Service Oriented Architecture

Tuesday, February 16, 2016

SOA Interview Questions : Service Oriented Architecture Interview Questions Part 2

This Post is in continuation with my Previous post

SOA Interview Questions : Service Oriented Architecture Interview Questions Part 1

http://osb-dheeraj.blogspot.in/2016/02/soa-interview-questions-service.html

Can you Explain loose coupling, and How to achieve it ?

Loose coupling is an approach to interconnecting the components in a system or network so that those components, also called elements, depend on each other to the least extent practicable.

The Mediation pattern, using an enterprise service bus (ESB/OSB), will help in achieving

loose coupling to the highest level. It will establish independence between consumers and providers on all levels, including message formats (including SOAP, REST, XML, binary) and transport protocols (including HTTP, FTP, JMS, File, MQ, JCA Adapter, DB etc).

Architecturally speaking this means the separation of concerns between consumers and providers on the transport, message type, and message format levels.

How do I integrate my Legacy applications with SOA ?

Legacy applications are frequently at the core of your IT enterprise. With the right skills and tools, you need to identify discrete elements within your legacy applications and “wrap” them in standards-based interfaces and use them as services within your SOA. It is possible to integrate your legacy system with other system using SOA applications.

SOA and ESB technology provides support to most available message formats (including SOAP, REST, XML, binary, CSV, Text etc) and transport protocols (including HTTP, FTP, JMS, File, MQ, JCA Adapter, DB etc).

The Service of a SOA should be engineered as stateless or stateful ?

Service should be stateless. It may have a context within its stateless execution, but it will not have an intermediary state waiting for an event or a call-back. The retention of state-related data must not extend beyond a request/response on a service. This is because state management consumes a lot of resources, and this can affect the scalability and availability that are required for a reusable service.

How does the ESB/OSB fits in an Enterprise IT system ?

The Enterprise Service Bus is a core element of any SOA. ESBs provide the “any to any” connectivity between services within your own company, and beyond your business to connect to your trading partners and External service provoders. But SOA does not stop at just implementing an ESB. Depending on what your goals are, you may want to use an ESB to connect other services within your SOA such as information services, interaction services and business process management services. Additionally, you will need to consider development services and IT service management services. The SOA reference architecture can help you lay out an SOA environment that meets your needs and priorities. The ESB is part of this reference architecture and provides the backbone of an SOA but it should not be considered an SOA by itself.

Challenges faced in SOA adoption

While implementing a service-oriented architecture, a company faces below challenges :

Service identification. What is a service? What is the business functionality to be provided by a given service? What is the optimal granularity of the service?
Service location. Where should a service be located within the enterprise or outside Enterprise Firewall over Internet ?
Service packaging. How is existing functionality within legacy mainframe systems to be re-engineered or wrapped into reusable services?
Service orchestration. How are composite services to be orchestrated?
Service routing. How are requests from service consumers to be routed to the appropriate service and/or service domain?
Service governance. How will the enterprise exercise governance processes to administer and maintain services?
Service messaging standards adoption. How will the enterprise adopt a given standard consistently?

What is Web Service ?

A Web service has an interface described in a machine-processable format (specifically WSDL). Other systems interact with the Web service in a manner prescribed by its description using SOAP (Simple Object Access Protocol) messages, typically conveyed using HTTP with an XML serialization in conjunction with other Web-related standards.
We can identify two major classes of Web services:
1. REST-compliant Web services, in which the primary purpose of the service is to manipulate representations of Web resources using a uniform set of stateless operations.
2. Arbitrary Web services, in which the service may expose an arbitrary set of operations.

While identifying services which one is better – top-down and bottom-up methodologies encourages re-use and maintenance?

Since the top-down approach is business-driven it can be practical to separate the different concerns of business and IT on different plans, providing a common ground in between. So in most situations it the most appropriate if you want to improve reuse and ROI in the medium/longterm.

What do you mean by SOA governance? What are the functions of governance?

SOA governance is a concept used for activities related to exercising control over services in service-oriented architecture (SOA) solutions. One viewpoint, from IBM and others, is that SOA governance is an extension (subset) of IT governance which itself is an extension of corporate governance.

Some key activities that are often mentioned as being part of SOA governance are:

11. Managing the portfolio of services: This includes planning development of new services and updating current services.

22. Managing the service lifecycle: This is meant to ensure that updates of services do not disturb current services to the consumers.

33. Using policies to restrict behavior: Consistency of services can be ensured by having the rules applied to all the created services.

44. Monitoring performance of services: The consequences of service downtime or underperformance can be severe because of service composition. Therefore action can be taken instantly when a problem occurs by monitoring service performance and availability.