MetricsManager.java

...

void activate(ComponentContext componentContext) {

System.out.println("Starting the metrics manager. Waiting for metrics providers . . .");

_executorService.execute(new Runnable() {

	@Override
	public void run() {
		while (true) {
			// run forever and collect metrics every 2 seconds

			List<Metric> metrics = collect();

			for (Metric metric : metrics) {
				System.out.println(metric.display());
			}

			try {
				Thread.currentThread().sleep(2000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}

	}
});
}

...

protected List<Metric> collect() {
	List<Metric> metrics = new ArrayList<Metric>();
	
	for (Long extensionId : _extensions.keySet()) {
		MetricsProvider metricsProvider = _extensions.get(extensionId);
	
		metrics.add(metricsProvider.collect());
	}
	
	return metrics;
}

private Map<Long, MetricsProvider> _extensions = new HashMap<Long, MetricsProvider>();