Ops-Scale: Scalable and Elastic Cloud Operations by a Functional Abstraction and Feedback Loops

Recent research has proposed new techniques to streamline the autoscaling of cloud applications, but little effort has been made to advance configuration management (CM) systems for such elastic operations. Existing practices use CM systems, from the DevOps paradigm, to automate operations. However, these practices still require human intervention to program ad hoc procedures to fully automate reconfiguration. Moreover, even after careful programming of cloud operations, the backing models are insufficient for re-running such programs unchanged in other platforms-which implies an overhead in rewriting the programs. We argue that CM programs can be designed to be deployment-agnostic and highly elastic with well-defined abstractions. In this paper, we introduce our abstraction based on declarative functional programming, and we demonstrate it using a feedback loop control mechanism. Our proposal, called Ops-Scale, is a family of cloud operations that are derived by making a functional abstraction over existing configuration programs. The hypothesis in this paper is twofold: 1) it should be possible to make a highly declarative CM system rich enough to capture fine-grained reconfigurations of autoscaling automatically, and; 2) that a program written for a specific deployment can be re-used in other deployments. To test this hypothesis, we have implemented an open source configuration engine called Karamel that is already used in industry for large-scale cluster deployments. Results show that at scale Ops-Scale can capture a polynomial order of reconfiguration growth in a fully automated manner. In practice, recent deployments have demonstrated that Karamel can provision clusters of 100 virtual machines consisting of many-layers distributed services on Google's IaaS Cloud in 'less than 10 minutes'.