The ability to scale up is an essential ability for large computer systems that handle numerous simultaneous tasks reliably. It follows that these systems must support parallelism for performance and redundancy for fault tolerance. But parallelism and redundancy are not the most important abilities needed for scalability. A scalable system will, simply because it is scalable, often be pushed beyond its capacity to work. It will be overloaded. Therefore, an essential ability of a scalable system is that it must be able to handle overload, when offered work exceeds the system’s capacity to process it. The essence of scalability is the ability to handle overload. In this talk I explain how to design systems to handle overload. I show that there are two fundamentally different kinds of overload, namely temporary overload and permanent overload, that require completely different mechanisms. Scalable systems must support both kinds and I explain how this can be done. I give examples of production systems that do this right. Unfortunately there are many systems that do it wrong, and I give examples of some famous catastrophes that have resulted. I conclude with some general laws that are observed in working scalable systems, both manmade and natural. This talk is part of an ongoing project on system design with PNSol (UK).

Peter Van Roy is professor in the ICTEAM Institute at the Université catholique de Louvain (Belgium). He has over 30 years experience in programming languages, distributed systems, and system design. He is author of the classic textbook Concepts, Techniques, and Models of Computer Programming, MIT Press (2004). He was a partner in numerous EU projects and he initiated and coordinated the LightKone Horizon 2020 project on edge computing based on CRDTs (2016-2019). He is currently working on the ΔQSD system design paradigm with PNSol (UK), on computer-aided music composition based on constraint programming with IRCAM (France), and on edge computing based on Erlang and GRiSP with Stritzinger GmbH (Germany). He will give a full-day tutorial on ΔQSD at ICPE 2024 (London) on May 7, 2024.

The seminar can also be followed on Teams

Sandwiches will be provided, please fill in the form. Deadline Day D 9:00 am