Combining Apache and Perl

This month Mr. Lerner gives us a look at mod-perl, a module for the Apache web server.

The CGI (Common Gateway Interface) standard has been around for several years and is beginning to show its age. CGI is great because all web servers support it, programmers can write in any language, and programs can be portable across a large number of platforms. Netscape's NSAPI and Microsoft's ISAPI bind more tightly to their respective web servers, but programmers interested in using these APIs are much more restricted than with CGI.

A particularly big problem with CGI is its inefficiency. Each invocation of a CGI program creates a new process on the server. If you write CGI programs in Perl, you are starting a new copy of Perl each time a CGI program runs, using additional memory and processor time. Wouldn't it be nice if we could have the flexibility of CGI programs without having to use all of those system resources? Better yet, wouldn't it be great if we could use our existing CGI programs in such a framework with little or no modification? The answer, of course, is “yes”; even as hardware continues to get cheaper and more powerful, it seems silly to be wasting memory and CPU time unnecessarily.

This month, we look at mod_perl--one of the proposed solutions to this problem. mod_perl is a module for the popular and powerful Apache web server, which runs on many operating systems including Linux. At the most basic level, mod_perl makes it possible to run server-side Perl programs more efficiently than when using the CGI protocol. However, mod_perl offers much more than efficiency, as we will see. It also provides a full interface to the Apache internals, giving Perl programmers a chance to modify the web server itself.

Retrieving and Installing mod_perl

Apache modules are configured and installed at compile time. If you are interested in installing mod_perl, you have to download and recompile the source code in Apache. Luckily, this is rather easy to do. Note that while anyone can download, configure and compile Apache, only someone with root access can install Apache to its default position. If you don't have root access, you will still be able to run, but only on an unrestricted port number, namely, one above 1024.

The latest version of mod_perl is always available from CPAN (Comprehensive Perl Archive Network). At this time, the latest version of mod_perl is 1.10, which means that you can retrieve it from http://www.perl.com/CPAN/modules/by-module/Apache/mod_perl-1.10.tar.gz. Later versions will have the same URL, with a different version number. In addition, try to use a CPAN mirror close to you, rather than loading down www.perl.com; go to http://www.perl.com/CPAN/ for help in finding one.

Once you have downloaded mod_perl, you will also have to download the latest version of Apache, 1.2.6, from http://www.apache.org/ or one of its mirrors. Unpack the Apache and mod_perl distributions in the same directory. On my system, I did the following:

cd /downloads
tar -zxvf apache_1.2.6.tar.gz
tar -zxvf mod_perl-1.10.tar.gz

If you want to modify the default Apache module set, now is the time to modify /src/Configuration. If you are not familiar with Apache configuration, don't worry—things will work just fine without customizing the module set.

The rest of the Apache configuration and compilation is done within the mod_perl directory. Move into the mod_perl directory (probably called something like mod_perl-1.10) and type:

perl Makefile.PL

On my system, mod_perl asks me two questions:

Configure mod_perl with ../apache_1.2.6/src ? [y]
to which I press return, and
Shall I build httpd in ../apache_1.2.6/src for you? [y]
to which I press return again. This configures all of the files necessary for building mod_perl and Apache. When the UNIX shell prompt returns, simply type make and press return. The resulting Apache binary (httpd) will be in the src subdirectory under the Apache directory. On my system, httpd resides in /usr/sbin/httpd, so copying the resulting binary will replace the old Apache with the new one.

Restart Apache by logging in as root and typing:

killall -1 -v httpd

Now, you're in business with your new version of Apache. If you're not sure whether the new version has been installed, connect to the web server and ask for its version information:

telnet localhost 80
After connecting, type:
HEAD / HTTP/1.0
On my system, I get the following response:
HTTP/1.1 200 OK
Date: Sun, 12 Apr 1998 19:02:41 GMT
Server: Apache/1.2.6 mod_perl/1.10
Connection: close
Content-Type: text/html
In other words, the web server running on port 80 (the default port for HTTP traffic) is running Apache 1.2.6, with mod_perl 1.10 compiled in.

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