Nginx FastCGI question

Server NGINX
1

Hi,

When you run a FastCGI application behind Nginx does Nginx pass all the
HTTP request headers to the FastCGI server / app? Or do you need to
explicitly pass them using fastcgi_param?

If Nginx does pass them, does it pass them all or only a subset of the
request headers? The FastCGI specification is not at all clear on
whether the HTTP headers are passed or not.

Also in the same way I’ve read through the FastCGI specification and can
find no information in which states which entity is responsible for
generating all the HTTP response headers. I would assume it would be my
FastCGI app and Nginx just forwards it on but does Nginx add or modify
any headers after I have sent my response from my FastCGI app back to
Nginx?

Thanks.

2

In addition to what Maxim said some people do not realize that not all
headers are created equally and that something as inane as underscores
versus dashes causes it to break RFC and nginx need you to explicitly
tell
it that that’s okay:
http://nginx.org/en/docs/http/ngx_http_core_module.html#underscores_in_headers

Posted at Nginx Forum:

3

On 01/01/13 20:45, Maxim D. wrote:

If Nginx does pass them, does it pass them all or only a subset of
would be my FastCGI app and Nginx just forwards it on but does Nginx
it’s needed.

Thanks for that. The CGI RFC certainly seems more useful than the
FastCGI specification.

4

On 02/01/13 05:36, Ensiferous wrote:

In addition to what Maxim said some people do not realize that not all
headers are created equally and that something as inane as underscores
versus dashes causes it to break RFC and nginx need you to explicitly tell
it that that’s okay:
Module ngx_http_core_module

I’ll bear that in mind. Thanks.

5

Hello!

On Tue, Jan 01, 2013 at 06:21:02PM +0000, Some D. wrote:

Hi,

When you run a FastCGI application behind Nginx does Nginx pass all
the HTTP request headers to the FastCGI server / app? Or do you need
to explicitly pass them using fastcgi_param?

If Nginx does pass them, does it pass them all or only a subset of
the request headers? The FastCGI specification is not at all clear
on whether the HTTP headers are passed or not.

All HTTP request headers are passed to a FastCGI application by
default. You may modify/clear some by using the fastcgi_param
directive.

Also in the same way I’ve read through the FastCGI specification and
can find no information in which states which entity is responsible
for generating all the HTTP response headers. I would assume it
would be my FastCGI app and Nginx just forwards it on but does Nginx
add or modify any headers after I have sent my response from my
FastCGI app back to Nginx?

FastCGI relies on CGI here, so you should read RFC 3875 for basics,
see RFC 3875 - The Common Gateway Interface (CGI) Version 1.1. In short - you
are responsible for headers like “Content-Type”, but must not add
headers like “Transfer-Encoding”.

Response from a FastCGI backend is treated by nginx more or less
like any other response, so response headers will be modified if
it’s needed.

–
Maxim D.