Connection Management

Proper connection configuration is critical for production reliability.

Connection Pool Sizing

Formula

pool_size = (concurrent_requests × redis_ops_per_request) / ops_per_connection_per_second

Guidelines

Application Size	Min Pool	Max Pool
Small (<100 RPS)	5	10
Medium (100-1000 RPS)	10	50
Large (1000-10000 RPS)	50	200

RedisModule.forRoot({
  clients: {
    host: 'redis',
    port: 6379,
    // Connection pool settings
    maxRetriesPerRequest: 3,
    enableReadyCheck: true,
    // ioredis doesn't have traditional pool
    // It uses single connection with pipelining
    // For true pooling, use multiple clients
  },
})

Multiple Clients Pattern

RedisModule.forRoot({
  clients: {
    default: {
      host: 'redis',
      port: 6379,
    },
    cache: {
      host: 'redis-cache',
      port: 6379,
    },
    locks: {
      host: 'redis-locks',
      port: 6379,
    },
  },
})

Timeout Configuration

Timeout Types

Timeout	Default	Purpose
Connect	10s	Initial connection
Command	0 (none)	Individual command
Socket	0 (none)	Network socket

{
  host: 'redis',
  port: 6379,
  connectTimeout: 10000,    // 10 seconds
  commandTimeout: 5000,     // 5 seconds per command
  // For socket timeout, use network-level config
}

Recommended Timeouts

Environment	Connect	Command
Local dev	5s	None
Cloud (same region)	10s	5s
Cross-region	30s	10s

Retry Strategy

Exponential Backoff

{
  retryStrategy: (times) => {
    if (times > 10) {
      // Stop retrying after 10 attempts
      return null;
    }
    // Exponential backoff: 100, 200, 400, 800, 1600, 3000, 3000...
    return Math.min(times * 100, 3000);
  },
}

With Jitter

{
  retryStrategy: (times) => {
    if (times > 10) return null;
    const delay = Math.min(times * 100, 3000);
    // Add ±20% jitter
    return delay + (Math.random() - 0.5) * delay * 0.4;
  },
}

Keep-Alive

Prevent connection drops in cloud environments:

{
  host: 'redis',
  port: 6379,
  keepAlive: 30000,  // Send keepalive every 30s
  noDelay: true,     // Disable Nagle's algorithm
}

TLS Configuration

{
  host: 'redis',
  port: 6379,
  tls: {
    // For self-signed certs
    rejectUnauthorized: false,
    // Or with CA
    ca: fs.readFileSync('ca.crt'),
  },
}

Sentinel Configuration

{
  sentinels: [
    { host: 'sentinel-1', port: 26379 },
    { host: 'sentinel-2', port: 26379 },
    { host: 'sentinel-3', port: 26379 },
  ],
  name: 'mymaster',
  sentinelPassword: 'sentinel-password',
  password: 'redis-password',
}

Cluster Configuration

{
  // ioredis cluster mode
  startupNodes: [
    { host: 'node-1', port: 6379 },
    { host: 'node-2', port: 6379 },
    { host: 'node-3', port: 6379 },
  ],
  redisOptions: {
    password: 'password',
  },
  scaleReads: 'slave',  // Read from replicas
}

Connection Events

@Injectable()
export class RedisEventListener implements OnModuleInit {
  constructor(@InjectRedis() private redis: Redis) {}

  onModuleInit() {
    this.redis.on('connect', () => {
      this.logger.log('Redis connected');
    });

    this.redis.on('ready', () => {
      this.logger.log('Redis ready');
    });

    this.redis.on('error', (err) => {
      this.logger.error('Redis error', err);
    });

    this.redis.on('close', () => {
      this.logger.warn('Redis connection closed');
    });

    this.redis.on('reconnecting', () => {
      this.logger.log('Redis reconnecting');
    });
  }
}

Monitoring Connections

# Active connections
redis_connected_clients

# Connection pool utilization (if using pool)
redis_pool_active / redis_pool_max

# Connection errors
rate(redis_connection_errors_total[5m])

# Command latency
histogram_quantile(0.99, redis_command_duration_seconds)

Troubleshooting

Symptom	Possible Cause	Solution
Connection timeout	Network/firewall	Check connectivity
Command timeout	Slow command/load	Check slow log
Connection refused	Redis down	Check Redis status
Too many connections	Pool exhausted	Increase pool size

Next Steps

• Deployment — Topology selection
• Tuning — Performance optimization