You can combine usage of Netsaint and power of Perl and LWP or HTTP::WebTest. As grep have said you can write Netsaint plugins in Perl.

It is quite good approach. Netsaint gives you powerful monitoring framework which provides messaging, web interface, ready to use plugins for many services, etc and LWP or <shameless plug>even better HTTP::WebTest</shameless plug> gives you ability to write very complex tests which can cover all functionality of your web applications.

BTW one user of HTTP::WebTest have sent me a script - plugin for Netsaint which uses HTTP::WebTest to test websites. I don't feel it is generic enough to make it public but if you want I can email you it. Drop me email to ilya@martynov.org if you need it.

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Ilya Martynov (http://martynov.org/)