====== Spring HTTP Streaming ======
  * [[html:html5:websocket|WebSocket]]과 유사한 효과를 낼 수 있는 방식
  * [[springframework:webflux|Spring WebFlux]] 사용시 더 깔끔하다.

===== ServerSentEvent Reverse Proxy(nginx) 설정 =====
  * [[:nginx|Ngnix]] 같은 reverse proxy 사용시에 buffering 을 끄는 등의 별도 설정이 필요하다.


  * [[https://serverfault.com/questions/801628/for-server-sent-events-sse-what-nginx-proxy-configuration-is-appropriate|For Server-Sent Events (SSE) what Nginx proxy configuration is appropriate? - Server Fault]]
  * [[https://github.com/wandenberg/nginx-push-stream-module|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.
  * [[https://www.nginx.com/resources/wiki/start/topics/examples/x-accel/|nginx x-accel-* 헤더를 통한 응답 제어]]
<code java>
@RequestMapping("/sseExamples")
public SseEmitter getRealTimeJudgeResultAction(HttpServletResponse response) throws IOException {
    // ....
    response.addHeader("X-Accel-Buffering", "no");
    SseEmitter sseEmitter = new SseEmitter();
    // ....
    sseEmitter.send("Established");
    return sseEmitter;
}
</code>
<code>
# 응답 결과를 보면 X-Accel-Buffering: no 헤더가 출력됨.
curl -D - http://....
HTTP/1.1 200
X-Accel-Buffering: no
Content-Type: text/event-stream
Transfer-Encoding: chunked
...
</code>
  * nginx 의 SSE 관련 url 프록시에 대해서만 ''proxy_buffering off;'' 및 기타 설정.
  * [[https://stackoverflow.com/questions/13672743/eventsource-server-sent-events-through-nginx|ruby - EventSource / Server-Sent Events through Nginx - Stack Overflow]] - https://stackoverflow.com/a/13673298/1051402

<code>
location /path/to/sse {
  proxy_pass http://upstream;
  proxy_buffering off; # X-Accel-Buffering: no 와 같은 효과
  proxy_cache off;
  proxy_set_header Host $host;
  proxy_set_header Connection '';
  proxy_http_version 1.1;
  chunked_transfer_encoding off;
}
</code>
  * [[https://medium.com/tokopedia-engineering/server-sent-events-26f75e3a5ed2|Server Sent Events. File Upload Progress API using Server… | by Somesh Singh | Tokopedia Engineering | Medium]] : 좀 더 잘 설명돼 있는 듯.
===== 참고 =====
  * [[https://supawer0728.github.io/2018/03/15/spring-http-stereamings/|Spring5에서 HTTP Streaming | 기록은 재산이다]]
  * [[https://www.logicbig.com/tutorials/spring-framework/spring-web-mvc/http_streaming.html|Spring MVC - HTTP Streaming using ResponseBodyEmitter]]
  * [[https://medium.com/@nithinmallya4/processing-streaming-data-with-spring-webflux-ed0fc68a14de|Processing streaming data with Spring WebFlux – Nithin Mallya – Medium]]
  * [[https://www.baeldung.com/spring-mvc-sse-streams|Spring MVC Streaming and SSE Request Processing | Baeldung]]
  * [[https://www.baeldung.com/spring-server-sent-events|Server-Sent Events in Spring | Baeldung]]
  * [[https://dzone.com/articles/event-streaming-using-spring-webflux|Event Streaming Using Spring WebFlux - DZone Java]]