Over the years, I have noticed an interesting and challenging problem when setting up transaction monitoring for various web applications. The root of the problem is the use of absolute paths in links, rather than relative paths.
For example, an absolute path would be "http://www.somesite.com/gotothispage.php" whereas the same URL in a relative path would be "/gotothispage.php".
When attempting to implement transaction monitoring that runs against individual servers in a load-balanced environment, the use of absolute paths makes this challenging. The reason is that the monitoring would point to the individual host, but the links, form submittals, etc. effectively redirect the monitoring to the full path of the application from the individual host.
To work around this, host files have to be used on the monitoring server, with the IP address for "www.somesite.com" being changed in between the transaction monitor runs against each individual server. This has it's own problems, in that the transaction monitors for various hosts may overlap and cause inaccurate results.
Developers: Please remember to us relative paths when writing code for web sites -- it will improve application monitoring, incident resolution and cause analysis a great deal.
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