Avoid crashing the FfiQueue when subscriber is not cleaned up (#219)

Author: davidzhao

examples/multiple_connections.py

@@ -0,0 +1,66 @@
+import os
+import asyncio
+from livekit import api, rtc
+
+# This example demonstrates running multiple connections sequentially in the same thread.
+# This is useful when interoperating with a synchronous framework like Django or Flask
+# where you would connect to a LiveKit room as part of a request handler.
+
+# LIVEKIT_URL needs to be set
+# also, set either LIVEKIT_TOKEN, or API_KEY and API_SECRET
+
+
+async def main():
+    url = os.environ["LIVEKIT_URL"]
+    token = os.getenv("LIVEKIT_TOKEN")
+    room = rtc.Room()
+    if not token:
+        token = (
+            api.AccessToken()
+            .with_identity("python-bot")
+            .with_name("Python Bot")
+            .with_grants(
+                api.VideoGrants(
+                    room_join=True,
+                    room="my-room",
+                )
+            )
+            .to_jwt()
+        )
+
+    track_sub = asyncio.Event()
+
+    @room.on("track_subscribed")
+    def on_track_subscribed(
+        track: rtc.Track,
+        publication: rtc.RemoteTrackPublication,
+        participant: rtc.RemoteParticipant,
+    ):
+        if track.kind == rtc.TrackKind.KIND_AUDIO:
+            stream = rtc.AudioStream(track)  # the error comes from this line
+            track_sub.set()
+            # any created streams would need to be closed explicitly to avoid leaks
+            asyncio.get_event_loop().create_task(stream.aclose())
+            print("subscribed to audio track")
+
+    await room.connect(url, token)
+    print(f"connected to room: {room.name}")
+    await track_sub.wait()
+    await room.disconnect()
+    print("disconnected from room")
+
+
+def ensure_event_loop():
+    try:
+        return asyncio.get_event_loop()
+    except RuntimeError:
+        # Create a new event loop if none exists (this can happen in some contexts like certain threads)
+        loop = asyncio.new_event_loop()
+        asyncio.set_event_loop(loop)
+        return loop
+
+
+if __name__ == "__main__":
+    asyncio.run(main())
+    asyncio.run(main())
+    print("successfully ran multiple connections")

livekit-rtc/livekit/rtc/_ffi_client.py

@@ -106,7 +106,12 @@ def __init__(self) -> None:
     def put(self, item: T) -> None:
         with self._lock:
             for queue, loop in self._subscribers:
-                loop.call_soon_threadsafe(queue.put_nowait, item)
+                try:
+                    loop.call_soon_threadsafe(queue.put_nowait, item)
+                except Exception as e:
+                    # this could happen if user closes the runloop without unsubscribing first
+                    # it's not good when it does occur, but we should not fail the entire runloop
+                    logger.error("error putting to queue: %s", e)
 
     def subscribe(self, loop: Optional[asyncio.AbstractEventLoop] = None) -> Queue[T]:
         with self._lock: