I am trying to understand the reason for buffering incoming request (client_body_buffer_size) in which nginx would either keep request in memory or write to file client_body_temp_path (based on request size).

What are the performance advantages and/or technical challenges to such an approach as opposed to piping directly (even for smaller requests) to unbuffered piping to remote server e.g. http://tengine.taobao.org/

Nginx allows disabling upstream (to client) buffering in which response is sent to the client synchronously while it is receiving it, why not the opposite is possible? What are the technical challenges/pros/cons of writing to disk (client_body_temp_path) or in-memory buffer (client_body_buffer_size)?

Please share your thoughts.

Thanks