storm中添加自定义metrics

storm中有时需要添加一些metrics监控项,这时需要添加metrics.
在spout或者bolt的prepare方法中注册metrics

	public void prepare(@SuppressWarnings("rawtypes") Map stormConf,
			TopologyContext context, OutputCollector collector) {
		this.collector = collector;
		barMetric = new CountMetric();
		context.registerMetric("bar", this.barMetric, 3);
	}

在恰当的时候更新metrics

	public void execute(Tuple input) {
		if (input.getSourceComponent().equals("bar")) {
			barMetric.incr();
		}
		collector.ack(input);
	}

启动拓扑的时候注册metrics的consumer

conf.registerMetricsConsumer(MetricsConsumer.class);