Delivering High Resilience in Designing Platform-as-a-Service Clouds

Platform-as-a-Service (PaaS) clouds allow faster and more effective application development than traditional non-PaaS ways. One issue in designing PaaSs is how to make the development process deliver applications resilient to potential changes of the constraints. This is because any successful applications today must be as resilient as possible to dynamic external or internal constraining factors. Along this line, the first type of dynamic constraints we need to consider is the compatibility between possible components of the application. PaaSs must only engage compatible components to collaborate with each other in the same instance of applications. Other constraints include the environment that the application is running as well as the preferences of the users (or devices) that interact with the application. We present a data-flow based approach, for PaaS clouds, to designing cloud-based applications that are resilient to failures due to dynamic constraints on resources and on component compatibility. The uniqueness of our approach is the following: The procedure of building cloud-based applications is time-stamped. In this way, the composition of the application is updated anytime in accordance to the constraints in order to maximize the resilience of the application at that time. We have designed a graph structure called Instance Dependency Graphs (IDGs), and have used time-based IDGs to capture, analysis and optimize the resilience of the application. We present a case study to validate our approach.