motivation for soauosis.mif.vu.lt › ~valdo › webs2014 › webservices.l01.pdf · software in...

Valdas Rapševičius Vilnius University

Faculty of Mathematics and Informatics

2014.02.28

Web Services Lecture I

2014.02.28 Valdas Rapševičius. Java Technologies 1

Outline

• Introduction to SOA • SOA Concepts:

– Services – Loose Coupling – Infrastructure

• SOA Layers • MEPs • Various Service Aspects • SOA Governance • Reference:

– Nicolai M. Josuttis “SOA In Practice”


Motivation for SOA

● Distributed business processing ● Different Owners ● Heterogeneity ● Flexibility ● IT as the key business value enabler

SOA is NOT

● Concrete architecture – it is something that leads to a concrete architecture.

● Concrete solution – can’t buy SOA

● Information technology ● a Silver Bullet

SOA is

● a way of information management. ● A set of principles and methodologies for designing and developing

software in the form of interoperable services. (Wikipedia, 2013.02.21) ● A method of design, deployment and management of applications and

software infrastructure where: – all software is organized into business services that are network accessible

and executable; – service interfaces are based on public standards for interoperability.

● SOA is a strategy that, although it might be driven by IT, always impacts the business as a whole

● SOA is a software architecture that starts with an interface definition and builds the entire application topology as a topology of interfaces, interface implementations and interface calls

● Interface-oriented architecture ● Might call it a style, paradigm, concept, perspective, philosophy, or

representation.

Important!

● Whether you introduce SOA is not what’s important

● The important thing is that the IT solution you introduce is appropriate for your context and requirements of your business

Large Systems

● SOA is a concept for large distributed systems ● Large systems

– deal with legacies – maintenance – heterogeneous – and their data have an incredibly long lifetime – complex – different owners – imperfect – redundancy – bottlenecks are suicide

Major Elements

● Services – self-contained business functionalities – can be part of one or more processes – can be implemented by any technology on any

platform

● Specific infrastructure (ESB) ● Policies and processes

Magic Bus

● Bus → EAI Bus → ESB

● Piece of infrastructure software

● High interoperability Instead of creating and maintaining individual communication

channels between different systems, each system only has to connect to the bus to be able to connect to all other systems.

SOA History

● 1994: Alexander Pasik, a former analyst at Gartner, coined the term SOA for a class on middleware that he was teaching. Pasik was working before XML or Web Services were invented, but the basic SOA principles have not changed.

● 1996: Gartner analysts Roy W. Schulte and Yefim V. Natis published the first reports about SOA in 1996.

● 2000: the real momentum for SOA was created by Web Services, which, initially driven by Microsoft, reached a broader public.

SOA Concepts

● Services ● Loose Coupling ● Infrastructure

Services

● Activities, Tasks ● Services Represent Business Functionality ● Definitions:

– The performance of work (a function) by one for another (dictionary)

– A self-contained, stateless business function that accepts one or more requests and returns one or more responses through a well-defined, standard interface (Wikipedia)

– A service represents a self-contained functionality that corresponds to a real-world business activity (SOA in Practice)

Interface

● A service is an interface for (multiple) messages that return information and/or change the state of an associated entity (backend)

● Interface properties: – Signature – describes the input parameters, output

parameters, and possible exceptions. – Well defined – a consumer of a service must know

the complete behavior and semantics of the service. – contract – the complete specification of a service

between a specific provider and a specific consumer.

Interface Types

● Technically Driven Interface

● Business-Driven Interface

Service Attributes

● Self-Contained (independent, autonomous, autarkic) ● Coarse-Grained ● Visible/Discoverable ● Stateless ● Idempotent ● Reusable ● Composable ● Technical ● QoS- and SLA-Capable ● Pre- and Post-Conditions ● Vendor-Diverse ● Interoperable ● Implemented As Web Services?

Loose Coupling

● It is a principle ● Minimize dependencies ● Motivation

– Scalability – Flexibility – Fault tolerance

Loose Coupling Examples

Forms of Loose Coupling

● Asynchronous Communication ● Heterogeneous Data Types ● Mediators (Broker or Name Server) ● Weak Type Checking ● Binding ● Platform Dependencies ● Interaction Patterns ● Compensation Transactions (not 2PC) ● Control of Process Logic ● Deployment ● Versioning

Enterprise Service Bus (ESB)

● Major piece of OSA infrastructure ● Tasks:

– Providing connectivity – Data transformation – (Intelligent) routing – Dealing with security – Dealing with reliability – Service management

● Business Activity Monitoring (BAM) ● Service Orchestrating, BPEL

– Monitoring and logging

Heterogeneous ESB

ESB: Point-to-Point vs Mediation

ESB: Interceptors

ESB: Protocol vs API

Service Layers

● Fundamental SOA – First stage of expansion – Basic services

● Federated (networked) SOA – Micro-flow – Orchestration or composition

layer – Second stage of expansion – Basic and composed services

● Process-enabled SOA – Macro-flow – Third stage of expansion – Basic, composed and

process services

Basic Services

● Guidelines for achieving an optimum level of granularity for a lowest level service: – describe the service in terms of function, information,

goals, and rules, but not in terms of groups of other services

– single responsibility role – self-contained as possible. Ideally – autonomous.

● ACID principle ● Types:

– Basic Data Services – Basic Logic Services

Basic Data Services

● Read or write data from or to one backend system. ● Represent a fundamental business operation of the

backend. ● Examples:

– Create a new customer – Change the address of a customer – Return the address of a customer – Create a new contract/portfolio/account – Return a list of customers according to some search criteria – Return a customer’s balance – Send an ordered item to a customer – Return the number of customers – Return details on a customer’s payment practices

Basic Logic Services

● Basic logic services represent fundamental business rules

● Examples: – Define product catalogs and price lists – Define rules for changing customer contracts – Return whether a year is a leap year – Define allowed dates

Fundamental SOA

Composed Services

● Orchestrated services ● Orchestration - composing new services out of

existing services ● Micro flow:

– Short-term running – Stateless

● Transactions: – Two-phase commit (2PC) – Compensation

● Examples: – Updates redundant data on multiple backends – Money transfer from one backend to another

Federated SOA

Process Services

● Long-term workflows or business processes. ● Macro-flow:

– Long-running flow of activities (services) – Interruptible (by human intervention) – Stateful

● In the Backend ● In the Service

● Examples: – Shopping cart – Insurance policy purchase

Process-enabled SOA

Choreography

● Orchestration: – One central controller that

coordinates all the activities of the process

– Composite pattern, which means that the whole composition itself can be used as a service

● Choreography: – No process control – Not identified as a whole

● Used in – Business process chains – Event-driven architecture

(EDA)

Example (1)

Example (2)

Example (3)

Message Exchange Patterns

● Basic MEPs – Request/Response – One way

● Complicated MEPs – Request-Callback – Publish-Subscribe

Request-Response MEP

One-Way MEP

Request/Callback MEP

Reliability

Service Lifecycle

Versioning

● Domain Versioning – Trivial (new version = new service) – Non-Trivial (i.e. backwards compatibility)

● Configuration-Management-Driven Versioning – Pick required interface from VCS

● Data Types Versioning – Use different types for typed interfaces – Use the same types for typed interfaces – Use generic code so that type differences don’t

matter

Performance

• ESB slows calls 5 to 10 times • Techniques:

– Call Constraints – Custom services

Customized Services


Security

• Characteristics: – Authentication (A) – Authorization (A) – Confidentiality – Integrity – Availability – Accounting (A) – Auditing


• Security is often neglected: – Requires effort – Impossible to achieve absolute

security (except by disconnecting systems)

– Usual security mechanisms for the Internet (firewalls and special protocols such as SSL) are enough.

– Infrastructures provide enough security

– Not clear whether security is an issue for the infrastructure team or the business teams.

SOA & Security

• Policy Decision Point – Policy Enforcement Point

• Transport protocols (https) • Message protocols

• DMZ


Stateless Services


Stateful Services


Idempotency


Governance

• Goals: – Making sure that people do what’s “right.” – Controlling the development and operation of software.

• Technical Tasks: – Documentation – Service management – Monitoring – Change and configuration management

• Non Technical Tasks: – Visions, objectives, business case, and funding model – Reference architecture(s) – Roles and responsibilities – Policies, standards, and formats – Processes and lifecycles


Policy Example


Establishing SOA

• SOA Steps (Josuttis): – Understand SOA – SOA Pilot – Second and third SOA projects – Become the General Strategy

• The “Four Ps” (Pulier and Taylor) – All people have to learn about the principles of SOA and their

associated technologies. – A pilot project helps to prove the concept. – A flexible multiphased project plan will help to integrate and validate

the SOA strategy in a day-to-day business. – Based on the first three Ps, you proceed by establishing SOA via

actual developments. • Architectural Roadmap (Krafzig, Banke, and Slama):

– Fundamental SOA (SOA with basic services only) – Networked SOA (SOA with composed/orchestrated services) – Process-enabled SOA (SOA with process services)


SOA Maturity


Conclusions

• Is SOA something new? • You can not buy SOA • Distributed computing increase complexity • Recent trends:

– Distributed computing costs – Loose coupling costs – ROA – RESTful APIs


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