Browsing by Author "Wagner, Lion"

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    Domain-driven monitoring of business-critical application systems
    (2023) Wagner, Lion
    Context. Many software companies use application performance management (APM) to track the technical healthiness of their systems. Modern frameworks, that are used to instrument such systems, like OpenTelemetry or AppDynamics, allow for an easy observation of many technical metrics, such as response times, throughout or boot times. Problem. However, underneath each systems lies usually a complex business process with its own non-technical characteristics, so called domain metrics. These characteristics are often not directly observable by technical metrics, which makes them hard to measure and understand, resulting in a conceptual gap between developers and domain experts. Objective. This thesis presents the domain-driven instrumentation (DDI) approach, which eases the process of instrumenting a software system to measure domain metrics, by automatically injecting instrumentation points into a running system, based on a provided domain-architecture-mapping (DAM). Additionally, the approach is tested and demonstrate on a realistic mock system, to keep the results representative. Method. Based on these objectives, first the mock system, which is strongly based on real world industry system was developed. Then, based on the work of Hofer and Schwentner [HS21b] and Vernon [Ver13] a meta-model, that can be used to model a DAM, based on the concepts of domain-driven design (DDD) and domain storytelling (DST), was developed. This model was then implemented in to the dqualizer tool chain, and executed on the mock system, to show its feasibility. Result. The demonstration revealed, that this approach can be effectively used to instrument a modern software system for monitoring domain metrics, by successfully instrumenting the mock with tracing and metric monitoring probes. However, it also revealed some major open problems, when it comes to instrumenting asynchronous behavior on a domain level, resulting in the collection, but non-usability of some metrics. Conclusion. In conclusion, the work of the thesis was able to successfully implement and demonstrate an automated domain-driven instrumentation approach and demonstrate it on a system that is closely related to a real world setting.
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    Simulating scenario-based chaos experiments for microservice architectures
    (2021) Wagner, Lion
    Context. With the growing popularity of microservice-based architectures, the need for effective resilience testing of such architectures occurred. In a preceding case study, we showed that transforming resilience scenarios to formalized scenario-based chaos tests, and executing those is a feasible way to do so. Problem. While producing very representative results, chaos testing can require a not insignificant expenditure of time and stresses the system under test. Simulating such experiments reduces these problems. Unfortunately, there are currently no simulators available that fulfill the requirements for simulating such scenarios to an acceptable level. Objective. Therefore, this thesis examines which simulators are suitable for which types of scenarios. Furthermore, the most promising of these simulators is extended to support a common scenario description and other features. Method. To properly elicit the requirements for such a simulator, stakeholders conduct a requirements analysis. Existing simulators are searched and evaluated based on these requirements. The simulator that looks the most promising is then extended. To verify the accuracy of the simulator, the scenarios from the preceding case study are utilized. They are transposed to models and simulated. The result data of the simulation is compared to the results of the case study. Result. This thesis presents five microservice simulators and which scenarios they currently potentially support best in a structured overview. Further, a re-engineering of the MiSim simulator results in better support of scenario-based chaos experiments and others of the aforementioned requirements. Conclusion. MiSim 3.0 is evaluated as a simulator that is capable of accurately simulating scenario-based chaos tests. Specifically, the newly implemented resilience patterns and chaos injections behave as expected. However, an inaccurate calibration may harm its accuracy. Conclusion. Previously existing microservice simulators could not simulate all types of scenariobased chaos experiments. In the context of this thesis MiSim 3.0 is created and evaluated as a simulator capable of correctly simulating many types of scenario-based chaos tests. In particular, the newly implemented resilience patterns and chaos injections behave as expected. However, inaccurate calibration can significantly affect its accuracy.