The get_token(String tokenIdentifier) HMS thrift API fails when HMS is deployed in remote mode and when there is no token found with that tokenIndentifier. This could happen when an application calls a renewDelegationToken on an expired/cancelled delegation token. The issue is that get_token tries to return a null result values which cannot be done in Thrift. The API call errors out with org.apache.thrift.TApplicationException unknown result exception which is uncaught and HS2 thrift server closes the client transport. So no further calls from that connection can be accepted unless client reconnects to HS2 again.