public void clearMetrics() {
    for (String name : metricsMap.keySet()) {
      helper.removeObjectName(name);
    }
    metricsMap.clear();
  }
Get a MetricMutableCounterLong from the storage. If it is not there atomically put it.
@param counterName            Name of the counter to get
@param potentialStartingValue starting value if we have to create a new counter
hbase-hadoop-compat/src/main/java/org/apache/hadoop/metrics2/lib/DynamicMetricsRegistry.java