Description

This project is a simple implementation of Circuit Breaker Pattern to be used as decorator in NestJS services

Installation

tested in node 16.4

$ npm install nestjs-circuit-breaker

Add to the App

export default class MyService {
    @CircuitBreaker({
        fallbackFunction: () => 'fallback return',
    })
    async execute() {
        ...
    }
}

Cache Manager

this application uses the NestJS Cache Manager by default. So your application need to configure this

Parameters in Circuit Breaker

| Parameters | Description | |-----------------------------------------|--------------------------------------------------------------------------------------------------------| | maxErrorsBeforeOpen | Max errors until circuit breaker open and only use the fallback function | | errorExpirationTimeInMilliseconds | Expiration time that will be used to decrement the count erros, this exists to avoid singular erros to be counted | | maxAttemptsInHalfOpenState | Max number of parallel tryings in half open state. this doesnt change the flow of circuit breaker, so if have a error in any of the attempts the circuit breaker will be opened again | | circuitCheckTimeoutInMilliseconds | Timeout until change the cricuit breaker status to HALF_OPEN. | | fallbackFunction | fallback function used when has an error in the service or when the circuit breaker is opened | | logger | (Optional) circuit breaker log, by default it uses the NestJS Logger | | key | unique key used to handle circuit breaker in cache|