Robust API Request Retries with Exponential Backoff

const axios = require('axios');

async function callApiWithRetries(apiCallFn, maxRetries = 5, initialDelay = 1000) {
  let retries = 0;
  while (retries < maxRetries) {
    try {
      return await apiCallFn();
    } catch (error) {
      // Check for common retryable errors: 429 Too Many Requests, 5xx server errors
      const statusCode = error.response ? error.response.status : null;
      if ([429, 500, 502, 503, 504].includes(statusCode) && retries < maxRetries - 1) {
        const delay = initialDelay * Math.pow(2, retries) + Math.random() * 500; // Exponential backoff with jitter
        console.warn(`API call failed (status: ${statusCode}). Retrying in ${delay}ms...`);
        await new Promise(resolve => setTimeout(resolve, delay));
        retries++;
      } else {
        // Not a retryable error or max retries reached
        console.error('API call failed permanently:', error.response ? error.response.data : error.message);
        throw error;
      }
    }
  }
  throw new Error('Max retries reached, API call failed.');
}

// Example API function to wrap
const fetchUserData = async (userId) => {
  console.log(`Attempting to fetch data for user ${userId}`);
  // Simulate an API call that might fail
  const randomFailure = Math.random();
  if (randomFailure < 0.3) { // 30% chance of a 429 error
    const error = new Error('Simulated 429 Too Many Requests');
    error.response = { status: 429, data: { message: 'Rate limit exceeded' } };
    throw error;
  }
  if (randomFailure > 0.8) { // 20% chance of a 500 error
    const error = new Error('Simulated 500 Internal Server Error');
    error.response = { status: 500, data: { message: 'Server error' } };
    throw error;
  }
  return { userId, name: `User ${userId}`, data: 'Some data from API' };
};

// Usage:
// (async () => {
//   try {
//     const data = await callApiWithRetries(() => fetchUserData(123));
//     console.log('Successfully fetched data:', data);
//   } catch (err) {
//     console.error('Failed after retries:', err.message);
//   }
// })();