DMDA A Dynamic Service Architecture for Scientific Computing Jesper Andersson Software Technology Group Växjö University

Motivation : LOIS/LOFAR Huge, wide-area, time-coherent sensor array under construction in Europe, with an outrigger in Scandinavia, centered around Växjö, Sweden Primarily intended for radio based astrophysics 13,500 digital receptor nodes clustered to about 100 stations Total data rate of 25 Tbps (more than 700 DVDs per second) 40 Tflops computational power distributed across the nodes and stations.

Requirements Programmability –The development of applications for the sensor network must be intuitive and have a short time-frame from idea to deployed application. Performance –The performance of the sensor network must match the combined data rate and quality of service requirements of all deployed software. Interoperability –The sensor network must be open, i.e. it must be able to interoperate with external applications, both in terms of providing and using data. Adaptability –The sensor network must be able to deal with run-time evolution.

Architecture Service Oriented Architecture Usability Loose coupling and dynamic discovery Loosing coupling comes at a cost –The overhead of implementations using current SOA technologies can be very high –WS/SOAP messages are more than an order of magnitude larger than the optimal

Architecture (cont’d) Data-Driven Architecture Performance can be achieved Solution is static, due to scheduling –All programs must be known before the system is deployed –If a new program is to be added, the entire system must be redeployed –All entry-points for interoperation with other entities must be known before- hand Well-known field with many nice results

Architecture Mapping MDA-like transformation PIM Services UML PSM task Services and Tasks Aggregations and Data- dependencies PSM schedule Sequential programs, assigned to processors Communication primitives

Dynamic Model Driven Architecture The MDA-like transformation is extended with dynamism General dynamism pattern Probes Actuators Validators Coordinators Generators

Design Decisions Issues Requirement – Architecture principle –Pattern Catalog? –“Best-fit principle”, trade-offs What is a design decision? A base-line? Including all decisions leading up to the “big-one” Discourse The rationale Decision interaction –Impact – Cross-cutting vs. local –Context dependent evaluation