rtc: route all FFI cleanup paths through a fork-safe helper

The fork guard raised from FfiClient.instance, which the *Stream/Room
__del__ methods and FfiHandle.dispose all call - so a fork child printed
'Exception ignored in __del__' to stderr for each inherited object. Add
FfiClient._owned_instance() (returns None when not the owning pid) and use
it in every cleanup/GC path so children no-op quietly instead of touching
(or dropping handles on) the inherited native state.

Author: theomonnom

livekit-rtc/livekit/rtc/_ffi_client.py

@@ -83,14 +83,9 @@ def disposed(self) -> bool:
     def dispose(self) -> None:
         if self.handle != INVALID_HANDLE and not self._disposed:
             self._disposed = True
-            try:
-                ffi = FfiClient.instance
-            except RuntimeError:
-                # Inherited across fork(): the handle belongs to the parent's
-                # FFI and is reclaimed when this process exits. Skip quietly so
-                # __del__ in the child doesn't spam "Exception ignored" to stderr.
-                return
-            assert ffi._ffi_lib.livekit_ffi_drop_handle(ctypes.c_uint64(self.handle))
+            ffi = FfiClient._owned_instance()
+            if ffi is not None:
+                assert ffi._ffi_lib.livekit_ffi_drop_handle(ctypes.c_uint64(self.handle))
 
     def __repr__(self) -> str:
         return f"FfiHandle({self.handle})"
@@ -235,6 +230,15 @@ def instance(cls) -> "FfiClient":
             cls._instance = inst = FfiClient()
         return inst
 
+    @classmethod
+    def _owned_instance(cls) -> Optional["FfiClient"]:
+        # Cleanup/GC paths (FfiHandle.dispose, *Stream.__del__, Room.__del__)
+        # use this instead of `instance` so they no-op in a fork child rather
+        # than raising the fork guard, which __del__ would surface on stderr as
+        # "Exception ignored in...". A child must not touch the inherited FFI.
+        inst = cls._instance
+        return inst if inst is not None and inst._pid == os.getpid() else None
+
     def __init__(self) -> None:
         self._pid = os.getpid()
         self._lock = threading.RLock()

livekit-rtc/livekit/rtc/audio_stream.py

@@ -246,7 +246,9 @@ def from_track(
         )
 
     def __del__(self) -> None:
-        FfiClient.instance.queue.unsubscribe(self._ffi_queue)
+        ffi = FfiClient._owned_instance()
+        if ffi is not None:
+            ffi.queue.unsubscribe(self._ffi_queue)
 
     def _create_owned_stream(self) -> Any:
         assert self._track is not None

livekit-rtc/livekit/rtc/room.py

@@ -190,7 +190,9 @@ def __init__(
 
     def __del__(self) -> None:
         if self._ffi_handle is not None:
-            FfiClient.instance.queue.unsubscribe(self._ffi_queue)
+            ffi = FfiClient._owned_instance()
+            if ffi is not None:
+                ffi.queue.unsubscribe(self._ffi_queue)
 
     @property
     async def sid(self) -> str:

livekit-rtc/livekit/rtc/video_stream.py

@@ -109,7 +109,9 @@ def from_track(
         )
 
     def __del__(self) -> None:
-        FfiClient.instance.queue.unsubscribe(self._ffi_queue)
+        ffi = FfiClient._owned_instance()
+        if ffi is not None:
+            ffi.queue.unsubscribe(self._ffi_queue)
 
     def _create_owned_stream(self) -> Any:
         assert self._track is not None