The EMI Registry: Discovering Services in a Federated World

The Distributed Computing Infrastructure (DCI) has become an indispensable tool for scientific research. Such infrastructures are composed of many independent services that are managed by autonomous service providers. The discovery of services is therefore a primary function, which is a precursor for enabling efficient workflows that utilise multiple cooperating services. As DCIs, such as the European Grid Initiative (EGI), are based on a federated model of cooperating yet autonomous service providers, a federated approach to service discovery is required that seamlessly fits into the operational and management procedures of the infrastructure. Many existing approaches rely on a centralised service registry, which is not suited to a federated deployment and operational model. A federated service registry is therefore required that is capable of scaling to handle the number of services and discovery requests found in a production DCI. In this paper we present the EMI Registry (EMIR), a decentralised architecture that supports both hierarchical and peering topologies, enabling autonomous domains to collaborate in a federated infrastructure. An EMIR pilot service is used in order to evaluate a prototype of this architecture under real-world conditions with a geographically-dispersed deployment. The results of this initial deployment are provided along with a few performance measurements.