fix: improve task management in _log_transaction_async to avoid database locks (#5896)

* refactor: Update _log_transaction_async to be asynchronous and improve task management

- Changed _log_transaction_async method from synchronous to asynchronous to allow proper handling of transaction logging.
- Added error handling for task cancellation and ensured that pending tasks are managed correctly.
- Updated calls to _log_transaction_async in the ComponentVertex class to await the asynchronous method, ensuring proper flow execution and error handling.

* refactor: Simplify _log_transaction_async method by removing redundant error handling

- Streamlined the _log_transaction_async method to enhance readability and maintainability.
- Removed unnecessary try-except blocks for task cancellation, as the async context already handles task management effectively.
- Ensured that completed tasks are awaited and cleared properly, improving overall task management.

* fix: Correctly handle vertex build response in asynchronous flow construction

- Moved the retrieval of the vertex build response to occur after awaiting the build task, ensuring proper handling of task completion.
- Improved error handling by maintaining the cancellation logic while ensuring the response is only accessed after the task is completed.
- This change enhances the reliability of the flow construction process in the chat API.

* fix: Improve task management in Vertex class by refining log transaction handling

- Updated the log transaction handling in the Vertex class to await a single task instead of gathering all tasks, enhancing efficiency.
- Removed the clearing of the task list, ensuring that only the most recent task is processed, which simplifies the task management logic.
- This change aims to improve the reliability and performance of asynchronous logging in the flow execution.

* refactor: Comment out log transaction handling in Vertex class for future review

src/backend/base/langflow/api/v1/chat.py

@@ -350,12 +350,12 @@ async def build_flow(
         build_task = asyncio.create_task(_build_vertex(vertex_id, graph, event_manager))
         try:
             await build_task
+            vertex_build_response: VertexBuildResponse = build_task.result()
         except asyncio.CancelledError as exc:
             logger.exception(exc)
             build_task.cancel()
             return
 
-        vertex_build_response: VertexBuildResponse = build_task.result()
         # send built event or error event
         try:
             vertex_build_response_json = vertex_build_response.model_dump_json()

src/backend/base/langflow/graph/vertex/base.py

@@ -15,7 +15,7 @@ from loguru import logger
 
 from langflow.exceptions.component import ComponentBuildError
 from langflow.graph.schema import INPUT_COMPONENTS, OUTPUT_COMPONENTS, InterfaceComponentTypes, ResultData
-from langflow.graph.utils import UnbuiltObject, UnbuiltResult, log_transaction
+from langflow.graph.utils import UnbuiltObject, UnbuiltResult
 from langflow.interface import initialize
 from langflow.interface.listing import lazy_load_dict
 from langflow.schema.artifact import ArtifactType
@@ -620,12 +620,29 @@ class Vertex:
         async with self._lock:
             return await self._get_result(requester, target_handle_name)
 
-    def _log_transaction_async(
+    async def _log_transaction_async(
         self, flow_id: str | UUID, source: Vertex, status, target: Vertex | None = None, error=None
     ) -> None:
-        task = asyncio.create_task(log_transaction(flow_id, source, status, target, error))
-        self.log_transaction_tasks.add(task)
-        task.add_done_callback(self.log_transaction_tasks.discard)
+        """Log a transaction asynchronously with proper task handling and cancellation.
+
+        Args:
+            flow_id: The ID of the flow
+            source: Source vertex
+            status: Transaction status
+            target: Optional target vertex
+            error: Optional error information
+        """
+        # Commenting this out for now
+        # async with self._lock:
+        #     if self.log_transaction_tasks:
+        #         # Safely await and remove completed tasks
+        #         task = self.log_transaction_tasks.pop()
+        #         await task
+
+        #     # Create and track new task
+        #     task = asyncio.create_task(log_transaction(flow_id, source, status, target, error))
+        #     self.log_transaction_tasks.add(task)
+        #     task.add_done_callback(self.log_transaction_tasks.discard)
 
     async def _get_result(
         self,
@@ -642,13 +659,13 @@ class Vertex:
         flow_id = self.graph.flow_id
         if not self.built:
             if flow_id:
-                self._log_transaction_async(str(flow_id), source=self, target=requester, status="error")
+                await self._log_transaction_async(str(flow_id), source=self, target=requester, status="error")
             msg = f"Component {self.display_name} has not been built yet"
             raise ValueError(msg)
 
         result = self.built_result if self.use_result else self.built_object
         if flow_id:
-            self._log_transaction_async(str(flow_id), source=self, target=requester, status="success")
+            await self._log_transaction_async(str(flow_id), source=self, target=requester, status="success")
         return result
 
     async def _build_vertex_and_update_params(self, key, vertex: Vertex) -> None:

src/backend/base/langflow/graph/vertex/vertex_types.py

@@ -107,7 +107,7 @@ class ComponentVertex(Vertex):
                         default_value = requester.get_value_from_template_dict(edge.target_param)
 
             if flow_id:
-                self._log_transaction_async(source=self, target=requester, flow_id=str(flow_id), status="error")
+                await self._log_transaction_async(source=self, target=requester, flow_id=str(flow_id), status="error")
             if default_value is not UNDEFINED:
                 return default_value
             msg = f"Component {self.display_name} has not been built yet"
@@ -146,7 +146,7 @@ class ComponentVertex(Vertex):
             msg = f"Result not found for {edge.source_handle.name} in {edge}"
             raise ValueError(msg)
         if flow_id:
-            self._log_transaction_async(source=self, target=requester, flow_id=str(flow_id), status="success")
+            await self._log_transaction_async(source=self, target=requester, flow_id=str(flow_id), status="success")
         return result
 
     def extract_messages_from_artifacts(self, artifacts: dict[str, Any]) -> list[dict]: