kafka-pub-sub/examples/financial/paymentProducer.js

Enterprise-grade Kafka publish/subscribe library for Node.js — producer pool, batch sending, DLQ, SSL/SASL, multi-broker, and real-world industry examples.

/**
 * Financial Services — Payment Transaction Producer
 *
 * Demonstrates:
 *  - Idempotent producer (KAFKA_IDEMPOTENT=true) for exactly-once semantics
 *  - Partitioning by currency for ordered processing per currency pair
 *  - SASL/SSL config (set env vars — see .env.example)
 *  - BatchProduceEvent for high-throughput trade confirmation bursts
 *
 * Regulatory note: every payment event is stamped with a correlationId that
 * ties together the originating API request, Kafka message, and downstream
 * processing for full audit trail compliance (PCI-DSS, SOX).
 *
 * Run:
 *   node examples/financial/paymentProducer.js
 */

require('dotenv').config({ path: require('path').resolve(__dirname, '../../.env') });

const { ProduceEvent, BatchProduceEvent } = require('../../index');

const TOPICS = {
  PAYMENT_TRANSACTION: 'payment.transaction',
  PAYMENT_FRAUD_ALERT: 'payment.fraud-alert',
  PAYMENT_SETTLED: 'payment.settled',
};

const randomAmount = () => parseFloat((Math.random() * 50000).toFixed(2));
const randomCurrency = () => ['USD', 'EUR', 'GBP', 'JPY', 'SGD'][Math.floor(Math.random() * 5)];
const txId = () => `TX-${Date.now()}-${Math.random().toString(36).slice(2, 7).toUpperCase()}`;

// eslint-disable-next-line no-console
const log = (...args) => console.log(`[${new Date().toISOString()}]`, ...args);

/**
 * Publishes a single high-value payment transaction.
 * Idempotent producer ensures the message is written exactly once
 * even if the network retries cause duplicate sends.
 */
async function publishPaymentTransaction() {
  const transactionId = txId();
  const currency = randomCurrency();
  const amount = randomAmount();

  const payload = {
    transactionId,
    type: 'PAYMENT',
    amount,
    currency,
    sender: { accountId: 'ACCT-001', bankCode: 'BOFAUS3N' },
    receiver: { accountId: 'ACCT-009', bankCode: 'CHASUS33' },
    description: 'Invoice payment INV-2024-00412',
    riskScore: Math.random(), // 0.0 (safe) – 1.0 (high risk)
    initiatedAt: new Date().toISOString(),
  };

  await ProduceEvent(
    TOPICS.PAYMENT_TRANSACTION,
    'PAYMENT_TX',
    payload,
    {
      'x-source': 'payments-api',
      'x-tenant': 'finco-global',
      'content-type': 'application/json',
    },
    {
      partitionKey: currency, // all USD txns go to the same partition — ordered processing
      correlationId: transactionId,
    }
  );

  log(`✓ Payment published | ${transactionId} | ${currency} ${amount}`);

  // Simulate fraud detection: high-risk transactions get a separate alert event
  if (payload.riskScore > 0.85) {
    await ProduceEvent(
      TOPICS.PAYMENT_FRAUD_ALERT,
      'FRAUD_ALERT',
      {
        transactionId,
        riskScore: payload.riskScore,
        reason: 'Risk score exceeds threshold (0.85)',
        requiresManualReview: true,
      },
      { 'x-source': 'fraud-detection-engine' },
      { correlationId: transactionId }
    );
    log(`⚠ Fraud alert raised for ${transactionId} (risk=${payload.riskScore.toFixed(3)})`);
  }

  return payload;
}

/**
 * Publishes a batch of end-of-day settlement confirmations.
 * Uses BatchProduceEvent for a single broker round-trip.
 */
async function publishSettlementBatch(count = 20) {
  log(`Publishing settlement batch (${count} records)...`);

  const messages = Array.from({ length: count }, () => {
    const id = txId();
    return {
      topic: TOPICS.PAYMENT_SETTLED,
      event: 'PAYMENT_SETTLED',
      data: {
        transactionId: id,
        settledAmount: randomAmount(),
        currency: randomCurrency(),
        settledAt: new Date().toISOString(),
        clearingHouseRef: `CH-${Math.random().toString(36).slice(2, 10).toUpperCase()}`,
      },
      headers: { 'x-source': 'settlement-engine', 'batch-run': 'EOD-DAILY' },
      partitionKey: id,
    };
  });

  await BatchProduceEvent(messages, {
    compression: 'gzip',
    correlationId: `SETTLE-BATCH-${Date.now()}`,
  });

  log(`✓ Settlement batch of ${count} records published`);
}

async function main() {
  // Publish 5 individual payment transactions
  for (let i = 0; i < 5; i++) {
    // eslint-disable-next-line no-await-in-loop
    await publishPaymentTransaction();
  }

  // Publish end-of-day settlement batch
  await publishSettlementBatch(20);

  await ProduceEvent.disconnect();
  await BatchProduceEvent.disconnect();

  log('Done.');
}

main().catch((err) => {
  // eslint-disable-next-line no-console
  console.error('Financial producer failed:', err);
  process.exit(1);
});