org.apache.cassandra.metrics

## Class RestorableMeter

- java.lang.Object
- - org.apache.cassandra.metrics.RestorableMeter

-     public class RestorableMeter
      extends java.lang.Object

  A meter metric which measures mean throughput as well as fifteen-minute and two-hour exponentially-weighted moving average throughputs. This is based heavily on the Meter and EWMA classes from codahale/yammer metrics.
  See Also:
    EMA

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `RestorableMeter()` Creates a new, uninitialized RestorableMeter.
    `RestorableMeter(double lastM15Rate, double lastM120Rate)` Restores a RestorableMeter from the last seen 15m and 2h rates.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `long` | `count()` The total number of events that have occurred since this object was created.
    `double` | `fifteenMinuteRate()` Returns the 15-minute rate in terms of events per second.
    `void` | `mark()` Mark the occurrence of an event.
    `void` | `mark(long n)` Mark the occurrence of a given number of events.
    `double` | `meanRate()` Returns the mean rate of events per second since this object was created.
    `double` | `twoHourRate()` Returns the two-hour rate in terms of events per second.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### RestorableMeter

          public RestorableMeter()

      Creates a new, uninitialized RestorableMeter.

    - #### RestorableMeter

          public RestorableMeter(double lastM15Rate,
                                 double lastM120Rate)

      Restores a RestorableMeter from the last seen 15m and 2h rates.
      Parameters:
        `lastM15Rate` - the last-seen 15m rate, in terms of events per second
        `lastM120Rate` - the last seen 2h rate, in terms of events per second

  - ### Method Detail

    - #### mark

          public void mark()

      Mark the occurrence of an event.

    - #### mark

          public void mark(long n)

      Mark the occurrence of a given number of events.
      Parameters:
        `n` - the number of events

    - #### fifteenMinuteRate

          public double fifteenMinuteRate()

      Returns the 15-minute rate in terms of events per second. This carries the previous rate when restored.

    - #### twoHourRate

          public double twoHourRate()

      Returns the two-hour rate in terms of events per second. This carries the previous rate when restored.

    - #### count

          public long count()

      The total number of events that have occurred since this object was created. Note that the previous count is *not* carried over when a RestorableMeter is restored.

    - #### meanRate

          public double meanRate()

      Returns the mean rate of events per second since this object was created. Note that the mean rate does *not* carry over when a RestorableMeter is restored, so the mean rate is only a measure since this object was created.

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