118 lines
3.9 KiB
Python
118 lines
3.9 KiB
Python
import threading
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import logging
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logger = logging.getLogger(__name__)
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class LoggingContext(object):
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"""Additional context for log formatting. Contexts are scoped within a
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"with" block. Contexts inherit the state of their parent contexts.
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Args:
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name (str): Name for the context for debugging.
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"""
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__slots__ = ["parent_context", "name", "__dict__"]
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thread_local = threading.local()
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class Sentinel(object):
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"""Sentinel to represent the root context"""
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__slots__ = []
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def __str__(self):
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return "sentinel"
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def copy_to(self, record):
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pass
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sentinel = Sentinel()
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def __init__(self, name=None):
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self.parent_context = None
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self.name = name
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def __str__(self):
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return "%s@%x" % (self.name, id(self))
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@classmethod
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def current_context(cls):
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"""Get the current logging context from thread local storage"""
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return getattr(cls.thread_local, "current_context", cls.sentinel)
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def __enter__(self):
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"""Enters this logging context into thread local storage"""
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if self.parent_context is not None:
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raise Exception("Attempt to enter logging context multiple times")
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self.parent_context = self.current_context()
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self.thread_local.current_context = self
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return self
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def __exit__(self, type, value, traceback):
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"""Restore the logging context in thread local storage to the state it
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was before this context was entered.
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Returns:
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None to avoid suppressing any exeptions that were thrown.
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"""
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if self.thread_local.current_context is not self:
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if self.thread_local.current_context is self.sentinel:
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logger.debug("Expected logging context %s has been lost", self)
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else:
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logger.warn(
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"Current logging context %s is not expected context %s",
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self.thread_local.current_context,
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self
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)
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self.thread_local.current_context = self.parent_context
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self.parent_context = None
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def __getattr__(self, name):
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"""Delegate member lookup to parent context"""
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return getattr(self.parent_context, name)
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def copy_to(self, record):
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"""Copy fields from this context and its parents to the record"""
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if self.parent_context is not None:
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self.parent_context.copy_to(record)
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for key, value in self.__dict__.items():
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setattr(record, key, value)
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class LoggingContextFilter(logging.Filter):
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"""Logging filter that adds values from the current logging context to each
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record.
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Args:
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**defaults: Default values to avoid formatters complaining about
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missing fields
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"""
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def __init__(self, **defaults):
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self.defaults = defaults
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def filter(self, record):
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"""Add each fields from the logging contexts to the record.
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Returns:
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True to include the record in the log output.
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"""
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context = LoggingContext.current_context()
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for key, value in self.defaults.items():
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setattr(record, key, value)
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context.copy_to(record)
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return True
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class PreserveLoggingContext(object):
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"""Captures the current logging context and restores it when the scope is
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exited. Used to restore the context after a function using
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@defer.inlineCallbacks is resumed by a callback from the reactor."""
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__slots__ = ["current_context"]
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def __enter__(self):
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"""Captures the current logging context"""
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self.current_context = LoggingContext.current_context()
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LoggingContext.thread_local.current_context = LoggingContext.sentinel
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def __exit__(self, type, value, traceback):
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"""Restores the current logging context"""
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LoggingContext.thread_local.current_context = self.current_context
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