code: private Connection<CL> getConnectionForTokenOnRackNoFallback(BaseOperation<CL, ?> op, Long token, String rack, int duration, TimeUnit unit, RetryPolicy retry)
              throws NoAvailableHostsException, PoolExhaustedException, PoolTimeoutException, PoolOfflineException {
          DynoConnectException lastEx = null;
  
          // find the selector for that rack,
  		HostSelectionStrategy<CL> selector = findSelectorForRack(rack);
  		// get the host using that selector
  		HostConnectionPool<CL>  hostPool = selector.getPoolForToken(token);
  
          if (hostPool != null) {
              try {
                  // Note that if a PoolExhaustedException is thrown it is caught by the calling
                  // ConnectionPoolImpl#executeXXX() method
                  return hostPool.borrowConnection(duration, unit);
              } catch (PoolTimeoutException pte) {
                  lastEx = pte;
                  cpMonitor.incOperationFailure(null, pte);
              }
          }
  
          if (lastEx == null) {
              throw new PoolOfflineException(hostPool == null ? null : hostPool.getHost(), "host pool is offline and we are forcing no fallback");
          } else {
              throw lastEx;
          }
      }
docs: Should be called when a connection is required on that particular zone with no fall backs what so ever