Topic3 Enterprise Application Integration

Enterprise Application Integration

Sanjoy Sanyal (Tech for NonGeek)

Application Integration in Perspective


Client Server Systems Separates the presentation layer from the application logic layerIncrease of bandwidth and availability of PCsIslands of client server clusters emerged

3 tier architecture and middleware Separates the application logic layer from the resource management layerAllows systems to be built on clusters and integrate different serversThis led to proliferation of services in several rounds of abstraction

The challenge now is the integration of services EAI is one response to the challenge of bridging 3-tier architectures

The Challenge of Application Integration


Example: Supply Chain

Quotation

Order Processing

Procurement

Shipment Managem

ent

Financials

A single implementation of a company-wide process requires integration between different systems which can:-Run on a different OS -Support different interfaces and functionality -Support different data formats -Support informational formats that cannot be easily cast into parameters of a procedure call-Have different security requirements -Have different communication protocols and infrastructure

EAI Middleware: Message Brokers Message Brokers create a “hub and spoke”

communication infrastructure between applications

Traditional RPC/MOM systems create point-to-point links

Message brokers provide additional functionality to transporting messages:Provide adapters that makes it possible to access

heterogenous systems Also filters. routes and processes the messagesIn other words attaches logic at the middleware layer

Examples:Tibco ActiveEnterprise, BEA WebLogic Integration,

WebMethods Enterprise and WebSphereSanjoy Sanyal (Tech for NonGeek)

Advantages of Message Brokers


Message Brokers de-couple receivers and senders:The message routing logic is specified in the

broker unlike in basic MOM where the sender specifies the receiver

Content transformation rules is specified in the broker

Advantages: Increased flexibility : for e,g. when a new system is

neeeded to interact with the supply chain process only the middleware logic needs to change

Integration between heterogeneous data formats/communication protocols

Publish-Subscribe Interaction Model

Applications publish to the middleware system Applications subscribe to messages specifying:

Type (type.subtype…..)Parameters (boolean based: type.subtype AND

<condition)Middleware:

receives messageretrieves the list of relevant subscribing

applicationsdelivers a copy to each of them

Widely supported model among message brokers


JMS

JMS tries to stanardize APIs and middleware infrastructure

JMS supports point-to-point middleware JMS supports publish/subscribe API (based

on topic)


Distributed Administration of a Message Broker


Administrative domain A

admin

Message Broker A

client client

Administrative domain B

admin

Message Broker B

client client

Administrative domain C

admin

Message Broker C

client clientThe administrator has the authority to define:1. Type of messages that can be sent and received 2, which users are authorized to send/receive and to customize routing logic

Different admin domains can correspond to separate cos/departments

Message brokers in different domains can be a client of each other thus allowing clients in one domain to interact with clients in another

Understanding MiddlewareOffers programming abstractions that hides the complexities

of bridging between heterogeneous platforms Middleware implements the functionality of the abstraction


Remote Procedure Call

Sockets

TCP/UDP

IP

A simple example

Remote Procedure Call: Hides communication details behind a procedure call

Sockets: operating system level interface to the underlying communication protocols

Underlying communication protocol

EAI with a Message BrokerEAI platforms are based on two components:

Adapters which hide heterogeneity Message brokers which facilitate communication


Message broker

Integrating application

Quotation adapter

Database adapter

Forecasting

adapter

Emailadapter

xyzadapter

High Level architecture of a typical EAI system

EAI: Example


RFQ Processing

Message Broker

Quotation Adapter

Forecast Adapter

A

B C2 4

1 5 6

7

At system startupA: subscription to message quote B: subscription to message quoterequest C: subscription to message newquote

At runtime1: publication of a quoterequest message2: delivery of message quoterequest 3: synchronous invocation of getquote function4: publication of a quote message5: delivery of message quote6: publication of a newquote message 7: delivery newquote message 8: invocation of createforecastentry function

B3

EAI: On the Balance

Lower Development and Opportunity CostsLower Maintenance Costs High software License costs


Workflow Management Systems

Origin in office automation Received interest from business process

reengineering Products:

WebSphere MQ Workflow (IBM) Vitra Business-Ware Tibco BPM BEA WebLogic Integration Microsoft BizTalk Orchestration


Workflow Definitions

Business Process E.gs: hiring new employees, process

purchase orders Workflow/Workflow process:

Formal executable description of a business process

Workflow specified by:Work node: represent work items Routing node: define order in which work

items should be executed Start and completion nodes: start and end

points of workflow


Workflow ExecutionExecuted by a workflow engine:

Retrieves the workflow definition from a repositoryDetermines the nodes to be executedSchedules the work to be done Assigns it to an appropriate resource (work executor)

Resources:Retrieve work from a work queue (work can also be

pushed)Executes and returns the work to the engine’s

inbound queue Evaluate the condition and determines which node

should be executed next Resource broker:

Helps in node selection by executing resource selection policy


Workflow Execution


Workflow Engine

Resource broker

Completed work itemsInbound queue

resource 1

resource 2

resource n

Workflow Definitions

Workflow Designer Outbound queues

EAI with WfMSEAI and WfmS are Complimentary

EAI tackles heterogenity, WfMs tackle workflowWfMs can sit on top of EAI


Message broker

WfMS adapter

Quotation adapter

Database adapter

Forecasting

adapter

Emailadapter

xyzadapter

WfMS

WfMS: On the Balance

Generated a lot of interest But did not live up to its promise:

High software licenses Difficult to automate real-life processes


Summary


EAI refers specifically to integration of heterogeneous, coarse grained applications

Platforms for choice are message brokers and Workflow Management systems

Message brokers play a much more important role Message brokers allow an asynchronous communication

model and loose coupling In general, implementations of EAI platforms is still

expensive and not seamless

(the material in this topic is based on Web Services: Concepts, Architectures and Applications by Alonso, Casati, Kuno, Machiraju)

Technology

Topic3 Enterprise Application Integration