Your edit log transactions are missing in the namenode metadata directory....
"We expected txid 8364, but got txid 27381" ---this mean the edit logs/transactions from 8364 to 27381 are missing....If you don't want to loose the data restore the edit logs from back up metadata if you have or just point the namenode to txid 27381, you may loose data if you point namenode to txid 27381.
Em Jay
