code: private long size(final Jedis jedis, final String queueName) {
          final String key = key(QUEUE, queueName);
          final long size;
          if (JedisUtils.isDelayedQueue(jedis, key)) { // If delayed queue, use ZCARD
              size = jedis.zcard(key);
          } else { // Else, use LLEN
              size = jedis.llen(key);
          }
          return size;
      }
docs: Size of a queue.
  
  @param jedis
  @param queueName
  @return