An Approach for the Automation of IaaS Cloud Upgrade
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An Infrastructure as a Service (IaaS) cloud provider is committed to each tenant by a service level agreement (SLA) which indicates the terms of commitment, e.g. the level of availability of the IaaS cloud service.The different resources providing this IaaS cloud service may need to be upgraded several times throughout their life-cycle; and these upgrades may affect the service delivered by the IaaS layer. This may violate the SLAs towards the tenants and result in penalty as they impact the tenant services relying on the IaaS.Therefore, it is important to handle upgrades properly with respect to the SLAs.The upgrade of IaaS cloud systems inherits all the challenges of clustered systems and faces other, cloud specific challenges, such as size and dynamicity due to elasticity.In this paper, we propose a novel approach to automatically upgrade an IaaS cloud system under SLA constraints such as availability and elasticity.In this approach, the upgrade methods and actions appropriate for each upgrade request are identified, scheduled, and applied automatically in an iterative manner based on the vendors descriptions of the infrastructure components, the tenant SLAs, and the status of the system. The proposed approach allows new upgrade requests during ongoing upgrades, which makes it suitable for continuous delivery.In addition, it also handles failures of upgrade actions through localized retry and undo operations automatically.
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