GEMINI: A Hybrid Byzantine Fault Tolerant Protocol for Reliable Composite Web Services Orchestrated Delivery

—To ensure reliable delivery for composite web services, we argue that Byzantine fault tolerance (BFT) must be guaranteed for the service delivery modules (such as BPEL execution engines and dispatchers) as well as for the realizing components of the composite web service. Existing BFT service delivery approaches are mainly focused on atomic web services. However, there are few approaches discussed BFT for composite web services delivery. Unfortunately, such approaches either ensured BFT for the service delivery modules alone or for the service realizing components alone; but not for both. To overcome such limitation, this paper proposes GEMINI; a hybrid BFT protocol for reliable composite web services orchestrated delivery. GEMINI uses a lightweight replication-based BFT protocol to ensure the BFT for service delivery modules, and uses a speculative quorum-based BFT protocol to ensure components BFT. Unlike existing quorum-based BFT approaches that ensure components redundancy via component replication; GEMINI ensures components redundancy via components parallel provisioning. Experimental results show that GEMINI increases the reliability and throughput of composite web service delivery when compared with existing composite web services delivery approaches.