90 lines
2.7 KiB
Python
90 lines
2.7 KiB
Python
import logging
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import time
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from logging import Handler, LogRecord
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from logging.handlers import MemoryHandler
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from threading import Thread
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from typing import Optional
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from twisted.internet.interfaces import IReactorCore
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class PeriodicallyFlushingMemoryHandler(MemoryHandler):
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"""
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This is a subclass of MemoryHandler that additionally spawns a background
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thread to periodically flush the buffer.
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This prevents messages from being buffered for too long.
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Additionally, all messages will be immediately flushed if the reactor has
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not yet been started.
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"""
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def __init__(
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self,
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capacity: int,
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flushLevel: int = logging.ERROR,
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target: Optional[Handler] = None,
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flushOnClose: bool = True,
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period: float = 5.0,
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reactor: Optional[IReactorCore] = None,
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) -> None:
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"""
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period: the period between automatic flushes
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reactor: if specified, a custom reactor to use. If not specifies,
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defaults to the globally-installed reactor.
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Log entries will be flushed immediately until this reactor has
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started.
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"""
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super().__init__(capacity, flushLevel, target, flushOnClose)
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self._flush_period: float = period
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self._active: bool = True
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self._reactor_started = False
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self._flushing_thread: Thread = Thread(
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name="PeriodicallyFlushingMemoryHandler flushing thread",
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target=self._flush_periodically,
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daemon=True,
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)
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self._flushing_thread.start()
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def on_reactor_running():
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self._reactor_started = True
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reactor_to_use: IReactorCore
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if reactor is None:
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from twisted.internet import reactor as global_reactor
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reactor_to_use = global_reactor # type: ignore[assignment]
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else:
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reactor_to_use = reactor
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# call our hook when the reactor start up
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reactor_to_use.callWhenRunning(on_reactor_running)
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def shouldFlush(self, record: LogRecord) -> bool:
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"""
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Before reactor start-up, log everything immediately.
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Otherwise, fall back to original behaviour of waiting for the buffer to fill.
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"""
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if self._reactor_started:
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return super().shouldFlush(record)
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else:
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return True
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def _flush_periodically(self):
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"""
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Whilst this handler is active, flush the handler periodically.
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"""
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while self._active:
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# flush is thread-safe; it acquires and releases the lock internally
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self.flush()
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time.sleep(self._flush_period)
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def close(self) -> None:
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self._active = False
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super().close()
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