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Scaling Server-Sent Events

By default, SseManager stores active HTTP connections in the server's local memory. In a distributed environment (e.g., Kubernetes cluster or mult-instance deployment), an event broadcast on Server A will not reach a user connected to Server B.

To solve this, node-auth provides a distribution adapter pattern.

The Solution: ISseDistributor​

You can provide an implementation of the ISseDistributor interface to synchronize events across instances.

1. Implement the Distributor (e.g. Redis)​

import { ISseDistributor } from 'awesome-node-auth';
import { createClient } from 'redis';

export class RedisSseDistributor implements ISseDistributor {
  private pub = createClient();
  private sub = createClient();

  async publish(topic: string, event: any): Promise<void> {
    await this.pub.publish('sse-channel', JSON.stringify({ topic, event }));
  }

  async subscribe(callback: (topic: string, event: any) => void): Promise<void> {
    await this.sub.subscribe('sse-channel', (message) => {
      const { topic, event } = JSON.parse(message);
      callback(topic, event);
    });
  }
}

2. Configure AuthTools​

Pass the distributor in the sseOptions:

const tools = new AuthTools(bus, {
  sse: true,
  sseOptions: {
    distributor: new RedisSseDistributor(),
  },
});

How it works​

  1. Broadcast: When you call tools.notify('topic', data), the manager publishes the event to the distributor instead of just sending it locally.
  2. Sync: The distributor sends the message to all instances of your application.
  3. Local Delivery: Every instance receives the message via subscribe() and forwards it to its own local HTTP connections matching that topic.

This ensures that real-time notifications work seamlessly across your entire cluster.