Towards Making NekoStat a Proper Measurement Tool for the Validation of Distributed Systems

NekoStat is a Java framework and tool developed for qualitative and quantitative evaluation of dependability attributes of distributed algorithms. In this paper NekoStat is analyzed along the lines of metrology. First the relevant metrological properties that a tool such as NekoStat should possess are introduced. The lack of a rigorous metrological characterization of the accuracy of collected measures is noticed as there is no estimation of how biased the collected data can be. To solve this a new component, called OffsetDetector, is introduced and described. OffsetDetector allows to estimate the uncertainty of collected data and enables NekoStat to be aware of the accuracy level of the local clocks during distributed executions. The collected time measurements can thus be distinguished depending on the synchronization quality at the instant they were collected. In this way the trustworthiness in the results is widely enhanced as shown through a case study illustrated in the paper