Abstract
New VM instances are created from static templates that contain the basic configuration of the VM to achieve elasticity with regards to capacity. Instance specific settings can be injected into the VM during the deployment phase through means of contextualization. So far this is limited to a single data source and data remains static throughout the lifecycle of the VM. We present a layered approach to contextualization that supports different classes of contextualization data available from several sources. The settings are made available to the VM through virtual devices. Inside each VM data from different classes are layered on top of each other to create a unified file hierarchy. Context data can be modified during runtime by updating the contents of the virtual devices, making our approach the first contextualization approach to natively support recontextualization. Recontextualization enables runtime reconfiguration of an executing service and can act as a trigger and key enabler of self-* techniques. This trigger provides a service with a mechanism to adapt or optimize itself in response to a changing environment. The runtime reconfiguration using recontextualization and its potential gains are illustrated in an example with a distributed file system, demonstrating the feasibility of our approach.
Highlights
One of the key characteristics of cloud computing is rapid elasticity [1]; the ability to quickly provision or release resources assigned to a cloud service in order to respond to current demand
In our previous work we argued that contextualization in cloud computing is a highly pervasive key technological requirement of any cloud service, where elastic resource management is critical to the on-demand scalability of a service [3]
We focus on Infrastructure as a Service (IaaS) contextualization of Virtual Machine (VM) comprising a cloud service
Summary
One of the key characteristics of cloud computing is rapid elasticity [1]; the ability to quickly provision or release resources assigned to a cloud service in order to respond to current demand. In the Infrastructure as a Service (IaaS) model, cloud services are normally comprised of a set of different components, each defined using a Virtual Machine (VM) template. The capacity of a cloud service can be adapted during runtime by adjusting the number of running VM instances of each template. This makes it possible to scale each part of the service independently. Virtualization Hardware virtualization techniques [7, 8] provide means of dynamically segmenting the physical hardware into smaller virtual compartments This makes it possible to run several different VMs in parallel on the same physical hardware. The physical resources are subdivided, managed, and made available to the executing VMs through a Hypervisor
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