Sse

Kind: Function

Source: packages/common/decorators/http/sse.decorator.ts

Part of: Common

Declares this route as a Server-Sent-Events endpoint

Sse() declares a controller route as a Server-Sent Events (SSE) endpoint. It configures the route to handle GET requests and marks it for streaming event data to connected clients, typically through an RxJS Observable.

Signature

ts
function Sse(path: string, options: { [METHOD_METADATA]?: RequestMethod }): MethodDecorator

Parameters

Returns: MethodDecorator

Diagram

mermaid
graph LR
  Client[Browser or SSE Client] -->|GET /events| Controller[Controller Method]
  Controller -->|@Sse()| Nest[NestJS SSE Handler]
  Nest -->|Observable stream| Client

Usage

ts
import { Controller, MessageEvent, Sse } from '@nestjs/common';
import { interval, map, Observable } from 'rxjs';

@Controller('notifications')
export class NotificationsController {
  @Sse('stream')
  streamNotifications(): Observable<MessageEvent> {
    return interval(1000).pipe(
      map((count) => ({
        data: {
          message: `Notification ${count}`,
          timestamp: new Date().toISOString(),
        },
      })),
    );
  }
}

ts
const events = new EventSource('/notifications/stream');

events.onmessage = (event) => {
  console.log(JSON.parse(event.data));
};

AI Coding Instructions

• Use @Sse() only on controller methods that return an RxJS Observable stream of SSE-compatible event objects.
• Return event payloads using the MessageEvent shape, typically { data: ... }, and optionally include id, type, or retry.
• Keep SSE streams long-lived; ensure subscriptions are cleaned up when clients disconnect or when the application shuts down.
• Use a normal @Get() endpoint for request-response APIs; SSE is intended for one-way server-to-client updates.
• Ensure clients connect with EventSource or another client that supports the text/event-stream protocol.

Used by

2 references from 2 files. Each is a place in this repository where the symbol is actually used — go read one rather than trusting an example.

Imported by (2)

• PassthroughInterceptor — integration/nest-application/sse/src/app.controller.ts:28
• AppController — sample/28-sse/src/app.controller.ts:8