Can't get SSE to work behind Nginx

[malteo]

I'm trying to serve the web interface through a Nginx reverse proxy, but the EventSource request is failing after not receiving anything for a couple of minutes with a 504 timeout.

Everything works in static interfaces (like the admin one) or when directly accessing the Django server.

These are the relevant Nginx config parts:

location ^/eventsource {
    proxy_pass http://localhost:8000;
    proxy_buffering off;
    proxy_cache off;
    proxy_set_header Host $host;

    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    proxy_http_version 1.1;
    chunked_transfer_encoding off;
}
location / {
    proxy_pass http://localhost:8000;
}

Have you managed to get it working? How's your deployment setup?

[ipmb]

Hi Mateo, it seems to work well on https://botbot.me. Here's the setup we have (using uWSGI behind Nginx):

upstream eventsource-botbot-backend {
  server unix:/var/run/uwsgi/eventsource_botbot.sock fail_timeout=30s;
}
...
location /eventsource {
    include uwsgi_params;
    uwsgi_pass eventsource-botbot-backend;
    uwsgi_buffering off;
    chunked_transfer_encoding off;
    proxy_cache off;
  }

We actually run a separate uwsgi worker under gevent to serve these requests. I'm not 100% sure that is necessary, but here's the relevant settings we're using there:

gevent = 1000
async = 100
gevent-monkey-patch

Keep us posted on what you find out. We should document some recommendations here.

[malteo]

I'm trying a similar setup, using a single uwsgi worker

uwsgi --gevent 1000 --async 100 --gevent-monkey-patch --socket botbot.sock --wsgi-file botbot/wsgi.py

and a single location in Nginx

upstream botbot {
    server unix:///path/to/botbot.sock fail_timeout=30s;
}

location / {
    include uwsgi_params;
    uwsgi_pass botbot;
    uwsgi_buffering off;
    chunked_transfer_encoding off;
    proxy_cache off;
}

still getting the timeouts though :(

I guess I'll wait for the deployment documentation...

[ipmb]

@malteo do you see the same issue on the channels on https://botbot.me ? I'd love to help you get this resolved, but want to make sure we have it right first :)

[malteo]

@ipmb you're right, it happens on botbot.me too! Just go on a channel without much traffic and wait ~60 seconds with (I'm using Firefox) the web console open and you'll see a 504 from Nginx and the page stops live-updating.

I guess the EventSource needs a sort of keep-alive ping or something...

[ipmb]

Give this a shot...

  location /eventsource {
    include uwsgi_params;
    uwsgi_pass eventsource-botbot-backend;
    uwsgi_buffering off;
    chunked_transfer_encoding off;
    proxy_cache off;
    access_log  /var/log/nginx/eventsource_botbot.access.log;
    error_page 504 =200 @eventsource-close-graceful;
  }

  location @eventsource-close-graceful {
    add_header Content-Type text/event-stream;
    return 200;
  }

It catches the timeout and returns a response that SSE is happy with.

[malteo]

Yes! Thank you