Scalability and Locality Awareness of Remote Procedure Calls: An Experimental Study in Edge Infrastructures

Cloud computing depends on communication mechanisms implying location transparency. Transparency is tied to the cost of ensuring scalability and an acceptable request responses associated to the locality. Current implementations, as in the case of OpenStack, mostly follow a centralized paradigm but they lack the required service agility that can be obtained in decentralized approaches. In an edge scenario, the communicating entities of an application can be dispersed. In this context, we focus our study on the inter-process communication of Openstack when its agents are geo-distributed. More precisely, we are interested in the different Remote Procedure Calls (RPCs) implementations of OpenStack and their behaviours with regards to three classical communication patterns: anycast, unicast and multicast. We discuss how the communication middleware can align with the geo-distribution of the RPC agents regarding two key factors: scalability and locality. Scales of ten of thousands of communicating agents are reached, and results show that a router-based deployment offers similar scalability than a broker-based approach while being lighter. In addition we show that a router-based middleware offers a better trade-off between locality and load-balancing.