Dynamic properties feature in IIS7 configurtion system lets you expose dynamic data as configuration system properties. RscaExt.xml which is part of IIS7 has all the RSCA (runtime status and control APIs) functionality exposed as dynamic properties through configuration system (read more here). One of the things RSCA let you do is expose custom runtime data from a worker process using GetCustomData method. You can call GetCustomData method for a worker process instance which sends a GL_RSCA_QUERY notification to the worker process. Once this notification is generated, IIS core engine then calls all the modules which subscribed to GL_RSCA_QUERY global notification. These modules can then return any runtime data they want to which is seen as the return value of GetCustomData method. RequestMonitorModule is one example of such module which subscribes to RQ_BEGIN_REQUEST, RQ_END_REQUEST to keep track of requests getting processed and also subscribes to GL_RSCA_QUERY to expose this requests in flight data through RSCA. CGlobalModule::OnGlobalRscaQuery method which gets invoked on GL_RSCA_QUERY event accepts IGlobalRSCAQueryProvider as an argument which can be used to get the function name (referred to as GuidOfFunctionCall in rscaext.xml), function parameters and also to set the return value of GetCustomData.

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-Kanwal-