fix: handle when no tracer

lcserve/backend/gateway.py

@@ -907,6 +907,7 @@ def _get_error_msg(e: Union[WebSocketDisconnect, ConnectionClosed]) -> str:
                             tracer=tracer, parent_span=get_current_span()
                         )
                     }
+
                     # If the function is a streaming response, we pass the websocket callback handler,
                     # so that stream data can be sent back to the client.
                     if include_ws_callback_handlers:

lcserve/backend/langchain_helper.py

@@ -25,6 +25,9 @@ def on_llm_start(
         parent_run_id: Optional[UUID] = None,
         **kwargs: Any
     ) -> None:
+        if not self.tracer:
+            return
+
         prompts_len = 0
         operation = "langchain.on_llm_start"
 
@@ -36,8 +39,12 @@ def on_llm_start(
             span.set_attribute("prompts_len", prompts_len)
 
     def on_llm_end(self, response: LLMResult, *, run_id: UUID, **kwargs: Any) -> None:
+        if not self.tracer:
+            return
+
         operation = "langchain.on_llm_end"
         token_usage = response.llm_output["token_usage"]
+
         context = set_span_in_context(self.parent_span)
         with self.tracer.start_as_current_span("llm end", context=context) as span:
             span.set_attribute("otel.operation.name", operation)