110 lines
4.8 KiB
Python
110 lines
4.8 KiB
Python
"""Fan-out of pipeline result frames and status to connected web clients.
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A single broadcaster task polls the :class:`WebController` off the event loop and
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pushes the freshest frame (latest-wins) plus a slower status heartbeat to every
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registered client. Each client is a bounded ``asyncio.Queue`` with a drop-oldest
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policy, so a slow socket can never stall the producer or the loop — if a client
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falls behind it simply skips intermediate frames and always gets the newest.
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"""
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from __future__ import annotations
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import asyncio
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import contextlib
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import logging
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from python_app.webui.controller import WebController
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logger = logging.getLogger(__name__)
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# Poll the controller this often; the C++ pipeline publishes well below this rate,
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# so this is a comfortable latest-wins cadence without busy-spinning the loop.
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_FRAME_INTERVAL_S = 0.05
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# Status is cheap but rarely changes; emit it about once a second.
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_STATUS_INTERVAL_S = 1.0
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class RingBroadcaster:
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"""Polls the controller and fans frames/status out to all WebSocket clients."""
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def __init__(self, controller: WebController) -> None:
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self._controller = controller
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self._clients: set[asyncio.Queue[dict]] = set()
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self._task: asyncio.Task[None] | None = None
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self._last_frame_seq: int | None = None
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self._last_settings: dict | None = None
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def register(self, queue: asyncio.Queue[dict]) -> None:
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"""Add a client queue to receive subsequent frames and status."""
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self._clients.add(queue)
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logger.debug("Registered web client queue (clients=%d)", len(self._clients))
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def unregister(self, queue: asyncio.Queue[dict]) -> None:
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"""Remove a client queue; safe to call more than once."""
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self._clients.discard(queue)
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logger.debug("Unregistered web client queue (clients=%d)", len(self._clients))
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def start(self) -> None:
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"""Launch the single polling task (idempotent)."""
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if self._task is None or self._task.done():
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self._task = asyncio.create_task(self._run(), name="ring-broadcaster")
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self._task.add_done_callback(self._on_task_done)
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logger.info("Ring broadcaster started")
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@staticmethod
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def _on_task_done(task: "asyncio.Task[None]") -> None:
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"""Surface an unexpected broadcaster death (the loop should never exit)."""
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if not task.cancelled() and task.exception() is not None:
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logger.error("ring broadcaster task exited unexpectedly: %r", task.exception())
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async def stop(self) -> None:
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"""Cancel the polling task and wait for it to unwind."""
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if self._task is None:
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return
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self._task.cancel()
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with contextlib.suppress(asyncio.CancelledError):
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await self._task
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self._task = None
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logger.info("Ring broadcaster stopped")
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def _publish(self, message: dict) -> None:
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"""Push a message to every client, dropping the oldest on a full queue."""
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for queue in self._clients:
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if queue.full():
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with contextlib.suppress(asyncio.QueueEmpty):
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queue.get_nowait()
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with contextlib.suppress(asyncio.QueueFull):
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queue.put_nowait(message)
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def _status_message(self) -> dict:
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"""Build a status broadcast from the controller's current state."""
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return {"type": "status", **self._controller.status()}
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async def _run(self) -> None:
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"""Poll on a fixed cadence; never block the loop or die on a bad frame."""
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loop = asyncio.get_running_loop()
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next_status = loop.time()
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while True:
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try:
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# peek_frame may touch shared memory / NumPy, so keep it off the loop.
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frame = await loop.run_in_executor(None, self._controller.peek_frame)
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if frame is not None and frame["seq"] != self._last_frame_seq:
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self._last_frame_seq = frame["seq"]
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self._publish(frame)
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now = loop.time()
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if now >= next_status:
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self._publish(self._status_message())
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# Push live settings (Qt -> web) only when they change, so the
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# browser form mirrors desktop edits in real time without churn.
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settings = self._controller.current_live_settings()
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if settings != self._last_settings:
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self._last_settings = settings
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self._publish({"type": "settings", "schema": settings})
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next_status = now + _STATUS_INTERVAL_S
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except asyncio.CancelledError:
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raise
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except Exception: # noqa: BLE001 - one bad frame must not stop streaming
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logger.warning("ring broadcaster iteration failed; continuing", exc_info=True)
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await asyncio.sleep(_FRAME_INTERVAL_S)
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