The lack of QoS attributes and their values is still one of the fundamental drawbacks of web service technology. Most approaches for modelling and monitoring QoS and web service performance focus either on client-side measurement and feedback of QoS attributes, or on ranking and discovery, developing extensions of the standard web service discovery models. However, in many cases, provider-side measurement can be of great additional value to aid the evaluation and selection of services and underlying implementations. We present a generic architecture and reference implementation for non-invasive provider-side instrumentation of data-processing tools exposed as QoS-aware web services, where real-time quality information is obtained through an extensible monitoring framework. In this architecture, dynamically configurable execution engines measure QoS attributes and instrument the corresponding web services on the provider side. We demonstrate the application of this framework to the tas...