Florian Wessling

Cloud Adaptation and Application (Re-)Distribution: Bridging the Two Perspectives

Cloud developers have to make several decisions when running their application in a cloud environment that may lead to conflicting objectives, inefficient deployment, and inappropriate or not existing adaptation strategies. Proper decision-support tools and processes are therefore needed to make cloud developers aware of the issues that need to be considered when deploying and running applications in the Cloud. Current decision support tools for cloud developers do not provide a structured and organized process in which the cloud developers can systematically check their choices when planning the deployment, execution, and adaptation of applications in the Cloud. In this paper, we combine two previous works and introduce an approach for identifying the options for (re-)deploying application in cloud providers infrastructures and the possible strategies of adaptation that can be used by the deployed application at runtime. The key contribution is a support process that synthesizes the two approaches. We also describe a case study where our support process is applied and we indicate the alternatives for application (re-)deployment and adaptation.

3-D cloud monitoring: Enabling effective cloud infrastructure and application management

A cloud environment is a complex environment composed of many different entities and layers. Each of these cloud entities may be furnished with mechanisms offering various management actions. For any given situation, different management actions may be applicable and often simultaneously. Enforcing isolated management actions or combining contradictory management actions may negatively affect cloud application quality and cloud infrastructure performance. This means that correctly selecting and effectively combining these management actions for a given situation becomes an important challenge in cloud computing. In this paper, we address the problem of identifying situations where more than one management action can be performed. The key contributions of our paper are: (1) a three dimensional (3-D) monitoring model for analyzing cloud monitoring information; (2) the concept and formalization of Context of Interest (CoI) that specifies how to retrieve meaningful information from the 3-D model to support the coordination of management actions between cloud infrastructure and application. We conducted experiments in a real testbed using Openstack and the WordPress Web site application. Our results show that analyzing cloud monitoring information using the 3-D model and the CoI can support a more effective identification of management actions to be taken.

Towards exploiting the full adaptation potential of cloud applications

Current technology for cloud application adaptation fails to capture two fundamental aspect of cloud environments: multiple adaptation options and interferences and dependencies among these multiple mechanisms. Addressing these aspects requires a significant extension of existing cloud tools and frameworks for engineering and executing cloud application adaptations. They should explicitly take into account: all entities of the cloud environment relevant for adaptation decisions; the concrete adaptation actions that these cloud entities may perform; and the mutual dependencies between those entities and actions. In this paper we provide the first insights towards such novel technology. As main contribution, we systematically elicit the key entities related to adaptations inside a cloud environment and explicitly document those in a conceptual model. To build this model we surveyed the literature, discussed with industrial partners with experience in cloud computing, and analyzed commercial solutions. We also provide a case study based on Amazon Web Services solutions, to show how our conceptual model can be instantiated and help developers to identify possible cloud application adaptation strategies.

How much blockchain do you need?: towards a concept for building hybrid DApp architectures

Adding blockchain technology to existing systems instead of building them from the ground up poses several challenges. It is difficult to find out which attributes of blockchains are important for a given use case (e.g. immutable, trustless, anonymous) and to decide which elements of an architecture should employ blockchain technologies. Current approaches generally only give a hint on whether blockchain technology makes sense for a given use case or not. This paper proposes a more fine-grained approach to decide which elements of an application architecture could benefit from the use of blockchain technology. We illustrate the first outline of our approach which identifies participants, their trust relations and interactions to derive a hybrid architecture (i.e. an architecture embedding blockchain technology in existing software systems or creating new systems using blockchain only in certain parts).

A decentralized architecture and simple consensus algorithm for autonomous agents

Autonomous agents not only need to make decisions, but also might need to negotiate situations with other autonomous systems and arrange how to proceed. Architecting such systems requires developers to weigh several options and decide, whether a central authority is beneficial or if consensus can be delegated to the agents themselves. We present a decentralized architecture accompanied by a simple consensus algorithm for autonomous agents and demonstrate its application within a simulated traffic system with model cars. We furthermore compare this concept with an older, centralized incarnation, and elaborate advantages and disadvantages.

Proof-of-property: a lightweight and scalable blockchain protocol

The expansion of blockchain technologies from financial applications to other fields intensifies the problem of an increasing size of data stored in the blockchain. Unfortunately, new participants of the blockchain network are required to download the whole blockchain to gain an overview about the state of the system and to validate incoming transactions. Approaches like IOTA, SegWit or the Lightning Network try to solve the scalability issues of blockchain applications. Unfortunately, they focus on strategies slowing down the blockchains growth instead of reducing the problems arising from a growing chain or introduce new concepts to oust the linear blockchain altogether. The approach proposed in this paper is based on the idea of Ethereum to keep the state of the system explicitly in the current block but further pursues this by including the relevant part of the current system state in new transactions as well. This enables other participants to validate incoming transactions without having to download the whole blockchain initially. Following this idea use cases can be supported that require scalable blockchain technology but not necessarily an indefinite and complete transaction history.

Codeless Engineering of Service Mashups - An Experience Report

Given that the number of ready-to-use web services is steadily growing, services will provide solutions to a vast range of business problems in the future. And thanks to findings in end-user development research, popular service integration platforms such as IFTTT and Zapier emerged, making process automation as easy as never before. This progress will affect software engineering increasingly: as fewer code is programmed, the more activities like identifying and connecting suitable services using integration platforms become prominent. To explore what it is like to engineer software without writing code, we conducted a workshop with experienced software engineers. With the objective of implementing a simple business process by integrating existing services in a mashup, we collected all lessons learned during that workshop and report them in this paper. Based on that experience, we introduce three different levels of integration and outline a software process model containing specific activities for engineering of service mashups.

Property-based routing in clustered message brokers for CPS: Doctoral Symposium

Cyber-Physical Systems (CPS) are interconnected systems that can measure, manipulate, and adapt their environment via sensors and actors. The high number of measured data means that a reliable and scalable communication infrastructure is indispensable, especially if data is processed in real time. Data can be available in different measurement qualities, which usability depends on the particular application. As a result, data is regularly discarded, resulting in network inefficiencies when they are previously transmitted. This effect becomes more important as the number of heterogeneous sensors increases. In this paper, we discuss the implications and show our first approach to solve the problem based on MQTT [1], one of the most widely used public-subscribe protocols in the area of IoT and CPS.

Finding optimized configurations for variability-intensive systems without constraint violations using a Regulatory Algorithm (RGA)

Feature selection is one of the important challenges in variability-intensive systems. The FCORE model is used for the description of the functional and non-functional requirements of a system from a systems engineering point of view. In addition we demonstrate a solution for feature selection using a regulator algorithm (RGA). The RGA is a two dimensional evolutionary algorithm, with regulator genes controlling the structural genes. This allows a direct transfer of the FCORE model into the RGA, which optimizes the feature selection without constraint violations.

Engineering a Cyber-Physical Intersection Management – An Experience Report

The engineering of cyber-physical systems (CPS) imposes a huge challenge for today’s software engineering processes. Not only are CPS very closely related to real objects and processes, also their internal structures are more heterogeneous than classical information systems. In this experience report, we account on a prototypical implementation for an intersection management system on the basis of physical models in the form of robotic cars. The steps to implement the working physical prototype are described. Lessons learned during the implementation are presented and observations compared against known software processes. The insights gained are consolidated into the novel Double Twin Peaks model. The latter extends the current software engineering viewpoints, specifically taking CPS considerations into account.