Redis Pubsub

Redis Pub/Sub & Streams Core Knowledge

Full Reference: See advanced.md for Streams consumer groups (Node.js, Java, Python), pending message recovery, TLS configuration, and Sentinel setup.

Deep Knowledge: Use mcp__documentation__fetch_docs with technology: redis-pubsub for comprehensive documentation.

Quick Start (Docker)

services:
  redis:
    image: redis:7-alpine
    ports:
      - "6379:6379"
    command: redis-server --appendonly yes

Core Concepts

Pub/Sub (Node.js)

import Redis from 'ioredis';

const publisher = new Redis({ host: 'localhost', port: 6379 });
const subscriber = new Redis({ host: 'localhost', port: 6379 });

// Subscriber
subscriber.subscribe('orders', 'notifications', (err, count) => {
  console.log(`Subscribed to ${count} channels`);
});

subscriber.on('message', (channel, message) => {
  const data = JSON.parse(message);
  console.log(`Received on ${channel}:`, data);
});

// Pattern subscription
subscriber.psubscribe('order.*');
subscriber.on('pmessage', (pattern, channel, message) => {
  console.log(`Pattern ${pattern}, Channel ${channel}:`, message);
});

// Publisher
await publisher.publish('orders', JSON.stringify({
  orderId: '123',
  status: 'created',
}));

Pub/Sub (Java - Spring)

@Configuration
public class RedisPubSubConfig {
    @Bean
    public RedisMessageListenerContainer container(
            RedisConnectionFactory connectionFactory) {
        RedisMessageListenerContainer container = new RedisMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);
        container.addMessageListener(orderListener(), new ChannelTopic("orders"));
        container.addMessageListener(orderPatternListener(), new PatternTopic("order.*"));
        return container;
    }

    @Bean
    public MessageListener orderListener() {
        return (message, pattern) -> {
            String body = new String(message.getBody());
            Order order = objectMapper.readValue(body, Order.class);
            processOrder(order);
        };
    }
}

@Service
public class OrderPublisher {
    @Autowired
    private StringRedisTemplate redisTemplate;

    public void publishOrder(Order order) {
        redisTemplate.convertAndSend("orders",
            objectMapper.writeValueAsString(order));
    }
}

Pub/Sub (Python)

import redis
import json

r = redis.Redis(host='localhost', port=6379, decode_responses=True)

# Subscriber (run in thread)
def subscriber():
    pubsub = r.pubsub()
    pubsub.subscribe('orders')
    pubsub.psubscribe('order.*')

    for message in pubsub.listen():
        if message['type'] in ('message', 'pmessage'):
            data = json.loads(message['data'])
            print(f"Received: {data}")

# Publisher
r.publish('orders', json.dumps({'orderId': '123', 'status': 'created'}))

Stream Commands Reference

When NOT to Use This Skill

• Guaranteed message delivery - Pub/Sub is fire-and-forget
• Complex routing patterns - RabbitMQ is better
• High-throughput event sourcing - Kafka provides better throughput
• Multi-datacenter replication - Kafka or Pulsar handle this better

Anti-Patterns

Quick Troubleshooting

Production Checklist

• Authentication enabled
• TLS configured
• Sentinel/Cluster for HA
• Stream trimming configured
• Consumer group monitoring
• Pending message handling
• Memory limits set
• Persistence configured (AOF)

Monitoring Metrics

Reference Documentation

Available topics: basics, pubsub, streams, patterns