Distributed Pub/Sub with Redis

Goal: Run multiple app replicas with cross-instance messaging.

Install

npm install svelte-adapter-uws-extensions ioredis

Set up the Redis client

// src/lib/server/redis.js
import { createRedisClient, createPubSub } from 'svelte-adapter-uws-extensions/redis';

export const redis = createRedisClient({
  url: process.env.REDIS_URL || 'redis://localhost:6379'
});
export const bus = createPubSub(redis);

Wire it into hooks

// src/hooks.ws.js
import { createMessage } from 'svelte-realtime/server';
import { bus } from '$lib/server/redis';

export function upgrade() {
  return { id: crypto.randomUUID() };
}

export function open(ws, { platform }) {
  bus.activate(platform);
}

export const message = createMessage({
  platform: (p) => bus.wrap(p)
});

Now ctx.publish() in any live() function reaches subscribers on all instances, not just the local one.

Run multiple replicas

SO_REUSEPORT=1 node build &
SO_REUSEPORT=1 node build &

Both instances share port 443. Redis forwards publishes between them.

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