• WebSocket과 유사한 효과를 낼 수 있는 방식
• Spring WebFlux 사용시 더 깔끔하다.

• For Server-Sent Events (SSE) what Nginx proxy configuration is appropriate? - Server Fault
• ruby - EventSource / Server-Sent Events through Nginx - Stack Overflow
• wandenberg/nginx-push-stream-module: A pure stream http push technology for your Nginx setup. Comet made easy and really scalable.
• 서버측에서 X-Accel-Buffering: no 응답 헤더를 내려주면 SSE 커넥션만 버퍼링 방지.

@RequestMapping("/sseExamples")
public SseEmitter getRealTimeJudgeResultAction(HttpServletResponse response) throws IOException {
    // ....
	response.addHeader("X-Accel-Buffering", "no");
	SseEmitter sseEmitter = new SseEmitter();
    // ....
    sseEmitter.send("Established");
	return sseEmitter;
}

• 아니면 nginx 의 SSE 관련 url 프록시에 대해서만 proxy_buffering off; 설정.

location /path/to/sse {
  proxy_pass http://chat_dev_upstream;
  proxy_buffering off;
  proxy_cache off;
  proxy_set_header Host $host;
  proxy_set_header Connection '';
  proxy_http_version 1.1;
  chunked_transfer_encoding off;
}

• Spring5에서 HTTP Streaming | 기록은 재산이다
• Spring MVC - HTTP Streaming using ResponseBodyEmitter
• Processing streaming data with Spring WebFlux – Nithin Mallya – Medium
• Spring MVC Streaming and SSE Request Processing | Baeldung
• Server-Sent Events in Spring | Baeldung
• Event Streaming Using Spring WebFlux - DZone Java