62 Smart SOA Solutions with WebSphere Enterprise Service Bus Registry Edition V7.5
3.4.1 Sizing WebSphere ESB
In this section, we describe the mediation flows that are designed, the adapters
that are used, and other factors to clarify how to perform sizing for WebSphere
ESB.
Mediation flow workload scenarios
Different scenarios can apply to a solution. In this section, we describe possible
workload mediations scenarios and describe samples of usage patterns.
Mediation scenarios for sizing are analyzed and improved to better reflect
supplied patterns and customer usage of the product and to list the types of
mediation that will be in the sizing tools in the future. This comparison is based
on multiple scenarios that are defined to compare workload. These mediation
scenarios are ordered by the associated cost in the workload, from the least
expensive to the most expensive:
Service Gateway Routing Mediation
Composite Mediation
Protocol Conversion Mediation
Data Warehouse Mediation
Chained Mediation
Aggregation Mediation
Service Gateway Routing Mediation
The Service Gateway Routing Mediation applies the Proxy Service Gateway
pattern (available in IBM Integration Designer). In this pattern, the workload
depends on whether the routing decision is in WebSphere ESB or WSRR. For
our example, the workload is in WebSphere ESB and uses internal routing
tables.
Routing can be achieved using either header-based or body-based routing,
according to the associated cost in the workload. Header-based routing is less
expensive than body-based routing.
Version note: The workload scenarios that we developed and describe in this
section do not apply for versions prior to 7.5.
Chapter 3. Topology overview 63
Figure 3-8 shows a sample of a request flow using this mediation.
Figure 3-8 Service Gateway Routing Mediation sample
This mediation uses the Gateway Endpoint Lookup primitive to provide a single
access point for multiple services and to perform common processing on all
inbound and outbound messages.
This type of processing might be used to process a car insurance quotation, for
example to obtain information that pertains to the make and model of the vehicle.
The mediation can provide a single access point. It uses the dynamic endpoint
lookup functionality to locate the appropriate service to invoke, depending on the
car brand. This scenario further allows for dynamic addition and removal of target
services as new makes or models of vehicles become available without the need
to modify the deployed application.
Composite Mediation
The Composite Mediation is a mediation that composes multiple service
interaction primitive invocations in a flow. It can also compose other pattern
directed flows, but for the workload perspective we do not include compositions
of other described flows. Otherwise, the associated cost of the mediation
depends on the composed mediation.
64 Smart SOA Solutions with WebSphere Enterprise Service Bus Registry Edition V7.5
Our sample of this mediation includes a request and its response flow. The
request, as shown in Figure 3-9, shows how the mediation flow receives the input
and calls services.
Figure 3-9 Composite Mediation request flow sample
Figure 3-10 shows the response flow and illustrates how the output message is
built.
Chapter 3. Topology overview 65
Figure 3-10 Composite Mediation response flow sample
This mediation uses the Message Filter primitive to provide static endpoint
resolution based on information that is stored within the body of the incoming
message. It also uses the XSLT Transform primitive to apply an appropriate
transformation to the incoming message to match the expected schema of the
target service.
This type of processing might be used to process a car insurance quotation by a
company that has a choice of multiple, functionally equivalent, back-end
services. For example, if a takeover of an existing company occurs, the company
can use the acquired services. An authorization is performed, and a log is made
of the request. The request is then formatted appropriately, and a particular
back-end service is invoked based on whether the quotation pertains to a car,
van, or motorcycle.
Protocol Conversion Mediation
The Protocol Conversion Mediation is used when protocol conversion is needed.

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