org.apache.solr.util.stats
Class EWMA

java.lang.Object
  org.apache.solr.util.stats.EWMA

public class EWMA
extends Object

An exponentially-weighted moving average.

See Also:

UNIX Load Average Part 1: How It Works, UNIX Load Average Part 2: Not Your Average Average

Constructor Summary

EWMA(double alpha, long interval, TimeUnit intervalUnit)
Create a new EWMA with a specific smoothing constant.

Method Summary

static EWMA	fifteenMinuteEWMA() Creates a new EWMA which is equivalent to the UNIX fifteen minute load average and which expects to be ticked every 5 seconds.
static EWMA	fiveMinuteEWMA() Creates a new EWMA which is equivalent to the UNIX five minute load average and which expects to be ticked every 5 seconds.
double	getRate(TimeUnit rateUnit) Returns the rate in the given units of time.
static EWMA	oneMinuteEWMA() Creates a new EWMA which is equivalent to the UNIX one minute load average and which expects to be ticked every 5 seconds.
void	tick() Mark the passage of time and decay the current rate accordingly.
void	update(long n) Update the moving average with a new value.

Methods inherited from class java.lang.Object

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

Constructor Detail

EWMA

public EWMA(double alpha,
            long interval,
            TimeUnit intervalUnit)

Create a new EWMA with a specific smoothing constant.

Parameters:

alpha - the smoothing constant

interval - the expected tick interval

intervalUnit - the time unit of the tick interval

Method Detail

oneMinuteEWMA

public static EWMA oneMinuteEWMA()

Creates a new EWMA which is equivalent to the UNIX one minute load average and which expects to be ticked every 5 seconds.

Returns:

a one-minute EWMA

fiveMinuteEWMA

public static EWMA fiveMinuteEWMA()

Creates a new EWMA which is equivalent to the UNIX five minute load average and which expects to be ticked every 5 seconds.

Returns:

a five-minute EWMA

fifteenMinuteEWMA

public static EWMA fifteenMinuteEWMA()

Creates a new EWMA which is equivalent to the UNIX fifteen minute load average and which expects to be ticked every 5 seconds.

Returns:

a fifteen-minute EWMA

update

public void update(long n)

Update the moving average with a new value.

Parameters:

n - the new value

tick

public void tick()

Mark the passage of time and decay the current rate accordingly.

getRate

public double getRate(TimeUnit rateUnit)

Returns the rate in the given units of time.

Parameters:

rateUnit - the unit of time

Returns:

the rate