Enterprise Application Integration - System Integration Methods

8/14/2019 Enterprise Application Integration - System Integration Methods

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Enterprise ApplicationIntegration

Paulo MarquesInformatics Engineering DepartmentUniversity of Coimbra

[email protected]

v/2009

Systems IntegrationMethodologies
mailto:[email protected]:[email protected]


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Whats this about?

Network

Presentation

Web Server

Business LogicApp Server

Data Tier

Database Server


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Motivating Example

Warehouse

(Amazon)

1

3

2

4

5

6

7


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How the Software Engineering world should look like


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The ugly reality

Spaghetti Code

Just-in-time Ad Hoc Construction
http://boone.calstatela.edu/spring476/prasarangkul.htm


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Ball-of-Mud Enterprise Application Integration


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Why Structured Enterprise Application Integration?

Information systems are getting more and more complex!

InterconnectedNowadays systems are not isolated: networks play a vital role! Also, newcommunication channels complicate issues (e.g. WAP, SMS, iPhone)

Constantly EvolvingTodays systems are stressed beyond their limits. People want more andmore functionality of the infrastructure in place. Thus, the size of systemscontinues to increase. Centralized monolithic solutions are no longer viable:cooperation among systems is paramount. Nevertheless, heterogeneitycomplicates things (e.g. J2EE, .NET, SAP)

Adhoc IS NOT AN OPTION- 70 to 90% of the software costs are maintenance- 40% of the code is within the databases- 1.000.000 lines of code is now low medium scale- How to create systems so that they can be easily integrated?

- How to create software that is reusable? And at what granularity?


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Enterprise Application Integration in Context

Databases

Networks Software Engineering

Programming Languages

Enterprise Application Integration

Service Oriented Architecture

Enterprise Service Bus

How to buildApplications

How to integrate applications


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Issues that need to be addressed

Any means used for Enterprise Application Integration must address,at least, the following issues:

How is Data Represented Each application has its own data modeland information schema. There may be shared concepts betweenapplications but, typically, they are represented in different ways. Itsessential to have ways ofmapping and transforming data.

Localization of Services Each application was developed as a

software silo. Thus, it can unexpectedly change localization. Itsessential to have ways oflocalizing and remotely accessing applicationsthat are executing autonomously.

Time and Synchronicity The RPC model is synchronous. This meansthat both parties have to be present when a call is made. Such constraintis not viable when communicating among autonomous independent

systems. Typically, its necessary to use an asynchronous and robustcommunication model between systems.

Fault Tolerance Networks are inherently fallible. Simplisticapproaches like re-trying operations do not work. Its necessary to haverobust mechanisms for tolerating faults and, in many cases, distributed

transactions (ACID or not).


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SOA in a nutshell

SystemA

Service

Interface

SystemB

Service

Interface

SystemC

Service

Interface

SystemD

Service

Interface

EnterpriseService Bus

ProcessOrchestrator

ServiceDirectory

A Service Oriented

Architecture


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Process Orchestrator?


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Why use a SOA?

Future, Scalability and Evolution!

An organization is made up of many different systems.Sooner or later they will have to talk to each other.(typically, sooner than latter!)

If systems are not thought from the beginning for integration, the

solutions found for doing so will be ad-hoc, without possibilityof evolution, and with high development and maintenancecosts

Using a Service Bus and a Service Oriented Architecture allows for

future evolution, both by easily adding new services and, ifnecessary, replacing existing service implementations

A SOA allows to do so with minimal disruption of the businessprocesses of an organization.


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IMPORTANT CONCEPT: Evolving Systems!


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Progressive Deployment


Phase 1 Phase 2 Phase 3


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The importance of Open Standards

Its absolutely important that a SOA is based on Open

Standards It allows the architecture to stay in place on the long-run

Allows external services to be easily integrated into theorganizations infrastructure

Allows for the substitution of existing systems by better ones (e.g.

better technology, with a lower cost of ownership, or that aremore adequate to the organizations strategy)

Technologies like XML, HTTP, SOAP play a vital role

It allows applications to bind to servicesthat evolve and improve over time withoutrequiring modification to the applicationsthat consume them


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Some Challenges

Nave Implementations use WebServices for Everything!

Web Services are Sexy!


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Problems associated to the Client/Server model

Synchronous interaction which forces both parties to be

present at the same time Normally blocking: who calls is forced to wait for the

server processing to be over

Maintaining sessions is expensive in terms of resources,

limiting the number of simultaneous clients Use ofconnection-pools

Use ofthread-pools

Use of Asynchronous I/O


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Faults affecting the synchronous model (Client/Server)

If a fault occurs, the session contextis lost

Re-synchronizing systems can beEXTREMELY complicated!

Especially so when nested calls areperformed.

Some examples of faults:

If a fault occurs before (1), havinghas actually happen.

If the fault takes place between (1)and (2) server fault the requestis lost

If the fault takes place between (2)and (3) subsystems fault datainconsistencies may occur

If the fault happens after (3),corresponding to a lost response,the client will retry the operation

Possible Solution:2PC

But its so

SLOW


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Motivating Example

Transfer 5000 from theCGD account to the MGaccount

(Application Server) (BD Server)

(DB Server)

(DB Server)

widraw(5000, #4598)

(Application Server)


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How to address this?

Transfer 5000 from theCGD account to the MGaccount

deposit(5000, #7653)

The server cashes after having

taken the money out, but beforethe money has been deposited.What now?

(Application Server) (BD Server)

(DB Server)

(DB Server)


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Bank Transfer using a Two-Phase Commit

Bank A Bank B

StartTransaction

Withdraw fromacct. A

Transfer

Credit onaccount B

Two-Phase Commit


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SOA Revisited

SystemA

Service

Interface

SystemB

Service

Interface

SystemC

Service

Interface

SystemD

Service

Interface


ProcessOrchestrator

ServiceDirectory


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Conclusion

Large Scale Enterprise Application Integration is much

more than simply writing network code

Service Oriented Architecture (SOA) is critical fordesigning systems that:

Are maintainable in the future with low costs Can adapt to the new business needs of organizations

Are reliable and easy to use

Creating an SOA is much more than simply calling webservices scattered throughout the organization (or inter-organizations)

Beware of the hype!


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Documents

Enterprise Application Integration - System Integration Methods