1. Patterns for Resource Reallocation in OODRE Systems Joe Cross joseph.k.cross@lmco.com Patrick Lardieri patrick.j.lardieri@lmco.com This work was sponsored by DARPA under contract number F33615-01-C-1847

2. Problem and Context These patterns apply to systems –on which the service requirements 1 change, or –in which the set of available resources 2 changes Hence resources must be allocated to different purposes at different times How and when are such resource reallocations –planned? –triggered? –implemented? 1.E.g., cycles per second for processing, bandwidth or reliability for inter-process communication 2.E.g., processors, switches, radios

3. Two Solution Patterns Proactive Resource Reallocation Reactive Resource Reallocation

4. Known Uses A web page server that reacts to changes in hits-per-minute Proactive Resource Reallocation Reactive Resource Reallocation An air traffic control system that has a normal mode and a degraded mode

5. How to Choose Reactive resource reallocation is good where QoS requirements loads component availability all change slowly relative to the time needed to plan and implement a reallocation. Proactive resource reallocation is good when you have hard time bounds on reallocations.

6. Common Features Require reflective capabilities for use in long-lived systems Require, in general, reflective capabilities that can forecast performance (e.g., under loads, performance would be provided) Raise concerns of convergence and stability Present challenges when Powerpointing a skeptical customer (cf. the Tacoma Narrows Bridge) Both proactive and reactive resource reallocation

7. Interaction in Proactive Resource Reallocation