Package instruments allows you to collects metrics over discrete time intervals. Collected metrics will only reflect observations from last time window only, rather than including observations from prior windows, contrary to EWMA based metrics. Instruments support two types of instruments: Discrete instruments return a single value, and Sample instruments a value distribution. Theses base instruments are available: - Counter: holds a counter that can be incremented or decremented. - Rate: tracks the rate of values per seconds. - Reservoir: randomly samples values. - Derive: tracks the rate of values based on the delta with previous value. - Gauge: tracks last value. - Timer: tracks durations. You can create custom instruments or compose new instruments form the built-in instruments as long as they implements the Sample or Discrete interfaces.