Unit-I-Introductionwith MSA Explanation.pptx
- 1. UNTI I - INTRODUCTION
- 2. SOA and MSA Basic • SOA and MSA based of the Concept of Services. • Service is a unit of functionality whos access is through defined interface. • Services are stateless, loosely coupled and communicated via messages. • In Service oriented Model Services are exposed by Service-producer and Invoked by Service-consumer. • Service-producer and Service-consumer applications are loosely coupled by the use of service contract and data contract. • Service Contract: - is an interface that defines the message type used by Service-producer and Service-consumer to exchange messages. • Data Contract:- Is formal agreement between service and client that abstracts the definition of the data to be exchanged
- 3. Service Orientation in Day Life Consider the service offered by mail order companies and how the principle of service orientation apply to the business of shipping goods in response to order received in mail.
- 4. Mail order Service 1. Mail order companies offer the service of ordering goods via mail. They are service providers of goods advertised by them. 2. Mail-order service provider publish catalog of goods in news papers and magazines. The catalog constitutes a service registry. 3. People availing the mail – order service are service consumers who browse the mail- order catalog to order the product of interest. 4. An order placed by service consumer constitute the service contract of the mail order service. The mail-order form that the service consumer fills is the order, is the order of goods to be shipped along with payment detail and constitute the contract. 5. The service consumer puts the mail order form into the envelop with the address detail on it. The postal department of a courier company reads the address details and ships the form to the address of mail order delivery 6. In response to a service call that is received via the email-order form, the mail-order company ships the goods to the service consumers.
- 5. Evaluation of SOA and MSA • SOA and MSA represents the next logical step in the evaluation of programming paradigm.
- 6. • Software application were initially developed using procedural approach supported by programming language (C & COBOL) • programming language are evolved to support structured programming principles (e.g. FORTRAN) • Then the Object Oriented programming languages such as small talk and C++ are used to model real world objects. • The development language such as Microsoft Visual Basic Supports rich user interface resulted in client-server application. • The limitation in client-server solution resulted in enhancements to languages and tool to support N-Tier application. • The innovation in managing the life cycle of objects lead to the development of component model for enterprise applications using Java and C# could be deployed in web application servers(e.g. IBM WebSphere Application Servers) • SOA and MSA, based on service oriented model is the the next step in the evaluation.
- 7. Drivers for SOA • The Key Drivers from SOA from business and technology perspective. • Business 1. Rapid business process changes. 2. Reproduction of process cycle times. 3. Protection of investment in legacy applications. 4. Lower total cast ownership. • Technology 1. Application Modernization. 2. Technology Change Management 3. Integration and interoperability of enterprise wide heterogeneous applications. 4. Support by product vendors.
- 8. Dimensions of SOA • The dimensions of SOA that enable the business transformation in enterprise. 1. Reuse – build once and used many times 2. Integration – stich together different components of execution to automate the execution process 3. Agility- is to externalize the component of execution so that the process of execution can be defined and changed easily through configuration Two additional dimensions are essential from operational perspective 4. Governance – Define policies that services need to adhere to at design time and run time. 5. Quality of Service – Monitor and enforce the policies at run-time.
- 9. Reuse • SOA Technique enable reuse through concept of services. • Services are defined to be coarse grained to provide reusable functionality from a business perspective. • Agility is brough about in SOA through externalizing the definition of business so that they may be altered through the configuration changes with relatively ease according the needs of the business. • The enter prise architecture based on SOA would have business process application implemented as set of services that are orchestrated( process defined and executed centrally) or choreographed(Process defined and executed in a distributed manner) • Changes in the to the business functionality of the any one service do not have the impact on the rest of the services
- 10. Integration • Integration of service providers and service consumers in SOA is handled efficiently through Enterprise Service Bus (ESB) Pattern. • ESB is having advantage over Hub-and-Spoke Architecture. In Hub-and-Spoke Architecture, centralized Hub act as a message broker that accept the request from multiple application that are connected via connectors as spoke. • Hub is capable for message transformation, validation, routing and asynchronous message delivery. • However the hub contributes to the single point of failure as all spokes as all spokes communicate with the hub. • The bus architecture on other hand constitute the blue print for a general purpose medium for services provider and consumer to communicate. • The bus architecture of ESB, with distributed service of message routing, transformation and event handling provides the capability required for loose coupling and efficient integration between providers and consumers.
- 11. • SOA, there fore, has reuse, agility and integration as dimensions that are critical to do business transformation in organization. • SOA Techniques allow for the degree of agility such business transformation demand by maintaining focus on the business process and their orchestration rather than be limited by technology used for implementing the application.
- 12. Conceptual Model of SOA
- 13. • Four Principles of SOA • Service boundaries are explicit and service interact through explicit message-passing over well defined boundaries. • Service are autonomous in terms of data isolation and loose coupling • All interactions are based on service contract, data contract and associated policies • Service compatibility is based on policy expressions(such as those of Ws- Policy) when service contract cannot be completely specify all aspects of service interaction.
- 14. Services • Service is the basic component SOA that enable recuse. • A Service is exposed by a service provider is coarse-grained in terms of business functionality it provides and is defined by a service contract and a data contract. • A business function of manageable size (e.g. EMI function for a Loan) is exposed by the service. • Service consumers invoke an operation published by a service as a part of the service contract and provide the data as per the data contract. • Characteristics of service autonomy, loose coupling, statelessness, composability and discoverability.
- 15. SOA Web Services Services can be implemented using a number of technologies such as XML Web services. Web Services are described using WSDL and are invoked using XML messages embedded in a SOAP envelop over a standard protocol such as HTTP. Simple Object Access Protocol originally defined as technology to bridge the gab between disparate system that communicate via Remote procedure calls(RPC). It has since evolved into a widely supported messaging format and protocol used with XML Web Services that describe how the messages between service providers and service consumers need to be structured leveraging XML as its core to promote interoperability.
- 16. Essentially, the SOAP protocol describes a wrapper around the message: 1.Where to place headers 2. Where to place the message payload 3. How to indicate the action to be taken. SOAP protocol address the basic requirements for service provider and consumers to process the message and communicate with each other. The processing of message (based on SOAP protocol) by service provider during service call involve extraction of header and body elements and they are converted to platform specific runtime types. SOAP and Webservice Definition Language (WSDL) specify how this needs to be done. SOAP describe what is exchanged between service provider and consumers. WSDL specifies an URI (Uniform Resource Indicator) where the service can be reached, the supported operation (action at that location and format of the message and related type definition,
- 17. • RESTful Webservices REST is coined by Roy Fielding in 2000. REST is a architectural style that may be used for service enablement. A related development is JSON as the format for data. JSON is a lightweight data interchange format written to a alternative for XML. It provide simple object serialization for remote calls and this is an option when architecting a lightweight SOA solution based on AJAX, REST and RSS as it is fast, compact and easy to consume with the browser. The ubiquitous nature of internet based on Hypertext Transfer Protocol(HTTP) has made it feasible to exchange data efficiently over it. Also policies of organization allow HTTP protocol to be permitted over the firewall for access to the internet. It presents a transport mechanism for service invocation. Conventional nature of HTTP can be extended to enable the interaction between service consumers and service providers.
- 18. • A Service consumer send requests using four methods supported by HTTP(namely GET,POST, PUT and DELETE). • The format of the data supported by RESTful webservice consumer is MIME(e.g JSON, XML and XHTML). • RESTful web service offer lower over head in interaction between service providers and service consumers when compared with XML web services. Enterprise Service BUS (ESB) It is an architectural pattern that acts as mediator/broker between service provide and service consumer. It forms the communication infrastructure for service consumers to interact with service providers across locations, supporting different transports and across organization boundaries. It provide integration capability through content routing, transformation and delivery between service providers and service consumers and has number of advantages over alternative integration approaches such as hub and spoke architecture. Major vendors have tools/products that implement ESB Pattern. Through ESP different vendors supports the core requirement of content routing, transformation and delivery, they are significantly different from one another in the implementation as pect.
- 19. Orchestration and Choreography. Orchestration is the execution of service based on pre defied sequence with central coordinator. The predefined sequence are correspond to workflow. It controls the process level integration and automation of services. Orchestration engines based on Business process level integration and automation of services. Orchestration engine based on Business Process Execution Language (BPEL) have gained wide acceptance. BPEL is a Language to specify Business process as workflow. Key Vendors and Open source project supports BPEL. Choreography is the execution of service based on predefined sequence in a distributed manner (without a coordinator) with each service having decision logic on when to execute.
- 20. Governance The SOA implementation in an enterprise is governed by defining policies to address the non functional requirements (such as message transportation, infrastructure availability and service availability) taking into account key performance indicators for business and SLA for IT. A registry / repository tool is often used for service governance Quality of service Quality of service for SOA implementation is achieved by monitoring service invocations and enforcing policies define in run time to meet SLA. A registry / repository tool that manages the policy definition in most cases is perform this task,
- 21. Standards and Guidelines for SOA Standard Bodies The world wide Web Consortium published a set of standards for web languages and protocols namely XML SOAP and WSDL to establish compatibility between fundamentals of web technology and enable hardware and software to access the web and worktogether. W3C defines WS-Policy standard that consists of set of specification that allow for description policies and standard means of attaining them to web services. W3C also publishes Service Modeling Language (SML) standard for creating models of complex service and system including structure, constraints, policies and best practises.
- 22. • WS1 – The web service Interoperability Organization(WS1) To promote the interoperable web service across platforms, Operating Systems and Programming languages profile specification have been developed by WS1 are. Key Specifications published by WS1- are: WS-1 Basic Profile 1.1 WS-1 Basic Profile 1.2 WS-1 Security Profile 1.0 WS-1 Basic Security Profile 1.1 WS-1 Simple SOAP Binding Profile 1.0 WS-1 Attachment Profile 1.0
- 23. OASIS – Organization for Advancement of Structured Information Standards. OASIS has developed a number of web service standards • Enable maintenance of context throughout a service activity . An active stateful context enables web service to support distributed transactions(e.g WS-Transaction and ES-TX, TC). • Ensure failsafe, flexible, and efficient communication framework capable of enterprise level automation(e.g WS-RX TC) • Institute of through security model consisting of a stack complementary specifications (e.g WS-RX TC). • Provide a process description vocabulary that can be compiled into runtime scripts, executed by middleware products that support orchestration(WS- BPEL)
- 24. • OASIS has developed a standard reference model for SOA with the global coming up with a vocabulary and a common understanding of SOA. It is an abstract frame work and provide understanding of entities and their relationship. • SOA has developed with three main views: 1. Service echo system viewed related to participants of a SOA echo system. 2. Realizing services with focus on requirement of SOA 3. Owning view related to governance and management of SOA systems.
- 25. • Object Management Group • OMG has developed standards for Modelling such as Business Process Modelling notation for business process. • UML for Service and Component Modeling • Common Warehouse Metamodel(CWM) for modelling database and business intelligence. • OMG has taken a platform independent view based on Model Driven Architecture (MDA) Standards. • According OMG Each of the SOA Layers can be driven from models. MDA standards offer the capability to design a complete SOA solution through models and minimize the effort invested in specific technologies and protocols. • A UML profile for SOA and metal model specification called SOAML has been developed by OMG with stereotypes such as Service Point, Service Channel and Service Contract and Service Interface.
- 26. • The SOA reference architecture consists of Several elements that are structured at logical level –layers, architecture building blocks and their interactions. • Implementation decision based on availability of vendor products are made for the element of reference architecture to define solution at physical level. • This results in definition of solution at both logical and physical level. • Figure 8.5 shows the pictorial representation of the key standards.
- 28. Emergence of SOA • The mobile application have been causing increasing demand for accessing functionality from outside the infrastructure of the enterprise. • Consumers are demanding information, relevant to their context anywhere, anytime, on any device • The rise of the “Internet of Things” as also caused a push for standard interface mechanism for device to communicate the data captured by them. (such as refrigerators and dish washers) • This has resulted in development of human readable, externally facing, light weight services that are referred to as Application Programming Interface(API) that can be published through portal. • Developer can learn about published API and sign up to use them. • API connect business process, services, contents and data to channel pattern
- 29. • From an architectural standpoint, all web services are API while all APIs are not web services. • A web service can be looked at API with additional wrappers that require computer processing. API’s are light weight without these additional wrappers and therefore human readable. • Web services are carefully modelled, designed and implemented for reuse, agility and integration to justify the business case and ROI for an enterprise. They protect the service consumers from the changes implementation aspect of service producer. • API creating capabilities for service consumers to derive benefits from. The capabilities are re-packed, productized and shared in easy to use form. Thus they protect the service producer from the changing implementation technologies of consumers. • An application built on SOA principle has been monolithic i.e built as a single unit. • Monolithic applications are success full in many cases and issues related to time to market in some cases especially those are related to could application • The dimensions of SOA reuse is not emphasised by micro service architecture.
- 30. The focus is on fine grained services, built for a particular application, that are not necessarily reused, that are self contained and have huge responsibility of delivering that are designed for Enterprise level reuse in not considered. The micro service architecture style is an approach for developing a single application as a suite for small services each running on its own process and communicating with light weight mechanisms often an HTTP resource of API. These services are built around business capabilities and independently deployable by fully automated deployment machinery. There is bare minimum of centralized management of these services, which may be written in different programming languages and use different storage technologies.