Server-sent events

Server-sent events let you push data to the client. It's a simple way to send data from the server to the client. The data is sent as a stream of messages, with an optional event name and id. It's a simple way to send data from the server to the client.

Installation

Before using the Server-sent events, we need to install the @tsed/sse module.

npm

npm install --save @tsed/sse

yarn

yarn add --save @tsed/sse

pnpm

pnpm add --save @tsed/sse

bun

bun add --save @tsed/sse

Then add the following configuration in your Server:

import {Configuration} from "@tsed/di";
import "@tsed/sse"; // import sse Ts.ED module

@Configuration({
  acceptMimes: ["application/json", "text/event-stream"]
})
export class Server {}

WARNING

There is a known issue with the compression middleware. The compression middleware should be disabled to work correctly with Server-sent events.

Features

• Support decorator usage to enable event-stream on an endpoint,
• Support Node.js stream like EventEmmiter to emit events from your controller to your consumer,
• Support Observable from rxjs to emit events from your controller to your consumer.
• Support @tsed/json-mapper to serialize your model before sending it to the client.
• Gives an API compatible with Express.js and Koa.js.

Enable event-stream

To enable the event-stream on an endpoint, you need to use the @EventStream() decorator on a method of a controller.

import {Controller} from "@tsed/di";
import {Get} from "@tsed/schema";
import {EventStream, EventStreamCtx} from "@tsed/sse";

@Controller("/sse")
export class MyCtrl {
  @Get("/events")
  @EventStream()
  events(@EventStreamCtx() eventStream: EventStreamCtx) {
    let intervalId: ReturnType<typeof setInterval>;

    eventStream.on("close", () => {
      clearInterval(intervalId);
    });

    eventStream.on("end", () => {
      clearInterval(intervalId);
    });

    intervalId = setInterval(() => {
      // Ts.ED support Model serialization using json-mapper here
      eventStream.emit("event", new Date());
    }, 1000);
  }
}

Stream events

You can use Node.js stream like EventEmmiter to emit events from your controller to your consumer:

import {EventStream} from "@tsed/sse";
import {Controller} from "@tsed/di";
import {Get} from "@tsed/schema";

@Controller("/sse")
export class MyCtrl {
  private eventEmitter = new EventEmitter();

  $onInit() {
    setInterval(() => {
      this.eventEmitter.emit("message", new Date());
    }, 1000);
  }

  @Get("/events")
  @EventStream()
  events() {
    return this.eventEmitter;
  }
}

Observable

You can also use Observable from rxjs to emit events from your controller to your consumer:

import {Controller} from "@tsed/di";
import {Get} from "@tsed/schema";
import {EventStream} from "@tsed/sse";
import {Observable} from "rxjs";

@Controller("/sse")
export class MyCtrl {
  @Get("/events")
  @EventStream()
  events() {
    const observable = new Observable((observer) => {
      setInterval(() => {
        observer.next(new Date());
      }, 1000);
    });

    return observable;
  }
}

Author

Maintainers Help wanted