ServiceBusses - Service Bus fundamentals DiFerent...

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Service Bus fundamentals Different situations call for different styles of communication. Sometimes, letting applications send and receive messages through a simple queue is the best solution. In other situations, an ordinary queue isn't enough; a queue with a publish-and-subscribe mechanism is better. And in some cases, all that's really needed is a connection between applications—queues aren't required. Service Bus provides all three options, letting your applications interact in several different ways. WORKERS ARE CONSUMERS OF MESSAGES Service Bus is a multi-tenant cloud service, which means that the service is shared by multiple users. Each user, such as an application developer, creates a namespace , then defines the communication mechanisms she needs within that namespace. Figure 1 shows how this looks. Figure 1: Service Bus provides a multi-tenant service for connecting applications through the cloud. Within a namespace, you can use one or more instances of four different communication mechanisms, each of which connects applications in a different way. The choices are:
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Queues , which allow one-directional communication. Each queue acts as an intermediary (sometimes called a broker ) that stores sent messages until they are received. Each message is received by a single recipient. Topics , which provide one-directional communication using subscriptions -a single topic can have multiple subscriptions. Like a queue, a topic acts as a broker, but each subscription can optionally use a filter to receive only messages that match specific criteria. Relays , which provide bi-directional communication. Unlike queues and topics, a relay doesn't store in-flight messages-it not a broker. Instead, it just passes them on to the destination application. Event Hubs , which provide event and telemetry ingress to the cloud at massive scale, with low latency and high reliability. When you create a queue, topic, relay, or Event Hub, you give it a name. Combined with whatever you called your namespace, this name creates a unique identifier for the object. Applications can provide this name to Service Bus, then use that queue, topic, relay, or Event Hub to communicate with one another. To use any of these objects, Windows applications can use Windows Communication Foundation (WCF). For queues, topics, and Event Hubs Windows applications can also use Service Bus-defined messaging APIs. To make these objects easier to use from non- Windows applications, Microsoft provides SDKs for Java, Node.js, and other languages. You can also access queues, topics, and Event Hubs using REST APIs over HTTP. It's important to understand that even though Service Bus itself runs in the cloud (that is, in Microsoft's Azure datacenters), applications that use it can run anywhere. You can use Service Bus to connect applications running on Azure, for example, or applications running inside your own datacenter. You can also use it to connect an application running on Azure or another cloud platform with an on-premises application or with tablets and phones. It's even possible to connect household appliances, sensors, and
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