Top Description Fields Constructors Methods
io.github.resilience4j.core.metrics

public Class FixedSizeSlidingWindowMetrics

extends Object
implements Metrics
Class Inheritance
All Implemented Interfaces
io.github.resilience4j.core.metrics.Metrics
Imports
java.util.concurrent.TimeUnit, java.util.concurrent.locks.ReentrantLock
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).

Field Summary

Modifier and TypeField and Description
pack-priv int
headIndex

private final ReentrantLock
lock

private final Measurement[]
measurements

private final TotalAggregation
totalAggregation

private final int
windowSize

Constructor Summary

AccessConstructor and Description
public
FixedSizeSlidingWindowMetrics(int
the window size
windowSize)

Creates a new FixedSizeSlidingWindowMetrics with the given window size.

Method Summary

Modifier and TypeMethod and Description
private Measurement

Returns:

the head partial aggregation of the circular array
getLatestMeasurement()

Returns the head partial aggregation of the circular array.

public Snapshot
getSnapshot()

Implements io.github.resilience4j.core.metrics.Metrics.getSnapshot.

Returns a snapshot.

pack-priv void
moveHeadIndexByOne()

Moves the headIndex to the next bucket.

private Measurement
moveWindowByOne()

public Snapshot
record(long
the duration of the call
duration, TimeUnit
the time unit of the duration
durationUnit, Metrics.Outcome
the outcome of the call
outcome)

Implements io.github.resilience4j.core.metrics.Metrics.record.

Records a call.

Inherited from java.lang.Object:
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Field Detail

headIndexback to summary
pack-priv int headIndex
lockback to summary
private final ReentrantLock lock
measurementsback to summary
private final Measurement[] measurements
totalAggregationback to summary
private final TotalAggregation totalAggregation
windowSizeback to summary
private final int windowSize

Constructor Detail

FixedSizeSlidingWindowMetricsback to summary
public FixedSizeSlidingWindowMetrics(int windowSize)

Creates a new FixedSizeSlidingWindowMetrics with the given window size.

Parameters
windowSize:int

the window size

Method Detail

getLatestMeasurementback to summary
private Measurement getLatestMeasurement()

Returns the head partial aggregation of the circular array.

Returns:Measurement

the head partial aggregation of the circular array

getSnapshotback to summary
public Snapshot getSnapshot()

Implements io.github.resilience4j.core.metrics.Metrics.getSnapshot.

Doc from io.github.resilience4j.core.metrics.Metrics.getSnapshot.

Returns a snapshot.

Returns:Snapshot

a snapshot

moveHeadIndexByOneback to summary
pack-priv void moveHeadIndexByOne()

Moves the headIndex to the next bucket.

moveWindowByOneback to summary
private Measurement moveWindowByOne()
recordback to summary
public Snapshot record(long duration, TimeUnit durationUnit, Metrics.Outcome outcome)

Implements io.github.resilience4j.core.metrics.Metrics.record.

Doc from io.github.resilience4j.core.metrics.Metrics.record.

Records a call.

Parameters
duration:long

the duration of the call

durationUnit:TimeUnit

the time unit of the duration

outcome:Metrics.Outcome

the outcome of the call

Annotations
@Override