SDSN@RT: a middleware environment for single-instance multi-tenant cloud applications

With the Single-Instance Multi-Tenancy (SIMT) model for composite Software-as-a-Service (SaaS) applications, a single composite application instance can host multiple tenants, yielding the benefits of better service and resource utilization, and reduced operational cost for the SaaS provider. An SIMT application needs to share services and their aggregation (the application) among its tenants while supporting variations in the functional and performance requirements of the tenants. The SaaS provider requires a middleware environment that can deploy, enact and manage a designed SIMT application, to achieve the varied requirements of the different tenants in a controlled manner. This paper presents the SDSN@RT (Software-Defined Service Networks @ RunTime) middleware environment that can meet the aforementioned requirements. SDSN@RT represents an SIMT composite cloud application as a multi-tenant service network, where the same service network simultaneously hosts a set of virtual service networks (VSNs), one for each tenant. A service network connects a set of services, and coordinates the interactions between them. A VSN realizes the requirements for a specific tenant and can be deployed, configured, and logically isolated in the service network at runtime. SDSN@RT also supports the monitoring and runtime changes of the deployed multi-tenant service networks. We show the feasibility of SDSN@RT with a prototype implementation, and demonstrate its capabilities to host SIMT applications and support their changes with a case study. The performance study of the prototype implementation shows that the runtime capabilities of our middleware incur little overhead

On-demand provisioning of services

Workflows and service oriented computing (SOC) are an integral part of today's business scenarios. The SimTech project aims to leverage these proven technologies in the context of scientific research. Yet, this field of eScience has different requirements on SOC than their business counterparts. One of these differences is, that services and resources needed by scientists are commonly only required for very specific amounts of time and do not need to follow the always-on principle of traditional SOC. Thus, a means is necessary to make services and resources available when required and also free them again as soon as they are no longer needed. As a solution to utilize SOC in eScience scenarios, SimTech promotes the use of Cloud Technologies to enable the on-demand provisioning of services and their necessary infrastructure. This diploma thesis is focused on describing different architectural concepts and designs that enable the on-demand provisioning of services and their underlying infrastructure and middleware. These designs and concepts aim to strike a middle ground between abstract high-level architectures and very low-level architectures that focus solely on software specifics. The concepts have been designed in context of a Scientific Workflow Management System. A prototypical implementation that demonstrates the developed concepts concludes this thesis