org.apache.hadoop.metrics2.lib
Classes 
AbstractMetricsSource
MetricMutable
MetricMutableCounter
MetricMutableCounterInt
MetricMutableCounterLong
MetricMutableFactory
MetricMutableGauge
MetricMutableGaugeInt
MetricMutableGaugeLong
MetricMutableStat
MetricsRegistry
Enums 
DefaultMetricsSystem