Hi,

I deployed a Flask app on an Ubuntu 18.04 VPS using Gunicorn and Nginx as the driving servers. I followed this official tutorial for help. I am using a separate server block for my domain on Nginx and not using the default.

The website loads just fine on my domain. However, there are two issues –

1. The JavaScript elements are often unresponsive or take too long to respond.
2. On a particular route, the app seems to enter an infinite page reload loop.

Interestingly, none of these issues exist when I run the Gunicorn instance on localserver (port 5000).

Details about the infinitely reloading route are –

It’s a separate blueprint for displaying and browsing tags that looks like this - @tags_bp.route('/<language>/tags/<selected_tags>', methods=['GET']).
This route renders a template with some responses.
There’s an allied route - @tags_bp.route('/<language>/tags/<selected_tags>/<variable_ID>', methods=['GET']) - that only returns a JSON object response to AJAX calls made by the JavaScript that then gets rendered on the page.

I am using the default .serivce and location block as shown below.
/etc/systemd/system/myproject.service

[Unit]
Description=Gunicorn instance to serve myproject
After=network.target

[Service]
User=sammy
Group=www-data
WorkingDirectory=/home/<USER>/myproject
Environment="PATH=/home/<USER>/myproject/myprojectenv/bin"
ExecStart=/home/<USER>/myproject/myprojectenv/bin/gunicorn --workers 3 --bind unix:myproject.sock -m 007 wsgi:app

[Install]
WantedBy=multi-user.target

/etc/nginx/sites-available/myproject

server {
    listen 80;
    server_name your_domain www.your_domain;

    location / {
        include proxy_params;
        proxy_pass http://unix:/home/<USER>/myproject/myproject.sock;
    }
}

I am suspecting the error is occurring somewhere between Nginx and Gunicorn. I have tried modifying the proxy_headers using this configuration on the Flask documentation but that didn’t help either.

Would greatly appreciate any help to fix this!

Cheers.