Chapter 4. Runtime patterns 57
򐂰 Domain firewall node
The domain firewall is typically implemented as a dedicated server node. See
“Protocol firewall node” on page 56 for a description of firewalls.
򐂰 Existing applications and data node
Existing applications are run and maintained on nodes, which are installed in
the internal network. These applications provide for business logic that uses
data maintained in the internal network. The number and topology of these
existing application and data nodes is dependent on the particular
configuration used by these existing systems.
򐂰 Business service directory
The role of the
business service directory is to provide details of services that
are available to perform business functions identified within a taxonomy. The
business service directory can be implemented as an open-standard UDDI
registry. Catalogs, such as a UDDI registry, can achieve one of the primary
goals of a business service directory: to publish the availability of services
and encourage their reuse across the development activity of an enterprise.
The vision of Web services defines an open-standard UDDI registry that
enables the dynamic discovery and invocation of business services. However
although technologies mature toward that vision, more basic solutions are
likely to be implemented in the near term.
򐂰 Enterprise service bus
The
ESB is a key enabler for a SOA as it provides the capability to route and
transport service requests from the service requester to the correct service
provider. The true value of the ESB concept, however, is to enable the
infrastructure for SOA in a way that reflects the needs of today’s enterprise: to
provide suitable service levels and manageability, and to operate and
integrate in a heterogeneous environment.
Furthermore the ESB needs to be centrally managed and administered and
have the ability to be physically distributed.
4.1.1 Why use an enterprise service bus?
Using an ESB node is key to designing an SOA solution. For that reason, we will
go into the ESB node in more detail to help you understand the advantages.
Selecting a Runtime pattern that uses an ESB helps you achieve the following:
򐂰 Minimizes the number of adapters required for each point-to-point connection
to link service consumers to service providers.
򐂰 Improves reuse in multiple point-to-point scenarios.
58 Patterns: Implementing Self-Service in an SOA Environment
򐂰 Addresses any technical and information model discrepancies between
services.
򐂰 Provides a single configuration point for distributed deployment.
򐂰 Decouples service requesters from providers
򐂰 Provides a common access point for service requesters
򐂰 Provides centralized security for services
The service bus can span across multiple system and application tiers, and can
extend beyond the enterprise boundary.
Figure 4-1 shows a first level decomposition of the major components that make
up an ESB node.
Figure 4-1 ESB runtime pattern: Level one
The ESB is a key enabler for an SOA because it provides the capability to route
and transport service requests from the service consumer to the correct service
provider. The ESB controls routing within the scope of a service namespace,
indicated symbolically in Figure 4-1 by the oval on the ESB Hub.
The true value of the ESB concept, however, is to enable the infrastructure for
SOA in a way that reflects the needs of today’s enterprise: to provide suitable
service levels and manageability and to operate and integrate a heterogeneous
environment. Furthermore, the ESB needs to be centrally managed and
administered and have the ability to be physically distributed.
Hub
Namespace
Directory
Enterprise Service Bus
Administration and
Security Services

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