Fail4ward-retry NPM

fail4ward-retry

NPM package to implement Retry Pattern in your nodejs applications. Created from this Cookiecutter Template.

Features

Uses the builder pattern, implementation is similar to resilience4j.
Uses the ardydedase/fail4ward docker image to run a service to test with.
Uses testcontainers-node to test against a running docker service.
Supports UntilLimit strategy. Based on the Medium article SRE: Resiliency: Retries in Action — Availability in Exchange for Latency

Specs

Tested on:

npm 6.13.4
node v10.19.0

Installation

npm install --save fail4ward-retry

Usage

Import what we need.

import { RetryConfigBuilder, RetryConfig, Retry, UntilLimit } from 'fail4ward-retry';

Set the configuration using the RetryConfigBuilder().

const maxAttempts = 5;
const waitDuration = 1000;

const retryConfig: RetryConfig = new RetryConfigBuilder()
        .withMaxAttempts(maxAttempts)
        .withWaitDuration(waitDuration)
        .withStrategy(UntilLimit)
        .build();

Builder properties we are setting

withMaxAttempts() number of attempts to retry.
withWaitDuration() backoff time in milliseconds.
withStrategy() retry strategy to use. This package currently supports UntilLimit.

Decorate the function that calls your service using the retryConfig instantiated with Retry.decoratePromise().

const retry = Retry.With(retryConfig);
const fn = retry.decoratePromise(failingFn);

Below is an example of the failingFn calls an API. Similar functions can be found in the /example and /__tests__ folders.

async function failingFn() {
  const url = 'http://localhost:8000/error';
  try {
    const res = await fetch(url);
    const {status} = res;
    if (status === 500) {
      throw new Error('server error');
    }
    return res;
  } catch(e) {
    throw new Error(e);
  }
}

Call the function that fetches the response from your API and retrieve the response.

try {
        const res = await fn();
        const retryResponse = await res.json();
        console.log('retryResponse: ', retryResponse);
} catch(e) {
        console.log(e);
}

Run the example

Checkout the repo

git clone git@github.com:ardydedase/fail4ward-retry.git

Change directory to the example folder
```
cd example/
```
Install dependencies
```
npm install
```

Run a test service

docker run --name fail-svc -p 8000:8000 -it ardydedase/fail4ward:latest

Run the example file
```
npm run dev
```

Development

Checkout the repo

    git clone git@github.com:ardydedase/fail4ward-retry.git

Install dependencies
```
npm install
```
Run build. This will generate the compiled code with type definitions in the dist folder.
```
npm run build
```
Formatting and linting.
```
npm run lint
npm run format
```
Run tests
```
npm test
```