webpage only can get the latest state of background process by refresh the webpage

Question

I have a painful problem. I use Flask-SocketIO to update the some states of background process onto webpage. For my example, my app is put in machine A with IP 170.8.8.8 monitoring port 5000, and I put nginx in machine B with IP 170.8.8.9 also monitoring port 5000. So I want to visit IP:5000 in B which skip to IP:5000 in A. The below is my nginx config in machine B:

upstream cuitccol.com{ #the name of server cluster
        server 170.8.8.8:5000 max_fails=5 fail_timeout=50s; #for the first web server
        }

    server {
        listen       5000;
        server_name  localhost;

        #charset koi8-r;

        #access_log  logs/host.access.log  main;

        location / {
            proxy_pass http://cuitccol.com;
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection "upgrade";
            proxy_set_header Host $host;
        } 

If I directly visit IP in A, the webpage of my browser can constantly updates the state of the background process. but if I visit B where nginx is put, the the webpage can not constantly updates the state, and I must refresh the webpage to get the next state. and the console of my browser has a mistake as below:

WebSocket connection to 'ws://170.8.8.9:5000/socket.io/?EIO=3&transport=websocket&sid=4a2ec29f7f834a0bb289b21f03c3e47c' failed: Error during WebSocket handshake: Unexpected response code: 200

I do not know where goes wrong. nginx or flask-socketio. Can you give some advises? thank you very much~

Answer 1

change your config to below

   location / {
        proxy_pass http://cuitccol.com;
        proxy_http_version 1.1;
    } 

   location /socket.io {
        proxy_pass http://cuitccol.com/socket.io;
        proxy_http_version 1.1;
        proxy_buffering off;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
    } 

And see if it helps. Upgrade headers should be used for Socket and not for rest of the endpoints