Confusion about rewritten uri passed to a fastcgi program

[Maxim Dounin]

Hello!

On Wed, Jan 09, 2019 at 03:05:22PM -0800, Mark Sellers wrote:

> 
> My module (ngx_http_fastimg_module) rewrites the uri of an image request. If the image is not yet in the filesystem, then it (using try_files) calls a fastcgi  (fastimg_fcgi)  that creates the image, serves it, and saves it in the file system.
> 
> I have noticed something that I don’t understand. When the fastcgi program is executed, it receives the original uri in the REQUEST_URI fastcgi param, and not the rewritten uri.
> 
> I also notice that the rewritten uri is available in the DOCUMENT_URI fastcgi param.
> 
> Is this what you would expect?

What is sent in FastCGI parameters is determined by the 
fastcgi_param directives used in your configuration, see 
http://nginx.org/r/fastcgi_param.  The example/default 
fastcgi_params file as shipped with nginx contains

fastcgi_param  REQUEST_URI        $request_uri;
fastcgi_param  DOCUMENT_URI       $document_uri;

so the REQUEST_URI param will get the original URI as sent by the 
client, and the rewritten URI will be available in DOCUMENT_URI, 
exactly as your observe.

-- 
Maxim Dounin
http://mdounin.ru/