code: public Object getMetric(String key) throws MetricsException {
  		MetricsKey mk = new MetricsKey(key);
  		MetricsProvider provider = getProvider(mk.getProvider());
  		return provider.getValue(mk);
  	}
docs: Retrieve a value from this MetricsContainer.
  @param key the fully-qualified key naming the metric.
  @return the requested value.
  @throws MetricsException when the fully-qualified key does not exist.