adding website

pipelines/web/db.py

@@ -0,0 +1,31 @@
+"""Database access for the FastAPI web app."""
+
+from __future__ import annotations
+
+from collections.abc import Iterator
+from contextlib import contextmanager
+from functools import lru_cache
+
+from sqlalchemy.engine import Engine
+from sqlalchemy.orm import Session
+
+from pipelines.orm.common import get_postgres_engine
+
+
+@lru_cache(maxsize=1)
+def get_engine() -> Engine:
+    """Return the lazily-created DATA_SCIENCE_DEV SQLAlchemy engine."""
+    return get_postgres_engine(name="DATA_SCIENCE_DEV")
+
+
+def validate_database_connection() -> None:
+    """Fail fast if the configured DATA_SCIENCE_DEV database is unavailable."""
+    with get_engine().connect():
+        pass
+
+
+@contextmanager
+def session_scope() -> Iterator[Session]:
+    """Yield a SQLAlchemy session for a read-only request."""
+    with Session(get_engine()) as session:
+        yield session