nginx upload client_max_body_size issue

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.

Does your upload die at the very end? 99% before crashing? Client body and buffers are key because nginx must buffer incoming data. The body configs (data of the request body) specify how nginx handles the bulk flow of binary data from multi-part-form clients into your app's logic.

The clean setting frees up memory and consumption limits by instructing nginx to store incoming buffer in a file and then clean this file later from disk by deleting it.

Set body_in_file_only to clean and adjust buffers for the client_max_body_size. The original question's config already had sendfile on, increase timeouts too. I use the settings below to fix this, appropriate across your local config, server, & http contexts.

client_body_in_file_only clean;
client_body_buffer_size 32K;

client_max_body_size 300M;

sendfile on;
send_timeout 300s;