Cloud Computing Lectures SOA

Transcription

1 Cloud Computing Lectures SOA 1/17/2012

2 Service Oriented Architecture

3 Service Oriented Architecture Distributed system characteristics Resource sharing - sharing of hardware and software resources Openness use of equipment and software from different vendors Concurrency - concurrent processing to enhance performance Scalability -increased throughput by adding new resources Fault tolerance - ability to continue in operation after a fault as occurred Security Manageability

4 What is a middleware?

5 Middleware Middleware Software that manages and supports the different components of a distributed system. In essence, it sits in the middle of the system. Middleware can be off-the-shelf rather than specially written software Examples Transaction processing monitors; Data converters; Communication controllers.

6 Which Architecture?

7 Service Oriented Architecture A loosely-coupled architecture designed to meet the business needs of the organization. SOA presents the big picture of what you can do with web services. Web services specifications define the details needed to implement services and interact with them. However, SOA is an approach to build distributed systems that deliver application functionality as services to end-user applications or to build other services. SOA can be based on web services, but it may use other technologies instead. A SOA does not necessarily require the use of Web Services Web Services are, for most organizations, the simplest approach for implementing a loosely coupled architecture. In the past, loosely coupled architectures have relied upon other technologies like CORBA and DCOM or document-based approaches In using SOA to design distributed applications, you can expand the use of web services from simple client-server models to systems of arbitrary complexity.

8 Characteristics of SOA Loose Coupling The binding from the service requester to the service provider should loosely couple the service. This means that the service requester has no knowledge of the technical details of the provider s implementation, such as the programming language, deployment platform, and so forth. The service requester typically invokes operations by way of messages -- a request message and the response -- rather than through the use of APIs or file formats. This loose coupling allows software on each side of the conversation to change without impacting the other, provided that the message schema stays the same.

9 Characteristics of SOA Well-defined interfaces The service interaction must be well-defined. Web services Description Language (WSDL) is a widely-supported way of describing the details A service Messages to invoke operations Details of constructing such messages Information on where to send messages for processing details of constructing such messages WSDL does not include any technology details of the implementation of a service. The service requester neither knows nor cares whether the service is written in Java code, C#, COBOL, or some other programming language.

10 SOA Protocol Stack Business Processes Business Process Execution Language for Web Services ( WS BPEL) Quality of Service (QoS) Reliability Transaction Management Description Web service description Language (WSDL) Messaging SOAP Extensible markup language (XML) Other Protocols and Services

11 Orchestration & Choreography Orchestration is centralized, so services managed centrally In case of a change that can be done in one place The interactions in an Orchestration can span organizations More matured organizations prefer Orchestration

12 Event Driven SOA or SOA Extension of SOA, to respond to events that occur as a result of a business process / cause, influence a business process - Analyzing the rate of sales in website to determine what events are influencing the buying decision. - Causal Vector Engine (CVE) adds a built in artificial intelligence to SOA Design. - Analyze event sequences and event relationships. - CVE then determines how to respond to the to condition based on a set of rules built in the system. - CVE sometime gives a console where an appropriate action can be chosen from a console. - It allows to query event data. - SOA component remains a black box to the client.

13 Enterprise Service Bus -The term Enterprise Service Bus (ESB) is widely used in the context of implementing an infrastructure for enabling a service-oriented architecture (SOA). - Enterprise Service Bus as a collection of architectural patterns based on traditional enterprise application integration (EAI), message-oriented middleware, Web services,.net and Java interoperability, host system integration, and interoperability with service registries and asset repositories. - A set of services that separate clients from components - Bus indicates high degree of connectivity or fabric quality in the system - ESB is not mandatory for SOA

14 ESB Contd.

15 Typical features / functionalities in ESB Monitoring Service : Process Management Services: Data Repositories and Registries: Data Service : Data Abstraction Service: Governance : Security Services :

16 Service Catalogs An enabler to find a relevant service as per need and use it. Contains What services available both internal and external How to use a service Which applications are related to a particular service How service relate with one another Who owns the service and how it is modified? Event history of a service, service levels, outages Service contracts Catalog servers can be Standalone ( Serving Single site ) Global ( 2-3 servers merged to serve multiple sites ) Federated ( two or more global service, trusted query relationship