An online evolutionary approach to developing Internet services

High dependability in Internet services is a difficult chal-lenge: new features are constantly added, the systems are be-ing scaled to support more users, and these systems are sub-ject to unpredictable workloads and inputs. To deal with these challenges, operators must constantly adapt and evolve their system in response to its dynamic behavior. We argue that this online evolution is necessary for the development and de-ployment of dependable Internet services. This paper presents a conceptual model of online evolution consisting of three phases—monitoring, analysis, and modification—and present techniques we have found useful in speeding the process of online evolution.