out.println("Context destroyed on " +
new Date() + ".");
}
}
Listing 2.30 web.xml (Excerpt declaring a listener)
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation=
"http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
version="2.4">
coreservlets.ContextReporter
2.17 Developing for the Clustered Environment 95
2.17 Developing for the Clustered
Environment
Enterprise-level Web applications are required to handle tens of thousands of concurrent
user activities. It would be close to impossible to have a machine powerful
enough to process that many requests by itself. It would certainly be extremely
expensive to purchase such a machine. In addition, if that enormously powerful
machine broke, it would mean downtime for the Web site hosted on that machine.
For high-traffic Web sites like Amazon or eBay, this downtime would amount to millions
of dollars of lost revenue an hour.
To address this problem, enterprise-level applications are deployed in a clustered
environment. A clustered environment usually consists of many machines connected
through the local area network (LAN) and sometimes even through the wide area
network (WAN).
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