Idempotent API Requests with Idempotency-Key (Node.js)

const axios = require('axios');
const { v4: uuidv4 } = require('uuid'); // For generating unique keys

// This function simulates making an idempotent request to an external API
async function makeIdempotentApiRequest(url, data, idempotencyKey = uuidv4()) {
    try {
        console.log(`Making idempotent request to ${url} with Idempotency-Key: ${idempotencyKey}`);
        const response = await axios.post(url, data, {
            headers: {
                'Content-Type': 'application/json',
                'Idempotency-Key': idempotencyKey
            }
        });
        console.log('API Response:', response.data);
        return response.data;
    } catch (error) {
        if (error.response) {
            console.error(`Error ${error.response.status}:`, error.response.data);
        } else if (error.request) {
            console.error('No response received:', error.request);
        } else {
            console.error('Request setup error:', error.message);
        }
        throw error;
    }
}

// Example Usage:
(async () => {
    const externalApiUrl = 'https://jsonplaceholder.typicode.com/posts'; // Using a public API for demonstration, though it won't process idempotency
    const payload = {
        title: 'Idempotent Test Post',
        body: 'This is a test post for idempotency demonstration.',
        userId: 1
    };

    // First request
    console.log('--- First Request ---');
    try {
        const key1 = uuidv4();
        await makeIdempotentApiRequest(externalApiUrl, payload, key1);
        console.log('First request successful.');
    } catch (e) {
        console.error('First request failed.');
    }

    // Sending the exact same request with the same idempotency key
    // A real idempotent API would process this only once, or return the original result.
    console.log('
--- Second Request with SAME Idempotency-Key ---');
    try {
        const key2 = 'a-fixed-unique-key-for-test'; // Use a fixed key to simulate re-sending
        await makeIdempotentApiRequest(externalApiUrl, payload, key2);
        console.log('Second request (same key) successful. A real API would handle this without side-effects.');
    } catch (e) {
        console.error('Second request (same key) failed.');
    }
})();