MACROMEDIA COLDFUSION MX-CLUSTERCATS, Руководство пользователя

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What is website availability? 25
Website availability scenario
Imagine that you have just built a robust, interactive e-commerce website on which you
plan to sell the most sought-after books and music in the world. You have used Java
scriptlets to build the application, so of course you’ve taken advantage of its many
built-in features, including secure database access, multithreading, and integrated session
management.
Upon finishing the development work and quality assurance testing, you deploy the
website onto one production web server that is hosted within your IT department. The
IT department informs you that it can use its existing Internet connection to make your
site live, avoiding the additional hosting support cost of using an outside vendor.
The site goes live, 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. Then,
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 lose significant business.
Although the application provided many useful features and capabilities, customers could
not access them, because the site’s performance degraded to the point that the site
became unavailable. Because the site was deployed on only one server, the incoming
traffic could not be load balanced. Also, without redundant servers in place, the site
could not intelligently load balance increasing traffic nor redirect traffic to other available
servers (no failover).
This simple scenario illustrates how critical adequate scalability, performance, and
failover planning are to any successful web development effort. Servers can become
overloaded or fail at any time, so ensure 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 failover unavailable servers 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 these topics:
•
“Hardware planning” on page 26
•
“Systems monitoring” on page 26
•
“Corrective actions” on page 26
Review the following considerations to ensure that you have a sound failover strategy in
place — one that guarantees your website’s availability.