Efficient customization of multi-tenant Software-as-a-Service applications with service lines

Application-level multi-tenancy is an architectural approach for Software-as-a-Service (SaaS) applications which enables high operational cost efficiency by sharing one application instance among multiple customer organizations (the so-called tenants). However, the focus on increased resource sharing typically results in a one-size-fits-all approach. In principle, the shared application instance satisfies only the requirements common to all tenants, without supporting potentially different and varying requirements of these tenants. As a consequence, multi-tenant SaaS applications are inherently limited in terms of flexibility and variability.This paper presents an integrated service engineering method, called service line engineering, that supports co-existing tenant-specific configurations and that facilitates the development and management of customizable, multi-tenant SaaS applications, without compromising scalability. Specifically, the method spans the design, implementation, configuration, composition, operations and maintenance of a SaaS application that bundles all variations that are based on a common core.We validate this work by illustrating the benefits of our method in the development of a real-world SaaS offering for document processing. We explicitly show that the effort to configure and compose an application variant for each individual tenant is significantly reduced, though at the expense of a higher initial development effort.     

SDSN@RT: A middleware environment for single-instance multitenant cloud applications

With the single-instance multitenancy (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 at runtime) middleware environment that can meet the aforementioned requirements. SDSN@RT represents an SIMT composite cloud application as a multitenant service network, where the same service network simultaneously hosts a set of virtual service networks, one for each tenant. A service network connects a set of services and coordinates the interactions between them. A virtual service network 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 multitenant 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.     

业务流程管理即服务中的多租户问题研究

分析软件即服务技术,针对业务流程管理即服务(BPMaaS)中的多租户问题,提出一种基于中间件的资源独占和共享方法。设计BPMaaS多租户应用程序接口,实现单个应用对多租户使用的支持,从而提高计算资源的利用率。通过JUnit对应用实例进行测试,结果验证了该方法的可行性。     

Tenant-based access control model for multi-tenancy and sub-tenancy architecture in Software-as-a-Service

Software-as-a-Service (SaaS) introduces multi-tenancy architecture (MTA). Sub-tenancy architecture (STA), is an extension of MTA, allows tenants to offer services for subtenant developers to customize their applications in the SaaS infrastructure. In a STA system, tenants can create subtenants, and grant their resources (including private services and data) to their subtenants. The isolation and sharing relations between parent-child tenants, sibling tenants or two non-related tenants are more complicated than those between tenants in MTA. It is important to keep service components or data private, and at the same time, allow them to be shared, and support application customizations for tenants. To address this problem, this paper provides a formal definition of a new tenant-based access control model based on administrative role-based access control (ARBAC) for MTA and STA in service-oriented SaaS (called TMS-ARBAC). Autonomous areas (AA) and AA-tree are proposed to describe the autonomy of tenants, including their isolation and sharing relationships. Authorization operations on AA and different resource sharing strategies are defined to create and deploy the access control scheme in STA models. TMS-ARBAC model is applied to design a geographic e-Science platform.     

面向SaaS应用的SMTDM可伸缩多租户数据管理框架

云计算是一种可以弹性并按需提供资源的技术.在多租户共享数据存储模式下,如何实现数据的动态伸缩存储是云数据管理的关键.针对SaaS应用如何随着租户数量及请求规模的变化而进行自适应伸缩的问题,在分析数据存储层的伸缩性需求的基础上,基于Walraven等人提出的多租户架构思想,扩展典型的云应用架构,设计了一个多租户数据管理框架,实现存储资源的弹性.基于该框架,开发了一个面向网络管理领域的SaaS原型系统,验证了其有效性和可用性.     

支持SaaS的安全权限管理系统

SaaS作为一种通过互联网向公众特别是中小企业提供应用软件的模式,其突出特点就是可扩展性、多用户、高效性、可配置性。文章基于SaaS第四级成熟度＂可扩展的多实例可配置级＂要求,设计和实现了一个可以支持多租户、多服务的SaaS系统架构和一个统一的安全认证与权限管理系统。其中所采用的存储模型和安全管理模型可适应于大规模租户的需要,可在满足系统性能要求下的架构灵活性和可扩展性,并满足多租户的定制化需求。     

SaaS 系统访问控制模型的研究

SaaS 作为新的软件模式,以本地部署、互联网访问的方式向客户提供服务,降低运维成本。本文在研究传统 RBAC 模型的基础上,结合SaaS 多租户、可配置、个性化的特点,提出一种SaaS 系统下分层的访问控制模型,实现系统多租户、 个性化服务的功能,给出实现方案和设计原理。     

Customer on-boarding strategies for cloud computing services with dynamic service-level agreements

A multi-tenant software as a service (SaaS) provider has to meet the needs of several tenants which adopt its services with diverse business requirements. The tenant needs vary widely with time, and the provider has to account for such fluctuations by suitable provisioning at its end. Handling this elasticity arising out of the tenant base is one of the key challenges for the SaaS provider. In this paper, we study the problem specifically in the SaaS context with the idea built around license provisioning in a tenant–provider perspective. For a given set of tenants with diverse license requirements, it is important to analyze whether there is any way to on-board them such that all constraints laid out as part of the service-level agreement can be honored. The total number of licenses available with the provider plays a crucial role in answering this question. We propose an intuitive model of elasticity that can capture anticipated license need variations at the tenant end. We propose an ILP-based approach for solving this schedulability problem for a collection of tenants. We also propose a simple-minded greedy heuristic to solve the on-boarding problem with elasticity constraints. Results show that our approach gives acceptable performance.     

Multi-tenant intrusion detection system for public cloud (MTIDS)

Cloud computing is an innovative paradigm technology that is known for its versatility. It provides many creative services as requested, and it is both cost efficient and reliable. More specifically, cloud computing provides an opportunity for tenants to reduce cost and raise effectiveness by offering an alternative method of service utilization. Although these services are easily provided to tenants on demand with minor infrastructure investment, they are significantly exposed to intrusion attempts since the services are offered under the administration of diverse supervision over the Internet. Moreover, the security mechanisms offered by cloud providers do not take into consideration the variation of tenants’ needs as they provide the same security mechanism for all tenants. So, meeting tenants’ security requirements are still a major challenge for cloud providers. In this paper, we concentrate on the security service offered to cloud tenants and service providers and their infrastructure to restrain intruders. We intend to provide a flexible, on-demand, scalable, and pay-as-you-go multi-tenant intrusion detection system as a service that targets the security of the public cloud. Further, it is designed to deliver appropriate and optimized security taking into consideration the tenants’ needs in terms of security service requirements and budget.     

PERSIST: Policy-Based Data Management Middleware for Multi-Tenant SaaS Leveraging Federated Cloud Storage

NoSQL data stores are often combined to address different requirements within the same application. The implication of this trend is particularly important and relevant in the context of multi-tenant SaaS applications where tenants commonly have different storage- and privacy-related requirements and thus they desire to customize the storage setup according to their specific needs. Consequently, application developers are increasingly combining storage resources: on-premise and public cloud resources in a hybrid cloud setup, different external public cloud storage resources and providers in a federated cloud storage setup, etc. The consequences of these trends are twofold: (i) application developers and SaaS providers have to deal with heterogeneous technologies, different APIs, and implement complex storage logic (to address different requirements of tenants), all within the application layer; and (ii) storage architectures have become less rigid, and techniques are required to flexibly change the storage configuration of running applications, up to the level of individual service requests. To address these challenges, we present PERSIST, a middleware architecture that (i) externalizes the complexity of a federated cloud storage architecture and the complex storage logic from the SaaS application to storage policies, allows tenants to enforce different storage- and privacy-related requirements at a fine-grained level; and (ii) supports the dynamic (re)configurability of the underlying federated cloud storage architecture. Application-specific policies can be customized by individual tenants at run time, and PERSIST offers support for run-time cross-provider polyglot persistence and the confidentiality of sensitive data through encryption. We have validated PERSIST in a working prototype implementation. Our extensive evaluation efforts show (i) the accomplished reduction in the required development effort to support complex storage policies, (ii) the reduction in cost/effort to change the data storage architecture itself, and finally (iii) the acceptability of the performance overhead (around 6% for insert, and 2% for read, update and delete transactions).     

基于可变性模型的可复用与可定制SaaS软件开发方法

云计算环境下,软件通过互联网向租户提供服务,这种基于互联网的软件交付模式称为SaaS（软件即服务）.与传统软件交付模式相比,SaaS软件通常运行于软件供应商的服务器端,同时为多个租户提供服务.由于需要支持不同租户的个性化需求,SaaS软件应具备足够的灵活性,以应对快速变化的租户需求;而且针对某一个租户的变更,不应影响其他租户.通过扩展课题组前期开发的基于可变性管理的适应性服务组装方法及其支持平台,提出了一种云计算环境下可复用、可定制的SaaS软件开发方法,开发了相应的支持平台,包括支持SaaS模式的服务组装引擎和远程定制工具.该方法针对不同租户的共性需求,提供一个抽象服务组装模型,支持平台在运行阶段解释执行抽象服务组装模型,根据租户的个性化需求派生不同的流程实例,这些运行时流程实例多态共存、互不影响.采用一个特定领域的SaaS软件实例来验证该方法的可行性,评估了支持平台的性能.实验结果表明,该方法及其支持平台可以支持多实例多租户的交付模式.     

一种适应SaaS多租户模式的数据迁移方法

基于多租户技术的SaaS应用在数据安全性方面提供了三种数据隔离方式,不同数据隔离方式下的数据存储具有差异性和规律性,传统的数据迁移方案不能够有效地应对数据隔离方式变化的要求,为此需要开发针对于SaaS多租户应用的数据迁移工具来帮助服务提供商进行数据的移植。通过对SaaS多租户模式特点的分析,同时在参考传统数据迁移方案的基础上,提出基于XML数据验证前置以及表复制的数据迁移方案,能有效地解决SaaS多租户模式下的数据迁移需求。     

一种SaaS交付平台的多租户数据迁移策略

现有的云数据放置策略未引入SaaS特征,租户作为独立个体的特征被忽略,导致多租户数据的混合放置,常用的数据迁移策略面临着识别及迁移租户数据的挑战。提出一种面向SaaS应用的云中多租户数据动态同步迁移策略,解决了共享存储模式下无法识别SaaS应用租户,难以使用快照、日志等数据库技术进行租户数据迁移的问题。通过SaaS平台数据层面的同步迁移,保证云中各数据节点的负载均衡及良好的用户体验。     

面向SaaS应用基于键值对模式的多租户索引研究

面向SaaS应用的多租户数据库为满足租户的数据隔离和按需定制的需求,需要提供支持隔离和易于定制的数据存储机制及索引机制.基于键值对存储方式,提出元数据驱动的映射表索引模型,该模型根据租户定制需求,为租户业务数据形成各自的索引元数据,通过元数据驱动实现了索引数据的隔离及定制效果;给出索引的维护策略,根据租户数据访问请求进行索引切片,以逐渐细化的索引切片作为数据访问的基本单位,快速返回租户结果集.实验结果表明,该方案在数据访问分布均衡的情况下,使索引维护及数据访问具有较好的总体性能.     

A distributed architecture for policy-customisable multi-tenant processes-as-a-service

Service-based business processes are often developed and deployed by single organisations. In distributed, shared resource environments like the cloud on the other hand, consumers share resources owned by cloud providers. This requires multi-tenancy capability for service processes that provide customised behaviour on shared process implementations to meet the varying needs of different process consumers as tenants of the process resource. In this paper, we define a distributed multi-tenant architecture for Business Process Execution Language (BPEL) processes provided as a service. A single-version BPEL process is deployed by a provider and offered for all process consumers, combined with a customisation and management functionality to create a unique experience for different consumers (process tenants). We provide two core components: a policy model for consumers to express customisation/business requirements of service processes and a coordination framework for policy enforcement between consumers and providers to achieve on-the-fly customisation of service processes.     

A search-based identification of variable microservices for enterprise SaaS

Recently, SaaS applications are developed as a composition of microservices that serve diverse tenants having similar but different requirements, and hence, can be developed as variability-intensive microservices. Manual identification of these microservices is difficult, time-consuming, and costly, since, they have to satisfy a set of quality metrics for several SaaS architecture configurations at the same time. In this paper, we tackle the multi-objective optimization problem of identifying variable microservices aiming optimal granularity (new metric proposed), commonality, and data convergence, with a search-based approach employing the MOEA/D algorithm. We empirically and experimentally evaluated the proposed method following the Goal-Question-Metric approach. The results show that the method is promising in identifying fully consistent, highly reusable, variable microservices with an acceptable multi-tenancy degree. Moreover, the identified microservices, although not structurally very similar to those identified by the expert architects, provide design quality measures (granularity, etc.) close to (and even better than) the experts.     

基于软件构件技术的多租户个性化框架

共享应用实例的应用级多租户模式是成熟度等级最高的软件即服务模式,能够提高资源利用率、降低应用升级维护成本,但是面临着不同租户的个性化需求支撑的技术难题。已有的研究和工业实践已经在多租户个性化方面进行了尝试,从实践项目中提炼出了基于构件软件开发（Component Based Software Development,CBSD）的多租户个性化方法框架,包括流程、扩展类型和技术支撑等,对多租户应用系统的业务逻辑、界面逻辑和数据实体三个部分的个性化扩展提出了解决方案。通过一个现实应用中的产品验证了框架的有效性。     

基于可信计算的多租户隐私数据保护

针对多租户应用的隐私数据保护问题, 在分析多租户应用的特点和隐私数据保护需求的基础上, 将可信计算技术引入多租户隐私数据保护, 基于虚拟可信平台模块vTPM提出了一种具有定制性的加密保护方案, 利用vTPM提供的加密密钥对租户的隐私数据进行加密, 同时利用vTPM的密钥保护和管理功能对加密密钥进行保护. 最后, 基于Xen实现的vTPM实现了本方案.     

面向多租约SaaS应用的负载均衡机制研究与实现

随着云计算的普及,SaaS作为一种新的软件交付模式得到了越来越广泛地关注.为了支持高速业务发展带来的大量用户的访问请求,多租约SaaS应用需要负载均衡机制以支持可扩展性.本文从对多租约SanS应用用户需求的分析入手,提出了一种面向租约功能类型的服务器负载模型和面向租约用户非功能需求的执行请求按需分配算法,设计了一个面向多租约SanS 应用的负载均衡系统.实验表明本文提出的面向多租约SaaS应用的负载均衡机制能在满足不同租约用户需求的同时提高系统整体执行效率.     

软件即服务应用框架中配置的设计与实现

The challenges for Software as a Service (SaaS) application are how to provide a set of methods to enable tenants to configure the application and how to ensure that after their configuration, the applications they subscribed will run accurately. In this study, we focus on application configuration which is one of the most significant features of SaaS and discuss the differences between configuration and customization. Furthermore, we bring up a more configurable Framework based on workflow management and rule management. In order to prove that the framework is able to provide more flexible configuration capabilities for tenants, we implement a conference management system (confOnline) based on this framework.