Package io.github.resilience4j.core.metrics

Class FixedSizeSlidingWindowMetrics

java.lang.Object

io.github.resilience4j.core.metrics.FixedSizeSlidingWindowMetrics

All Implemented Interfaces:

Metrics

public class FixedSizeSlidingWindowMetrics
extends Object
implements Metrics

A Metrics implementation is backed by a sliding window that aggregates only the last N calls.

The sliding window is implemented with a circular array of N measurements. If the time window size is 10, the circular array has always 10 measurements.

The sliding window incrementally updates a total aggregation. The total aggregation is updated incrementally when a new call outcome is recorded. When the oldest measurement is evicted, the measurement is subtracted from the total aggregation. (Subtract-on-Evict)

The time to retrieve a Snapshot is constant 0(1), since the Snapshot is pre-aggregated and is independent of the window size. The space requirement (memory consumption) of this implementation should be O(n).

Nested Class Summary

Nested classes/interfaces inherited from interface io.github.resilience4j.core.metrics.Metrics

Metrics.Outcome

Field Summary

Fields

Modifier and Type	Field	Description
(package private) int	headIndex
private final Measurement[]	measurements
private final TotalAggregation	totalAggregation
private final int	windowSize

Constructor Summary

Constructors

Constructor	Description
FixedSizeSlidingWindowMetrics(int windowSize)	Creates a new FixedSizeSlidingWindowMetrics with the given window size.

Method Summary

Modifier and Type	Method	Description
private Measurement	getLatestMeasurement()	Returns the head partial aggregation of the circular array.
Snapshot	getSnapshot()	Returns a snapshot.
(package private) void	moveHeadIndexByOne()	Moves the headIndex to the next bucket.
private Measurement	moveWindowByOne()
Snapshot	record(long duration, TimeUnit durationUnit, Metrics.Outcome outcome)	Records a call.

Methods inherited from class java.lang.Object

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

Field Details

windowSize

private final int windowSize

totalAggregation

private final TotalAggregation totalAggregation

measurements

private final Measurement[] measurements

headIndex

int headIndex

Constructor Details

FixedSizeSlidingWindowMetrics

public FixedSizeSlidingWindowMetrics(int windowSize)

Creates a new FixedSizeSlidingWindowMetrics with the given window size.

Parameters:

windowSize - the window size

Method Details

record

public Snapshot record(long duration,
 TimeUnit durationUnit,
 Metrics.Outcome outcome)

Description copied from interface: Metrics

Records a call.

Specified by:

record in interface Metrics

Parameters:

duration - the duration of the call

durationUnit - the time unit of the duration

outcome - the outcome of the call

getSnapshot

public Snapshot getSnapshot()

Description copied from interface: Metrics

Returns a snapshot.

Specified by:

getSnapshot in interface Metrics

Returns:

a snapshot

moveWindowByOne

private Measurement moveWindowByOne()

getLatestMeasurement

private Measurement getLatestMeasurement()

Returns the head partial aggregation of the circular array.

Returns:

the head partial aggregation of the circular array

moveHeadIndexByOne

void moveHeadIndexByOne()

Moves the headIndex to the next bucket.