Melvin Strobl
ecc4bee4bb
- Volatile frames are held in memory with a byte-bounded queue instead of the /dev/shm ring scanned on every put; workers keep writing to the directory, which is trimmed on a timer. A volatile upload no longer spools to disk. ARTIFACT_VOLATILE_BYTES=0 turns the ring off. - A device sends camera frames as binary messages on its socket, held and published in one step and credited to its device node; refused frames are logged and dropped. Its snapshot carries demand and the uplink (binary, or http through the portal). - One demand registry for every socket's wanted media, the tunnel's included, plus what running flows read, mapped onto on-demand ports and published as device_demand; at most 8 media names per socket. - Per-message deflate off in serve and dev; a device may fetch the last 8 digests of a message; published dashboards cached per store revision; a revoked device socket is closed with 1008. - Media tiles want bytes only while on screen; the Devices tab previews a wired camera; the device node warns when a flow reads an on-demand port.
125 lines
5.1 KiB
Python
125 lines
5.1 KiB
Python
"""Event bus bridging the engine's worker threads to async subscribers.
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Nodes execute in a thread pool; websocket clients live on the event loop.
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Publishers are therefore thread-safe and never block: a subscriber that cannot
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keep up loses its oldest queued events rather than stalling the engine.
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"""
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from __future__ import annotations
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import asyncio
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import logging
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import threading
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from collections import deque
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from collections.abc import AsyncIterator
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from contextlib import asynccontextmanager
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from typing import Any
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logger = logging.getLogger(__name__)
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QUEUE_SIZE = 256
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LOG_HISTORY = 400
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#: How many of a message's last artifact digests are remembered.
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RECENT_DIGESTS = 8
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class EventBus:
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"""Fan-out of engine events to any number of async subscribers."""
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def __init__(self) -> None:
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self._loop: asyncio.AbstractEventLoop | None = None
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self._subscribers: set[asyncio.Queue[dict[str, Any]]] = set()
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# Events published since the last flush was scheduled. A cascade
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# publishes 13-16 of them and each used to cost its own
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# `call_soon_threadsafe`; they now cost one between two turns of the
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# loop, which is what a wave is.
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self._pending: list[dict[str, Any]] = []
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self._pending_lock = threading.Lock()
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self._flush_scheduled = False
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# Kept whether or not anyone is listening, so opening the log panel
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# shows what just happened rather than an empty box.
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self.recent_logs: deque[dict[str, Any]] = deque(maxlen=LOG_HISTORY)
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# How often each qualified node has emitted, for the same reason: a
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# client that reconnects between two pages would otherwise start from
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# zero and draw a busy graph as idle. A session count, not a metric —
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# the rollups in `metrics.py` are what survives a restart.
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self.emits: dict[str, int] = {}
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#: The last few artifacts each message pointed at, newest last. A
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#: screen fetching a camera frame by frame asks for one the message
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#: may already have moved past, and a device's credential reaches
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#: these as well as the current one.
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self.digests: dict[str, deque[str]] = {}
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def bind(self, loop: asyncio.AbstractEventLoop) -> None:
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"""Attach the bus to the running event loop (called once at startup)."""
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self._loop = loop
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def publish(self, event: dict[str, Any]) -> None:
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"""Publish an event from any thread."""
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kind = event.get("type")
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if kind == "node_log":
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# deque.append is atomic, so worker threads need no lock here.
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self.recent_logs.append(event)
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elif kind == "node_executed" and event.get("outputs"):
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# The condition the canvas animates on, so both ends agree on what
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# counts as an emission. Two worker threads racing here can lose an
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# increment, which is a count nobody is going to miss.
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node = str(event.get("node") or "")
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self.emits[node] = self.emits.get(node, 0) + 1
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elif kind == "message_value":
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value = event.get("value")
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if isinstance(value, dict) and isinstance(value.get("digest"), str):
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name = str(event.get("name") or "")
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recent = self.digests.get(name)
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if recent is None:
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recent = self.digests[name] = deque(maxlen=RECENT_DIGESTS)
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recent.append(value["digest"])
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loop = self._loop
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if loop is None or not self._subscribers:
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return
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with self._pending_lock:
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self._pending.append(event)
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if self._flush_scheduled:
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# A flush is already on its way and has not run yet, so it
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# will find this event too.
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return
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self._flush_scheduled = True
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try:
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loop.call_soon_threadsafe(self._dispatch)
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except RuntimeError:
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# Loop already closed — shutting down.
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with self._pending_lock:
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self._pending.clear()
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self._flush_scheduled = False
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def _dispatch(self) -> None:
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"""Hand everything published since the last turn to every subscriber."""
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with self._pending_lock:
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batch = self._pending
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self._pending = []
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self._flush_scheduled = False
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if not batch:
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return
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for queue in self._subscribers:
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for event in batch:
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if queue.full():
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# Drop the oldest so a slow client never blocks the engine.
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try:
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queue.get_nowait()
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except asyncio.QueueEmpty:
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pass
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queue.put_nowait(event)
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@asynccontextmanager
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async def subscribe(self) -> AsyncIterator[asyncio.Queue[dict[str, Any]]]:
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"""Yield a queue receiving every event published while subscribed."""
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queue: asyncio.Queue[dict[str, Any]] = asyncio.Queue(maxsize=QUEUE_SIZE)
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self._subscribers.add(queue)
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try:
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yield queue
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finally:
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self._subscribers.discard(queue)
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event_bus = EventBus()
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