Some operation ModifyColumnFamily, AddDeleteColumnFamily, DeleteColumnFamily, ModifyTable, TruncateTable are still synchronous on the master side. with a wait until the operation completes before returning.
this was done to keep the sync behavior for old client. but instead of using the procLatch which recognize the client version and decide if the operation should be sync or not it just always wait. making the client side proc fault tolerance ineffective.
also the add/delete/modifyColumnFamily operation does not seems to follow the Async() naming in master. and the comment claim to be async but everyone uses them as sync. (this is something from