hi, i read source, maybe this is true? after the pool started, the conn in pool can be always healthy. in real word, conn can be disconnected.
in this situation, client get a conn from pool, when using the conn,  executing or querying can get a exception when conn is disconnected.
how to process the exception? conn need a reconnection operator or free conn and new a connection.

may be Connection need a status and reaper thread can check conn's status and try reconnect and keep enough connection when db service function recover.