Fastify SSE Plugin

Fastify plugin for sending Server-sent events.

For fastify@2.x use fastify-sse-v2@1.x!

How to use?

yarn add fastify-sse-v2

Register fastify-sse-v2 plugin into your fastify instance:

import {FastifySSEPlugin} from "fastify-sse-v2";

const server = fastify();
server.register(FastifySSEPlugin);

Sending events from AsyncIterable source

import {FastifySSEPlugin} from "fastify-sse-v2";

const server = fastify();
server.register(FastifySSEPlugin);

server.get("/", function (req, res) {
    res.sse((async function * source () {
          for (let i = 0; i < 10; i++) {
            sleep(2000);
            yield {id: String(i), data: "Some message"};
          }
    })());
});

Sending events from EventEmmiters

Using EventIterator dependency:

import {FastifySSEPlugin} from "fastify-sse-v2";
import EventIterator from "event-iterator";

const server = fastify();
server.register(FastifySSEPlugin);

server.get("/", function (req, res) {
    const eventEmitter = new EventEmitter();
    res.sse(new EventIterator(
                (push) => {
                  eventEmitter.on("some_event", push)
                  return () => eventEmitter.removeEventListener("some_event", push)
                }
        )
    );
});

Without additional dependency (not supported in all nodejs versions:

import {FastifySSEPlugin} from "fastify-sse-v2";
import {on} from "events";

const server = fastify();
server.register(FastifySSEPlugin);

server.get("/", function (req, res) {
    res.sse(
  (async function* () {
    for await (const event of on(eventEmmitter, "update")) {
      yield {
        type: event.name,
        data: JSON.stringify(event),
      };
    }
  })()
);
});

Note

• to remove event listeners (or some other cleanup) when client closes connection, you can listen on fastify's req.raw connection close event: