Asynchronous/multiplexing FastCGI for nginx (incl. ref server implementation)
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Asynchronous FastCGI.

Primarily a modified version of the Nginx FastCGI module which implements multiplexing of connections, allowing a single FastCGI server to handle many concurrent requests.

This paves the way for long-lived connections in web apps without wasting resources -- i.e. optimally you only need to run one server process per CPU (or one server with one thread per CPU) instead of one process per request.


  • nginx/ contains the modified ngx_http_fastcgi_module.c along with a "prefix" (conf, logs, etc) for running a test server.

  • servers/ contains a set of asynchronous FastCGI server implementations, most notably the original libevent-based server written with the purpose to test afcgi.


Nginx module

The nginx module is built by replacing the original ngx_http_fastcgi_module.c:

tar xzf nginx-0.8.29.tar.gz
cd nginx-0.8.29/src/http/modules
mv ngx_http_fastcgi_module.c ngx_http_fastcgi_module.c.dist
cp /path/to/afcgi/nginx/src/http/modules/ngx_http_fastcgi_module.c .
cd ../../..

This module has been developed for and tested with nginx version 0.8.29 and is still in an experimental stage. No warranties, no guarantees -- use at own risk ;)

Server reference implementation

The FCGI server reference implementation in servers/afcgitest is built by using regular make and linking against libevent:

cd /path/to/afcgi/servers/afcgitest

The last line assumes a FastCGI client (i.e. nginx) is connecting to port 5000 on

At the moment the Makefile is prepared for Mac OS X and contains a few lines which will not work in other environments. Simply remove or comment-out these lines when building on another platform:

# If Mac OS X:
CFLAGS += -arch i386
LDFLAGS += -arch i386


# If Mac OS X:
#CFLAGS += -arch i386
#LDFLAGS += -arch i386

OS X users: This assumes libevent is built for the i386 architecture. Your libevent library might use another architecture and then you should change the -arch argument value to match the architecture of libevent.

License & redistribution

Most parts of this software is licensed under the MIT license (see the LICENSE file for details) while the nginx module is licensed under the nginx license (details in the file nginx/LICENSE).

In short; you are free to use this software for commercial and non-commercial applictions as long as the license(s) and copyright notice(s) are properly reproduced. Read the LICENSEs files for details.


  • Rasmus Andersson

  • Igor Sysoev (author of the original, synchronous fastcgi module)