Patterns: Broker Interactions for Intra- and Inter-enterprise

Chapter 9. Broker solutions using WebSphere Business Integration Message Broker 237

򐂰 The AggregateReply node marks the end of an aggregation fan-in. It collects

replies and combines them into a single aggregated reply message.

An aggregation message flow will most likely contain Compute nodes using

ESQL scripts to implement logic needed during the fan-out or fan-in process. In

particular, Compute nodes are handy for manipulation of the aggregated reply

before returning it to the client. Message flows can also interact with external

databases to store or retrieve information needed during processing.

When determining whether to use aggregation, keep the following considerations

in mind:

1. Message flows using aggregation are generally the most complex message

flows to be constructed.

2. In production you would want the fan-out and fan-in flows to be in two

different message flows. This allows the input flow to be stopped first while

allowing inflight requests to complete before the fan-in flow is stopped.

3. Good design is necessary to ensure that all fan-out and fan-in messages are

captured and processed.

4. A good knowledge of ESQL and the logical message tree is necessary to

manipulate the combined messages.

9.5 System design overview

With the design guidelines in mind, ITSO Electronics decided to implement their

solution in three stages using WebSphere Business Integration Message Broker

V5 as the broker.

9.5.1 Stage 1: Internal “Get earliest delivery date” solution

In the first stage of the solution, the Retail department will use a broker to access

the internal Wholesale departments.

Figure 9-10 shows a high-level design view of the solution.

238 Broker Interactions for Intra- and Inter-enterprise

Figure 9-10 Aggregation design

The solution will consist of the following elements:

򐂰 A Retail application that requests delivery dates from Wholesale applications

using the part number as input. This application invokes a Web service in

order to get the delivery date.

򐂰 A message flow deployed on WebSphere Business Integration Message

Broker that distributes the request to all the Wholesale systems that can

provide that part. The message flow is built using aggregate nodes in order to

make the fact that there are multiple Wholesale systems transparent to the

client. The message flow will collect the responses from the Wholesale

systems, examine them to determine which date is the earliest, and send that

date back to the client.

This message flow is available to the client as a Web service.

򐂰 A Wholesale system that returns a delivery date for a part it contains in its

inventory. The application is implemented using an EJB and has been

Web-service enabled.

To simplify and standardize the access to the broker process, the WebSphere

MQ Web Services Transport features of WebSphere Business Integration

Message Broker will be used. The requests for delivery dates are non-critical to

the business and if a response is not received in a reasonable amount of time,

the request can be easily sent again.

In this scenario, we are combining two aspects of Web service support provided

by WebSphere Business Integration Message Broker:

򐂰 The message flow is available to clients as a Web service and is accessed

using HTTP.

Message Broker

<Aggregator>

Wholesale1

Wholesale2

Retailer

SOAP/

HTTP

SOAP/HTTP

<subflow>

<subflow>

Chapter 9. Broker solutions using WebSphere Business Integration Message Broker 239

򐂰 The message flow sends a message to a Web service to get a reply for the

client. This also uses the HTTP protocol.

The primary message flow uses the aggregator node to send the request to

multiple Wholesale systems. It is important to note that the aggregator node is

designed for MQ message input so in this stage you will see examples of

converting messages from one format to another.

9.5.2 Stage 2: Internal sales forecast publish/subscribe

Stage 2 will use a publish/subscribe model to allow the Retail systems to publish

their sales forecast information to large numbers of Wholesale system

subscribers (Figure 9-11).

Figure 9-11 Real-time flow design

The solution will consist of a publish/subscribe mechanism to allow the Retail

clients to distribute sales information to the Wholesale applications

Because a large number of messages need to be published and persistent

delivery is not required, this design will use the WebSphere MQ Real-time

Transport features of WebSphere Business Integration Message Broker.

9.5.3 Stage 3: External “Get earliest delivery date” solution

Stage 3 will extend the solution in stage 1 to allow the Retail departments to

access external Wholesale suppliers. The addition of a gateway will allow the

internal Retail departments to access the external Wholesale processes through

a standard interface (Figure 9-12).

Event Broker

Wholesale System

Wholesale System

Wholesale System

<Broker Real-time flow>

Retail System

JMS/IP

JMS/IP