fix: fetch memory of LLM node may cause out of flask context (#36253)

api/core/workflow/node_factory.py

@@ -6,11 +6,11 @@ from functools import lru_cache
 from typing import TYPE_CHECKING, Any, cast, final, override
 
 from sqlalchemy import select
-from sqlalchemy.orm import Session
 
 from configs import dify_config
 from core.app.entities.app_invoke_entities import DIFY_RUN_CONTEXT_KEY, DifyRunContext
 from core.app.llm.model_access import build_dify_model_access, fetch_model_config
+from core.db.session_factory import session_factory
 from core.helper.code_executor.code_executor import (
     CodeExecutionError,
     CodeExecutor,
@@ -39,7 +39,6 @@ from core.workflow.nodes.agent.plugin_strategy_adapter import (
 from core.workflow.nodes.agent.runtime_support import AgentRuntimeSupport
 from core.workflow.system_variables import SystemVariableKey, get_system_text, system_variable_selector
 from core.workflow.template_rendering import CodeExecutorJinja2TemplateRenderer
-from extensions.ext_database import db
 from graphon.entities.base_node_data import BaseNodeData
 from graphon.entities.graph_config import NodeConfigDict, NodeConfigDictAdapter
 from graphon.enums import BuiltinNodeTypes, NodeType
@@ -229,10 +228,14 @@ def fetch_memory(
     node_data_memory: MemoryConfig | None,
     model_instance: ModelInstance,
 ) -> TokenBufferMemory | None:
+    """Build prompt memory for node construction without requiring Flask-local state."""
     if not node_data_memory or not conversation_id:
         return None
 
-    with Session(db.engine, expire_on_commit=False) as session:
+    # Node construction can happen in graph initialization paths where Flask's
+    # app context is not active. Use the app-configured session factory instead
+    # of resolving db.engine through Flask-SQLAlchemy's current_app proxy.
+    with session_factory.create_session() as session:
         stmt = select(Conversation).where(Conversation.app_id == app_id, Conversation.id == conversation_id)
         conversation = session.scalar(stmt)
         if not conversation:

api/tests/unit_tests/core/workflow/test_node_factory.py

@@ -109,9 +109,8 @@ class TestFetchMemory:
             def scalar(self, _stmt):
                 return None
 
-        monkeypatch.setattr(node_factory, "db", SimpleNamespace(engine=sentinel.engine))
+        monkeypatch.setattr(node_factory, "session_factory", SimpleNamespace(create_session=FakeSession))
         monkeypatch.setattr(node_factory, "select", MagicMock(return_value=FakeSelect()))
-        monkeypatch.setattr(node_factory, "Session", FakeSession)
 
         result = node_factory.fetch_memory(
             conversation_id="conversation-id",
@@ -144,9 +143,8 @@ class TestFetchMemory:
                 return conversation
 
         token_buffer_memory = MagicMock(return_value=memory)
-        monkeypatch.setattr(node_factory, "db", SimpleNamespace(engine=sentinel.engine))
+        monkeypatch.setattr(node_factory, "session_factory", SimpleNamespace(create_session=FakeSession))
         monkeypatch.setattr(node_factory, "select", MagicMock(return_value=FakeSelect()))
-        monkeypatch.setattr(node_factory, "Session", FakeSession)
         monkeypatch.setattr(node_factory, "TokenBufferMemory", token_buffer_memory)
 
         result = node_factory.fetch_memory(
@@ -162,6 +160,41 @@ class TestFetchMemory:
             model_instance=sentinel.model_instance,
         )
 
+    def test_uses_configured_session_factory_without_flask_app_context(self, monkeypatch: pytest.MonkeyPatch):
+        class FakeSelect:
+            def where(self, *_args):
+                return self
+
+        class FakeSession:
+            def __enter__(self):
+                return self
+
+            def __exit__(self, *_args):
+                return False
+
+            def scalar(self, _stmt):
+                return sentinel.conversation
+
+        class RaisingDB:
+            @property
+            def engine(self):
+                raise RuntimeError("Working outside of application context.")
+
+        token_buffer_memory = MagicMock(return_value=sentinel.memory)
+        monkeypatch.setattr(node_factory, "db", RaisingDB(), raising=False)
+        monkeypatch.setattr(node_factory, "session_factory", SimpleNamespace(create_session=FakeSession))
+        monkeypatch.setattr(node_factory, "select", MagicMock(return_value=FakeSelect()))
+        monkeypatch.setattr(node_factory, "TokenBufferMemory", token_buffer_memory)
+
+        result = node_factory.fetch_memory(
+            conversation_id="conversation-id",
+            app_id="app-id",
+            node_data_memory=object(),
+            model_instance=sentinel.model_instance,
+        )
+
+        assert result is sentinel.memory
+
 
 class TestDifyGraphInitContext:
     def test_to_graph_init_params_preserves_explicit_values(self):