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Web Performance Tuning, 2nd Edition by Patrick Killelea

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Monitoring Tools

A common problem with automated performance monitoring (or automated testing of any kind) is that it does not work well if your content or environment are constantly changing. This is because human intervention is often required to cope with those changes, and human intervention is the opposite of automation. The gains from test automation are generally larger from a static environment.

On the other hand, a coworker of mine effectively used Perl and the DBI interface to validate constantly changing dynamic web pages. He did this by first querying certain database fields for content and then validating that the same content appeared on the web page in the right place. In this way, he got ahead of the “chase” condition in which most test writers find themselves (altering their tests every time a web page changes).

One class of monitoring tools called “transaction trackers” generally claim to provide “end-to-end” visibility of what is going on in your application, often by tagging packets with specific identifiers. This generally does not work well for two reasons. First, requests go through pooling points where packet tagging cannot follow. For example, a web site hit may cause a database query, but if that query is over a connection in a database connection pool, you probably cannot figure out which connection was used. Second, to really gain visibility past the pooling points, in-depth application knowledge and custom programming is required. This means that generic ...

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