Harden database startup for Portainer

backend/app/main.py

@@ -6,7 +6,8 @@ from datetime import date, datetime, timezone
 
 from fastapi import Depends, FastAPI, HTTPException, Query, WebSocket, WebSocketDisconnect
 from fastapi.middleware.cors import CORSMiddleware
-from sqlalchemy import func, select
+from sqlalchemy import func, select, text
+from sqlalchemy.exc import OperationalError
 from sqlalchemy.orm import Session
 
 from .config import get_settings
@@ -112,8 +113,23 @@ async def downtime_monitor() -> None:
         await asyncio.sleep(settings.downtime_check_interval_sec)
 
 
+async def wait_for_database() -> None:
+    last_error: OperationalError | None = None
+    for _ in range(settings.database_startup_retries):
+        try:
+            with engine.connect() as connection:
+                connection.execute(text("SELECT 1"))
+            return
+        except OperationalError as error:
+            last_error = error
+            await asyncio.sleep(settings.database_startup_retry_delay_sec)
+    if last_error is not None:
+        raise last_error
+
+
 @asynccontextmanager
 async def lifespan(app: FastAPI):
+    await wait_for_database()
     Base.metadata.create_all(bind=engine)
     with SessionLocal() as session:
         seed_defaults(session)