Heartbeat Messages Message Session Session Session Session Session Session Observer Router Actor Reference

The actor model is a popular paradigm for programming scalable cloud applications. Building elastic and scalable cloud applications requires application developers to carefully adjust the application scale (the required resources) and the placement of actors at the runtime. Unfortunately, there is no efficient solution which could manage application elasticity automatically during runtime without disrupting ongoing requests. This paper proposes the idea of programmable elasticity approach, which allows application developers to define a set of elasticity rules for different actors. The runtime service endeavors to apply the elasticity rules while relieving the application programmer from dealing with the management of distributed state and efficient utilization of cloud resources. CCS Concepts • Computing methodologies → Distributed programming languages;