Chapter 13: Implementing Shared Tomcat Hosting

Overview

This chapter shows how you can use Tomcat to implement shared hosting, which means that many hosts can run on the same server and thus share resources. Shared hosting has been a popular and useful part of the Apache Web server’s architecture for a long time, and Tomcat has an analogous mechanism.

In this chapter, a Web site refers to the contents of a distinct fully qualified domain name (FQDN), which is served by a Web server. A FQDN consists of two parts: a host name and a domain name. For example, the FQDN www.apress.com consists of the host name www and the domain name apress.com. The domain name can have other hosts, such as mail or java. The FQDNs would be mail.apress.com and java.apress.com.

A standard Web server in its default configuration allows only one domain to be served from the machine. In this case, if you wanted to serve hundreds of domains from your servers, you would have to set up hundreds of computers to serve all these Web sites. This is clearly not a scalable solution.

Also, IP addresses are a scarce resource. A Web-hosting provider gets a limited number of IP addresses from its connectivity providers for hosting. Using one IP address for every Web host would quickly eat up all the allocated IP addresses. To overcome these limitations, virtual hosting uses all your available resources, be they services, IP addresses, or other computing resources, in an optimal way.