Dragonfly is an intelligent P2P based image and file distribution system. It aims to resolve issues related to low-efficiency, low-success rate and waste of network bandwidth in file transferring process. Especially in large-scale file distribution scenarios such as application distribution, cache distribution, log distribution, image distribution, etc. In Alibaba, Dragonfly is invoked 2 Billion times and the data distributed is 3.4PB every month. Dragonfly has become one of the most important pieces of infrastructure at Alibaba. The reliability is up to 99.9999% (*1).