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

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.