added comment for issue #266

Co-authored-by: Dion Häfner <[email protected]>

terracotta/drivers/relational_meta_store.py

@@ -89,6 +89,7 @@ def __init__(self, path: str) -> None:
             echo=False,
             future=True,
             connect_args={self.SQL_TIMEOUT_KEY: db_connection_timeout},
+            # automatically re-spawn stale connections, see terracotta#266
             pool_pre_ping=True
         )
         self.sqla_metadata = sqla.MetaData()