A Service Framework for Managing Cloud Services form
Consumer Perspective
Student: Hong Thai Tran Suppervisor: George Feuerlicht Submit Date: 08 September 2014.
ABSTRACT:
Innovation of web service and cloud computing introduced a new form of application module delivery in which software functionality is consumed as a service provided by external provider. This new availability is significant research area however to offer a novel challenge of service evolution where service providers are lack information of the how service consumers use their services. More precisely, this study addressed main problems of client applications in this cloud computing context: QoS of client applications are sticky impacted by QoS of cloud services; in case of a important serivce is unavalable, consequently, client system is also be unavailable; client application need to re-act immediate with uncompatible changes to avoid crash. This research is concerned with the design of model to protect client applications from unexpected service changes of providers. For the purpose of this work, a service consumer framework is introduce to manage service evolution and then to minimize the impact of change on consumer systems from the changes of external service providers. Service evolution is handled and management from consumer perspective. The aim of this research is to develop a mechanism to manage external services and how to overcome the changes or temporary unavailable of external cloud service. The approach will be to use participatory design techniques to develop a midleware framework for use as intermediate layer in consumer system and the to manage using of cloud services. The results of study indentified a model of management external service in client systems using workflow engine and service repository. At design time, service consumer can browse services‘ information and verify them to use this service in their applications. When consumers verify service information in service repository, they are assitant to select service to sastify thier applications‘ requirments especially QoS requirements such as response time and avalability. The more complex, services are able to composed to provide a busisness activities of consumers as a deliver services and payment services can be composed to become an online shopping service. The result of this work is model of managing services in client system and help service consumers overcome the issue of service evolution. This is an intermediate platform supporting service consumer applications in term of service evolution, cost saving and performance elasticity. In this research, we propose a Service Consumer Framework that provides client applications ability of evolution management, integration, and arbitrage. The framework is intermediation management layer between an application owner and the cloud services provider.
CONTENTS
1 Introduction ... 3
2 Literature review... 6
2.1
Service evolution ... 6
2.1.1
Evolution management approaches ... 6
2.1.2
Service change classification ... 7
2.1.3
Dealing with changes ... 7
2.1.4
Service evolution analysis ... 8
2.2
Cloud service brokers ... 9
3 Research Methodology ... 12
4 Proposed Model ... 13
5 Service Consumer Framework ... 13
6 Conclusion ... 13
1
Introduction
Over a decade, the evolution of service oriented applications has been investigated in order to analyze the impact of changes and enhance the service development and maintenance processes. Service oriented architecture (SOA) enterprise systems day by day become more complex as they contain a vast array of business processes and workflows integrated to both internal domains and external partners. For example, a conference management system (Figure 1) normally use a list of service providers to support business functionality like Paypal, OnePay, or SecurePay gateway for credit card payment functionality; FlightAware, Flight Explorer for pick-up service; and Google Geocoding API or QAS Pro Web for customer address validation. Other fi-nancial application or supply change applications can involve a vast range of external services such as logistic services from FedEx, Amazon Service, eBay or PayPal. In an environment of constant change of business requirements to support business agility and innovation, these services need to be upgraded to introduce new functionalities to customers. They are also required to maintain, fix bugs, improve performance or en-hance business processes. Although whenever services are changed, reputed providers often try to manage the change and predict the effect on consumer system to keep the reputation of their services. Those evolutions are actions possibly cause some risks to clients’ applications. In some cases, it can break the clients’ system and disrupt busi-ness operations because of the inconsistency between services and applications. The research question is how to minimize the impact of consumer system when external service provider evolved their services.
Services are subjects of evolution over their life due to new requirements and changes in business process. In both enterprise SOA application and service domain provider, services are in demand of introduction new functionality or modification to fix bugs, enhance and improve performance. Therefore, service providers should be aware of the impact of changes on their service consumer to guarantee there is no disruption in clients system due to these changes. Many researchers have been dis-cussing on the topic of service evolution and focus on how to minimizing impact of changes on clients. They present results of their work on groups of topic of service evolution analysis and main solutions in service evolution management: versioning service changes and management service development life cycle. While most of the research on this topic deals with service evolution from the service provider perspec-tive and introduced some approaches such as versioning and conversion, role-based management, user driven or Quality of service (QoS) driven. My research considers this problem from the perspective of service consumer and develops effective meth-ods to protect service consumer applications from changes in externally provided services
Cloud technology has been growing and delivering a significant part in enterprise system and software industry that offer an elastic and scalable service to business owners, especially small and medium sized businesses. Cloud technology is widely agreed that associated with a number of benefits include cost savings, elasticity, scalability, load “bursting”, on demand system and competitiveness. In consumer perspective, many organizations today rely on cloud-based services for a significant
part of their IT (Information Technology) infrastructure and applications. Given the compelling economic and technical advantages the adoption of cloud computing solu-tions is likely to accelerate the trend towards Cloud computing adoption.
With the diversity of cloud services, same type of services can be provided by var-ious cloud service providers with different API and quality of service (QoS). API management (www.programmableweb.com/apis/directory) can give an overview vision of multiplicity in (cloud) service’s market which creates a challenge for cloud customer to make decision among a bunch of services. In the cloud technology area, these enterprise applications will come to depend more and more on the cloud service providers which seems an application is a composed of a group of services and quali-ty of applications is contingent on the qualiquali-ty of services which it is composed of.
Services are subjects of continuous evolution over their life due to new require-ments and changes in business process. In a competitive environment, service provid-ers are in demand of introduction new functionality or modification to fix bugs, en-hance and improve performance. Therefore, service providers should be aware of the impact of changes on their service consumer to guarantee there is no disruption in clients system due to these changes. Dealing with the service evolution from cloud service providers becomes an important challenge of application owners in this con-text. Thus, as new service providers join to market or new services are introduced, businesses also need to flexible in their selection and able to change an in-use service to other equivalent service that are cheaper or better. The change process should be transparent and not impact on applications as well as business activities.
Many researchers have been discussing on the topic of service evolution and focus on how to minimizing impact of changes on clients. While most of the research on this topic deals with service evolution from the service provider perspective and in-troduced some approaches such as versioning and conversion, role-based manage-ment, user driven or Quality of service (QoS) driven, this research consider the prob-lem from the perspective of service consumer and develop effective methods to pro-tect service consumer applications from changes in externally provided services.
Because of the distributed nature and inherent dependencies of services, there is a losing coupled connection between service providers and service consumers [1-4]. On one hand, service providers do not necessarily have information of whom or how services are used by service consumers in their own systems. On another hand, ser-vice consumers seem to not know the changes of external serser-vice until they invoke them and their system crashes. Moreover, changes in service provider frequently lead to the service consumer putting their system back to the development process (analy-sis, design, coding, testing, deploy) to upgrade their applications. This requires effort (time and cost) for their clients. For that reason, the service provider needs to be re-sponsive to the impact of service evolution on their partners, especially some im-portant partners to avoid potential crash in business operations.
This research proposes a Service Consumer Framework (SCF) as an intermediate framework support service consumers in identify, select and implement services in their client system. Besides offering all aspects of aggregation, arbitrage, integration and intermediation, SCF provide a characteristic of redundancy that able to automati-cally switch among the same type of service when a service is evolved or become
temporarily unavailable to overcome service evolution. The objective of SCF is to provide (simulate) environment that provides transparency against failure and evolu-tion of cloud services – similar to what exists in intra-enterprise environments. The related works on service evolution and cloud service brokerage are discussed in sec-tion 2. In secsec-tion 4 and 5, the proposed model of SCF is presented and explained in detail. One module of SCF is an assistant website with information of services in service repository to assist service customer in select suitable services with their needs. Another module is wrapped APIs that include service router and service adap-tors to protect client applications form external changes of service providers. Service provider will contribute functionality of redundancy by determining and invoke the first priority service based on their availability, status stored in Service Repository and user references. The conclusion and directions of future work will be presented in section 6.
2
Literature review
In this section, I reviewed two research topics that are closely related to my re-search: service evolution (section 2.1), and cloud service brokerage (section 2.2).
2.1 Service evolution
2.1.1 Evolution management approaches
A common approach to manage service evolution is apply knowledge from software evolution that is studied for decades and a Laws of Software Evolution is formulated by Lehman [6]. Eisfeld et al. [2], Fokaefs et al. [3], and Romano, Pinzger [1] agree that service evolution is even more critical and challenging due to loosely coupled feature of web services. Similarly, Papazoglou et al. [7] listed subtle differences in coupling, invocation, binding and composition between service oriented and component oriented and highlight the challenges of service evolution. They proposed a systematic revision of theories for component evolution to able to apply in service evolution. Despite this, some software evolution approaches are still applied in service evolution. Researchers like Borovskiy and Zeier (2008), Fokaefs et al. (2011), Papazoglou (2008), Papazoglou et al. (2011), and Romano and Pinzger (2012) suggested the traditional techniques such as versioning, version compatibility and conversion to manage the service evolution. Regarding this approach, service provider will provide a list of different versions of services and keep maintain these versions to serve their clients. In software evolution management, maintenance is recognized as a significant component of overall costs and time spent [8]. By the same token, maintain number of versions of service will be costly for service providers so this technique may only suit for a few famous providers which have enough infrastructure and work forces.
Another interesting approach in minimizing the impact of service evolution is methodologies to perfectly improve the service design. The good service design in the early stage can help to reduce maintenance cost of production and provide a wide flexibility of changes to system [9]. Thus, Perepletchikov et al. [10] indicated the relationship between interface changes and external cohesion metric. This relationship between quality of service design and maintainability of applications is also the research topic of other researcher [11-13]. Although it is widely accepted that high quality service design can promote flexibility and maintainability of services and help them be more adaptable to change in future but the impact of service evolution on client applications can be entirely avoided by service design.
Although there are some other views in minimizing the impact of service evolution management such as framework of role [14-16], QoS driven approach [17], or user’s requirement driven approach [18], a limitation of these research is that most researchers only focused on the service provider side in service usage connection. The methodology to minimize the impacts of change on service consumer side is also significant because the consumer application is more vulnerable when service
providers evolve their services. This limitation is recognized in an article of Fokaefs et al. [3].
2.1.2 Service change classification
In an earlier article named ‘The challenges of service evolution’, Papazoglou [4] proposed a classification of service evolution into two different types of shallow change and deep change to suggest different management methodologies for each type. While the shallow changes are defined as small-scale incremental evolution or enhancement bound in a service, deep changes are broad-scale evolution that possibly change entire value chain of services [7,4]. The authors used an ‘Automotive Purchase Order Processing’ industrial case study a systematic way of looking at service evolution and analysis various evolutionary scenarios to demonstrate their findings. Support for this classification, Fokaefs et al. [3] give more explanation about shallow changes and deep changes where shallow changes are simply immediate operation change and deep changes deeply happened in the chain of types having effect on the various elements Developing these ideas, Andrikopoulos et al. [19] introduced a theoretical framework as service evolution management mechanism of shallow change. As a particular part of this research, they show two dimensions of horizontally and vertically service compatibility introduced in form of a T-shaped changes model.
In contrast, other researchers use difference views in classification service changes. For example, Borovskiy, Zeier [20] identified two main types of service change in domain service: intrinsic and extrinsic. Sub-categories of service changes are also deeply explained in this article such as poor design and poor implementation quality for intrinsic type; and market drivers, differentiation drivers, business requirement drivers, operational process drivers, legislative or regulatory drivers, user related drivers for extrinsic types. In different way, Ziyan et al. [18] focus on user’s requirement driven to classify service changes. This paper introduced a service adaptation framework based on user preferences using “i-context”. Service changes are considered user’s profile changes, user preferences over different non-functional parameters changes, or operating environment state changes.
2.1.3 Dealing with changes
Based on the classification of service changes, there are two common methodologies to deal with service evolution. Whereas, service versioning methodology is used to manage shallow changes included structural-level changes and business protocol changes, deep change or entire end-to-end service changes present several complexities that require a ‘change-oriented service life-cycle’ methodology to handle these changes [7]. Service evolution also need to carefully analyze and evaluate the level of change to apply the suitable methodology.
a. Dealing with shallow changes
Support for versioning methodology, Andrikopoulos et al. [19], Borovskiy, Zeier [20], Fokaefs et al. [3], Romano, Pinzger [1] discussed on how to implemented version of services. Although, these researchers agree that maintain multiple versions
of service is required costly and more payload on system infrastructure of service provider but they give some industrial case studies such as PayPal, FedEx, Amazon EC2 that still apply versioning methodology in their service to manage service evolution. The authors generally agreed that minimizing the number of current versions of service by provided full compatibility (backward compatibility and forward compatibility) can significant reduce the maintenance cost of service provider. Therefore, compatibility through service versions is discussed in several studies. For example, Andrikopoulos et al. [19] introduced the notion ‘T shaped changes’ that analyze compatibility among service versions in horizontal and vertical dimensions. As other examples, Borovskiy, Zeier [20], Papazoglou et al. [7] also presented some mechanisms like message conversion or version comparison to optimize the number of different versions of services lead to reduce cost and lightweight the infrastructure.
b. Dealing with deep changes
To deal with deep changes, it is significant to have a service development life cycle because the complex of changes may require entire service redesign [7]. There are three main phrases in this service changed-oriented life cycle included:
- Phrase 1 – Need to evolve: this is phrase of understand reason of change, determine the cause and scope of change and collect the detail information of service metrics.
- Phrase 2 – Analysis impact of changes: this phrase focuses on the analysis, redesign services as well as deeply determine the different between new service and existing service.
- Phrase 3 – Align, refine, and define: this is final phrase of putting new service in production, testing and executing service operation
Having similar ideas service changes-oriented life cycle, Wittern, Fischer [21] introduced a life cycle model of software service engineer and explained in details of all development activities that guide providers in service development and provision consumers in service consumption.
2.1.4 Service evolution analysis
The second phrase and also the most important phrase of service evolution life cycle is analyzing the change of service to identify impact of these changes on service consumer system. Fokaefs et al. [3], Romano and Pinzger (2012) presented empirical studies on Web Service Description Language (WSDL) evolution analysis of Amazon EC2 service, PayPal payment gateway service and FedEx services. On one hand, Fokaefs et al. developed a tool named VTracker based on tree-alignment algorithm comparing complex WSDL specification to produce a tree distance between every pair of service versions. As the outcome of these tools, service evolution will be group in different types such as
- Operation Deletions is scenario of an operation is disconnected or deleted that might immediately break client systems using it. Existing clients should be noticed the absence of operation and new client should not able to used it so that in the properly time, this operation can totally remove. This can be considered as a deep change.
- Inline Type is a shallow change such as a type in message is changed to parent type. Although it will not affect the use of existing client but customer should be noticed to handle this type change.
- Aggressive Evolution is another interesting change which numerous of improvements were made. In this case, the latest version of services can be extremely different from the previous version.
- Renaming Variables is noticed when a variable have changed its name during evolution process. This can cause a mismatch between messages of old service and new service.
- Adding New Types sometimes does not lead to the functionality breaks unless the new type or new elements relate the result of the operation.
- Changing Input or Output Types is a sensitive change of service able to break the interface of service. In this case, service consumer is frequently updated in order to invoke the operation correctly.
On another hand, Romano, Pinzger [1] proposed another tool called WSDLDiff based on UMLDiff algorithm of Xing, Stroulia [22] to extract changes from subsequent versions of a web service by comparing the WSDL interface. The WSDLDiff tool will analyze the fine-grained changes of services to help consumers highlight the most frequent types of changes on XSD element, attributes, references and enumeration. These elements were affected by the following fine-grained changes:
- XSD Element changes contain changes due to add, delete or move XSD Types or XSD elements.
- Attribute changes: contain changes due to update of an attribute value or specifically change the attributes name.
- Reference Changes: contain changes of referenced values.
- Enumeration Changes contain changes due to add, delete enumerations.
2.2 Cloud service brokers
The NIST Cloud Computing Reference Architecture [23] incorporates a Cloud Broker that manages the use, performance, and delivery of cloud services, and negotiates relationships between Cloud Providers and Cloud Consumers. Cloud Service Broker (CSB) forms an intermediate layer between service provider and plays an important role in the management of service evolution [24,25]. CSB typically supports a combination of functions that can be categorized as service intermediation, aggregation, and arbitrage [26]. Service intermediation involves enhancing some specific service property such as security or identity management. Service aggregation involves creating composite services from existing cloud services, combining data and service components into a single new service. In service arbitrage the broker monitors service properties such as price or performance and assists service consumers with selecting services that best matches their requirements.
Cloud service brokers are subject of extensive current research interest. For example, Flowley et al. [27] propose a comparison framework for service brokerage solutions, and Usha et al. [28] use QoS (Quality of Service) attributes to identify
suitable services from a range of services of the same type with the objective of minimizing response time and cost. The QoS attributes used to select the service provider are based on the user preferences, automating the process of matching these preferences against QoS attributes of available services from different providers. Pawlur et al. [29] introduce a cloud broker service called STRATOS which represents an initial step toward an automated cross-cloud resource provisioning platform. The objective of STRATOS is to defer decisions about provider selection until runtime, using KPIs (Key Performance Indicators) to automatically identify suitable providers and services. The authors present experimental results that demonstrate how cross-cloud distribution of applications can decrease the cost and improve the match with service consumer objectives.
Cloud service broker (CSB) as an intermediate layer between service provider and service consumer is becoming a key concern topic of future research and development on service oriented computing and cloud computing. In service lifecycle model of cloud service brokerage, service evolution is a component which goes along whole lifespan of a service [24,25]. In particular purpose, service brokerage is a layer playing the important role in quality insurance and normalization. According to an early Gartner [26] research report on the topic, cloud service brokerage can be categorized into following types:
a. Intermediation: An intermediation broker provides a service that directly enhances a given service delivered to one or more service consumers, essentially adding value on top of a given service to enhance some specific capability. CSBs will offer intermediation for multiple services of any kind such as identity management or access management. Individual cloud service consumers will acquire these intermediation services through some consumer-focused service providers, such as AT&T, Verizon, Telstra or Virgin Media. Intermediation brokers could also supervise pricing and billing.
Intermediation brokerages and the broker products that support them will exist in three places. First they may reside in the cloud at the service provider’s location, allowing the provider to deliver a level of governance beyond the original service. Second, the broker may reside at the consumer’s location and may allow local management or administration of service levels. Finally, the service broker may exist in the cloud as a service and in this situations, a true brokerage service business exists independent of the original service provider or the consumer.
b. Aggregation: It’s unlikely that consumer organizations or individuals will be able to provide the data integration, process integrity or intermediation needed to bring multiple services together. An aggregation brokerage service combines multiple services into one or more new services. It will ensure that data is modelled across all component services and integrated as well as ensuring the movement and security of data between the service consumer and multiple providers. These aggregation brokers will exist primarily in the cloud as service providers in their own right, forming a layer of service provisions that approximates the application layer in traditional computing. In aggregation-style brokerages, the services brokered are generally fixed and won’t change frequently.
c. Arbitrage: Cloud service arbitrage is similar to cloud service aggregation. The difference between them is that the services being aggregated aren’t fixed. Indeed the goal of arbitrage is to provide flexibility and opportunistic choices for the service aggregator e.g., providing multiple e-mail services through one service provider or providing a credit-scoring service that checks multiple scoring agencies and selects the best score.
d. Integration: Flowley et al [27] and ComputeNext,[30], one of the commercial cloud service brokerage platform, stated that a cloud service brokerage platform enable one more important category is Integration. Integration Cloud Service Brokerage is a function which maintains the data fidelity for organizations using multiple on-demand B2B software services, SaaS, PaaS, or IaaS and the resulting silos they create.
Usha et al [28] propose a cloud broker service framework to decide on an appropriate service offered by different CSPs depending on the QoS requirements from the users. They discussed that same type of services is provided by different Cloud service providers (CSPs) with varying quality. Therefore it is important to provide the best service among the services offered by the CSPs. The objective of this framework is to provide the requested services with minimum searching time, with cheapest cost and access mechanisms. The QoS parameters considered are based on the user preferences and these constraints are used to select the best provider from all the available service providers. Their proposed work focuses on the QoS parameters throughput and response time. The primary functionality of this framework is as an automate framework to select the appropriate service for users based on QoS parameters (throughput, response time) stored in user references. Differently, SCF invoke services by user selection’s priority and assist user using accurate QoS data. Our framework support service composition of same type of services to satisfy service availability. Ex: system requirements require 95% availability for payment service, however there are only some services that maximum is 90% availability. So SCF can compose two or three different payment services from different providers and make ability of redundancy to achieve user requirement of 95%.
In another project work paper, Pawlur et al [29] introduce an initial version of broker service layer named STRATOS which represents an initial step toward the automated cross-cloud resource provisioning and inter-cloud platform. While abstraction layers to IaaS already exist, their focus is on delaying choosing a cloud provider from design/develop time to deployment time, with the ability to change the decision with limited development effort. STRATOS automate the decision entirely, and move the decision point from deployment time to runtime. STRATOS allows the application deployer to specify what is important to them in terms of KPIs so that when a request for resource acquisition is made it is able to consider the request against all providers’ offerings and select the acquisition that is best aligned with the objectives. Some experiments are presented in this paper that demonstrate how cross-cloud distribution of an application can decrease the cost of the topology and create one that is better fitted to the deployer’s objectives. They also discussed on exploring the design issues and challenges.
3
Research Methodology
The research approach will be to use participatory design techniques to develop a midleware framework for using as intermediate layer in consumer system. The framework is to manage cloud services’s usage in consumer system which help to handle service changes from service provider. This framework includes four modules:
service repository is a "service store" used to search, identify and verify services‘
information; service APIs are web-services using to integrate in client application;
notification center is used to notify application administrators the statuses and
changes of consumed services; and run-time statistic is updated service QoS information based on real-time accurate data . A prototype of framework is available at www.scframework.com with more practical details of how to use framework in client system. Service Consumer Framework will be applied in case studies to get the experimental results. The Membership Information System (MIS) is a simplified sce-nario based on a real-world application system that consumes both internal (on-premise) and external (cloud) services. On-premise applications include:
Contributions: application used to manage member donations and corporate contributions
Subscriptions: application which allows customers to subscribe to publications online; and hard copies will be delivered to their home as well as they can read online via this application.
Conference Management: is a simplified scenario based on a real-world con-ference management application which supports a number of concon-ference man-agement functions, including enrollment of participants, online payments, booking of accommodation and transportation, and management of related con-ference documentation
Externally provided services include:
Payment services: Paypal Payment Gateway (www.paypal.com),
SecurePay (www.securepay.com) Subscriptions Conf. Management Contributions On-Premise Applications Cloud Services
Flight tracking services: FlightAware (flightaware.com), live flight tracking
maps, flight status, and airport information,
Flight Explorer (www.flightexplorer.com) - real-time aircraft position display and management tool used for organizing customer pick-up service
Address validation services: Google Geocoding API (develop-ers.google.com/maps/documentation)
QAS Pro Web (www.qas.com)
Shipment tracking services: FedEx Express (http://www.fedex.com/us/)
The MIS system operates in an environment where external services continually evolve with providers upgrading their services by adding and removing interface ele-ments and operations. In addition, services are subject to outages and may become temporarily unavailable due to communications failures and site crashes. A key re-quirement for the MIS system is to maintain operation in this challenging environ-ment. Contribution, Subscription and Conference Management use PayPal Pro service as a primary online payment method for donation, publication subscription and con-ference enrollment. This is viral business of corporation so that the payment service availability is sensitive system requirement. This is facilitated by the SCF Framework that uses adaptors to shield internal services from changes in external services as well as provide ability of service redundancy for MIS system. For example (Figure 2), in case of the main payment service (Paypal) is unavailable or changed that can caused a failure in applications, an alternative service (SecurePay) will be used to avoid busi-ness interruption. At this time, SCF will notify application administrators and system developers to analyze the failure and re develop system to adapt with new Paypal service.
