Josef Spillner

Ad-Hoc Usage of Web Services with Dynvoker

While web services are often targeted at machine-to-machine communication, they are also increasingly used directly in the interactions between humans and machines. Instead of developing specialised client applications for the invocation of these services, a generic human-driven ad-hoc usage is beneficial in many scenarios, including rapid service testing and dynamic inclusion of services as plugins into applications. We argue for the need for such a usage and extract requirements for generic web service clients. We then present a few selected use cases and introduce the Dynvoker client which already passes the majority of evaluation criteria. With its technical capabilities and open and vivid development, we consider it the most suitable and flexible generic client available and therefore highlight its role as a central component in a user-centric web service research project.

Information Dispersion over Redundant Arrays of Optimal Cloud Storage for Desktop Users

Data storage in cloud computing centres is gaining popularity for personal and institutional data backups as well as for highly scalable access from software applications running on attached compute servers. The data is usually access-protected, encrypted and replicated depending on the security and scalability needs. Despite the advances in technology, the practical usefulness and longevity of so-called cloud storage is limited in todays systems which severely impacts the acceptance and adoption rates. Therefore, we introduce a novel cloud storage management architecture which combines storage resources from multiple providers so that redundancy, security and other non-functional properties can be adjusted adequately to the needs of the user. Furthermore, we present NubiSave, a user-friendly implementation with configurable adequate overhead which runs on and integrates into contemporary desktop systems. Finally, a brief analysis of measurements performed by us shows how well the system performs in a real distributed cloud storage environment.

Dynamic SLA Template Adjustments Based on Service Property Monitoring

Service Level Agreements (SLAs) are used to manifest guarantees about certain functional and non-functional aspects of service execution.Service providers are confronted with a hard problem when trying to estimate reasonable QoS levels and other default settings for SLA templates.The insufficient use of formal service behavior descriptions, varying resource demands and a choice of configuration options expected by users contribute to this issue.We present our solution of gathering monitoring data at runtime and feeding it back into the service registry to adjust descriptions and make contract template derivation a more realistic process. In addition, we show how to extend SOA building blocks such as service discoveries and SLA managers with the adjustment mechanism.

Self-managing cloud-native applications : design, implementation and experience

Abstract Running applications in the cloud efficiently requires much more than deploying software in virtual machines. Cloud applications have to be continuously managed: (1) to adjust their resources to the incoming load and (2) to face transient failures replicating and restarting components to provide resiliency on unreliable infrastructure. Continuous management monitors application and infrastructural metrics to provide automated and responsive reactions to failures (health management) and changing environmental conditions (auto-scaling) minimizing human intervention. In the current practice, management functionalities are provided as infrastructural or third party services. In both cases they are external to the application deployment. We claim that this approach has intrinsic limits, namely that separating management functionalities from the application prevents them from naturally scaling with the application and requires additional management code and human intervention. Moreover, using infrastructure provider services for management functionalities results in vendor lock-in effectively preventing cloud applications to adapt and run on the most effective cloud for the job. In this paper we discuss the main characteristics of cloud native applications, propose a novel architecture that enables scalable and resilient self-managing applications in the cloud, and relate on our experience in porting a legacy application to the cloud applying cloud-native principles.

Distributed Contracting and Monitoring in the Internet of Services

The recent approval of the EU Services Directive is fostering the Internet of Services (IoS) and will promote the emergence of marketplaces for business and real-world services. From a research perspective, the IoS will require a new bread of technological infrastructures to support the concepts of business service description, contract management from various perspectives, end-to-end marketplaces, and business monitoring. The IoS is a vision referring to web service-based digital societies. When service hosting moves from best-effort provisioning to guaranteed service delivery, monitoring becomes a crucial point of proof for providers and consumers of such services. We present the uplifting of technical contract monitoring results to business effects based on the distributed service infrastructure developed in project THESEUS, use case TEXO.

Experimental evaluation of the cloud-native application design

Cloud-Native Applications (CNA) are designed to run on top of cloud computing infrastructure services with inherent support for self-management, scalability and resilience across clustered units of application logic. Their systematic design is promising especially for recent hybrid virtual machine and container environments for which no dominant application development model exists. In this paper, we present a case study on a business application running as CNA and demonstrate the advantages of the design experimentally. We also present Dynamite, an application auto-scaler designed for containerised CNA. Our experiments on a Vagrant host, on a private OpenStack installation and on a public Amazon EC2 testbed show that CNA require little additional engineering.

Energy-Efficient Databases Using Sweet Spot Frequencies

Database management systems (DBMS) are typically tuned for high performance and scalability. Nevertheless, carbon footprint and energy efficiency are also becoming increasing concerns. Unfortunately, existing studies mainly present theoretical contributions but fall short on proposing practical techniques. These could be used by administrators or query optimizers to increase the energy efficiency of the DBMS. Thus, this paper explores the effect of so-called sweet spots, which are energy-efficient CPU frequencies, on the energy required to execute queries. From our findings, we derive the Sweet Spot Technique, which relies on identifying energy-efficient sweet spots and the optimal number of threads that minimizes energy consumption for a query or an entire database workload. The technique is simple and has a practical implementation leading to energy savings of up to 50% compared to using the nominal frequency and maximum number of threads.

Flexible data distribution policy language and gateway architecture

Concerns about the security and reliability of data storage in online systems, alias cloud storage services, have led to the design of application-independent storage overlays and controllers which guarantee security and optimality with regards to the requirements of their users. In roaming and multi-user environments, the configuration and rules steering these controllers should be easily extensible and migratable in order to not simply shift the vendor lock-in from the service provider to the controller software or appliance. Despite this requirement, there is no language available yet to express such rules and policies. Therefore, we introduce the Flexible Data Distribution Policy Language (FlexDDPL) to formulate storage policies, evaluate it against language design guidelines, and demonstrate its practical usability within a dispersing cloud storage gateway architecture.

Analysis of overhead and profitability in nested cloud environments

The on-demand provisioning of computing and storage resources and the corresponding pay-as-you-go billing have made cloud computing a popular paradigm to achieve a high technological utility. While most use cases can adequately be covered by the offers of existing public cloud providers, the granularity in provisioning and pricing is not high enough for several task execution scenarios. Nested cloud environments are among the concepts to circumvent these problems. They let consumers manage their allocations with a higher degree of flexibility, including the reselling or repurposing to other sub-consumers. In this paper, we take a critical look at the state of the art of nesting technologies and reason about the resource consumption overhead and the resulting economic profitability of employing a nested cloud. The results are validated within a cloud resource broker.

Zusicherung nichtfunktionaler Eigenschaften und Dienstgüte im Future Internet of Services

ZUSAMMENFASSUNG Zur Verwirklichung der Vision des Future Internet of Services werden Infrastrukturen benötigt, die eine flexible, dynamische und vertraglich garantierte Vermittlung zwischen Dienstanbietern und Dienstnutzern erlauben. Mit bisherigen Web-Service-Technologien können nichtfunktionale Eigenschaften und Dienstgüte nur für einzelne Dienste beschrieben und bewertet werden. Diese Informationen dienen als Entscheidungsgrundlage für eine dynamische Auswahl von Diensten zur Laufzeit. Sollen nichtfunktionale Eigenschaften und Dienstgüte für komplexe Geschäftsprozesse beschrieben werden, stößt man an die Grenzen gängiger Prozess- und Dienstbeschreibungssprachen. Darüber hinaus gibt es bisher keine Ansätze zur dynamischen Aushandlung dieser Dienstgüteverträge zwischen Anbieter und Nutzer, als auch zwischen Diensten, die gemeinsam in einen Geschäftsprozess integriert werden. In diesem Artikel wird vorgestellt, wie nichtfunktionale Eigenschaften im gesamten Lebenszyklus der Dienstnuzung verwendet werden können und welche Lösungen hierfür zum Einsatz kommen. Wir geben einen generellen Überblick und konzentrieren uns auf den Abschluss und die Einhaltung von Dienstgütevereinbarungen, sowie deren Überwachung und die abschließende Bewertung der Dienstqualität durch den Dienstnutzer. Die Nutzung unserer Ergebnisse erfolgt im Rahmen des Forschungsprojektes THESEUS TEXO, in dem eine Service-Plattform zur Bereitstellung und Nutzung adaptiver Dienste mit umfassender Unterstützung nichtfunktionaler Eigenschaften über den gesamten Lebenszyklus der Services entwickelt wird.