Class ErrorRateCircuitBreakerCounter

Package: @litert/concurrentImport path: @litert/concurrent / @litert/concurrent/class/CircuitBreakerSource: CircuitBreaker.ErrorRateCounter.tsImplements: ICircuitBreakerCounter

An error-rate based request counter for CircuitBreaker. This counter tracks both total requests and error requests using sliding window counters, and reports blocked when the error rate exceeds a configurable threshold.

This is the recommended counter for new implementations. For backward-compatible absolute-count behavior, see LegacyCircuitBreakerCounter.

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Import

import { ErrorRateCircuitBreakerCounter } from '@litert/concurrent';
// or
import { ErrorRateCircuitBreakerCounter } from '@litert/concurrent/class/CircuitBreaker';

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Constructor

Signature

new ErrorRateCircuitBreakerCounter(options: IErrorRateCircuitBreakerCounterOptions): ErrorRateCircuitBreakerCounter;

Parameters

• Parameter options: IErrorRateCircuitBreakerCounterOptions

  The constructor options. See IErrorRateCircuitBreakerCounterOptions for the full type definition.

  Option	Type	Default	Description
  errorRateThreshold	number	(required)	Error rate threshold to trigger the circuit break, in range (0, 1) exclusive
  minRequest	number	(required)	Minimum request count before evaluating the error rate, to avoid false positives on low traffic
  createCounter	() => ICounter?	SlideWindowCounter(...)	Factory function to create counter instances. Called twice — once for total requests, once for error requests. Each call must return an independent counter instance.

Error Handling

• RangeError — Thrown when errorRateThreshold is not in range (0, 1), or when minRequest is not a non-negative integer.

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Methods

Method record

Records the result of a request. Always increments the total counter; increments the error counter only when success is false.

Signature

record(success: boolean): void

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Method isBlocked

Returns true if the error rate has reached or exceeded the configured threshold, and the total request count is at least minRequest.

Signature

isBlocked(): boolean

The blocked condition is:

totalRequests >= minRequest AND (errorRequests / totalRequests) >= errorRateThreshold

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Method reset

Resets both the total and error counters to their initial state.

Signature

reset(): void

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Scoped Types

Interface IErrorRateCircuitBreakerCounterOptions

Source: CircuitBreaker.ErrorRateCounter.ts

import type { IErrorRateCircuitBreakerCounterOptions } from '@litert/concurrent';

interface IErrorRateCircuitBreakerCounterOptions {
    errorRateThreshold: number;
    minRequest: number;
    createCounter?: () => ICounter;
}

Property	Type	Default	Description
errorRateThreshold	number	(required)	Error rate threshold to trigger the circuit break. Must be in range (0, 1) exclusive.
minRequest	number	(required)	Minimum request count before evaluating the error rate. Must be a non-negative integer. Set to 0 to evaluate immediately.
createCounter	() => ICounter?	SlideWindowCounter({ windowSizeMs: 10000, windowQty: 6 })	Factory to create counter instances. Called twice to create independent counters for total and error tracking.

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Example

Basic usage with 50% error rate threshold

import { CircuitBreaker, ErrorRateCircuitBreakerCounter } from '@litert/concurrent';

const breaker = new CircuitBreaker({
    requestCounter: new ErrorRateCircuitBreakerCounter({
        errorRateThreshold: 0.5,  // open when error rate >= 50%
        minRequest: 10,           // require at least 10 requests
    }),
    cooldownTimeMs: 30_000,
});

Using a custom counter factory

import { ErrorRateCircuitBreakerCounter, SlideWindowCounter } from '@litert/concurrent';

const counter = new ErrorRateCircuitBreakerCounter({
    errorRateThreshold: 0.3,
    minRequest: 20,
    createCounter: () => new SlideWindowCounter({
        windowSizeMs: 60_000,  // 1-minute window
        windowQty: 6,
    }),
});