Refactor graph building and caching

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

@@ -22,7 +22,6 @@ from langflow.api.v1.schemas import (
     VerticesOrderResponse,
 )
 from langflow.graph.graph.base import Graph
-from langflow.graph.vertex.base import StatelessVertex
 from langflow.processing.process import process_tweaks_on_graph
 from langflow.services.auth.utils import (
     get_current_active_user,
@@ -275,6 +274,25 @@ async def try_running_celery_task(vertex, user_id):
     return vertex
 
 
+def build_and_cache_graph(
+    flow_id: str,
+    session: Session,
+    chat_service: "ChatService",
+    graph: Optional[Graph] = None,
+):
+    """Build and cache the graph."""
+    flow: Flow = session.get(Flow, flow_id)
+    if not flow or not flow.data:
+        raise ValueError("Invalid flow ID")
+    other_graph = Graph.from_payload(flow.data)
+    if graph is None:
+        graph = other_graph
+    else:
+        graph = graph.update(other_graph)
+    chat_service.set_cache(flow_id, graph)
+    return graph
+
+
 @router.get("/build/{flow_id}/vertices", response_model=VerticesOrderResponse)
 async def get_vertices(
     flow_id: str,
@@ -288,17 +306,7 @@ async def get_vertices(
         graph = None
         if cache := chat_service.get_cache(flow_id):
             graph: Graph = cache.get("result")
-
-        flow: Flow = session.get(Flow, flow_id)
-        if not flow or not flow.data:
-            raise ValueError("Invalid flow ID")
-        other_graph = Graph.from_payload(flow.data)
-        if graph is None:
-            graph = other_graph
-        else:
-            graph = graph.update(other_graph)
-        chat_service.set_cache(flow_id, graph)
-
+        graph = build_and_cache_graph(flow_id, session, chat_service, graph)
         if component_id:
             try:
                 vertices = graph.sort_up_to_vertex(component_id)
@@ -332,34 +340,48 @@ async def build_vertex(
     """Build a vertex instead of the entire graph."""
     try:
         cache = chat_service.get_cache(flow_id)
-        graph = cache.get("result")
+        if not cache:
+            # If there's no cache
+            logger.warning(
+                f"No cache found for {flow_id}. Building graph starting at {vertex_id}"
+            )
+            graph = build_and_cache_graph(
+                flow_id=flow_id, session=get_session(), chat_service=chat_service
+            )
+        else:
+            graph = cache.get("result")
         result_dict = {}
         duration = ""
         start_time = time.perf_counter()
         if tweaks:
             graph = process_tweaks_on_graph(graph, tweaks)
-        if not isinstance(graph, Graph):
-            raise ValueError("Invalid graph")
         if not (vertex := graph.get_vertex(vertex_id)):
-            raise ValueError("Invalid vertex")
+            raise ValueError(f"Invalid vertex {vertex_id}")
         try:
-            if isinstance(vertex, StatelessVertex) or not vertex._built:
+            if not vertex.pinned or not vertex._built:
                 await vertex.build(user_id=current_user.id)
-            params = vertex._built_object_repr()
-            valid = True
-            result_dict = vertex.get_built_result()
-            # We need to set the artifacts to pass information
-            # to the frontend
-            vertex.set_artifacts()
-            artifacts = vertex.artifacts
-            timedelta = time.perf_counter() - start_time
-            duration = format_elapsed_time(timedelta)
-            result_dict = ResultDict(
-                results=result_dict,
-                artifacts=artifacts,
-                duration=duration,
-                timedelta=timedelta,
-            )
+                params = vertex._built_object_repr()
+                valid = True
+                result_dict = vertex.get_built_result()
+                # We need to set the artifacts to pass information
+                # to the frontend
+                vertex.set_artifacts()
+                artifacts = vertex.artifacts
+                timedelta = time.perf_counter() - start_time
+                duration = format_elapsed_time(timedelta)
+                result_dict = ResultDict(
+                    results=result_dict,
+                    artifacts=artifacts,
+                    duration=duration,
+                    timedelta=timedelta,
+                )
+                vertex.set_result(result_dict)
+            elif vertex.result is not None:
+                params = vertex._built_object_repr()
+                valid = True
+                result_dict = vertex.result
+            else:
+                raise ValueError(f"No result found for vertex {vertex_id}")
             chat_service.set_cache(flow_id, graph)
         except Exception as exc:
             params = str(exc)