Astrolabe

Abstract

Scalable management and self-organizational capabilities are emerging as central requirements for a generation of large-scale, highly dynamic, distributed applications. We have developed an entirely new distributed information management system called Astrolabe. Astrolabe collects large-scale system state, permitting rapid updates and providing on-the-fly attribute aggregation. This latter capability permits an application to locate a resource, and also offers a scalable way to track system state as it evolves over time. The combination of features makes it possible to solve a wide variety of management and self-configuration problems. This paper describes the design of the system with a focus upon its scalability. After describing the Astrolabe service, we present examples of the use of Astrolabe for locating resources, publish-subscribe, and distributed synchronization in large systems. Astrolabe is implemented using a peer-to-peer protocol, and uses a restricted form of mobile code based on the SQL query language for aggregation. This protocol gives rise to a novel consistency model. Astrolabe addresses several security considerations using a built-in PKI. The scalability of the system is evaluated using both simulation and experiments; these confirm that Astrolabe could scale to thousands and perhaps millions of nodes, with information propagation delays in the tens of seconds.