Resynchronizing Model-based Self-adaptive Systems with Environments

Self-adaptive systems are attractive due to their ability of adapting to changeable environments automatically. However, such systems may be subject to runtime failures when all environmental dynamics cannot be adequately considered at design time. When such failures occur at runtime, a system's internal adaptation logic usually has become inconsistent with its environment, according to our observation. We call this inconsistency sync-loss error. From our project experiences, we empirically identified a strong correlation between sync-loss error and system failure. This motivated us to fix sync-loss error in order to reduce failure for self-adaptive systems. In this paper, we formulate the problem of detecting sync-loss error, and present a framework ReSync to automatically fix sync-loss errors by resynchronizing a system with its environment. We experimentally evaluated ReSync on real robot cars with 20 different system versions. The evaluation reported promising results that ReSync can automatically recover our robot car systems from sync-loss errors, and significantly reduce the failure rate from 90.9% to 11.7-28.8%.