Merge pull request #3629 from pipecat-ai/fix/telephony-websocket-stopasynciteration

Fix StopAsyncIteration in parse_telephony_websocket

changelog/3629.fixed.md

@@ -0,0 +1 @@
+- Fixed `StopAsyncIteration` exceptions in `parse_telephony_websocket()` when WebSocket connections close before sending expected messages.

src/pipecat/runner/utils.py

@@ -96,6 +96,9 @@ def _detect_transport_type_from_message(message_data: dict) -> str:
 async def parse_telephony_websocket(websocket: WebSocket):
     """Parse telephony WebSocket messages and return transport type and call data.
 
+    Args:
+        websocket: FastAPI WebSocket connection from telephony provider.
+
     Returns:
         tuple: (transport_type: str, call_data: dict)
 
@@ -136,6 +139,9 @@ async def parse_telephony_websocket(websocket: WebSocket):
                 "to": str,
             }
 
+    Raises:
+        ValueError: If WebSocket closes before sending any messages.
+
     Example usage::
 
         transport_type, call_data = await parse_telephony_websocket(websocket)
@@ -143,25 +149,31 @@ async def parse_telephony_websocket(websocket: WebSocket):
             user_id = call_data["body"]["user_id"]
     """
     # Read first two messages
-    start_data = websocket.iter_text()
+    message_stream = websocket.iter_text()
+    first_message = {}
+    second_message = {}
 
     try:
-        # First message
-        first_message_raw = await start_data.__anext__()
+        # First message - required
+        first_message_raw = await message_stream.__anext__()
         logger.trace(f"First message: {first_message_raw}")
-        try:
-            first_message = json.loads(first_message_raw)
-        except json.JSONDecodeError:
-            first_message = {}
+        first_message = json.loads(first_message_raw) if first_message_raw else {}
+    except json.JSONDecodeError:
+        pass
+    except StopAsyncIteration:
+        raise ValueError("WebSocket closed before receiving telephony handshake messages")
 
-        # Second message
-        second_message_raw = await start_data.__anext__()
+    try:
+        # Second message - optional, some providers may only send one
+        second_message_raw = await message_stream.__anext__()
         logger.trace(f"Second message: {second_message_raw}")
-        try:
-            second_message = json.loads(second_message_raw)
-        except json.JSONDecodeError:
-            second_message = {}
+        second_message = json.loads(second_message_raw) if second_message_raw else {}
+    except json.JSONDecodeError:
+        pass
+    except StopAsyncIteration:
+        logger.warning("Only received one WebSocket message, expected two")
 
+    try:
         # Try auto-detection on both messages
         detected_type_first = _detect_transport_type_from_message(first_message)
         detected_type_second = _detect_transport_type_from_message(second_message)

tests/test_runner_utils.py

@@ -0,0 +1,153 @@
+#
+# Copyright (c) 2024-2026, Daily
+#
+# SPDX-License-Identifier: BSD 2-Clause License
+#
+
+import json
+import unittest
+from unittest.mock import MagicMock
+
+from pipecat.runner.utils import parse_telephony_websocket
+
+
+class MockAsyncIterator:
+    """Mock async iterator for WebSocket messages."""
+
+    def __init__(self, messages):
+        self.messages = messages
+        self.index = 0
+
+    def __aiter__(self):
+        return self
+
+    async def __anext__(self):
+        if self.index >= len(self.messages):
+            raise StopAsyncIteration
+        message = self.messages[self.index]
+        self.index += 1
+        return message
+
+
+class TestParseTelephonyWebSocket(unittest.IsolatedAsyncioTestCase):
+    async def test_no_messages_raises_value_error(self):
+        """Test that no messages raises ValueError."""
+        mock_websocket = MagicMock()
+        mock_websocket.iter_text.return_value = MockAsyncIterator([])
+
+        with self.assertRaises(ValueError) as context:
+            await parse_telephony_websocket(mock_websocket)
+
+        self.assertIn("WebSocket closed before receiving", str(context.exception))
+
+    async def test_one_message_logs_warning_and_continues(self):
+        """Test that one message logs warning but continues processing."""
+        twilio_message = json.dumps(
+            {
+                "event": "start",
+                "start": {
+                    "streamSid": "MZ123",
+                    "callSid": "CA123",
+                    "customParameters": {"user_id": "test_user"},
+                },
+            }
+        )
+
+        mock_websocket = MagicMock()
+        mock_websocket.iter_text.return_value = MockAsyncIterator([twilio_message])
+
+        transport_type, call_data = await parse_telephony_websocket(mock_websocket)
+
+        self.assertEqual(transport_type, "twilio")
+        self.assertEqual(call_data["stream_id"], "MZ123")
+        self.assertEqual(call_data["call_id"], "CA123")
+
+    async def test_two_messages_normal_operation(self):
+        """Test normal operation with two messages."""
+        first_message = json.dumps({"event": "connected"})
+        twilio_message = json.dumps(
+            {
+                "event": "start",
+                "start": {
+                    "streamSid": "MZ456",
+                    "callSid": "CA456",
+                    "customParameters": {},
+                },
+            }
+        )
+
+        mock_websocket = MagicMock()
+        mock_websocket.iter_text.return_value = MockAsyncIterator([first_message, twilio_message])
+
+        transport_type, call_data = await parse_telephony_websocket(mock_websocket)
+
+        self.assertEqual(transport_type, "twilio")
+        self.assertEqual(call_data["stream_id"], "MZ456")
+        self.assertEqual(call_data["call_id"], "CA456")
+
+    async def test_telnyx_detection(self):
+        """Test Telnyx provider detection."""
+        telnyx_message = json.dumps(
+            {
+                "stream_id": "stream_123",
+                "start": {
+                    "call_control_id": "cc_123",
+                    "media_format": {"encoding": "PCMU"},
+                    "from": "+15551234567",
+                    "to": "+15559876543",
+                },
+            }
+        )
+
+        mock_websocket = MagicMock()
+        mock_websocket.iter_text.return_value = MockAsyncIterator([telnyx_message])
+
+        transport_type, call_data = await parse_telephony_websocket(mock_websocket)
+
+        self.assertEqual(transport_type, "telnyx")
+        self.assertEqual(call_data["stream_id"], "stream_123")
+        self.assertEqual(call_data["call_control_id"], "cc_123")
+
+    async def test_plivo_detection(self):
+        """Test Plivo provider detection."""
+        plivo_message = json.dumps(
+            {"start": {"streamId": "stream_plivo_123", "callId": "call_plivo_123"}}
+        )
+
+        mock_websocket = MagicMock()
+        mock_websocket.iter_text.return_value = MockAsyncIterator([plivo_message])
+
+        transport_type, call_data = await parse_telephony_websocket(mock_websocket)
+
+        self.assertEqual(transport_type, "plivo")
+        self.assertEqual(call_data["stream_id"], "stream_plivo_123")
+        self.assertEqual(call_data["call_id"], "call_plivo_123")
+
+    async def test_exotel_detection(self):
+        """Test Exotel provider detection."""
+        exotel_message = json.dumps(
+            {
+                "event": "start",
+                "start": {
+                    "stream_sid": "stream_exo_123",
+                    "call_sid": "call_exo_123",
+                    "account_sid": "acc_123",
+                    "from": "+15551111111",
+                    "to": "+15552222222",
+                },
+            }
+        )
+
+        mock_websocket = MagicMock()
+        mock_websocket.iter_text.return_value = MockAsyncIterator([exotel_message])
+
+        transport_type, call_data = await parse_telephony_websocket(mock_websocket)
+
+        self.assertEqual(transport_type, "exotel")
+        self.assertEqual(call_data["stream_id"], "stream_exo_123")
+        self.assertEqual(call_data["call_id"], "call_exo_123")
+        self.assertEqual(call_data["account_sid"], "acc_123")
+
+
+if __name__ == "__main__":
+    unittest.main()