Website OK on Firefox but not on Safari (kCFErrorDomainCFNetwork error 303) neither Chrome (net::ERR_SPDY_PROTOCOL_ERROR)

We have had a problem with nginx and HTTP/2 which resulted in the same error in Safari and a similar error in Internet Explorer.

When we tweaked the nginx buffers to be:

http2_max_field_size 16k;http2_max_header_size 128k;

the issue was gone.

My problem was disappearing after reloading the page. So it always shows the error on the first load after nginx reload. Error log shown:

2018/10/21 06:26:54 [crit] 9439#9439: *54 open() "/var/cache/nginx/proxy_temp/2/01/0000000012" failed (13: Permission denied) while reading upstream, client: 37.9.113.93, server: anvileight.com, request: "GET /ar/ HTTP/1.1", upstream: "http://unix:/run/a8/gunicorn.sock:/ar/", host: "anvileight.com"

My problem was that nginx has directive:

user       deploy deploy;

and indeed, permissions on that folder were incorrect:

ll /var/cache/nginx/proxy_temptotal 40Kdrwx------ 102 www-data www-data 4.0K Jan  6  2018 0drwx------ 102 www-data www-data 4.0K Jan  6  2018 1

When I changed it to

user       www-data www-data;

problem has gone

The problem is a result of Safari holding too much local data for the site in question and failing to deal with that correctly. I use archive.org a lot so I had lots of LocalStorage and Cookie data for that site. The fact that this data is only in my main browser Safari and not in any of my other browsers explains why they could browse the site just fine.

So, the solution:

1. Go into Safari > Preferences > Privacy
2. Search for the affected domain name (for me this was "archive.org")
3. Click Remove
4. The problem goes away!

Here's a video showing the problem before and after: https://imgur.com/gallery/d1P1FCi