mod_cgi for nginx - anyone?

Manlio Perillo manlio_perillo at
Sat Feb 7 23:38:41 MSK 2009

Igor Sysoev ha scritto:
> [...]
> nginx is not general purpose server, it's rather highload server.
> CGI is not compatible with highload: if you run Apache/CGI, then CGI
> will became bottleneck much earlier than Apache.

This is not a problem from the Nginx point of view.
Nginx should however put a limit on the number of concurrent CGI requests.
It can use a queue to store outgoing request, and if the queue grows too 
much return a 503 Service Unavailable, setting Retry-After to a 
reasonable (computed?) value.

No browser support 503 response, however.

> There are two ways to implement CGI inside nginx:
> 1) simple one: just fork()ing worker process that has received a request
> for CGI and exec() a CGI program. It's simple enough, but has a lot
> of overhead. Besides CGI programs will run with worker privilege only.

Nginx could use seteuid, instead of setuid.
So that it can reacquire root privileges.

As for CGI support, some time ago I was trying to implement it.
The idea was to use unix domain sockets (socketpair), and reusing the 
http_upstream module.

However I gave up, a lot of code for connection/upstream setup must be 
rewritten, and I hate to write boiler plate code; and expecially having 
to maintain it :).

In Nginx one can also easily close all current opened file descriptors, 
in child process; Nginx keeps all opened connection in the 
ngx_cycle->free_connections variable so one can write a closefrom function.

Regards  Manlio Perillo

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