I have a similar problem here.
My handler module in Nginx is supposed to intercept POST requests, analyse it and send response( the response body maybe larger than 64k).
Of course, I used ngx_http_read_client_request_body to register my request_body_handler.
The request_body_handler does some computing and calls ngx_http_output_filter(r,out) to send the response.
Here is the problem. If this response is less than 64k, it works fine. But if this response is larger than 64k, the ngx_http_output_filter will return NGX_AGAIN. However, since it's in the request_body_handler function and it has nothing to return. I can't figure out how to handle this NGX_AGAIN.

Can anyone help me out? Thanks a lot.