User manual MACROMEDIA COLDFUSION 4.5-ADMINISTRING COLDFUSION SERVER

[. . . ] Administering ColdFusion Server ColdFusion 4. 5 Allaire Corporation Copyright Notice © 1999 Allaire Corporation. This manual, as well as the software described in it, is furnished under license and may be used or copied only in accordance with the terms of such license. The content of this manual is furnished for informational use only, is subject to change without notice, and should not be construed as a commitment by Allaire Corporation. Allaire Corporation assumes no responsibility or liability for any errors or inaccuracies that may appear in this book. [. . . ] A sound strategy includes a minimum of two Web servers but preferably three. · Software failures -- The types of software failures that will most likely affect a Web application involve the Web server's operating system, the Web server software itself, or the Web application software. If the operating system crashes or becomes corrupt, the Web server cannot function properly (or perhaps at all), causing your Web application's availability, reliability, and performance to be compromised. Similarly, if the Web server software crashes or acts erratically, it will likely cause the Web server to stop running when you didn't intend it to. It's hard to prepare for software failures, but if you have mirrored secondary hardware systems in place to account for failures, you'll minimize your Web application's downtime. · Server failures -- In addition to the Web server, other servers on which your Web application depends can also fail, causing either downtime or diminished capabilities on your site. For example, for distributed applications, a proxy server may go down, causing requests for your Web application's services to go unanswered. Or, the database server can crash, making it impossible for users to submit or retrieve information from your database. Or, a mail server can go down, making it impossible for your users to successfully send mail to you. Ensure that your organization's IT architecture includes network monitoring and notification software that can quickly report on the general health of your network and alert you about any failed servers. A Web site availability scenario Imagine that you've just built a robust, interactive e-commerce Web site on which you plan to sell the most sought-after books and music in the world. You've used ColdFusion to build the application, so of course you've taken advantage of it's many built-in features, including: · back-end relational database support to manage inventory control and order submissions Chapter 6: Creating Scalable and Highly Available Web Sites 147 · advanced personalization and membership capabilities to provide a customized experience and superior authentication · ad management features to generate additional revenues and enrich partner relationships · 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. 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: · Hardware planning · Systems monitoring · 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. 148 Administering ColdFusion Server Hardware planning As illustrated in the availability example above, it's important to acquire all of the necessary hardware and configure it before you deploy the application. [. . . ] To add individual users enter the name in the entry field and click Add. For our example, let's assume all the MARS developer's are in a MARS group which you add to the policy. Now all members of this group can access the resources that are members of the MARS policy. Now do the same for the VENUS directory. 2. 3. Okay now each group of users has access to the resources which are members of that policy. [. . . ]