Apache Cookbook

Chapter 9. Error Handling

When you’re running a web site, things go wrong. And when they do, it’s important that they are handled gracefully, so that the user experience is not too greatly diminished. In this chapter, you’ll learn how to handle error conditions, return useful messages to the user, and capture information that will help you fix the problem so that it does not happen again.

9.1. Handling a Missing Host Field

Problem

You have multiple virtual hosts in your configuration, and at least one of them is name-based. For name-based virtual hosts to work properly, the client must send a valid Host field in the request header. This recipe describes how you can deal with situations in which the field is not included.

Solution

Add the following lines to your httpd.conf file:

Alias /NoHost.cgi /usr/local/apache/cgi-bin/NoHost.cgi
RewriteEngine On
RewriteCond "%{HTTP_HOST}" "^$"
RewriteRule "(.*)" "/NoHost.cgi$1" [PT]

The file NoHost.cgi can contain something like the following:

#! /usr/bin/perl -Tw

my $msg = "To properly direct your request, this server requires that\n"
        . "your Web client include the HTTP 'Host' request header field.\n"
        . "The request which caused this response did not include such\n"
        . "a field, so we cannot determine the correct document for you.\n";
print "Status: 400 Bad Request\r\n\"
    . "Content-type: text/plain\r\n\"
    . 'Content-length: ' . length($msg) . "\r\n\"
    . "\r\n\"
    . $msg;
exit(0);

Discussion

Once the directives in the solution are in place, all requests made ...