74 lines
2.2 KiB
Python
74 lines
2.2 KiB
Python
"""Logging utilities."""
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from __future__ import annotations
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import logging
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import logging.handlers
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import queue
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from typing import Any
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class SupervisorQueueHandler(logging.handlers.QueueHandler):
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"""Process the log in another thread."""
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listener: logging.handlers.QueueListener | None = None
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def prepare(self, record: logging.LogRecord) -> logging.LogRecord:
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"""Prepare a record for queuing.
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This is added as a workaround for https://bugs.python.org/issue46755
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"""
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record = super().prepare(record)
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record.stack_info = None
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return record
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def handle(self, record: logging.LogRecord) -> Any:
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"""Conditionally emit the specified logging record.
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Depending on which filters have been added to the handler, push the new
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records onto the backing Queue.
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The default python logger Handler acquires a lock
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in the parent class which we do not need as
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SimpleQueue is already thread safe.
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See https://bugs.python.org/issue24645
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"""
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return_value = self.filter(record)
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if return_value:
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self.emit(record)
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return return_value
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def close(self) -> None:
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"""Tidy up any resources used by the handler.
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This adds shutdown of the QueueListener
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"""
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super().close()
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if not self.listener:
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return
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self.listener.stop()
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self.listener = None
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def activate_log_queue_handler() -> None:
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"""Migrate the existing log handlers to use the queue.
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This allows us to avoid blocking I/O and formatting messages
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in the event loop as log messages are written in another thread.
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"""
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simple_queue: queue.SimpleQueue[logging.Handler] = queue.SimpleQueue()
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queue_handler = SupervisorQueueHandler(simple_queue)
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logging.root.addHandler(queue_handler)
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migrated_handlers: list[logging.Handler] = []
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for handler in logging.root.handlers[:]:
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if handler is queue_handler:
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continue
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logging.root.removeHandler(handler)
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migrated_handlers.append(handler)
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listener = logging.handlers.QueueListener(simple_queue, *migrated_handlers)
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queue_handler.listener = listener
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listener.start()
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