feat: add foreign key constraints and metrics for blockchain node

apps/pool-hub/src/poolhub/database.py

@@ -0,0 +1,54 @@
+from __future__ import annotations
+
+from collections.abc import AsyncGenerator
+
+from sqlalchemy.ext.asyncio import AsyncEngine, AsyncSession, async_sessionmaker, create_async_engine
+
+from .settings import settings
+
+_engine: AsyncEngine | None = None
+_session_factory: async_sessionmaker[AsyncSession] | None = None
+
+
+def create_engine() -> AsyncEngine:
+    global _engine, _session_factory
+    if _engine is None:
+        _engine = create_async_engine(
+            settings.postgres_dsn,
+            pool_size=settings.postgres_pool_max,
+            max_overflow=0,
+            pool_pre_ping=True,
+        )
+        _session_factory = async_sessionmaker(
+            bind=_engine,
+            expire_on_commit=False,
+            autoflush=False,
+        )
+    return _engine
+
+
+def get_engine() -> AsyncEngine:
+    if _engine is None:
+        return create_engine()
+    return _engine
+
+
+def get_session_factory() -> async_sessionmaker[AsyncSession]:
+    if _session_factory is None:
+        create_engine()
+    assert _session_factory is not None
+    return _session_factory
+
+
+async def get_session() -> AsyncGenerator[AsyncSession, None]:
+    session_factory = get_session_factory()
+    async with session_factory() as session:
+        yield session
+
+
+async def close_engine() -> None:
+    global _engine
+    if _engine is not None:
+        await _engine.dispose()
+        _engine = None
+