Events

Use primate/events for small in-memory event channels inside one running app process.

// services/ItemEvents.ts
import events from "primate/events";

type ItemEvent =
  | { type: "comment.created"; comment: { id: number; body: string } }
  | { type: "item.status.changed"; status: string };

export default events.channel<number, ItemEvent>();

Emit events with a key.

import ItemEvents from "@/services/ItemEvents";

ItemEvents.emit(item.id, {
  type: "comment.created",
  comment: { id: comment.id, body: comment.body },
});

Subscribe to events for a key. subscribe returns an unsubscribe function.

const unsubscribe = ItemEvents.subscribe(item.id, event => {
  console.log(event.type);
});

unsubscribe();

With SSE

Channels pair naturally with response.sse.

import ItemEvents from "@/services/ItemEvents";
import response from "primate/response";
import route from "primate/route";

export default route({
  get(request) {
    const item_id = Number(request.query.get("item"));

    return response.sse(source => {
      return ItemEvents.subscribe(item_id, event => {
        source.send(event.type, event);
      });
    });
  },
});

When the browser disconnects, Primate calls the function returned from response.sse, which unsubscribes from the channel.

Scope

primate/events is local and in-memory. It does not persist events and does not broadcast across multiple server processes or machines. If your app runs more than one instance, events only reach clients connected to the same instance that emitted them.