refactor: reuse single session when getting variables from db (#8814)

* refactor: enhance database session management in custom components

- Updated `get_variables` method in `CustomComponent` to accept an optional session parameter, allowing for session reuse and reducing connection pool exhaustion.
- Modified `update_params_with_load_from_db_fields` to pass the session when calling `get_variables`.
- Adjusted `get_instance_results` to support session management for database operations.
- Increased connection pool size and max overflow in settings for improved performance under load.

* [autofix.ci] apply automated fixes

* Prefer single session by default:

* remove unused session

* Revert pool size changes

* refactor: update get_variables method for backward compatibility

- Added a new async `get_variables` method in `CustomComponent` to maintain backward compatibility with the deprecated method, ensuring it calls the existing `get_variable` method with session management.
- This change enhances the robustness of the component while preserving existing functionality.

* refactor: remove unused session import from endpoints.py

- Eliminated the unused `session_scope` import from the `endpoints.py` file to streamline the code and improve clarity. This change contributes to maintaining a clean and efficient codebase.

* refactor: update deprecated variables method in CustomComponent

- Modified the `variables` method to call the new `get_variables` method for improved clarity and consistency. This change maintains backward compatibility while encouraging the use of the updated async method.

* refactor: update method calls to use get_variables because we don't have session in update_build_config

- Replaced instances of the deprecated `get_variable` method with the new `get_variables` method in `LMStudioEmbeddingsComponent`, `LMStudioModelComponent`, and `ChatOllamaComponent`. This change enhances code clarity and maintains consistency across components while ensuring backward compatibility.

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Jordan Frazier <jordan.frazier@datastax.com>
Co-authored-by: Gabriel Luiz Freitas Almeida <gabriel@langflow.org>
Co-authored-by: Carlos Coelho <80289056+carlosrcoelho@users.noreply.github.com>

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

@@ -717,6 +717,7 @@ async def custom_component_update(
                 for field_name, field_dict in template.items()
                 if isinstance(field_dict, dict) and field_dict.get("load_from_db") and field_dict.get("value")
             ]
+
             params = await update_params_with_load_from_db_fields(cc_instance, params, load_from_db_fields)
             cc_instance.set_attributes(params)
         updated_build_config = code_request.get_template()

src/backend/base/langflow/components/lmstudio/lmstudioembeddings.py

@@ -2,7 +2,6 @@ from typing import Any
 from urllib.parse import urljoin
 
 import httpx
-from typing_extensions import override
 
 from langflow.base.embeddings.model import LCEmbeddingsModel
 from langflow.field_typing import Embeddings
@@ -15,8 +14,7 @@ class LMStudioEmbeddingsComponent(LCEmbeddingsModel):
     description: str = "Generate embeddings using LM Studio."
     icon = "LMStudio"
 
-    @override
+    async def update_build_config(self, build_config: dict, field_value: Any, field_name: str | None = None):  # noqa: ARG002
-    async def update_build_config(self, build_config: dict, field_value: Any, field_name: str | None = None):
         if field_name == "model":
             base_url_dict = build_config.get("base_url", {})
             base_url_load_from_db = base_url_dict.get("load_from_db", False)

src/backend/base/langflow/custom/custom_component/custom_component.py

@@ -405,6 +405,11 @@ class CustomComponent(BaseComponent):
         return run_until_complete(self.get_variables(name, field))
 
     async def get_variables(self, name: str, field: str):
+        """DEPRECATED - This is kept for backward compatibility. Use get_variable instead."""
+        async with session_scope() as session:
+            return await self.get_variable(name, field, session)
+
+    async def get_variable(self, name: str, field: str, session):
         """Returns the variable for the current user with the specified name.
 
         Raises:
@@ -425,7 +430,6 @@ class CustomComponent(BaseComponent):
         else:
             msg = f"Invalid user id: {self.user_id}"
             raise TypeError(msg)
-        async with session_scope() as session:
         return await variable_service.get_variable(user_id=user_id, name=name, field=field, session=session)
 
     async def list_key_names(self):

src/backend/base/langflow/interface/initialize/loading.py

@@ -12,7 +12,7 @@ from pydantic import PydanticDeprecatedSince20
 from langflow.custom.eval import eval_custom_component_code
 from langflow.schema.artifact import get_artifact_type, post_process_raw
 from langflow.schema.data import Data
-from langflow.services.deps import get_tracing_service
+from langflow.services.deps import get_tracing_service, session_scope
 
 if TYPE_CHECKING:
     from langflow.custom.custom_component.component import Component
@@ -59,7 +59,10 @@ async def get_instance_results(
     base_type: str = "component",
 ):
     custom_params = await update_params_with_load_from_db_fields(
-        custom_component, custom_params, vertex.load_from_db_fields, fallback_to_env_vars=fallback_to_env_vars
+        custom_component,
+        custom_params,
+        vertex.load_from_db_fields,
+        fallback_to_env_vars=fallback_to_env_vars,
     )
     with warnings.catch_warnings():
         warnings.filterwarnings("ignore", category=PydanticDeprecatedSince20)
@@ -111,12 +114,13 @@ async def update_params_with_load_from_db_fields(
     *,
     fallback_to_env_vars=False,
 ):
+    async with session_scope() as session:
         for field in load_from_db_fields:
             if field not in params or not params[field]:
                 continue
 
             try:
-            key = await custom_component.get_variables(params[field], field)
+                key = await custom_component.get_variable(name=params[field], field=field, session=session)
             except ValueError as e:
                 if any(reason in str(e) for reason in ["User id is not set", "variable not found."]):
                     raise