Package com.tnsai.quality.slo

Class InMemorySLOEvaluator

java.lang.Object

com.tnsai.quality.slo.InMemorySLOEvaluator

All Implemented Interfaces:

SLOEvaluator

public final class InMemorySLOEvaluator
extends Object
implements SLOEvaluator

Process-local SLOEvaluator that holds attempt records in an in-memory rolling buffer (issue #92). Suitable for dev, tests, and single-process deployments; production multi-process deployments should swap in a metric-store-backed evaluator (Prometheus implementation lands in a follow-up PR).

How it works

• Callers push InMemorySLOEvaluator.Attempt records via record(Attempt).
• evaluate(SLODefinition, Instant) filters the buffer by the SLO's SLOScope.matches(EventScope) and SLODefinition.window(), then computes compliance / budget / burn-rate per SLODefinition.type().
• Records older than retainFor are evicted on each record(Attempt) call so the buffer can't grow unbounded.

Concurrency

Backed by a ReentrantReadWriteLock: many concurrent evaluations but exclusive writes during record(Attempt). Per-SLO evaluation is O(N) over the live buffer — acceptable for the dev-scale buffer size this evaluator is meant for.

Since:

0.5.0 (issue #92)

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final record	InMemorySLOEvaluator.Attempt	One observed attempt feeding the SLO calculation.

Constructor Summary

Constructors

Constructor	Description
InMemorySLOEvaluator(Duration retainFor)

Method Summary

Modifier and Type	Method	Description
SLOState	evaluate(SLODefinition def, Instant now)	Compute the current state of definition as of now.
void	record(InMemorySLOEvaluator.Attempt a)	Push an attempt into the rolling buffer.
int	size()

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.tnsai.quality.slo.SLOEvaluator

evaluate

Constructor Details

InMemorySLOEvaluator

public InMemorySLOEvaluator(Duration retainFor)

Parameters:

retainFor - how far back to keep attempts. Must be at least as long as the longest SLO window the evaluator will be asked about — older records are evicted.

Method Details

record

public void record(InMemorySLOEvaluator.Attempt a)

Push an attempt into the rolling buffer.

size

public int size()

Returns:

current live attempt count (after eviction). For tests / monitoring.

evaluate

public SLOState evaluate(SLODefinition def,
 Instant now)

Description copied from interface: SLOEvaluator

Compute the current state of definition as of now. Implementations MUST be safe for concurrent calls; an SLO dashboard may evaluate dozens of definitions in parallel.

Specified by:

evaluate in interface SLOEvaluator