Seminar by Bhaskar Raman
An Architecture for Highly Available Wide Area Service Composition
Bhaskar Raman, PhD candidate
Computer Science Division
University of California, Berkeley, CA, USA
Date: Thursday, August 08, 2002
Time: 04:15 PM
Venue: CS-101
Abstract
Service composition is a powerful tool for rapid creation of new services by stringing together existing component services. A simple example is that of composition of a video-on-demand server with a transcoding service to enable video on a thin client. We envision a scenario where different service providers deploy and manage services at different Internet locations. Third-party portal providers compose these to enable new user applications. When composition is done across the Internet, the client session could stretch across Internet domains. Recent research has shown that inter-domain Internet path availability can be quite low (95% in some cases). Further, when outages happen on inter-domain paths, the time to recovery is of the order of several tens of seconds to a few minutes. This translates to poor availability for the composed client session, and is especially bad for real-time streaming applications.
We have developed an architecture based on an overlay network of service clusters to address this issue. We use service replicas as well as redundant paths on the overlay network to detect and recover from path failure quickly. Using traces collected over the wide-area, as well as emulation-based experiments, we show that failure detection and recovery can be achieved within 4-5 seconds. This is of immense use for real-time applications and represents orders of magnitude better performance than Internet-path recovery. We demonstrate overall improvements in availability through wide-area experiments involving a composed text-to-speech application that we have implemented. We have also developed mechanisms for load-balancing across service replicas at the different service clusters of our architecture. This talk focuses on the failure detection and recovery aspects of the system.
About the Speaker
Bhaskar Raman is a PhD candidate in Computer Science at the University of California, Berkeley. He received his BTech (Computer Science and Engineering) from IIT Madras in 1997, and his MS from University of California, Berkeley, in 1999. His research interests are broadly in the areas of computer networks and distributed systems.