@setu-ts/realtime-backplane-plugin — share room and channel broadcasts

Add it: setu add realtime-backplane adds it and wires RealtimeBackplanePlugin() in a recognized functional config. It provides CAPABILITIES.REALTIME_BACKPLANE (IRealtimeBackplane); use a cross-process transport for replicas.

Connect replicas through Redis

Replace the default registration in setu.config.ts:

import { RealtimeBackplanePlugin } from '@setu-ts/realtime-backplane-plugin';

export const backplane = RealtimeBackplanePlugin({
  transport: 'redis', url: 'redis://localhost:6379', topic: 'setu-ts.realtime',
});

Broadcast through the existing SSE service

With SSE registered, use its channel API; it publishes through the backplane automatically:

import { CAPABILITIES } from '@setu-ts/common';
import type { IRouterApi, ISseService } from '@setu-ts/common';

export function registerDeployRoutes(router: IRouterApi): void {
  router.post('/deployments', {
    handler: (ctx) => {
      const sse = ctx.services.get<ISseService>(CAPABILITIES.SSE);
      sse.channel('deploys').publish({ event: 'deployment', data: { status: 'live' } });
      return ctx.response.json({ accepted: true });
    },
  });
}

Behaviour the types do not show

• The default 'memory' transport shares frames only inside one process. Its default bus name is default; a bare registration does not connect replicas.
• Redis needs two connections: injected client and subscriber must be supplied together. Otherwise the transport lazily loads ioredis and builds both.
• Instances must share topic, default setu-ts.realtime; origin defaults to a generated id and prevents replaying an instance’s own frames.
• The plugin orders before its WebSocket and SSE consumers. Their room/channel broadcasts fan out automatically; membership counts stay local and exclusions apply only on the sender.
• Health remains up during a backend outage; inspect data.reachable. Local delivery continues.
• Redis commands on built connections have a 15000 ms bound. A timed-out publication can still arrive later, so do not treat failure as proof of non-delivery.

Other options

• 'messaging' requires CAPABILITIES.MESSAGING; its reach depends on that broker’s transport.
• 'custom' uses instance: IRealtimeBackplane; 'memory' accepts a named bus.
• commandTimeoutMs: 0 disables the Redis bound; diagnostics observes transport activity and localNotice: false suppresses the memory notice.