Nesjs Circuit Breaker
## Description
This project is a simple implementation of [Circuit Breaker Pattern](https://en.wikipedia.org/wiki/Circuit_breaker_design_pattern) to be used as decorator in NestJS services
## Installation
tested in node 16.4
```bash
$ npm install nestjs-circuit-breaker
```
## Add to the App
```ts
export default class MyService {
@CircuitBreaker({
fallbackFunction: () => 'fallback return',
})
async execute() {
...
}
}
```
## Cache Manager
this application uses the [NestJS Cache Manager](https://docs.nestjs.com/techniques/logger) 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](https://docs.nestjs.com/techniques/logger) |
| `key` | unique key used to handle circuit breaker in cache|
---
_Source: https://npm.io/package/nestjs-circuit-breaker · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._