nginx upload client_max_body_size issue

Question

I'm running nginx/ruby-on-rails and I have a simple multipart form to upload files. Everything works fine until I decide to restrict the maximum size of files I want uploaded. To do that, I set the nginx client_max_body_size to 1m (1MB) and expect a HTTP 413 (Request Entity Too Large) status in response when that rule breaks.

The problem is that when I upload a 1.2 MB file, instead of displaying the HTTP 413 error page, the browser hangs a bit and then dies with a "Connection was reset while the page was loading" message.

I've tried just about every option there is that nginx offers, nothing seems to work. Does anyone have any ideas about this?

Here's my nginx.conf:

worker_processes  1;
timer_resolution  1000ms;
events {
    worker_connections  1024;
}

http {
    passenger_root /the_passenger_root;
    passenger_ruby /the_ruby;

    include       mime.types;
    default_type  application/octet-stream;

    sendfile           on;
    keepalive_timeout  65;

    server {
      listen 80;
      server_name www.x.com;
      client_max_body_size 1M;
      passenger_use_global_queue on;
      root /the_root;
      passenger_enabled on;

      error_page 404 /404.html;
      error_page 413 /413.html;    
    }    
}

Thanks.

---

**Edit**

Environment/UA: Windows XP/Firefox 3.6.13

Answer 1

nginx "fails fast" when the client informs it that it's going to send a body larger than the client_max_body_size by sending a 413 response and closing the connection.

Most clients don't read responses until the entire request body is sent. Because nginx closes the connection, the client sends data to the closed socket, causing a TCP RST.

If your HTTP client supports it, the best way to handle this is to send an Expect: 100-Continue header. Nginx supports this correctly as of 1.2.7, and will reply with a 413 Request Entity Too Large response rather than 100 Continue if Content-Length exceeds the maximum body size.