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Chapter 6: Creating Scalable and Highly Available Web Sites 147
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advanced personalization and membership capabilities to provide a
customized experience and superior authentication
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ad management features to generate additional revenues and enrich partner
relationships
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ordering and payment features, including shopping carts and secure sockets
layer, to ensure easy and safe online transactions
Upon finishing the development work and quality assurance testing, you deploy the
Web site onto a single production Web server that is hosted within your IT department.
The IT department informs you that it is able to use its existing Internet connection to
make your site “live” while minimizing additional hosting support costs by going to an
outside vendor. The site goes live the following day and it’s an instant success. Orders
start pouring in the very first day, and huge numbers of people log on to browse and
buy. Everything seems perfect. Except, on the second day of business, the load hitting
the site is so high, the Web server’s performance slows to a crawl, eventually causing
the server to become unavailable. Suddenly, your tech support lines are ringing off the
hook with complaints that users cannot access your site, causing you to miss out on
tons of sales.
Although the application may have contained many useful features and capabilities,
the customers were not able to use them for very long because the site’s performance
degraded to the point that the site eventually became unavailable. Because the site was
deployed on only a single server, there was no way to load balance the incoming traffic.
Additionally, without multiple redundant servers in place, the site was not capable of
intelligently load balancing increasing traffic nor able to redirect traffic to other
available servers (no failover).
This simple scenario illustrates that a critical part of any successful Web development
effort must include adequate scalability, performance, and failover planning. Servers
can become overloaded or fail at any time for many reasons, so make sure that your
design, development, testing, and deployment strategies are sound, promote good
communication between necessary departments, and include adequate disaster
recovery capabilities.
Failover considerations
The ability to fail over servers that have become unavailable to redundant servers is a
cornerstone of any mission-critical application, one that ensures an application’s
continuous and reliable operation. Such disaster planning and recovery can be broken
down into:
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Hardware planning
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Systems monitoring
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Corrective actions
Review the following considerations to ensure that you have a sound failover strategy
in place — one that guarantees your Web site’s availability.