code: public synchronized ListenableFuture<?> reserve(long bytes)
      {
          checkArgument(bytes >= 0, "bytes is negative");
  
          if ((currentBytes + bytes) >= maxBytes) {
              throw exceededLocalLimit(succinctBytes(maxBytes));
          }
          currentBytes += bytes;
  
          return NOT_BLOCKED;
      }
docs: Reserves the given number of bytes to spill. If more than the maximum, throws an exception.
  
  @throws ExceededSpillLimitException