Jörg Domaschka

SRL: A Scalability Rule Language for Multi-cloud Environments

The benefits of cloud computing have led to a proliferation of infrastructures and platforms covering the provisioning and deployment requirements of many cloud-based applications. However, the requirements of an application may change during its life cycle. Therefore, its provisioning and deployment should be adapted so that the application can deliver its target quality of service throughout its entire life cycle. Existing solutions typically support only simple adaptation scenarios, whereby scalability rules map conditions on fixed metrics to a single scaling action targeting a single cloud environment (e.g., Scale out an application component). However, these solutions fail to support complex adaptation scenarios, whereby scalability rules could map conditions on custom metrics to multiple scaling actions targeting multi-cloud environments. In this paper, we propose the Scalability Rule Language (SRL), a language for specifying scalability rules that support such complex adaptation scenarios of multi-cloud applications. SRL provides Eclipse-based tool support, thus allowing modellers not only to specify scalability rules but also to syntactically and semantically validate them. Moreover, SRL is well integrated with the Cloud Modelling Language (Cloud ML), thus allowing modellers to associate their scalability rules with the components and virtual machines of provisioning and deployment models.

COSCA: an easy-to-use component-based PaaS cloud system for common applications

The emergence of cloud computing marks a significant change in the way computers are used in both enterprise and personal environments. Yet, as a young technology, cloud computing is far from being mature. Platform-as-a-service (PaaS) clouds promise to reduce maintenance and administration costs, but current frameworks lack crucial features for supporting a broad range of applications. Especially rigid constraints of the current PaaS programming models limit broader usage. Based on this observation we compiled eleven requirements of typical business applications such as programming model, placement, scalability, routing, isolation, load balancing, accounting, adaptability and modularity. We further observe that none of current platforms support a majority of these requested features. As a result, we present our own PaaS system, called COSCA that meets all of these requirements. COSCAs component-based design especially supports adaptability and modularity. We believe that our requirements and architecture may serve as a valuable guide for PaaS designers, implementers, and providers.

Beyond IaaS and PaaS: An Extended Cloud Taxonomy for Computation, Storage and Networking

Cloud computing is currently classified by the generally accepted terms IaaS, PaaS and SaaS. These are not precise enough to give users and providers a common terminology to differentiate between existing cloud offers. Furthermore, there is no common and accepted terminology for storage and network cloud services. Terms like StaaS and NaaS have been coined but lack a clear definition. This paper contributes a fine-grained taxonomy for computation, storage and network services which is still compliant with existing terminology. Our taxonomy is based on abstractions cloud services provide to tenants, it does not consider implementation aspects. In addition to our taxonomy, we provide a classification of many existing services and simple decision trees that allow an easy classification of any cloud offer of interest. Our comprehensive and fine-grained taxonomy is a new basis for the determination of existing and future cloud offerings.

The CACTOS Vision of Context-Aware Cloud Topology Optimization and Simulation

Recent advances in hardware development coupled with the rapid adoption and broad applicability of cloud computing have introduced widespread heterogeneity in data centers, significantly complicating the management of cloud applications and data center resources. This paper presents the CACTOS approach to cloud infrastructure automation and optimization, which addresses heterogeneity through a combination of in-depth analysis of application behavior with insights from commercial cloud providers. The aim of the approach is threefold: to model applications and data center resources, to simulate applications and resources for planning and operation, and to optimize application deployment and resource use in an autonomic manner. The approach is based on case studies from the areas of business analytics, enterprise applications, and scientific computing.

Fault-tolerant replication based on fragmented objects

This paper describes a novel approach to fault-tolerance in distributed object-based systems. It uses the fragmented-object model to integrate replication mechanisms into distributed applications. This approach enables the use of customised code on a per-object basis to access replica groups and to manage consistency. The addition of fault tolerance to the infrastructure has only little overhead, is fully transparent for clients, and does not require internal modifications to the existing middleware. Semantic annotations at the interface level allow the developer to customise the provision of fault tolerance. Operations can be marked as read-only to allow an execution with weaker ordering semantics or as parallelisable to allow true multithreaded execution. A code-generation tool is provided to automatically produce object-specific fragment code for client access and for replica consistency management, taking into account the annotations, the interface specification, and the non-replicated implementation. A further contribution of our code-generation approach is the support of deterministic multithreading in replicated objects.

Cloud orchestration features: are tools fit for purpose?

Even though the cloud era has begun almost one decade ago, many problems of the first hour are still around. Vendor lock-in and poor tool support hinder users from taking full advantage of main cloud features: dynamic and scale. This has given rise to tools that target the seamless management and orchestration of cloud applications. All these tools promise similar capabilities and are barely distinguishable what makes it hard to select the right tool. In this paper, we objectively investigate required and desired features of such tools and give a definition of them. We then select three open-source tools (Brooklyn, Cloudify, Stratos) and compare them according to the features they support using our experience gained from deploying and operating a standard three-tier application. This exercise leads to a fine-grained feature list that enables the comparison of such tools based on objective criteria as well as a rating of three popular cloud orchestration tools. In addition, it leads to the insight that the tools are on the right track, but that further development and particularly research is necessary to satisfy all demands.

Towards a Generic Language for Scalability Rules

The PaaSage project aims at facilitating the specification and execution of cloud-based applications by leveraging upon model-driven engineering (MDE) techniques and methods, and by exploiting multiple cloud infrastructures and platforms. Models are frequently specified using domain-specific languages (DSLs), which are tailored to a specific domain of concern. In order to cover the necessary aspects of the specification and execution of multi-cloud applications, PaaSage encompasses a family of DSLs called Cloud Application Modelling and Execution Language (CAMEL). In this paper, we present one DSL within this family, namely the Scalability Rules Language (SRL), which can be regarded as a first step towards a generic language for specifying scalability rules for multi-cloud applications.

The COSCA PaaS platform: on the way to flexible and dependable cloud computing

This talk will address our current research projects about cloud computing. The focus is on COSCA an OSGi-inspired PaaS system that allows applications to be composed from components. These can be individually updated and deployed similar to bundles in OSGi. COSCA further supports sockets for arbitrary communication. In the second part of the talk, we will address replication mechanisms and how they can be connected to COSCA. We will present multiple building blocks for fault-tolerant applications that were developed within COSCAs predecessor projects and are ready to be integrated.

Highly available and scalable grid services

Grid computing infrastructures create many new challenges related to data management. Grids are typically deployed at a large scale, and one can only expect this scale to grow even more in terms of number of machines, locations and administrative domains.

Is elasticity of scalable databases a Myth

The age of cloud computing has introduced all the mechanisms needed to elastically scale distributed, cloud-enabled applications. At roughly the same time, NoSQL databases have been proclaimed as the scalable alternative to relational databases. Since then, NoSQL databases are a core component of many large-scale distributed applications. This paper evaluates the scalability and elasticity features of the three widely used NoSQL database systems Couchbase, Cassandra and MongoDB under various workloads and settings using throughput and latency as metrics. The numbers show that the three database systems have dramatically different baselines with respect to both metrics and also behave unexpected when scaling out. For instance, while Couchbases throughput increases by 17% when scaled out from 1 to 4 nodes, MongoDBs throughput decreases by more than 50%. These surprising results show that not all tested NoSQL databases do scale as expected and even worse, in some cases scaling harms performances.