Computerworld - As more companies utilize the Internet in their business, Web applications have come into widespread use. These Web applications are typically delivered via tools such as load balancers, HTTP Web servers, caching servers, messaging systems, transaction-processing monitors, application servers and databases. A typical enterprise application infrastructure is shown below.
As performance and geographic reach requirements expand, it becomes increasingly difficult to scale the Web site infrastructure. IT managers must continually evaluate capacity plans to keep pace with the expected peak demand, and planning must consider events such as marketing promotions, news events, and other events that inevitably create more planning uncertainty. Errors in planning can result in overloads that can crash sites or cause unacceptably slow response times and lead to lost revenue.
Pre-provisioning extra capacity as insurance against overload is financially unacceptable for most enterprises. Ideally, enterprises want the needed resources when – and only when – they are needed; they do not want to buy extra resources that sit idle when they are not needed.-[1] "On-demand" computing provides better utilization of computing resources and represents a model in which computing resources are brought into service as needed.
On-Demand Application Platforms
Today, on-demand computing technologies have been integrated into centralized enterprise application platforms, and generally offer enterprises improved fault tolerance and better scalability, using intelligent scheduling and load balancing of application workloads.
However, for many of today's Web applications, end users are inherently spread across the Internet. Congestion and failures in this end-user environment are common and because of this, centralized enterprise applications can have unpredictable reliability and performance for end users.
One solution for enterprises is to use an on-demand distributed computing (ODDC) model for improved application performance and reliability. Deployed at the "edge" of the Internet – close to users' access points – this gridlike distributed platform consists of hundreds of servers deployed in many networks around the globe.
Enterprises can deploy applications to this distributed platform; thus, enterprises can fight service bottlenecks and failures, and at the same time provide on-demand scalability, global reach and high performance for the application users.
This widely distributed application environment consists of the end user typically using a browser, the enterprise (origin) running business logic, legacy systems and databases, and the edge servers running an embeddable server, such as WebSphere Application Server or Tomcat, that supports the Java 2 Enterprise Edition (J2EE) Web application programming model.
Developing Applications for an ODDC Platform
The development model remains standard J2EE for edge applications and doesn't require the use of any proprietary application programming interfaces; it's the deployment model that changes, not the programming model.
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