If the master is dispatching a RPC call to RS when aborting. A connection exception may be thrown by the RPC layer(A IOException with "Connection closed" message in this case). The RSProcedureDispatcher will regard is as an un-retryable exception and pass it to UnassignProcedue.remoteCallFailed, which will expire the RS.
Actually, the RS is very healthy, only the master is restarting.
I think we should deal with those kinds of connection exceptions in RSProcedureDispatcher and retry the rpc call