fix install diogram

bd/__init__.py

@@ -43,4 +43,30 @@ def make_engine():
     """Создаёт SQLAlchemy engine с правильными параметрами для pg8000."""
     from sqlalchemy import create_engine
     s = Settings()
-    return create_engine(s.DATABASE_URL_syncpg, connect_args=s.PG8000_CONNECT_ARGS, future=True)
+    return create_engine(
+        s.DATABASE_URL_syncpg,
+        connect_args=s.PG8000_CONNECT_ARGS,
+        future=True,
+        pool_pre_ping=True,       # проверяет соединение перед каждым запросом
+    )
+
+
+def wait_for_db(retries: int = 15, delay: float = 2.0) -> None:
+    """Ждёт, пока PostgreSQL станет доступен. Вызывается при старте приложения."""
+    import time
+    import logging
+    from sqlalchemy import text
+
+    logger = logging.getLogger("bd")
+    engine = make_engine()
+    for attempt in range(1, retries + 1):
+        try:
+            with engine.connect() as conn:
+                conn.execute(text("SELECT 1"))
+            logger.info("PostgreSQL is ready.")
+            return
+        except Exception as exc:
+            logger.warning("DB not ready (attempt %d/%d): %s", attempt, retries, exc)
+            if attempt < retries:
+                time.sleep(delay)
+    raise RuntimeError("PostgreSQL did not become ready in time.")