Formal Analysis of Load Balancing in Microservices with Scenario Calculus

Load balancing plays a crucial role in realising the benefits of microservices, especially to achieve elastic scalability and performance optimisation. However, it is different from load balancing for virtual machines, because workloads on microservices are harder to predict and the number of services in the systems is large. In this paper, we formalise load balance as an emergent property of the microservices ecosystem, and employ scenario calculus to formally analyse the impact of scheduling on service capability and scalability. We discovered that elastic round robin scheduling is highly scalable but the service capability is limited by the slowest microservice instance. In contrast, shortest waiting queue scheduling is less scalable, but the service capability is higher.