@Override
    public void declareOutputFields(final OutputFieldsDeclarer declarer) {
        declarer.declare(this.scheme.getOutputFields());
    }
Time in milliseconds to wait for a message from the queue if there is no
message ready when the topology requests a tuple (via
{@link #nextTuple()}).
metamorphosis-storm-spout/src/main/java/com/taobao/metamorphosis/storm/spout/MetaSpout.java