perform small connection test on startup

app.py

@@ -144,13 +144,16 @@ async def my_periodic_task():
 async def init_helpers(app: web.Application):
     """Initialize a connection pool."""
     try:
-        app["helpers"] = Helpers(
+        helpers = Helpers(
             MessageHelper(app, ADAPTER, CONFIG),
             MSGraphHelper(app, ADAPTER, CONFIG),
             DBHelper(app, CONFIG),
         )
+        app["helpers"] = helpers
+        await helpers.db.check_connection()
     except Exception as e:
         logger.exception(e)
+        raise e
 
     yield
 

helpers/db_helper.py

@@ -63,6 +63,10 @@ async def pool(self) -> asyncpg.Pool:
     async def acquire(self) -> asyncpg.pool.PoolAcquireContext:
         return (await self.pool()).acquire()
 
+    async def check_connection(self):
+        async with await self.acquire() as connection:
+            await connection.fetchval("SELECT 1")
+
     async def save_message_for_deletion(self, conv_id: str, activity_id: str) -> None:
         connection: asyncpg.pool.PoolConnectionProxy
         async with await self.acquire() as connection: