🐛 fix(base.py): refactor database engine creation and retrieval to use a singleton pattern for better performance and maintainability

✨ feat(base.py): add support for LANGFLOW_DATABASE_URL environment variable to override the database URL configuration

src/backend/langflow/database/base.py

@@ -1,21 +1,48 @@
 from contextlib import contextmanager
-from langflow.settings import settings
+import os
+
 from sqlmodel import SQLModel, Session, create_engine
 from langflow.utils.logger import logger
 
-if settings.database_url and settings.database_url.startswith("sqlite"):
-    connect_args = {"check_same_thread": False}
-else:
-    connect_args = {}
-if not settings.database_url:
-    raise RuntimeError("No database_url provided")
-engine = create_engine(settings.database_url, connect_args=connect_args)
+
+class Engine:
+    _instance = None
+
+    @classmethod
+    def get(cls):
+        logger.debug("Getting database engine")
+        if cls._instance is None:
+            cls.create()
+        return cls._instance
+
+    @classmethod
+    def create(cls):
+        logger.debug("Creating database engine")
+        from langflow.settings import settings
+
+        if langflow_database_url := os.getenv("LANGFLOW_DATABASE_URL"):
+            settings.DATABASE_URL = langflow_database_url
+            logger.debug("Using LANGFLOW_DATABASE_URL")
+
+        if settings.DATABASE_URL and settings.DATABASE_URL.startswith("sqlite"):
+            connect_args = {"check_same_thread": False}
+        else:
+            connect_args = {}
+        if not settings.DATABASE_URL:
+            raise RuntimeError("No database_url provided")
+        cls._instance = create_engine(settings.DATABASE_URL, connect_args=connect_args)
+
+    @classmethod
+    def update(cls):
+        logger.debug("Updating database engine")
+        cls._instance = None
+        cls.create()
 
 
 def create_db_and_tables():
     logger.debug("Creating database and tables")
     try:
-        SQLModel.metadata.create_all(engine)
+        SQLModel.metadata.create_all(Engine.get())
     except Exception as exc:
         logger.error(f"Error creating database and tables: {exc}")
         raise RuntimeError("Error creating database and tables") from exc
@@ -23,7 +50,7 @@ def create_db_and_tables():
     # and we need to create the tables again.
     from sqlalchemy import inspect
 
-    inspector = inspect(engine)
+    inspector = inspect(Engine.get())
     if "flow" not in inspector.get_table_names():
         logger.error("Something went wrong creating the database and tables.")
         logger.error("Please check your database settings.")
@@ -36,7 +63,7 @@ def create_db_and_tables():
 @contextmanager
 def session_getter():
     try:
-        session = Session(engine)
+        session = Session(Engine.get())
         yield session
     except Exception as e:
         print("Session rollback because of exception:", e)