Connecting with the Service Bus

The second major piece of Windows Azure platform AppFabric is the Service Bus. As adoption of service-oriented architecture (SOA) increases, developers are seeking better ways of connecting their services together. At the simplest level, the Service Bus does this for any service out there. It makes it easy for services to connect to each other and for consumers to connect to services. In this section, we’re going to look into what the Service Bus is, why you’d use a bus, and, most importantly, how you can connect your services to it. You’ll see how easy it is to use the Service Bus.

What is a Service Bus?
Enterprise service buses (ESBs) have been around for years, and they’ve grown out of the SOA movement. As services became popular, and as the population of services at companies increased, companies found it harder and harder to maintain the infrastructure. The services and clients became so tightly coupled that the infrastructure became very brittle. This was the exact problem services were created to avoid. ESBs evolved to help fix these problems.

ESBs have several common characteristics, all geared toward building a more dynamic and flexible service environment:

- ESBs provide a service registry—Developers and dynamic clients needed ways to find available services, and to retrieve the contract and usage information they needed to consume them.

- ESBs provide a way to name services—This involves creating a namespace around services so there isn’t a conflict in the service names and the message types defined.

- ESBs provide some infrastructure for security—Generally, this includes a way to allow or deny people access to a service, and a way to specify what they’re allowed to do on that service.

- ESBs provide the “bus” part of ESB—The bus provides a way for the messages to move around from client to service, and back. The important part of the bus is the instrumentation in the endpoints that allows IT to manage the endpoint. IT can track the SLA of the endpoint, performance, and faults on the service.

- ESBs commonly provide service orchestration—Orchestration is the concept of composing several services together into a bigger service that performs some business process.

A common model for ESBs is similar to the typical n-tier architecture model, where each tier relies on the abstractions provided by the layer below it. The orchestration has become not only a way to have lower-level services work together, but it also provides a layer of indirection on top of those services. In the orchestration layer you can route messages based on content, policy, or even service version. This is important as you connect services together, and as they mature.

Source of Information : Manning Azure in Action 2010


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