1. A computer-implemented method comprising: providing an application system accessible by a plurality of users at the same time, the application system comprising one or more applications or one or more application modules, at least one of the one or more applications or one or more application modules is operable in both a first mode and a second mode at the same time for different users, the first mode comprising a production mode which does not include user initiated logging and the second mode comprising a debug mode that includes user initiated logging initiated on a user-by-user basis; performing, in response to a user invoking the second mode and a corresponding user-initiated logging specification that comprises a type and amount module of the one or more applications or the one or more application modules, the application or application module operated in the first mode and the second mode by different users at the same time, the second mode performing user-directed diagnostics implemented by: configuring a set of instrumentation components for the user based at least in part on one or more aspects of the user-initiated logging specification, measuring, using a set of instrumentation components, at a set of one or more testpoints, retrieving a rulebase from a storage area, the rulebase comprising one or more conditions and corresponding corrective actions; detecting an occurrence of the one or more conditions using at least some of the testpoints; and applying at least one of the corrective actions corresponding to the occurrence of the one or more conditions.