7409fc7 · blender-bridge

blender-bridge commits / 7409fc7

Fix reconnect loop: handle send buffer backpressure

Root cause: baking textures generates hundreds/thousands of tile_ready
messages. sendall() on the non-blocking UDS socket raises BlockingIOError
when the kernel send buffer fills up (~200KB). The except OSError handler
treated this as a fatal disconnect, triggering reconnect. Reconnect clears
_texture_ids, causing re-request → re-bake → re-flood → infinite loop.

Fix: Replace sendall() with manual send()+select() loop. When the send
buffer is full (BlockingIOError), wait up to 5s for writability via
select() instead of disconnecting. Also fix Godot-side _write_all() to
use poll() instead of spinning on EAGAIN.

v0.17.1

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

7409fc769739099691270d3e65374551451b98ef

by plankatron <fleeky@gmail.com> · 2026-03-04T19:46:15.000Z

Changed files (4) +36 -9

blender_addon/blender_manifest.toml +1 -1

…	…	@@ -2,7 +2,7 @@ schema_version = "1.0.0"
2	2	id = "blender_godot_bridge"
3	3	name = "Blender-Godot Bridge"
4	4	tagline = "Real-time bidirectional scene sync with Godot"
5		version = "0.17.0"
	5	version = "0.17.1"
6	6	blender_version_min = "4.2.0"
7	7	type = "add-on"
8	8	maintainer = "blender-bridge <noreply@localhost>"

blender_addon/connection.py +26 -5

…	…	@@ -4,6 +4,7 @@ Length-prefixed messages: [4-byte LE length] [payload].
4	4	Non-blocking receive for use with Blender's timer callbacks.
5	5	"""
6	6
	7	import select
7	8	import socket
8	9	import struct
9	10
…	…	@@ -71,13 +72,33 @@ class BridgeConnection:
71	72	# ── Send ─────────────────────────────────────────────────────────────
72	73
73	74	def send_message(self, data: bytes):
74		"""Send a length-prefixed message."""
	75	"""Send a length-prefixed message.
	76
	77	Handles BlockingIOError (send buffer full) by waiting for writability
	78	instead of treating it as a fatal disconnect. This is critical when
	79	streaming many tile_ready messages — the non-blocking socket's send
	80	buffer can fill up, and sendall() would raise BlockingIOError.
	81	"""
75	82	if self._sock is None:
76	83	return
77		try:
78		self._sock.sendall(struct.pack("<I", len(data)) + data)
79		except OSError:
80		self._close_unexpected()
	84	frame = struct.pack("<I", len(data)) + data
	85	sent = 0
	86	while sent < len(frame):
	87	try:
	88	n = self._sock.send(frame[sent:])
	89	if n == 0:
	90	self._close_unexpected()
	91	return
	92	sent += n
	93	except BlockingIOError:
	94	# Send buffer full — wait up to 5s for writability
	95	_, writable, _ = select.select([], [self._sock], [], 5.0)
	96	if not writable:
	97	self._close_unexpected()
	98	return
	99	except OSError:
	100	self._close_unexpected()
	101	return
81	102
82	103	# ── Receive (non-blocking) ───────────────────────────────────────────
83	104

src/blender_bridge.cpp +1 -1

…	…	@@ -264,7 +264,7 @@ Error BlenderBridge::start_server(const String &socket_path) {
264	264	_known_instance_ids.clear();
265	265	_next_object_id = 1;
266	266
267		UtilityFunctions::print("BlenderBridge v0.17.0: Server started (shm=", _shm_name, ", sock=", socket_path, ", regions=2x", (int)_region_size, ")");
	267	UtilityFunctions::print("BlenderBridge v0.17.1: Server started (shm=", _shm_name, ", sock=", socket_path, ", regions=2x", (int)_region_size, ")");
268	268	return OK;
269	269	}
270	270

src/uds_server.h +8 -2

…	…	@@ -234,8 +234,14 @@ private:
234	234	} else if (n < 0) {
235	235	if (errno == EINTR)
236	236	continue;
237		if (errno == EAGAIN \|\| errno == EWOULDBLOCK)
238		continue; // Spin briefly for non-blocking (messages are small)
	237	if (errno == EAGAIN \|\| errno == EWOULDBLOCK) {
	238	// Wait for socket to become writable (up to 2s)
	239	struct pollfd pfd = { fd, POLLOUT, 0 };
	240	int r = ::poll(&pfd, 1, 2000);
	241	if (r <= 0)
	242	return false; // Timeout or error
	243	continue;
	244	}
239	245	return false; // Real error
240	246	}
241	247	}