Basic websocket message passer for Cloudflare Durable Objects

index.ts

declare global {
  interface Env {
    readonly CASTER: DurableObjectNamespace;
    readonly RATE_LIMITER: {
      limit(opt: { key: string }): Promise<{ success?: boolean }>;
    };
  }
}

// noinspection JSUnusedGlobalSymbols
export class Caster {
  constructor(private readonly state: DurableObjectState) {
    this.state.setWebSocketAutoResponse(
      new WebSocketRequestResponsePair("ping", "pong"),
    );
  }

  async fetch(request: Request) {
    const url = new URL(request.url);

    switch (request.method) {
      case "GET": {
        if (request.headers.get("upgrade") !== "websocket") {
          return new Response(null, { status: 422 });
        }

        const tags = url.searchParams.getAll("t");
        const pair = new WebSocketPair();
        this.state.acceptWebSocket(
          pair[1],
          tags.length >= 0 ? tags : undefined,
        );
        return new Response(null, { status: 101, webSocket: pair[0] });
      }

      case "POST": {
        if (
          !request.headers.get("content-type")?.startsWith("application/json")
        ) {
          return new Response(null, { status: 422 });
        }

        const tag = url.searchParams.get("t");
        let payload: any;
        try {
          payload = await request.json();
        } catch {
          return new Response(null, { status: 400 });
        }
        const clients = this.state.getWebSockets(tag ?? undefined);
        const message = JSON.stringify(payload);
        clients.forEach((client) => client.send(message));
        return new Response(null, { status: 201 });
      }

      default:
        return new Response(null, { status: 422 });
    }
  }
}

// noinspection JSUnusedGlobalSymbols
export default {
  async fetch(request: Request, env: Env) {
    const url = new URL(request.url);
    const uuid = url.searchParams.get("id");
    if (!uuid) {
      return new Response(null, { status: 403 });
    }

    const { success } = await env.RATE_LIMITER.limit({ key: uuid });

    if (!success) {
      return new Response(null, { status: 429 });
    }

    const id = env.CASTER.idFromName(uuid);
    const caster = env.CASTER.get(id);
    return caster.fetch(request);
  },
};

wrangler.toml

name = "caster"
main = "index.ts"
compatibility_date = "2024-04-06"

[[unsafe.bindings]]
name = "RATE_LIMITER"
type = "ratelimit"
namespace_id = "1001"
simple = { limit = 100, period = 60 }

[[durable_objects.bindings]]
name = "CASTER"
class_name = "Caster"

[[migrations]]
tag = "v1"
new_classes = ["Caster"]

Basic websocket message passer.

# Connect
websocat 'wss://<worker>.worker.dev?id=foo'

# Connect with tags
websocat 'wss://<worker>.worker.dev?id=foo&t=user.create&t=user.delete'

# Post message
curlie 'https://<worker>.worker.dev?id=foo' value:=42
# Post message with tag
curlie 'https://<worker>.worker.dev?id=foo&t=user.delete' uid:=42

NOT MEANT FOR PUBLIC ROUTE. USE PROPER SERVICE BINDING OR ADD CUSTOM AUTH