| 1. |
- Farokhi, Soodeh, et al.
(author)
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A hybrid cloud controller for vertical memory elasticity : a control-theoretic approach
- 2016
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In: Future generations computer systems. - : Elsevier. - 0167-739X .- 1872-7115. ; 65, s. 57-72
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Journal article (peer-reviewed)abstract
- Web-facing applications are expected to provide certain performance guarantees despite dynamic and continuous workload changes. As a result, application owners are using cloud computing as it offers the ability to dynamically provision computing resources (e.g., memory, CPU) in response to changes in workload demands to meet performance targets and eliminates upfront costs. Horizontal, vertical, and the combination of the two are the possible dimensions that cloud application can be scaled in terms of the allocated resources. In vertical elasticity as the focus of this work, the size of virtual machines (VMs) can be adjusted in terms of allocated computing resources according to the runtime workload. A commonly used vertical resource elasticity approach is realized by deciding based on resource utilization, named capacity-based. While a new trend is to use the application performance as a decision making criterion, and such an approach is named performance-based. This paper discusses these two approaches and proposes a novel hybrid elasticity approach that takes into account both the application performance and the resource utilization to leverage the benefits of both approaches. The proposed approach is used in realizing vertical elasticity of memory (named as vertical memory elasticity), where the allocated memory of the VM is auto-scaled at runtime. To this aim, we use control theory to synthesize a feedback controller that meets the application performance constraints by auto-scaling the allocated memory, i.e., applying vertical memory elasticity. Different from the existing vertical resource elasticity approaches, the novelty of our work lies in utilizing both the memory utilization and application response time as decision making criteria. To verify the resource efficiency and the ability of the controller in handling unexpected workloads, we have implemented the controller on top of the Xen hypervisor and performed a series of experiments using the RUBBoS interactive benchmark application, under synthetic and real workloads including Wikipedia and FIFA. The results reveal that the hybrid controller meets the application performance target with better performance stability (i.e., lower standard deviation of response time), while achieving a high memory utilization (close to 83%), and allocating less memory compared to all other baseline controllers.
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| 2. |
- Filieri, Antonio, et al.
(author)
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Control Strategies for Self-Adaptive Software Systems
- 2017
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In: ACM Transactions on Autonomous and Adaptive Systems. - : Association for Computing Machinery (ACM). - 1556-4665 .- 1556-4703. ; 11:4
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Journal article (peer-reviewed)abstract
- The pervasiveness and growing complexity of software systems are challenging software engineering to design systems that can adapt their behavior to withstand unpredictable, uncertain, and continuously changing execution environments. Control theoretical adaptation mechanisms have received growing interest from the software engineering community in the last few years for their mathematical grounding, allowing formal guarantees on the behavior of the controlled systems. However, most of these mechanisms are tailored to specific applications and can hardly be generalized into broadly applicable software design and development processes.This article discusses a reference control design process, from goal identification to the verification and validation of the controlled system. A taxonomy of the main control strategies is introduced, analyzing their applicability to software adaptation for both functional and nonfunctional goals. A brief extract on how to deal with uncertainty complements the discussion. Finally, the article highlights a set of open challenges, both for the software engineering and the control theory research communities.
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| 3. |
- Filieri, Antonio, et al.
(author)
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Software Engineering Meets Control Theory
- 2015
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In: 2015 10th International Symposium on Software Engineering for Adaptive and Self-Managing Systems. - Piscataway, NJ, USA : IEEE Press. - 9780769555676 ; , s. 71-82
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Conference paper (peer-reviewed)abstract
- The software engineering community has proposed numerous approaches for making software self-adaptive. These approaches take inspiration from machine learning and control theory, constructing software that monitors and modifies its own behavior to meet goals. Control theory, in particular, has received considerable attention as it represents a general methodology for creating adaptive systems. Control-theoretical software implementations, however, tend to be ad hoc. While such solutions often work in practice, it is difficult to understand and reason about the desired properties and behavior of the resulting adaptive software and its controller. This paper discusses a control design process for software systems which enables automatic analysis and synthesis of a controller that is guaranteed to have the desired properties and behavior. The paper documents the process and illustrates its use in an example that walks through all necessary steps for self-adaptive controller synthesis.
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| 4. |
- Pahl, Claus, et al.
(author)
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Cloud architecture continuity : Change models and change rules for sustainable cloud software architectures
- 2017
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In: Journal of Software. - : Wiley-Blackwell. - 2047-7473 .- 2047-7481. ; 29:2
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Journal article (peer-reviewed)abstract
- Cloud systems provide elastic execution environments of resources that link application and infrastructure/platform components, which are both exposed to uncertainties and change. Change appears in 2 forms: the evolution of architectural components under changing requirements and the adaptation of the infrastructure running applications. Cloud architecture continuity refers to the ability of a cloud system to change its architecture and maintain the validity of the goals that determine the architecture. Goal validity implies the satisfaction of goals in adapting or evolving systems. Architecture continuity aids technical sustainability, that is, the longevity of information, systems, and infrastructure and their adequate evolution with changing conditions. In a cloud setting that requires both steady alignment with technological evolution and availability, architecture continuity directly impacts economic sustainability. We investigate change models and change rules for managing change to support cloud architecture continuity. These models and rules define transformations of architectures to maintain system goals: Evolution is about unanticipated change of structural aspects of architectures, and adaptation is about anticipated change of architecture configurations. Both are driven by quality and cost, and both represent multidimensional decision problems under uncertainty. We have applied the models and rules for adaptation and evolution in research and industry consultancy projects.
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| 5. |
- Trubiani, Catia, et al.
(author)
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Performance Issues? : Hey DevOps, Mind the Uncertainty!
- 2019
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In: IEEE Software. - 0740-7459 .- 1937-4194. ; 36:2, s. 110-117
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Journal article (peer-reviewed)abstract
- DevOps is a novel trend that aims to bridge the gap between software development and operation teams. When applied to the performance evaluation process, it brings new challenges since developers need to be aware of the deployment settings and application runtime characteristics. At the operational stage, several uncertainties, e.g., workload fluctuations and resource availability, may affect the performance analysis. The goal of this paper is to identify the uncertain parameters and quantify their propagation to performance analysis results, in order to bring upfront the main system criticisms. To this end, we make use of a popular big data system showing that the sources of uncertainty may span on different characteristics and the performance analysis results can be heavily affected by these uncertainties. The paper contributes as an experience report aiming to better identify performance uncertainties through a case study. It provides a step-by-step guide to practitioners for controlling system uncertainties.
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| 6. |
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| 7. |
- Weyns, Danny, et al.
(author)
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Guidelines for Artifacts to Support Industry-Relevant Research on Self-Adaptation
- 2022
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In: Software Engineering Notes. - : ACM Press. - 0163-5948 .- 1943-5843. ; 47:4, s. 18-24
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Journal article (other academic/artistic)abstract
- Artifacts support evaluating new research results and help comparing them with the state of the art in a field of interest. Over the past years, several artifacts have been introduced to support research in the field of self-adaptive systems. While these artifacts have shown their value, it is not clear to what extent these artifacts support research on problems in self-adaptation that are relevant to industry. This paper provides a set of guidelines for artifacts that aim at supporting industry-relevant research on selfadaptation. The guidelines that are grounded on data obtained from a survey with practitioners were derived during working sessions at the 17th International Symposium on Software Engineering for Adaptive and Self-Managing Systems. Artifact providers can use the guidelines for aligning future artifacts with industry needs; they can also be used to evaluate the industrial relevance of existing artifacts. We also propose an artifact template.
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