Christoph Fehling

Cloud computing patterns

ing them into more general ones, such as progress bars, traffic lights, or change tendencies (increase/decrease) as depicted in Fig. 4.16. If the application scenario for such abstractions and approximations, thus, if the user of the applications does not require consistent data values, a data abstractor should be implemented to increase the beneficial effects of eventually consistent storage offerings.

A Framework for Optimized Distribution of Tenants in Cloud Applications

To be successful a cloud service provider has to target a preferably large customer group to leverage economies of scale. Therefore an application offered as a service in the cloud is often configurable regarding non-functional qualities, such as location or availability. Since many of these qualities depend on the resources on which the service is hosted, a large number of computing environments has to be managed by the service provider. This paper analyses the challenges arising from such a scenario and identifies several optimization opportunities originating from an intelligent distribution of users among the functionally equal resources with different quality of services. A framework enabling the development of distribution strategies exploiting these opportunities is defined. It allows modeling of resources, their deployment dependencies, and users with specific demands. An architecture and prototype of a management system is introduced to handle the required resource provisioning and user request routing. Several optimization strategies are defined and their performance is evaluated using statistical data of an existing cloud service provider.

An architectural pattern language of cloud-based applications

The properties of clouds -- elasticity, pay-per-use, and standardization of the runtime infrastructure -- enable cloud providers and users alike to benefit from economies of scale, faster provisioning times, and reduced runtime costs. However, to achieve these benefits, application architects and developers have to respect the characteristics of the cloud environment. To reduce the complexity of cloud application architectures, we propose a pattern-based approach for cloud application design and development. We defined a pattern format to describe the principles of cloud computing, available cloud offerings, and cloud application architectures. Based on this format we developed an architectural pattern language of cloud-based applications: through interrelation of patterns for cloud offering descriptions and cloud application architectures, developers are guided during the identification of cloud environments and architecture patterns applicable to their problems. We cover the proceeding how we identified patterns in various information sources and existing productively used applications, give an overview of previously discovered patterns, and introduce one new pattern. Further, we propose a framework for the organizations of patterns and the guidance of developers during pattern instantiation.

Pattern-Based Development and Management of Cloud Applications

Cloud-based applications require a high degree of automation regarding their IT resource management, for example, to handle scalability or resource failures. This automation is enabled by cloud providers offering management interfaces accessed by applications without human interaction. The properties of clouds, especially pay-per-use billing and low availability of individual resources, demand such a timely system management. We call the automated steps to perform one of these management tasks a “management flow”. Because the emerging behavior of the overall system is comprised of many such management flows and is often hard to predict, we propose defining abstract management flows, describing common steps handling the management tasks. These abstract management flows may then be refined for each individual use case. We cover abstract management flows describing how to make an application elastic, resilient regarding IT resource failure, and how to move application components between different runtime environments. The requirements of these management flows for handled applications are expressed using architectural patterns that have to be implemented by the applications. These dependencies result in abstract management flows being interrelated with architectural patterns in a uniform pattern catalog. We propose a method by use of a catalog to guide application managers during the refinement of abstract management flows at the design stage of an application. Following this method, runtime-specific management functionality and management interfaces are used to obtain automated management flows for a developed application.

Combining horizontal and vertical composition of services

Service composition is a well-established field of research in the service community. Services are commonly regarded as black boxes with well-defined interfaces that can be recursively aggregated into new services. The black-box nature of services does not only include the service implementation but also implies the use of middleware and hardware to run the services. Thus, service composition techniques are typically limited to choosing between a set of available services. In this paper, we keep the black-box nature and the principle of information hiding of services, but in addition we break up services vertically. By introducing vertical service composition, we allow services to be provisioned on demand using the middleware and runtime environment that specifically meets user-required quality of services. Therefore, a service is setup individually for services requestors instead of providing them with a pre-determined list of available services to choose from. We introduce the concept of vertical service composition and present an extension to an enterprise service bus that implements the concept of vertical service composition by combining concepts from provisioning with those of (dynamic) service binding.

Capturing Cloud Computing Knowledge and Experience in Patterns

The industry-driven evolution of cloud computing tends to obfuscate the common underlying architectural concepts of cloud offerings and their implications on hosted applications. Patterns are one way to document such architectural principles and to make good solutions to reoccurring (architectural) cloud challenges reusable. To capture cloud computing best practice from existing cloud applications and provider-specific documentation, we propose to use an elaborated pattern format enabling abstraction of concepts and reusability of knowledge in various use cases. We present a detailed step-by-step pattern identification process supported by a pattern authoring toolkit. We continuously apply this process to identify a large set of cloud patterns. In this paper, we introduce two new cloud patterns we identified in industrial scenarios recently. The approach aims at cloud architects, developers, and researchers alike to also apply this pattern identification process to create traceable and well-structured pieces of knowledge in their individual field of expertise. As entry point, we recap challenges introduced by cloud computing in various domains.

Flexible Process-Based Applications in Hybrid Clouds

Cloud applications target large costumer groups to leverage economies of scale. To increase the number of customers, a flexible application design is of major importance. It enables customers to adjust the application to their individual needs in a self-service manner. In this paper, we classify the required variability of these flexible applications: data variability -- changes to handled data structures, functional variability -- changes to the processes that the application supports, user interface variability -- changes to the appearance of the application, provisioning variability -- the ability of the application to be deployed in different runtime environments. Existing and new technologies and tools are leveraged to realize these classes of variability. Further, we cover architectural principles to follow during the design of flexible cloud applications and we introduce an abstract architectural pattern to enable data variability.

Service Migration Patterns -- Decision Support and Best Practices for the Migration of Existing Service-Based Applications to Cloud Environments

In many ways cloud computing is an extension of the service-oriented computing (SOC) approach to create resilient and elastic hosting environments and applications. Service-oriented Architectures (SOA), thus, share many architectural properties with cloud environments and cloud applications, such as the distribution of application functionality among multiple application components (services) and their loosely coupled integration to form a distributed application. Existing service-based applications are, therefore, ideal candidates to be moved to cloud environments in order to benefit from the cloud properties, such as elasticity or pay-per-use pricing models. In order for such an application migration and the overall restructuring of an IT application landscape to be successful, decisions have to be made regarding (i) the portion of the application stack to be migrated and (ii) the process to follow during the migration in order to guarantee an acceptable service level to application users. In this paper, we present best practices how we addressed these challenges in form of service migration patterns as well as a methodology how these patterns should be applied during the migration of a service-based application or multiples thereof. Also, we present an implementation of the approach, which has been used to migrate a web-application stack from Amazon Web Services to the T-Systems cloud offering Dynamic Services for Infrastructure (DSI).

Compliance Domains: A Means to Model Data-Restrictions in Cloud Environments

It is crucial for enterprises to execute business operations in a compliant way. This is especially true for IT-driven business processes as enterprises may face considerable fines when violating laws and regulation in their business processes. Through the advent of cloud computing, a new dimension of compliance requirements within the research area of compliant business process design has emerged. Data-sovereignty is one of the major compliance concerns enterprises have to deal with when moving applications and data to the cloud. Enterprises are fully responsible for their data, also when the data is not present within their IT premises anymore. This lead to the policy that specific data must not leave the IT premises of the enterprise. In this paper we present an approach to support the human process designer in modelling compliant business processes. We are focusing on compliance requirements which have to be considered in the field of cloud computing. These requirements have been created to meet laws and regulations. These laws and regulations are considering data which is to other countries, for example. Looking at the characteristics of these requirements, we deal with data-centric compliance rules here.

Composite as a Service: Cloud Application Structures, Provisioning, and Management

Abstract Cloud computing and corresponding “as a service” models have transformed the way in which IT resources can be consumed. By taking advantage of the properties of the cloud — elasticity, pay-per-use and standardization — customers and providers alike can benefit from economies of scale, faster provisioning times and reduced costs. However, to fully exploit the potentials of the cloud, it is necessary, that applications, to be deployed on the cloud, support the inherent cloud properties. In this article we investigate how applications can be designed to comply with cloud infrastructures. We present a framework that allows modeling the variability within such applications regarding their structure, functional, and non-functional properties, as well as their deployment. Using these models the framework guides the user during the customization of an application, provisions it on available clouds, and enables common management functionality for cloud applications, such as elasticity, suspend, and resume. Zusammenfassung Cloud Computing und die dazugehörigen Geschäftsmodelle haben die Art und Weise, in der IT Ressourcen genutzt werden, dramatisch verändert. Aufgrund der Cloud spezifischen Eigenschaften, wie Elastizität, flexiblen Preismodellen und Standardisierung, können Anbieter und Kunden gleichermaßen von Skaleneffekten, kürzeren Bereitstellungszeiten und Kostenreduktion profitieren. Um allerdings diese positiven Eigenschaften von Clouds ausnutzen zu können, ist es notwendig, dass diese auch innerhalb der Anwendung berücksichtigt werden. In diesem Artikel stellen wir ein Framework vor, mit dem die Variabilität solcher Anwendungen bezüglich ihrer Struktur, funktionalen und nicht-funktionalen Eigenschaften, sowie ihres Deployments modelliert werden kann. Auf Basis der hierzu erstellten Modelle begleitet das Framework den Nutzer während der Anpassung der Anwendung an seine Bedürfnisse und provisioniert sie auf verfügbaren Clouds. Weiterhin nutzt es die Modelle, um kundenspezifische Managementfunktionalität, wie Elastizität, Suspend und Resume, zu realisieren.