Wei-Tek Tsai

Service-oriented system engineering: a new paradigm

In the past a few years, we witnessed a rapid progress in service-oriented computing (SOC), which represents a paradigm shift from the current mainstream object-oriented computing (OOC) paradigm to the SOC paradigm. This paradigm shift is changing the way we develop and use software and hardware. Conferences, journals, books, research, experimentation, tools, and products in SOC, service-oriented architecture (SOA), service-oriented enterprise (SOE), service-oriented infrastructure (SOI), Web services (WS), and associated protocols and standards have emerged and a solid foundation for the new paradigm is being grounded. This paper focuses on the system engineering issues in the new paradigm.

Testing as a Service over Cloud

Testing-as-a-service (TaaS) is a new model to provide testing capabilities to end users. Users save the cost of complicated maintenance and upgrade effort, and service providers can upgrade their services without impact on the end-users. Due to uneven volumes of concurrent requests, it is important to address the elasticity of TaaS platform in a cloud environment. Scheduling and dispatching algorithms are developed to improve the utilization of computing resources. We develop a prototype of TaaS over cloud, and evaluate the scalability of the platform by increasing the test task load, analyze the distribution of computing time on test task scheduling and test task processing over the cloud, and examine the performance of proposed algorithms by comparing others

Cloud testing tools

Cloud platform provides an infrastructure for resource sharing, software hosting and service delivering in a pay-per-use approach. To test the cloud-based software systems, techniques and tools are necessary to address unique quality concerns of the cloud infrastructure such as massive scalability and dynamic configuration. The tools can also be built on the cloud platform to benefit from virtualized platform and services, massive resources, and parallelized execution. The paper makes a survey of representative approaches and typical tools for cloud testing. It identifies the needs for cloud testing tools including multi-layer testing, SLA-based testing, large scale simulation, and on-demand test environment. To address the needs, it investigates the new architecture and techniques for designing testing tools for the cloud and in the cloud. Tool implementations are surveyed considering different approaches including migrated conventional tools, research tools, commercial tools and facilities like benchmark and testbed. Based on the analysis of state-of-the-art practices, the paper further investigates future trend of testing tool research and development from both capability and usability perspectives.

SaaS performance and scalability evaluation in clouds

Cloud computing not only changes todays computing infrastructure, but also alters the way of obtaining computing resources, managing and delivering software and services. Meanwhile, cloud computing brings new issues, challenges, and needs in performance testing, evaluation and scalability measurement due to the special features of cloud computing, such as elasticity and scalability. This paper focuses on performance evaluation and scalability measurement issue for Software as a Service (SaaS) in clouds. It proposes new formal graphic models and metrics to evaluate SaaS performance and analyze system scalability in clouds. In addition, the paper reports an evaluation approach based on Amazons EC2 cloud technology and detailed case study results using the proposed models and metrics.

Testing the scalability of SaaS applications

Cloud computing and SaaS (Software-as-a-Service) received significant attention recently. Testing SaaS applications is important because many mission-critical applications will be deployed on the cloud. However, to the best of our knowledge, testing framework designed specifically for SaaS applications is not developed. The issue of testing the scalability of SaaS applications remains untouched. This paper discusses the unique features and challenges in testing SaaS applications, and proposes scalability metrics that can be used to test the scalability of SaaS applications.

Testing as a Service (TaaS) on Clouds

Cloud computing leads an opportunity in offering testing as a service (TaaS) for SaaS, clouds, and cloud-based applications. This brings new business opportunities, challenges, and demands in innovative service models, testing techniques, QoS standards, and requirements. This paper provides a comprehensive tutorial on testing as a service in a cloud environment. It answers the common questions raised by engineers and managers, and provides clear conceptual discussions about testing as a service (TaaS), including its scope, objectives, motivations and values, distinct features, required techniques, as well as testing environments. It not only presents a classification of different types of testing services in TaaS, but also offers a clear comparative view and perspectives between conventional software testing service and cloud-based testing as a service. In addition, it examines underlying issues, challenges, and emergent needs.

Two-Tier Multi-tenancy Scaling and Load Balancing

Cloud computing often uses the multi-tenancy architecture where tenants share system software. To support dynamically increasing demands from multi-tenants, the cloud service providers have to duplicate computing resources to cope with the fluctuation of requests from tenants. This is currently handled by virtualization and duplication at the application level in the existing cloud environment, such as Google App Engine. However, duplicating at the application level only may result in significant resource waste as the entire application is duplicated. This paper proposes a two-tier SaaS scaling and scheduling architecture that works at both service and application levels to save resources, and the key idea is to increase the resources to those bottleneck components only. Several duplication strategies are proposed, including lazy duplication and pro-active duplication to achieve better system performance. Additionally, a resource allocation algorithm is proposed in a clustered cloud environment. The experiment results showed that the proposed algorithms can achieve a better resource utilization rate.

Scalable Architectures for SaaS

An important issue faced by Software-as-a-Service (SaaS) application is scalability. Each SaaS application is typically shared by multiple (tens or hundreds) organizations (tenants). Each tenant may have hundreds or thousands of users. Thus, the number of concurrent accesses is high. Handling a large number of user requests effectively is critical for SaaS applications. Various aspects of SaaS can have a significant impact on its scalability, including levels of scalability mechanisms, automated migration, tenant awareness, workload support, fault-tolerance and recovery, software architecture and database access. This paper identifies scalability factors and discusses their impacts on the scalability of SaaS applications. Existing approaches for addressing the scalibility of SaaS applications are also analyzed, and this paper suggests some alternatives to improve SaaS scalability based on the factors identified.

EasySaaS: A SaaS development framework

Software-as-a-Service (SaaS) often adopts multi-tenancy architecture (MTA). However, building a MTA SaaS application requires significant effort, either from scratch or using existing platforms such as Force.com or Google App Engine. This paper introduces EasySaaS — a SaaS development framework designed to simplify SaaS development. EasySaaS provides two alternatives to build a SaaS application. First alternative allows tenants to publish their application specifications with their requirements, as well as test scripts and let the SaaS providers customize their SaaS solutions to meet tenants requirements. The second alternative allows tenants to compose the application using templates provided in EasySaaS. This framework alleviates the workload of tenant developers, and provides an easy approach for customization according to tenants requirements in a collaborative manner. Most services in the platform is domain independent as the domain knowledge are stored in ontology to support cross-domain development.

SaaS Multi-tenant Application Customization

Cloud computing often uses the multi-tenancy architecture where tenants share system software. It is one of the key features of Software as a Service (SaaS) that enables higher profit margin by leveraging the economics of scale. Tenants residing on a multi-tenant application appear to be the sole owner of the application and not aware of the existence of others. A multi-tenant SaaS application accommodates each tenants unique requirements by allowing tenant-level customization. A complex SaaS application that supports hundreds, even thousands of tenants could have hundreds of customization points with each of them providing multiple options, and this could result in a huge number of ways to customize the application. This paper proposes an innovative customization approach that studies similar tenants customization choices and provides guided semi-automated customization process for the future tenants. A semi-automated customization process could enable tenants to quickly implement the customization that best suits their business needs.