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Contrôle des applications fondé sur la qualité de service pour les plate-formes logicielles dématérialisées (Cloud)

Abstract : Cloud computing is a new computing model. Infrastructure, application and data are moved from local machines to internet and provided as services. Cloud users, such as application owners, can greatly save budgets from the elasticity feature, which refers to the “pay as you go” and on-demand characteristics, of cloud service. The goal of this thesis is to manage the Quality of Service (QoS) for applications running in cloud environments Cloud services provide application owners with great flexibility to assign “suitable” amount of resources according to the changing needs, for example caused by fluctuating request rate. “Suitable” or not needs to be clearly documented in Service Level Agreements (SLA) if this resource demanding task is hosted in a third party, such as a Platform as a Service (PaaS) provider. In this thesis, we propose and formally describe PSLA, which is a SLA description language for PaaS. PSLA is based on WS-Agreement, which is extendable and widely accepted as a SLA description language. Before signing the SLA contract, negotiations are unavoidable. During negotiations, the PaaS provider needs to evaluate if the SLA drafts are feasible or not. These evaluations are based on the analysis of the behavior of the application deployed in the cloud infrastructure, for instance throughput of served requests, response time, etc. Therefore, application dependent analysis, such as benchmark, is needed. Benchmarks are relatively costly and precise feasibility study usually imply large amount of benchmarks. In this thesis, we propose a benchmark based SLA feasibility study method to evaluate whether or not a SLA expressed in PSLA, including QoS targets, resource constraints, cost constraints and workload constraints can be achieved. This method makes tradeoff between the accuracy of a SLA feasibility study and benchmark costs. The intermediate of this benchmark based feasibility study process will be used as the workload-resource mapping model of our runtime control method. When application is running in a cloud infrastructure, the scalability feature of cloud infrastructures allows us to allocate and release resources according to changing needs. These resource provisioning activities are named runtime control. We propose the Runtime Control method based onSchedule, REactive and PROactive methods (RCSREPRO). Changing needs are mainly caused by the fluctuating workload for majority of the applications running in the cloud. The detailed workload information, for example the request arrival rates at scheduled points in time, is difficult to be known before running the application. Moreover, workload information listed in PSLA is too rough to give a fitted resource provisioning schedule before runtime. Therefore, runtime control decisions are needed to be performed in real time. Since resource provisioning actions usually require several minutes, RCSREPRO performs a proactive runtime control which means that it predicts future needs and assign resources in advance to have them ready when they are needed. Hence, prediction of the workload and workload-resource mapping are two problems involved in proactive runtime control. The workload-resource mapping model, which is initially derived from benchmarks in SLA feasibility study is continuously improved in a feedback way at runtime, increasing the accuracy of the control.To sum up, we contribute with three aspects to the QoS management of application running in the cloud: creation of PSLA, a PaaS level SLA description language; proposal of a benchmark based SLA feasibility study method; proposal of a runtime control method, RCSREPRO, to ensure the SLA when the application is running. The work described in this thesis is motivated and funded by the FSN OpenCloudware project (www.opencloudware.org).
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Ge Li. Contrôle des applications fondé sur la qualité de service pour les plate-formes logicielles dématérialisées (Cloud). Informatique mobile. Université Grenoble Alpes, 2015. Français. ⟨NNT : 2015GREAA018⟩. ⟨tel-01204770⟩

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