fix(azure-stt): handle canceled events and add cancellation tracing

changelog/4017.changed.md

@@ -0,0 +1 @@
+- Added Azure STT cancellation tracing attributes and session termination guards so canceled recognition sessions surface structured observability data and stop accepting audio as if still healthy.

changelog/4017.fixed.md

@@ -0,0 +1 @@
+- Fixed Azure STT silent failures by handling recognizer canceled and session lifecycle events and surfacing cancellation errors through `ErrorFrame` propagation.

src/pipecat/services/azure/stt.py

@@ -31,11 +31,10 @@
 from pipecat.services.stt_service import STTService
 from pipecat.transcriptions.language import Language
 from pipecat.utils.time import time_now_iso8601
-from pipecat.utils.tracing.service_decorators import traced_stt
+from pipecat.utils.tracing.service_decorators import trace_stt_cancellation, traced_stt
 
 try:
     from azure.cognitiveservices.speech import (
-        CancellationReason,
         ResultReason,
         SpeechConfig,
         SpeechRecognizer,
@@ -156,6 +155,10 @@ def __init__(
 
         self._audio_stream = None
         self._speech_recognizer = None
+        self._audio_sent = False
+        self._recognition_active = False
+        self._recognition_terminated = False
+        self._shutdown_requested = False
 
     def can_generate_metrics(self) -> bool:
         """Check if this service can generate performance metrics.
@@ -205,7 +208,12 @@ async def run_stt(self, audio: bytes) -> AsyncGenerator[Frame, None]:
         try:
             await self.start_processing_metrics()
             if self._audio_stream:
+                if self._recognition_terminated and not self._shutdown_requested:
+                    logger.warning("Azure STT recognition terminated, dropping audio chunk")
+                    yield None
+                    return
                 self._audio_stream.write(audio)
+                self._audio_sent = True
             yield None
         except Exception as e:
             yield ErrorFrame(error=f"Unknown error occurred: {e}")
@@ -242,6 +250,11 @@ async def _connect(self):
         if self._audio_stream:
             return
 
+        self._audio_sent = False
+        self._recognition_active = False
+        self._recognition_terminated = False
+        self._shutdown_requested = False
+
         try:
             stream_format = AudioStreamFormat(samples_per_second=self.sample_rate, channels=1)
             self._audio_stream = PushAudioInputStream(stream_format)
@@ -254,12 +267,46 @@ async def _connect(self):
             self._speech_recognizer.recognizing.connect(self._on_handle_recognizing)
             self._speech_recognizer.recognized.connect(self._on_handle_recognized)
             self._speech_recognizer.canceled.connect(self._on_handle_canceled)
-            self._speech_recognizer.start_continuous_recognition_async()
+            self._speech_recognizer.session_started.connect(self._on_handle_session_started)
+            self._speech_recognizer.session_stopped.connect(self._on_handle_session_stopped)
+
+            start_future = self._speech_recognizer.start_continuous_recognition_async()
+            await self.get_event_loop().run_in_executor(None, start_future.get)
         except Exception as e:
             await self.push_error(
                 error_msg=f"Uncaught exception during initialization: {e}", exception=e
             )
 
+    async def stop(self, frame: EndFrame):
+        """Stop the speech recognition service.
+
+        Cleanly shuts down the Azure speech recognizer and closes audio streams.
+
+        Args:
+            frame: Frame indicating the end of processing.
+        """
+        await super().stop(frame)
+
+        self._shutdown_requested = True
+        self._recognition_active = False
+        self._recognition_terminated = True
+        await self._disconnect()
+
+    async def cancel(self, frame: CancelFrame):
+        """Cancel the speech recognition service.
+
+        Immediately stops recognition and closes resources.
+
+        Args:
+            frame: Frame indicating cancellation.
+        """
+        await super().cancel(frame)
+
+        self._shutdown_requested = True
+        self._recognition_active = False
+        self._recognition_terminated = True
+        await self._disconnect()
+
     async def _disconnect(self):
         """Stop recognition and close audio streams."""
         if self._speech_recognizer:
@@ -277,6 +324,25 @@ async def _handle_transcription(
         """Handle a transcription result with tracing."""
         await self.stop_processing_metrics()
 
+    async def _trace_cancellation(
+        self,
+        *,
+        reason: str,
+        code: str,
+        recoverable: bool,
+        phase: str,
+    ):
+        """Record a trace span for a canceled Azure STT recognition."""
+        trace_stt_cancellation(
+            self,
+            error_type="azure.stt.canceled",
+            cancel_reason=reason,
+            cancel_code=code,
+            recoverable=recoverable,
+            phase=phase,
+            region=self._settings.region if isinstance(self._settings.region, str) else None,
+        )
+
     def _on_handle_recognized(self, event):
         if event.result.reason == ResultReason.RecognizedSpeech and len(event.result.text) > 0:
             language = getattr(event.result, "language", None) or self._settings.language
@@ -305,11 +371,88 @@ def _on_handle_recognizing(self, event):
             asyncio.run_coroutine_threadsafe(self.push_frame(frame), self.get_event_loop())
 
     def _on_handle_canceled(self, event):
-        details = event.result.cancellation_details
-        if details.reason == CancellationReason.Error:
-            error_msg = f"Azure STT recognition canceled: {details.reason}"
-            if details.error_details:
-                error_msg += f" - {details.error_details}"
-            asyncio.run_coroutine_threadsafe(
-                self.push_error(error_msg=error_msg), self.get_event_loop()
+        details = getattr(event, "cancellation_details", None)
+        reason = self._normalize_cancellation_value(getattr(details, "reason", "UNKNOWN"))
+        code = self._normalize_cancellation_value(getattr(details, "code", "UNKNOWN"))
+        error_details = getattr(details, "error_details", "")
+        phase = self._get_cancellation_phase()
+        recoverable = self._is_cancellation_recoverable(reason, code)
+
+        self._recognition_active = False
+        self._recognition_terminated = True
+
+        logger.error(
+            "Azure STT recognition canceled: reason={}, code={}, phase={}, recoverable={}, details={}",
+            reason,
+            code,
+            phase,
+            recoverable,
+            error_details,
+        )
+
+        asyncio.run_coroutine_threadsafe(
+            self._trace_cancellation(
+                reason=reason,
+                code=code,
+                recoverable=recoverable,
+                phase=phase,
+            ),
+            self.get_event_loop(),
+        )
+
+        error_message = f"Azure STT recognition canceled: {reason} ({code})"
+        asyncio.run_coroutine_threadsafe(
+            self.push_error(error_msg=error_message), self.get_event_loop()
+        )
+
+    def _on_handle_session_started(self, event):
+        self._recognition_active = True
+        self._recognition_terminated = False
+        logger.info(
+            "Azure STT session started: session_id={}",
+            getattr(event, "session_id", "unknown"),
+        )
+
+    def _on_handle_session_stopped(self, event):
+        self._recognition_active = False
+        self._recognition_terminated = True
+        if self._shutdown_requested:
+            logger.info(
+                "Azure STT session stopped during shutdown: session_id={}",
+                getattr(event, "session_id", "unknown"),
             )
+        else:
+            logger.warning(
+                "Azure STT session stopped: session_id={}",
+                getattr(event, "session_id", "unknown"),
+            )
+
+    @staticmethod
+    def _normalize_cancellation_value(value: Any) -> str:
+        normalized = getattr(value, "name", None)
+        if normalized:
+            return normalized
+        return str(value)
+
+    def _get_cancellation_phase(self) -> str:
+        if self._shutdown_requested:
+            return "shutdown"
+        if not self._recognition_active and not self._audio_sent:
+            return "startup"
+        return "streaming"
+
+    @staticmethod
+    def _is_cancellation_recoverable(reason: str, code: str) -> bool:
+        if reason == "CancelledByUser":
+            return True
+        if reason != "Error":
+            return False
+
+        return code in {
+            "ConnectionFailure",
+            "ServiceRedirectPermanent",
+            "ServiceRedirectTemporary",
+            "ServiceTimeout",
+            "ServiceUnavailable",
+            "TooManyRequests",
+        }

src/pipecat/utils/tracing/service_decorators.py

@@ -373,6 +373,51 @@ async def wrapper(self, transcript, is_final, language=None):
     return decorator
 
 
+def trace_stt_cancellation(
+    service,
+    *,
+    error_type: str,
+    cancel_reason: str,
+    cancel_code: str,
+    recoverable: bool,
+    phase: str,
+    region: Optional[str] = None,
+) -> None:
+    """Create a trace span for STT cancellation events.
+
+    Args:
+        service: STT service instance generating the cancellation.
+        error_type: Stable error classification.
+        cancel_reason: Provider cancellation reason.
+        cancel_code: Provider cancellation code.
+        recoverable: Whether the application should attempt recovery.
+        phase: Service lifecycle phase where cancellation happened.
+        region: Cloud region associated with the service, if known.
+    """
+    if not is_tracing_available() or not getattr(service, "_tracing_enabled", False):
+        return
+
+    service_class_name = service.__class__.__name__
+    parent_context = _get_turn_context(service) or _get_parent_service_context(service)
+
+    tracer = trace.get_tracer("pipecat")
+    with tracer.start_as_current_span("stt.cancel", context=parent_context) as current_span:
+        current_span.set_attribute(
+            "gen_ai.system", service_class_name.replace("STTService", "").lower()
+        )
+        current_span.set_attribute("gen_ai.operation.name", "stt.cancel")
+        current_span.set_attribute("error.type", error_type)
+        current_span.set_attribute("stt.cancel.reason", cancel_reason)
+        current_span.set_attribute("stt.cancel.code", cancel_code)
+        current_span.set_attribute("stt.cancel.recoverable", recoverable)
+        current_span.set_attribute("stt.cancel.phase", phase)
+        if region:
+            current_span.set_attribute("cloud.region", region)
+
+        if cancel_reason == "Error":
+            current_span.set_status(trace.Status(trace.StatusCode.ERROR, cancel_code))
+
+
 def traced_llm(func: Optional[Callable] = None, *, name: Optional[str] = None) -> Callable:
     """Trace LLM service methods with LLM-specific attributes.