Thomas S. Repantis

University of California, Riverside Department of Computer Science & Engineering 351 Engineering Building Unit II Riverside, CA 92521, USA

http://www.cs.ucr.edu/~trep/ +1 951 827 2893 (voice) +1 951 827 4643 (fax)

Research Interests

Distributed Systems

Distributed Stream Processing Systems, Middleware, Peer-to-Peer Systems, Mobile and Ubiquitous Computing, Distributed Shared Memory Systems, Cluster and Grid Computing.

Education

University of California, Riverside

Ph.D. Candidate in Computer Science, degree expected summer 2008
Thesis: Synergy: Quality of Service Support for Distributed Stream Processing Systems

M.Sc. in Computer Science, August 2005
Thesis: Adaptive Data Dissemination and Content-Driven Routing in Peer-to-Peer Systems
Advisor: Prof. Vana Kalogeraki
GPA: 3.900/4.000

University of Patras, Greece

Diploma (5-year program) in Electrical & Computer Engineering, March 2003
Thesis: Implementation of Page Forwarding on Clusters
Advisors: Prof. Theodore S. Papatheodorou, Prof. Dimitrios N. Serpanos
GPA: 7.70/10.00

Professional Experience

University of California, Riverside
Department of Computer Science & Engineering, Distributed Real-Time Systems Laboratory

January 2004-Present, Graduate Student Researcher
Advisor: Prof. Vana Kalogeraki
Leading the development in Java of the Synergy distributed stream processing middleware; supervising other student research projects now using the platform.

Sharing-aware component composition.

Distributed stream processing systems need to satisfy application QoS requirements despite the shared, dynamic, and large-scale environment. I have designed and implemented in Synergy techniques for composing distributed stream processing applications with QoS demands. Synergy enhances QoS provision and reduces resource load by efficiently reusing both data streams and processing components. To achieve this goal Synergy provides a set of fully distributed algorithms to discover and evaluate the reusability of available data streams and processing components when instantiating new stream applications. For QoS provision, Synergy performs QoS impact projection to examine whether the shared processing can cause QoS violations on currently running applications. Projection is based on queueing theoretical models for both regular and bursty traffic. For initial component deployment Synergy employs a decentralized replica placement protocol that aims to maximize availability, while respecting resource constraints, and making performance-aware placement decisions.

Load prediction and hot-spot alleviation.

Managing the load of the nodes of a large-scale, dynamic distributed stream processing system in real-time and without centralized supervision is challenging. I have designed and implemented in Synergy a self-managing resource monitoring architecture for identifying and relieving overloaded nodes. Monitoring responsibilities are shared among all nodes using a completely decentralized DHT-based architecture. Nodes proactively predict application QoS violations at run-time using a statistical forecasting framework based on auto- and cross-correlation, as well as linear regression. To alleviate hot-spots, nodes autonomously migrate the execution of stream processing components using a non-disruptive migration protocol. I have evaluated Synergy's performance over PlanetLab by implementing a network traffic monitoring application operating on real streaming data.

Managing large-scale, distributed, real-time applications.

Satisfying end-to-end QoS requirements in large-scale distributed real-time applications is challenging, due to the unpredictability and heterogeneity of the environment. Focusing on media streaming and transcoding as an example, I have co-designed in C++ a decentralized architecture that enables nodes to collaborate to offer composite applications. A resource allocation algorithm distributes the processing and communication loads fairly, while satisfying application end-to-end QoS demands. Nodes adapt to variable resource conditions by optimizing their resource usage locally, selecting from discrete QoS output levels. Multiple nodes participating in a composite application coordinate their QoS through feedback from the service receiver.

Data dissemination in peer-to-peer systems.

Efficiently locating data or services in a fully decentralized, self-organizing, unstructured overlay network is challenging, due to the large scale and the lack of global view. I have designed in Java a content-driven routing mechanism that guides queries to peers most probable to provide results. Intelligently routing queries is based on Bloom filter synopses of peers' content. Adaptive dissemination algorithms propagate synopses according to peers' interactions. A decentralized trust management architecture enables peers to evaluate reputation information and avoid lying and colluding.

IBM Research
T.J. Watson Research Center, Hawthorne, NY

June 2007-September 2007, Research Intern
Mentors: Dr. Arun Iyengar, Dr. Isabelle Rouvellou
As a member of the advanced enterprise middleware group, designed, implemented in Java, evaluated, and documented a replication middleware for distributed, multi-tier, server architectures. Proposed and incorporated in the middleware an efficient, distributed strong consistency protocol. Quantified the server replication and data partitioning performance benefits, as well as the consistency overhead, using the TPC-W transactional web commerce benchmark.

Intel Research
Pittsburgh, PA

June 2006-September 2006, Research Intern
Mentors: Dr. Michael Kaminsky, Dr. Haifeng Yu
As a member of the research team of the reliable email project, designed, implemented in C++, and documented an event-driven software prototype of a collaborative spam filter that employs a distributed protocol to defend against sybil attacks.

Hewlett-Packard
Technology Solutions Group, Enterprise Storage & Servers, Colorado Springs, CO

June 2005-September 2005, Software Intern
Mentors: Dr. Debby Levinson, Chris Stroberger
As a member of the replication team of an upcoming product of HP's grid storage portfolio, designed, implemented in C++, and documented a logging mechanism used for asynchronous replication in a distributed disk array.

University of California, Riverside
Department of Computer Science & Engineering

September 2003-December 2003, Teaching Assistant
Instructor: Wagner Truppel
Instructed a lab on C++ programming, and evaluated assignments and exams. Anonymous student reviews included: "Very caring TA. Will teach and willing to spend extra time.", "The best TA I ever had."

University of Patras, Greece
Department of Computer Engineering & Informatics, High Performance Information Systems Laboratory

January 2001-November 2002, Undergraduate Student Researcher
Advisors: Dr. Christos D. Antonopoulos, Prof. Theodore S. Papatheodorou
Designed and implemented in C a protocol for dynamic memory page migration across the nodes of a Software Distributed Shared Memory System, as part of an inter-departmental diploma thesis. Dynamic page migration improves performance by increasing locality and adaptability, while remaining transparent to the application programmer.

FGAN e.V.
Research Institute for Communication, Information Processing and Ergonomics, Computer Networks Department, Bonn, Germany

July 2000-August 2000, Intern
Mentors: Dr. Christian Riechmann, Peter Sevenich
Analyzed the H.323 protocol family, used for multimedia applications (VoIP) in packet switched networks, and summarized the results in a technical report, including detailed protocol description and performance evaluation of applications under IPv6 in Solaris.

University of Patras, Greece
Department of Electrical & Computer Engineering

October 1998-March 1999, Web Developer
Supervisors: Prof. Nikolaos Avouris, Prof. Athanasios Safacas
As a member of the team that created the department's web site, developed and tested web pages in HTML.

Refereed Publications

Conference and Workshop Proceedings:

Hot-Spot Prediction and Alleviation in Distributed Stream Processing Applications

Thomas Repantis, Vana Kalogeraki, Proceedings of the 38th Annual IEEE/IFIP International Conference on Dependable Systems and Networks (DSN 2008). Acceptance rate (PDS track): 19/87=22%

Replica Placement for High Availability in Distributed Stream Processing Systems

Thomas Repantis, Vana Kalogeraki, Proceedings of the 2nd International Conference on Distributed Event-Based Systems (DEBS 2008).

Alleviating Hot-Spots in Peer-to-Peer Stream Processing Environments

Thomas Repantis, Vana Kalogeraki, Proceedings of the 5th International Workshop on Databases, Information Systems and Peer-to-Peer Computing (DBISP2P 2007) (in conjunction with VLDB 2007). Acceptance rate: 21%

Synergy: Sharing-Aware Component Composition for Distributed Stream Processing Systems

Thomas Repantis, Xiaohui Gu, Vana Kalogeraki, Proceedings of the 7th ACM/IFIP/USENIX International Middleware Conference (MIDDLEWARE 2006). Acceptance rate: 21/122=17%

Decentralized Trust Management for Ad-Hoc Peer-to-Peer Networks

Thomas Repantis, Vana Kalogeraki, Proceedings of the 4th International Workshop on Middleware for Pervasive and Ad-Hoc Computing (MPAC 2006) (in conjunction with MIDDLEWARE 2006). Acceptance rate: 6/24=25%

Load Balancing Techniques for Distributed Stream Processing Applications in Overlay Environments

Yannis Drougas, Thomas Repantis, Vana Kalogeraki, Proceedings of the 9th IEEE International Symposium on Object- and Component-Oriented Real-Time Distributed Computing (ISORC 2006). Acceptance rate: 35%

A Comprehensive Comparison of Routing Protocols for Large-Scale Wireless MANETs

Ioannis Broustis, Gentian Jakllari, Thomas Repantis, Mart Molle, Proceedings of the 3rd International Workshop on Wireless Ad Hoc and Sensor Networks (IWWAN 2006) (in conjunction with SECON 2006).

A Case for Dynamic Page Migration in Multiple-Writer Software DSM Systems

Thomas Repantis, Christos D. Antonopoulos, Vana Kalogeraki, Theodore S. Papatheodorou, Proceedings of the 7th IEEE International Conference on Cluster Computing (CLUSTER 2005). Acceptance rate: 45/138=33%

Data Dissemination in Mobile Peer-to-Peer Networks

Thomas Repantis, Vana Kalogeraki, Proceedings of the 6th International Conference on Mobile Data Management (MDM 2005). Acceptance rate: 25%

Coordinated Media Streaming and Transcoding in Peer-to-Peer Systems

Fang Chen, Thomas Repantis, Vana Kalogeraki, Proceedings of the 19th IEEE International Parallel and Distributed Processing Symposium (IPDPS 2005). Acceptance rate: 116/338=34%

Adaptive Resource Management in Peer-to-Peer Middleware

Thomas Repantis, Yannis Drougas, Vana Kalogeraki, Proceedings of the 13th International Workshop on Parallel and Distributed Real-Time Systems (WPDRTS 2005) (in conjunction with IPDPS 2005).

Towards Self-Managing QoS-Enabled Peer-to-Peer Systems

Vana Kalogeraki, Fang Chen, Thomas Repantis, Demetris Zeinalipour-Yazti, Self-Star Properties in Complex Information Systems, Hot Topics in Computer Science, Springer LNCS, vol. 3460, 2005.

Dynamic Page Migration in Software DSM Systems

Thomas Repantis, Christos D. Antonopoulos, Vana Kalogeraki, Theodore S. Papatheodorou, Proceedings of the 6th IEEE International Conference on Cluster Computing (CLUSTER 2004) (poster session).

Manuscripts Under Review

Sharing-Aware Dynamic Component Composition for Distributed Stream Processing Systems

Thomas Repantis, Xiaohui Gu, Vana Kalogeraki

Consistent Replication in Distributed Multi-Tier Architectures

Thomas Repantis, Arun Iyengar, Vana Kalogeraki, Isabelle Rouvellou

Technical Reports

Logging Service Architecture Strategy and Design

Chris Stroberger, Thomas Repantis, Internal Report, Hewlett-Packard, 2005.

A Performance Comparison of Routing Protocols for Large-Scale Wireless Mobile Ad Hoc Networks

Ioannis Broustis, Gentian Jakllari, Thomas Repantis, Mart Molle, Technical Report UCR-CS-2003-12001, University of California, Riverside, 2003.

Analysis of the H.323 Protocol Suite

Thomas Repantis, Peter Sevenich, Technical Report FKIE-KOM 2000/4, FGAN e.V., 2000.

Posters

Synergy: Quality of Service Support for Distributed Stream Processing Systems

Thomas Repantis, Vana Kalogeraki, Xiaohui Gu, Graduate Research Awards and Colloquium, University of California, Riverside, 2008. Graduate Research Award.

Synergy: Quality of Service Support for Distributed Stream Processing Systems

Thomas Repantis, Vana Kalogeraki, Xiaohui Gu, Graduate Students Association Annual Research Conference, University of California, Riverside, 2008.

The Synergy Distributed Stream Processing Middleware

Thomas Repantis, Xiaohui Gu, Vana Kalogeraki, Board of Advisors Meeting, University of California, Riverside, 2007.

Replication Trade-Offs in Composite Distributed Applications

Thomas Repantis, Arun Iyengar, Isabelle Rouvellou, IBM Summer Student Poster Session 2007.

The Synergy Distributed Stream Processing Middleware

Thomas Repantis, Xiaohui Gu, Vana Kalogeraki, TechHorizons, University of California, Riverside, 2007.

Synergy: A Distributed Stream Processing Middleware

Thomas Repantis, Xiaohui Gu, Vana Kalogeraki, Graduate Research Awards and Colloquium, University of California, Riverside, 2007. Honorable Mention.

Defending Against Sybil Attacks in the Reliable Email Project

Thomas Repantis, Haifeng Yu, Michael Kaminsky, Phillip B. Gibbons, Abraham Flaxman, Poster and Demo Session, Intel Research Symposium 2006.

Cooperative Media Processing and Streaming

Thomas Repantis, Fang Chen, Vana Kalogeraki, 7th Annual Industry Day Poster Session, University of California, Riverside, 2005. Second Best Graduate Poster Award.

Dynamic Page Migration in Software DSM Systems

Thomas Repantis, Christos D. Antonopoulos, Vana Kalogeraki, Theodore S. Papatheodorou, 6th Annual Industry Day Poster Session, University of California, Riverside, 2004.

Patent Application

Method and System for Coordinating Updates to Replicated Data

Arun Iyengar, Thomas Repantis, IBM YOR9-2007-0716, 2008.

Technical Skills

Operating Systems

UNIX (Linux, FreeBSD, Solaris, HP-UX), MS Windows, Mac OS X, DOS.

Languages

C++, C, Java, Assembly (i8085, i80x86, ADSP-21xx), Shell, Python, Perl, SQL, LISP, PROLOG, FORTRAN, UML, HTML, XML, JavaScript, MS Visual Basic, BASIC.

APIs

STL, RPC, libasync, pthreads, TCP/IP (sockets), FreePastry, Servlets, Swing.

Applications

PlanetLab, gdb, make, ant, CVS, ClearCase, Subversion, Eclipse, emacs, doxygen, CppUnit, valgrind, log4j, samba, tomcat, apache, mod_ssl, OpenSSL, MySQL, matlab, spice, LabVIEW, ns-2, NeuroGrid P2P Simulator, ComNet III, QualNet, ERwin, LaTeX, gnuplot, MS Office.

Scholarships and Awards

University of California, Riverside

Award at the Graduate Research Awards and Colloquium, 4 awards granted throughout the university, the only recipient from Computer Science & Engineering Department, June 2008.

Gerondelis Foundation

Graduate study scholarship, May 2008.

IFIP

Student travel award for attending DSN 2008, June 2008.

University of California, Riverside

Honorable mention at the Graduate Research Awards and Colloquium, 4 awards and 4 honorable mentions granted throughout the university, the only recipient from Computer Science & Engineering Department, April 2007.

ACM

Student travel award for attending MIDDLEWARE 2006, November 2006.

City of Riverside

Honorary residency for pursuing an international academic goal, May 2006.

University of California, Riverside

Second best graduate poster award at the 7th Annual Industry Day Poster Session, 3 out of 36 nominees selected, the only awardee from Computer Science & Engineering Department, October 2005.

IEEE Computer Society, Technical Committee on Scalable Computing

Student travel award for attending CLUSTER 2005, September 2005.

IEEE Computer Society, Technical Committee on Parallel Processing

Student travel award for attending IPDPS 2005, 35 out of 75 nominees selected, April 2005.

University of California, Riverside

Dean's graduate fellowship award, September 2003-May 2005.

Erdös Number

4 (Vana Kalogeraki, Dimitrios Gunopulos, Bela Bollobas, Paul Erdös).

University of Patras

Honor for the highest GPA in the Department of Electrical & Computer Engineering on the commencement of March 2003.

Zosima Foundation

Scholarship for excellence during university studies, received after open examination from the Greek Ministry of Education, September 1997-May 2002.

International Association for the Exchange of Students for Technical Experience, German Academic Exchange Service

Scholarship for practical traineeship abroad, July 2000-August 2000.

Municipality of Patras

Honor for ranking first in the national exams for admission to the Department of Electrical & Computer Engineering of the University of Patras, approximately 150,000 total participants, September 1997.

Greek Ministry of Education

Annual honors and awards for the highest GPA in class, 1990-1996.

Professional Activities

Student member

IEEE, IEEE Computer Society, ACM, USENIX

Reviewer

Elsevier Computer Communications, IGI Handbook on Mobile P2P Computing, ICC'08, CCNS'08, PV'07, ISORC'06, LCN'05, ICPS'05, RTAS'04

External Reviewer

WWW'08, RTSS'08, WOWMOM'08, NETWORKING'08, ICDCS'07, ICPP'07, DOA'07, NETWORKING'07, INFOSCALE'07, DSN'06, SIGCOMM'05, RTSS'05, PODS'05, MDM'05, GLOBECOM'04, DBISP2P'04

Student Volunteer

CLUSTER'04

Volunteer

HP Employee Demo Day'05

Languages

English

Cambridge Certificate of Proficiency in English: Grade A, June 1999

German

Grosses Deutsches Sprachdiplom: Gut, November 2002

Greek

Native

References

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