org.apache.kafka.common.metrics.stats

Class SampledStat

java.lang.Object

org.apache.kafka.common.metrics.stats.SampledStat

All Implemented Interfaces:

Measurable, MeasurableStat, MetricValueProvider<Double>, Stat

Direct Known Subclasses:

Avg, Frequencies, Max, Min, Percentiles, WindowedSum

public abstract class SampledStat
extends Object
implements MeasurableStat

A SampledStat records a single scalar value measured over one or more samples. Each sample is recorded over a configurable window. The window can be defined by number of events or elapsed time (or both, if both are given the window is complete when either the event count or elapsed time criterion is met).

All the samples are combined to produce the measurement. When a window is complete the oldest sample is cleared and recycled to begin recording the next sample. Subclasses of this class define different statistics measured using this basic pattern.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	SampledStat.Sample

Field Summary

Fields

Modifier and Type	Field and Description
protected List<SampledStat.Sample>	samples

Constructor Summary

Constructors

Constructor and Description
SampledStat(double initialValue)

Method Summary

Modifier and Type	Method and Description
abstract double	combine(List<SampledStat.Sample> samples, MetricConfig config, long now)
SampledStat.Sample	current(long timeMs)
double	measure(MetricConfig config, long now) Measure this quantity and return the result as a double
protected SampledStat.Sample	newSample(long timeMs)
SampledStat.Sample	oldest(long now)
protected void	purgeObsoleteSamples(MetricConfig config, long now)
void	record(MetricConfig config, double value, long timeMs) Record the given value
protected abstract void	update(SampledStat.Sample sample, MetricConfig config, double value, long timeMs)

Methods inherited from class java.lang.Object

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

Field Detail

samples

protected List<SampledStat.Sample> samples

Constructor Detail

SampledStat

public SampledStat(double initialValue)

Method Detail

record

public void record(MetricConfig config,
                   double value,
                   long timeMs)

Description copied from interface: Stat

Record the given value

Specified by:

record in interface Stat

Parameters:

config - The configuration to use for this metric

value - The value to record

timeMs - The POSIX time in milliseconds this value occurred

newSample

protected SampledStat.Sample newSample(long timeMs)

measure

public double measure(MetricConfig config,
                      long now)

Description copied from interface: Measurable

Measure this quantity and return the result as a double

Specified by:

measure in interface Measurable

Parameters:

config - The configuration for this metric

now - The POSIX time in milliseconds the measurement is being taken

Returns:

The measured value

current

public SampledStat.Sample current(long timeMs)

oldest

public SampledStat.Sample oldest(long now)

update

protected abstract void update(SampledStat.Sample sample,
                               MetricConfig config,
                               double value,
                               long timeMs)

combine

public abstract double combine(List<SampledStat.Sample> samples,
                               MetricConfig config,
                               long now)

purgeObsoleteSamples

protected void purgeObsoleteSamples(MetricConfig config,
                                    long now)