Error uploading large files (>2gb) through nginx reverse proxy to container

I am running an application in a docker container (https://github.com/filebrowser/filebrowser/) that I am trying to upload very large (>2) gb files to. The container exposes the app on a nonstandard port on localhost which I connect to through a reverse proxy (so I can run multiple apps on one machine). The problem is when I upload a file over 2097152 bytes it errors out. I can see that the files is fully uploaded to nginx and that it partially makes it to the contianerized app but then hangs for a long time at 2097152 bytes before erroring out causing the containerized app to give a unexpected EOF error. I suspect it's something wrong with nginx becuase when I upload a file to the containerized app directly it works fine. I've tried adding a variety of directives to the nginx config and am stumped. My nginx config for the site is:

server {
    server_name example.com;
    client_max_body_size    30g;
    proxy_buffer_size       1024k;
    proxy_buffers 4 1024k;
    proxy_busy_buffers_size 1024k;
    proxy_max_temp_file_size 10000m;
    proxy_connect_timeout   10000;
    proxy_send_timeout      10000;
    proxy_read_timeout      10000;
    send_timeout            10000;
    client_header_timeout   10000;
    client_body_timeout     10000;
    
    location / {
    proxy_pass http://localhost:8088/;
    proxy_http_version 1.1;
    proxy_cache_bypass $http_upgrade;

    proxy_set_header Upgrade           $http_upgrade;
    proxy_set_header Connection        "upgrade";
    proxy_set_header Host              $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-Proto $scheme;
    proxy_set_header X-Forwarded-Host  $host;
    proxy_set_header X-Forwarded-Port  $server_port;

    proxy_connect_timeout              10000s;
    proxy_send_timeout                 10000s;
    proxy_read_timeout                 10000s;
    }}

The error I get in nginx is:

2022/04/14 20:26:56 [error] 3286524#3286524: *13184 connect() failed (111: Connection refused) while connecting to upstream, client: xxx.xxx.xxx.xxx, server: example.com, request: "POST /api/resources/Fedora-KDE-Live-x86_64-35-1.2.iso?override=false HTTP/1.1", upstream: "http://[::1]:8088/api/resources/Fedora-KDE-Live-x86_64-35-1.2.iso?override=false", host: "example.com", referrer: "https://example.com/files/" 

Edit: After doing lots of digging, it seems that the solution was to remove the proxy_buffer_size, proxy_buffers, and proxy_busy_buffer_size and add proxy_request_buffer no; I don't know why this works but it does.

Simple answer:

• proxy_request_buffering off; fixes your issue because that is the only option that is relevant to uploads (requests).

All the other options apply only to downloads to the client (responses). Quoting from the docs:

• proxy_buffer_size

  ... size of the buffer used for reading the first part of the response received from the proxied server ...

• proxy_buffers

  ... buffers used for reading a response from the proxied server ...

• proxy_busy_buffers_size

  ... When buffering of responses from the proxied server ...

I also hit the 2GB limit. proxy_request_buffering off; did not work for me. Adding the two options below to the / location is the only thing that did work for me:

proxy_buffering      off;
client_max_body_size 0;