Replication stuck after switching to new WAL but the queue is empty

When the speed of consuming replication WALs is high, and there are something wrong when creating new WAL, the swith of replcation source reader to new WAL in the queue may happen before the new WAL is created, then the replcation will stuck since it can not consume the new WALs soon afterwards anymore. Restarting the RS that replication stucking can make the replication recover.