Server-sent events

You want to push live updates to a browser over a long-lived HTTP connection. Call ctx.sse(producer) on FlareHttpContext. Flare returns a FlareResponse with Content-Type: text/event-stream and runs your producer with an SseWriter.

Basic tick loop

import { FlareHost } from "@flare-ts/core";
import { node } from "@flare-ts/core/node";

function delay(ms: number) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

const host = new FlareHost(node);

host.http.get("/events", (ctx) => {
  return ctx.sse(async (sse, signal) => {
    while (!signal.aborted) {
      await sse.send({ event: "tick", data: { now: Date.now() } });
      await delay(1000);
    }
  });
});

const app = host.build();
app.run();

The signal argument is the request’s AbortSignal. Stop the loop when the client disconnects.

SseWriter API

Method	Purpose
sse.send(event)	Send one event frame (required data; optional event, id, retry)
sse.comment(text)	Send a comment frame (keep-alive; clients ignore)

send and comment return promises that resolve when the transport has pulled the frame, so awaiting each call paces the producer (at most one frame buffered).

From a controller

import { ControllerBase, FlareHost } from "@flare-ts/core";
import { Get } from "@flare-ts/core/decorators";
import { node } from "@flare-ts/core/node";

class EventsController extends ControllerBase {
  public static override deps = [];
  public static override state = [];

  @Get("")
  stream() {
    return this.ctx.sse(async (sse, signal) => {
      await sse.send({ data: { hello: "world" } });
      await sse.comment("keep-alive");
      while (!signal.aborted) {
        await sse.send({ event: "ping", data: {} });
        await new Promise((r) => setTimeout(r, 5000));
      }
    });
  }
}

const host = new FlareHost(node);
host.http.controller("/events", EventsController);

const app = host.build();
app.run();

Notes

• SSE is a response mechanism. You still register a normal GET route.
• The stream ends when the producer settles or the request aborts.
• For generic byte streaming (not the SSE wire format), see Streaming bodies.

Related

• Requests: ctx.sse on FlareHttpContext
• API: SseWriter