render this
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format string.
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@param kwargs: additional key/value pairs to include in the event.
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Note that values which are later mutated may result in
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non-deterministic behavior from observers that schedule work for
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later execution.
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"""
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self.emit(LogLevel.critical, format, **kwargs)
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def failuresHandled(
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self, format: str, level: LogLevel = LogLevel.critical, **kwargs: object
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) -> ContextManager[Operation]:
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"""
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Run some application code, logging a failure and emitting a traceback
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in the event that any of it fails, but continuing on. For example::
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log = Logger(...)
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def frameworkCode() -> None:
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with log.failuresHandled("While frobbing {knob}:", knob=knob) as op:
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frob(knob)
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if op.succeeded:
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log.info("frobbed {knob} successfully", knob=knob)
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This method is meant to capture unexpected exceptions from application
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code; an exception that is caught and handled somehow should be logged,
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if appropriate, via L{Logger.error} instead. If some unknown exception
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occurs and your code doesn't know how to handle it, as in the above
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example, then this method provides a means to describe the failure.
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This is done at L{LogLevel.critical} by default, since no corrective
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guidance can be offered to an user/administrator, and the impact of the
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condition is unknown.
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@param format: a message format using new-style (PEP 3101) formatting.
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The logging event (which is a L{dict}) is used to render this
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format string.
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@param level: a L{LogLevel} to use.
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@param kwargs: additional key/value pairs to include in the event, if
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it is emitted. Note that values which are later mutated may result
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in non-deterministic behavior from observers that schedule work for
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later execution.
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@see: L{Logger.failure}
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@see: L{Logger.failureHandler}
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@return: A context manager which yields an L{Operation} which will have
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either its C{succeeded} or C{failed} attribute set to C{True} upon
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completion of the code within the code within the C{with} block.
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"""
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return _FailCtxMgr(lambda f: self.failure(format, f, level, **kwargs))
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def failureHandler(
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self,
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staticMessage: str,
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level: LogLevel = LogLevel.critical,
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) -> ContextManager[None]:
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"""
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For performance-sensitive frameworks that needs to handle potential
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failures from frequently-called application code, and do not need to
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include detailed structured information about the failure nor inspect
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the result of the operation, this method returns a context manager that
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will log exceptions and continue, that can be shared across multiple
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invocations. It should be instantiated at module scope to avoid
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additional object creations.
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For example::
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log = Logger(...)
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ignoringFrobErrors = log.failureHandler("while frobbing:")
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def hotLoop() -> None:
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with ignoringFrobErrors:
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frob()
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This method is meant to capture unexpected exceptions from application
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code; an exception that is caught and handled somehow should be logged,
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if appropriate, via L{Logger.error} instead. If some unknown exception
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occurs and your code doesn't know how to handle it, as in the above
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example, then this method provides a means to describe the failure in
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nerd-speak. This is done at L{LogLevel.critical} by default, since no
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corrective guidance can be offered to an user/administrator, and the
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impact of the condition is unknown.
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@param format: a message format using new-style (PEP 3101) formatting.
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The logging event (which is a L{dict}) is used to render this
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format string.
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@param level: a L{LogLevel} to use.
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@see: L{Logger.failure}
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@return: A context manager which does not return a value, but will
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always exit from exceptions.
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"""
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return _FastFailCtxMgr(lambda f: self.failure(staticMessage, f, level))
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_log = Logger()
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def _loggerFor(obj: object) -> Logger:
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"""
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Get a L{Logger} instance attached to the given class.
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"""
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return _log.__get__(obj, obj.__class__)
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