73 lines
2.3 KiB
Python
73 lines
2.3 KiB
Python
"""Shared asyncio loop lifecycle helpers for the desktop application.
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The GUI runs on Tk's main thread, while database calls are executed on a
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dedicated background event loop. These helpers expose that loop as a lazy
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singleton so every module can schedule work on the same async runtime.
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"""
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import asyncio
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import threading
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import contextlib
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class _LoopHolder:
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"""Store the global loop instance and its worker thread."""
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def __init__(self):
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self.loop = None
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self.thread = None
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self.closing = False
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_GLOBAL = _LoopHolder()
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def get_global_loop() -> asyncio.AbstractEventLoop:
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"""Return the shared background event loop.
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The loop is created lazily the first time the function is called and kept
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alive for the lifetime of the application.
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"""
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if _GLOBAL.loop and not _GLOBAL.closing:
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return _GLOBAL.loop
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ready = threading.Event()
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def _run():
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_GLOBAL.loop = asyncio.new_event_loop()
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asyncio.set_event_loop(_GLOBAL.loop)
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ready.set()
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try:
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_GLOBAL.loop.run_forever()
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finally:
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loop = _GLOBAL.loop
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if loop is not None:
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pending = [task for task in asyncio.all_tasks(loop) if not task.done()]
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for task in pending:
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task.cancel()
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if pending:
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with contextlib.suppress(Exception):
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loop.run_until_complete(asyncio.gather(*pending, return_exceptions=True))
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with contextlib.suppress(Exception):
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loop.run_until_complete(loop.shutdown_asyncgens())
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with contextlib.suppress(Exception):
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loop.run_until_complete(loop.shutdown_default_executor())
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with contextlib.suppress(Exception):
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loop.close()
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_GLOBAL.thread = threading.Thread(target=_run, name="asyncio-bg-loop", daemon=True)
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_GLOBAL.thread.start()
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ready.wait()
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return _GLOBAL.loop
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def stop_global_loop():
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"""Stop the shared loop and join the background thread if present."""
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if _GLOBAL.loop and _GLOBAL.loop.is_running():
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_GLOBAL.closing = True
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_GLOBAL.loop.call_soon_threadsafe(_GLOBAL.loop.stop)
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_GLOBAL.thread.join(timeout=2)
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_GLOBAL.loop = None
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_GLOBAL.thread = None
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_GLOBAL.closing = False
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