Occasional "Offline" in BasicUI when proxying via nginx / connection timed out

Hi,
I am running OH 2.4 official and did set up an Nginx-Proxy to access my internal installation from the outside according to the Wiki.
All runs well besides an occasional “offline” in BasicUI and nginx error-log telling:

upstream timed out (110: Connection timed out) while reading upstream, client: xx.xx.xx.xx, server: openhab.xx.xx, request: “GET /rest/sitemaps/events/0846c4f0-ce6c-4606-b278-786aa03c2cee?sitemap=yyy&pageid=yyy HTTP/1.1”

I found related posts talking about the scheme (http/https) but this did not solve it.

Further analysis showed that the problem is only the event-stream XHR backchannel from OH via nginx to the browser.

Nginx does some default buffering/caching and that does not play well with the XHR streams. I real fix would probably be in the Runtime/Jetty to set an HTTP-header only for the XHR-backchannel like this

Cache-Control: no-cache;
X-Accel-Buffering: no;

as mentioned here.

As a workaround (that indeed works works for me) is to really disable any kind of buffering and a large timeout while proxying to OH:

    location / {
            proxy_pass                      http://your-openhab-server-and-port;
            proxy_buffering                 off;
            proxy_request_buffering         off;
            proxy_http_version              1.1;

            proxy_set_header                Host $http_host;
            proxy_set_header                X-Real-IP $remote_addr;
            proxy_set_header                X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header                X-Forwarded-Host $server_name;
            proxy_set_header                X-Forwarded-Proto $scheme; // or just "https" to force it

            client_body_buffer_size         0;
            client_max_body_size            0;
            proxy_max_temp_file_size        0;
            proxy_read_timeout              18000;
            proxy_send_timeout              18000;

            gzip                            off;
    }

If anybody else is experiencing these “offline” messages, please give my workaround a try and post your results here (so the wiki for proxying with nginx could be updated).

As this disables any buffering/caching of other stuff as well (sitemaps, icons and so on) it would be great to give this extra http-header a try (does not hurt other proxies or if no proxy is used at all).
I am not a Java-guy, so I can’t do it myself, but I could test a nightly/special build.

Thanks,
-Markus

A very late reply to your excellent post - unfortunately this doesn’t work for me… I still get offline messages and errors in the nginx log.