CloudGC: Recycling Idle Virtual Machines in the Cloud

Cloud computing conveys the image of a pool of unlimited virtual resources that can be quickly and easily provisioned to accommodate the user requirements. However, this flexibility may require to adjust physical resources at the infrastructure level to keep the pace of user requests. While elasticity can be considered as the de facto solution to support this issue, this elasticity can still be broken by budget requirements or physical limitations of a private cloud. In this paper, we therefore explore an alternative, yet complementary, solution to the problem of resource provisioning by adopting the principles of garbage collection in the context of cloud computing. In particular, our approach consists in detecting idle virtual machines to recycle their resources when the cloud infrastructure reaches its limits. We implement this approach, named CloudGC, as a new middleware service integrated within OpenStack and we demonstrate its capacity to stop the waste of cloud resources. CloudGC periodically recycles idle VM instances and automatically recovers them whenever needed. Thanks to CloudGC, cloud infrastructures can even switch between operational configurations depending on periods of activities.