Effective fault treatment for improving the dependability of cots- and legacy-based applications

In this paper, we present a complete architecture suitable for improving the dependability of a wide class of distributed systems consisting of COTS components and Legacy systems. The paper advocates the need for careful diagnosis and damage assessment, and for precise and effective recovery actions, specifically tailored to the affecting fault and/or to the extent of the damage in the affected unit. In our pro- posal, threshold-based mechanisms are exploited to trigger alternative actions. The design and implementation of the resulting solution is illustrated with respect to a case study. This consists of a distributed architectural framework which replicates an application built from COTS components and Legacy systems. Replication and voting are used for error detection and masking. Dependability analysis has been conducted via combined use of direct measurements and analytical modeling.