@Override
  public void incGauge(String gaugeName, long delta) {
    MutableGaugeLong gaugeInt = metricsRegistry.getGauge(gaugeName, 0L);
    gaugeInt.incr(delta);
  }
Add some amount to a gauge.
@param gaugeName The name of the gauge to increment.
@param delta     The amount to increment the gauge by.
hbase-hadoop-compat/src/main/java/org/apache/hadoop/hbase/metrics/BaseSourceImpl.java