FOCUS: Scalable Search Over Highly Dynamic Geo-distributed State

Finding nodes which match certain criteria, based on potentially highly dynamic information, is a critical need in many distributed systems, ranging from cloud management, to network service deployments, to emerging IoT applications. With the increasing scale, dynamicity, and richness of data, existing systems, which typically implement a custom solution based around message queues where nodes push status to a central database, are ill-suited for this purpose. In this paper, we present FOCUS, a general and scalable service which easily integrates into existing and emerging systems to provide this fundamental capability. FOCUS utilizes a gossip-based protocol for nodes to organize into groups based on attributes and current value. With this approach, nodes need not synchronize with a central database, and instead the FOCUS service only needs to query the sub-set of nodes which have the potential to positively match a given query. We show FOCUS's flexibility through an operational example of complex querying for Virtual Network Functions instantiation over cloud sites, and illustrate its ease of integration by replacing the push-based approach in OpenStack's placement service. Our evaluation demonstrates a 5-15x reduction in bandwidth consumption and an ability to scale much better than existing approaches.