Redis Pub/Sub

You are a Redis expert implementing publish-subscribe messaging patterns. The user wants to set up Redis Pub/Sub to handle real-time message broadcasting between publishers and subscribers.

What to check first

• Verify Redis server is running with redis-cli ping (should return PONG)
• Check that you have the redis npm package installed with npm list redis
• Confirm Redis version supports PUBSUB commands with redis-cli INFO server

Steps

1. Install the redis client library with npm install redis
2. Create a Redis client instance using createClient() and connect with .connect()
3. Subscribe to a channel using .subscribe(channelName, callback) on the subscriber client
4. Create a separate publisher client instance to avoid blocking the subscriber
5. Publish messages using .publish(channelName, message) on the publisher client
6. Handle incoming messages in the subscriber callback with the message data
7. Implement error handling with .on('error') for connection issues
8. Gracefully disconnect clients with .disconnect() when shutting down

Code

const { createClient } = require('redis');

// ===== SUBSCRIBER =====
async function setupSubscriber() {
  const subscriber = createClient({
    host: 'localhost',
    port: 6379
  });

  subscriber.on('error', (err) => console.error('Subscriber error:', err));

  await subscriber.connect();

  // Subscribe to channel with message handler
  await subscriber.subscribe('notifications', (message, channel) => {
    console.log(`[${channel}] Received: ${message}`);
  });

  console.log('Subscriber listening on "notifications" channel');
  return subscriber;
}

// ===== PUBLISHER =====
async function publishMessage(message) {
  const publisher = createClient({
    host: 'localhost',
    port: 6379
  });

  publisher.on('error', (err) => console.error('Publisher error:', err));

  await publisher.connect();

  const numSubscribers = await publisher.publish('notifications', message);
  console.log(`Message sent to ${numSubscribers} subscribers`);

  await publisher.disconnect();
}

// ===== PATTERN MATCHING =====
async function setupPatternSubscriber() {
  const subscriber = createClient({
    host: 'localhost',
    port: 6379
  });

  await subscriber.connect();

  // Subscribe to channels matching pattern
  await subscriber.pSubscribe('user:*:notifications', (message, channel) => {
    console.log(`[${channel}] Pattern match: ${message}`);
  });

  console.log('Pattern subscriber listening to "user:*:notifications"');
  return subscriber;
}

// ===== MAIN EXECUTION =====
async function main() {
  try {
    const subscriber = await setupSubscriber();
    const patternSubscriber = await setupPatternSubscriber();

    // Simulate

Note: this example was truncated in the source. See the GitHub repo for the latest full version.

Common Pitfalls

• Treating this skill as a one-shot solution — most workflows need iteration and verification
• Skipping the verification steps — you don't know it worked until you measure
• Applying this skill without understanding the underlying problem — read the related docs first

When NOT to Use This Skill

• When a simpler manual approach would take less than 10 minutes
• On critical production systems without testing in staging first
• When you don't have permission or authorization to make these changes

How to Verify It Worked

• Run the verification steps documented above
• Compare the output against your expected baseline
• Check logs for any warnings or errors — silent failures are the worst kind

Production Considerations

• Test in staging before deploying to production
• Have a rollback plan — every change should be reversible
• Monitor the affected systems for at least 24 hours after the change