Optimized Fault-Tolerant Placement of Microservices in Distributed Fog Networks

We propose a fault-tolerance aware placement algorithm for microservices in distributed fog environments that combines a reactive Dynamic Connections Load Balancer (DCLB) with a proactive, fault-threshold driven migration and backup-predetermination mechanism. The DCLB places services only on healthy nodes by using active-connection-based load metrics, while the proactive module preassigns backup nodes for critical services and triggers rapid migration when a node crosses a fault threshold. We evaluate the approach using extensive iFogSim simulations on a smart-home management microservice composition under controlled failure injections. This paper presents a fault–tolerance–aware microservice placement strategy that integrates health-aware primary placement with proactive backup node predetermination. Experimental results show that the strategy effectively limits service disruption, achieving an average service downtime of less than 30% of the total simulation time across failure scenarios. System reliability remains consistently high, with values exceeding 0.85 in single-failure cases and remaining above 0.75 under multiple failures. Resource utilization across fog nodes remains balanced, with moderate memory usage and stable energy consumption. These results demonstrate that proactive, health-aware placement improves service continuity and resilience in fog-based microservice deployments.