public static Token<AuthenticationTokenIdentifier> obtainToken(
Configuration conf) throws IOException {
HTable meta = null;
try {
meta = new HTable(conf, TableName.META_TABLE_NAME);
CoprocessorRpcChannel rpcChannel = meta.coprocessorService(HConstants.EMPTY_START_ROW);
AuthenticationProtos.AuthenticationService.BlockingInterface service =
AuthenticationProtos.AuthenticationService.newBlockingStub(rpcChannel);
AuthenticationProtos.GetAuthenticationTokenResponse response = service.getAuthenticationToken(null,
AuthenticationProtos.GetAuthenticationTokenRequest.getDefaultInstance());