113 lines
3.2 KiB
Python
113 lines
3.2 KiB
Python
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# -*- test-case-name: twisted.logger.test.test_observer -*-
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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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Basic log observers.
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"""
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from typing import Callable, Optional
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from zope.interface import implementer
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from twisted.python.failure import Failure
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from ._interfaces import ILogObserver, LogEvent
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from ._logger import Logger
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OBSERVER_DISABLED = (
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"Temporarily disabling observer {observer} due to exception: {log_failure}"
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)
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@implementer(ILogObserver)
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class LogPublisher:
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"""
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I{ILogObserver} that fans out events to other observers.
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Keeps track of a set of L{ILogObserver} objects and forwards
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events to each.
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"""
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def __init__(self, *observers: ILogObserver) -> None:
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self._observers = list(observers)
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self.log = Logger(observer=self)
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def addObserver(self, observer: ILogObserver) -> None:
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"""
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Registers an observer with this publisher.
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@param observer: An L{ILogObserver} to add.
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"""
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if not callable(observer):
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raise TypeError(f"Observer is not callable: {observer!r}")
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if observer not in self._observers:
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self._observers.append(observer)
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def removeObserver(self, observer: ILogObserver) -> None:
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"""
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Unregisters an observer with this publisher.
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@param observer: An L{ILogObserver} to remove.
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"""
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try:
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self._observers.remove(observer)
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except ValueError:
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pass
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def __call__(self, event: LogEvent) -> None:
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"""
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Forward events to contained observers.
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"""
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if "log_trace" not in event:
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trace: Optional[Callable[[ILogObserver], None]] = None
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else:
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def trace(observer: ILogObserver) -> None:
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"""
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Add tracing information for an observer.
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@param observer: an observer being forwarded to
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"""
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event["log_trace"].append((self, observer))
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brokenObservers = []
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for observer in self._observers:
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if trace is not None:
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trace(observer)
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try:
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observer(event)
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except Exception:
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brokenObservers.append((observer, Failure()))
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for brokenObserver, failure in brokenObservers:
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errorLogger = self._errorLoggerForObserver(brokenObserver)
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errorLogger.failure(
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OBSERVER_DISABLED,
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failure=failure,
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observer=brokenObserver,
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)
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def _errorLoggerForObserver(self, observer: ILogObserver) -> Logger:
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"""
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Create an error-logger based on this logger, which does not contain the
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given bad observer.
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@param observer: The observer which previously had an error.
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@return: A L{Logger} without the given observer.
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"""
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errorPublisher = LogPublisher(
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*(obs for obs in self._observers if obs is not observer)
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)
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return Logger(observer=errorPublisher)
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@implementer(ILogObserver)
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def bitbucketLogObserver(event: LogEvent) -> None:
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"""
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I{ILogObserver} that does nothing with the events it sees.
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"""
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