retryWithCircuitBreaker.js

retryWithCircuitBreaker.js

const CircuitBreaker = require('opossum');
const fetch = require('node-fetch');

// Function to fetch data from an API
async function fetchData(url) {
  const response = await fetch(url);
  if (!response.ok) throw new Error('Request failed');
  return await response.json();
}

// Circuit Breaker Configuration
const breakerOptions = {
  timeout: 3000, // Fail request if it takes longer than 3s
  errorThresholdPercentage: 50, // Open circuit if 50% of requests fail
  resetTimeout: 10000, // Wait 10s before allowing requests after circuit opens
};

// Wrap the function inside the circuit breaker
const breaker = new CircuitBreaker(fetchData, breakerOptions);

// Handle circuit breaker events
breaker.on('open', () => console.log('Circuit breaker OPENED! No further retries.'));
breaker.on('close', () => console.log('Circuit breaker CLOSED! Requests are allowed again.'));
breaker.on('halfOpen', () => console.log('Circuit breaker HALF-OPEN! Testing service availability.'));

// Function to retry with exponential backoff, using circuit breaker per request
async function retryWithCircuitBreaker(url, retries = 5, baseDelay = 500) {
  for (let i = 0; i < retries; i++) {
    try {
      console.log(`Attempt ${i + 1}/${retries}`);
      const data = await breaker.fire(url); // Each retry attempt is counted separately
      return data; // Success, return data
    } catch (error) {
      console.log(`Retry ${i + 1} failed: ${error.message}`);
      if (breaker.opened) {
        console.log('Circuit breaker is OPEN! Stopping further retries.');
        throw new Error('Service unavailable, circuit breaker is open.');
      }
      const delay = baseDelay * Math.pow(2, i);
      console.log(`Waiting ${delay}ms before next retry...`);
      await new Promise(res => setTimeout(res, delay));
    }
  }
  throw new Error('All retries failed');
}