Package io.github.resilience4j.core.metrics

Class LockFreeSlidingTimeWindowMetrics

java.lang.Object

io.github.resilience4j.core.metrics.LockFreeSlidingTimeWindowMetrics

All Implemented Interfaces:

Metrics

public class LockFreeSlidingTimeWindowMetrics
extends Object
implements Metrics

Implements a lock-free time sliding window using a single linked list, represented by a head and a tail reference. The algorithm of the sliding window is very similar as for LockFreeFixedSizeSlidingWindowMetrics.

Each node of the sliding window represents the aggregated stats across 1 second (time slice). During a time slice, the algorithm is very simple consisting of a classical CAS-loop, in which the stats are copied, incremented, and a swap is attempted.

The complexity of the algorithm comes when the time slice is advanced. The algorithm needs to ensure that only one thread succeeds in advancing the time slice, i.e. a single time slice is advanced not multiple. This is achieved via an extra check when adding a new entry to the window, which guarantees that it is added only if it respects the time order, i.e. ith time slice is added only if it is preceded by the (i-1)th time slice.

It also needs to ensure that no stats updates are lost by updating a time slice in the past. This is accounted via a processed flag in the time slice, which marks that no further increments should happen for it.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	LockFreeSlidingTimeWindowMetrics.TimeSlice

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

Metrics.Outcome

Constructor Summary

Constructors

Constructor	Description
LockFreeSlidingTimeWindowMetrics(int windowSize)
LockFreeSlidingTimeWindowMetrics(int windowSize, Clock clock)

Method Summary

Modifier and Type	Method	Description
Snapshot	getSnapshot()	Returns a snapshot.
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

Constructor Details

LockFreeSlidingTimeWindowMetrics

public LockFreeSlidingTimeWindowMetrics(int windowSize,
 Clock clock)

LockFreeSlidingTimeWindowMetrics

public LockFreeSlidingTimeWindowMetrics(int windowSize)

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