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Saturday, January 31, 2009 2:19 PM
The failure of CNET.com and its causes.









An Example of an E-commerce failure and its causes

An example of E-commerce failure is such as the technology website CNET.com. There are lists over 40 incidents of real-world site outages, outlining how these failures were detected, the estimated downtime, and the subsequent recovery action of this websites. We mainly classified the causes of failures in Web applications into four categories namely: software failures, operator error, hardware and environmental failures, and security violations. We focus on non-malicious failures but list some failures that occur due to security violations for the sake of completeness. First, the incidents of software failures on the Web suggest that a large number of non-malicious failures occur during routine maintenance, software upgrades and system integration. It is unclear whether these failures are mainly due to system complexity, inadequate testing and/or poor understanding of system dependencies since site owners tend to be vague about the underlying cause of the failure. Other significant causes of software failure are system overload, resource exhaustion and complex fault-recovery routines. Next, Human/Operator Errors which are classified configuration errors, procedural errors and miscellaneous accidents. Configuration errors occur when operators define incorrect settings for system parameters, example specifying an insufficient number threads to service user requests to the web server. Procedural errors occur when the operator either omits an action or executes an incorrect action during system maintenance. Beside this, hardware and environmental failures can occur for several reasons. For example, wear and tear of mechanical parts, design flaws and loose wiring. Next, the causes of failures can also due to the security violations for the sake of completeness. Some of the common security violations that occur in websites are password disclosures, Denial of Service (DOS) attacks, worms and viruses, browser vulnerabilities, authentication failures and thefts. While for the manifestation of the failure typically falls within the following broad categories which are partial or entire site unavailable for example the user’s request times out causing the user to receive error notices such as "404 file not found". This may be due to server crashes and hangs, network congestion or denial of service attacks. System exceptions and access violations which means the executing process often terminates abruptly when a system exception is thrown. The error messages that arise vary depending on the error handling within the application that crashed, example the system may display a very detailed access violation message with addresses and numbers, or nothing at all. Incorrect results which means the executing process does not terminate but returns erroneous results, example the site serves blank pages, returns wrong pages or wrong items. Since no exceptions are thrown, these failures are usually discovered only after a customer complains. Next, data loss or corruption occurs when users are unable to access data from a previously functioning computer system, example due to the accidental erasure of data. Corruption is probably the most difficult problem to diagnose. Corruption typically occurs from a boundary overwrite in memory. Lastly, performance slowdowns may occur due to a variety of reasons, example server overload, process hangs, deadlocks, resource exhaustion and network congestion.




Related link: http://www.cnet.com/