Dragonfly is an intelligent P2P based file distribution system. It resolves issues like low-efficiency, low-success rate and waste of network bandwidth in large-scale file distribution scenarios such as application deployment, large-scale cache file distribution, data file distribution, image distribution etc. At Alibaba, the system transfers 2 billion times and distributes 3.4PB of data every month, it has become one of the most important piece of infrastructure at Alibaba. The reliability is up to 99.9999%.