The Taub Faculty of Computer Science Events and Talks

Delivery of social notifications has become a popular component in many electronic services. While a small number of services for social notifications, e.g., Twitter, are dedicated, an increasingly large number of such services are provided as an enhancement of the main functionality. For example, the main music streaming service of Spotify is accompanied by an engine that delivers real-time notifications to each online user. These notifications report when a user's friend comes online and goes offline, what music track a user's friend listens to, when a user's friend updates a shared content, such as a playlist, etc. Similar services for social notifications are provided alongside most real-time cooperative activities: video and audio streaming, mobile and ad-hoc interaction, online gaming, large-scale human gatherings during the commute, Olympic games, exhibitions, as well as many others. The volume of social notifications is quite staggering. For example, the notification service at Spotify delivers over a billion notifications every single day, with a total volume of over 2 terabytes. In this talk, I will provide a brief analysis of the Spotify data, with the aim to facilitate design and validation of new solutions. Traditionally notification services have been deployed on in-house enterprise datacenters. However, with the advent of cloud computing, a viable alternative of running such services in the cloud became available. In this talk, I will present a few key challenges of delivery semantics as well as resource provisioning for deployment of notification services, define corresponding optimization problems, and describe our solutions to these challenges. We evaluate the proposed solutions experimentally using real traces from Spotify and Twitter along with the Amazon EC2 pricing model. The solution runs in under 30 seconds for the Spotify workload with 5 million subscribers and 1.1 million topics and under 25 minutes for the Twitter workload with 30 million subscribers and 8 million topics, using a commodity hardware. The content of the talk is based on publications in the DEBS 2013, Infocom 2014, and ICDCS 2014 conferences. Short Bio: ========== Roman Vitenberg is a Professor at the Department of Informatics at the University of Oslo. He received his PhD in Computer Science from the Technion - Israel Institute of Technology. In the past, he was a visiting researcher at the University of California at Santa-Barbara, Universita di Roma La Sapienza, and Universidad Politecnica de Madrid. He also spent three years as a research staff member at IBM Research where he contributed to the design of the high-availability component of WebSphere. His research interests are broadly in the area of distributed applications, middleware and algorithms; including specification, design, analysis, implementation, performance evaluation, and software engineering. In particular, he has been working on large-scale communication, object-oriented and component-based platforms, distributed event-based systems, consistency models, and fault-tolerant distributed computing. He is recipient of best paper awards at ACM/IFIP/USENIX Middleware, ACM SAC, and ACM DEBS conferences. =========================================== Refreshments will be served from 14:15 Lecture starts at 14:30