I. Introduction
Cloud computing has tremendously changed the way we live, work, and study since its inception around 2005 [1]. For example, software as a service (SaaS) instances, such as Google Apps, Twitter, Facebook, and Flickr, have been widely used in our daily life. Moreover, scalable infrastructures as well as processing engines developed to support cloud service are also significantly influencing the way of running business, for instance, Google File System [2], MapReduce [3], Apache Hadoop [4], Apache Spark [5], and so on.