56 lines
1.8 KiB
Python
56 lines
1.8 KiB
Python
import asyncio
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import os
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from pathlib import Path
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from typing import Callable, Awaitable, Optional
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class LogWatcher:
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POLL_INTERVAL = 0.1
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FILE_RETRY_INTERVAL = 1.0
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def __init__(
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self,
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path: str,
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on_line: Callable[[str], Awaitable[None]],
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on_offline: Optional[Callable[[], Awaitable[None]]] = None,
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offline_timeout: float = 60.0,
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):
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self._path = Path(path)
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self._on_line = on_line
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self._on_offline = on_offline
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self._offline_timeout = offline_timeout
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self._task: Optional[asyncio.Task] = None
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def start(self) -> asyncio.Task:
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self._task = asyncio.create_task(self._run())
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return self._task
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def stop(self):
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if self._task:
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self._task.cancel()
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async def _run(self):
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offline_since: Optional[float] = None
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while True:
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try:
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with open(self._path, 'r', errors='replace') as f:
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f.seek(0, 2) # start at end of file (tail -f behaviour)
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offline_since = None
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while True:
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line = f.readline()
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if line:
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await self._on_line(line)
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else:
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await asyncio.sleep(self.POLL_INTERVAL)
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except OSError:
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now = asyncio.get_event_loop().time()
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if offline_since is None:
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offline_since = now
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elif now - offline_since >= self._offline_timeout and self._on_offline:
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await self._on_offline()
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offline_since = None # reset so we don't spam
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await asyncio.sleep(min(self.FILE_RETRY_INTERVAL, self._offline_timeout))
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except asyncio.CancelledError:
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return
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