Microsoft Azure Service Bus Event Hubs provide a topic based publish/subscribe messaging platform that allows for high throughput and low latency message processing. A preview version has been recently released by the Microsoft Azure team.
Event Hubs is a component of the service bus, and works alongside service bus topics and queues. Event Hubs provide a perfect platform for collecting event streams from multiple devices and sending them to an analytics engine for processing. This makes it ideal for an Internet of Things (IoT) scenario, where you can capture events from various connected devices and make meaningful decisions based on the ingested event stream.
You can also make use of analytics on the ingress to perform tenant billing, and performance monitoring amongst many possibilities. Event Hubs not only provide a reliable message processing platform, but also support durability for a predefined retention period allowing consumers to connect back in case of a failure.
An Event Hub is part of a Service Bus namespace, and typically consists of a Publisher Policy, Consumer Groups and Partition Keys. A publisher is a logical concept for publishing a message into an Event Hub, and a consumer is a logical concept for receiving messages. Partition allows for scaling Event Hubs and subscribers connect to a partition. Events in a partition are also ordered for delivery.
Currently the supported protocols for pub-sub are HTTP and AMQP. Note that for receiving data only AMQP is currently supported.
The Azure Service Bus NuGet package provides the
EventProcessorHost and the
EventHubClient API to process messages and send messages to the hub respectively. To start a host that can listen for incoming messages you can create a new instance of the
EventProcessorHostas shown below:
host = new EventProcessorHost( hostName, eventHubName, consumerGroupName, eventHubConnectionString, storageConnectionString, eventHubName.ToLowerInvariant());
Note that it is a good practice to share the hub name in lowercase to avoid any case conflicts on names that the subscribers may present. You need to provide the connection strings for the event hub on the service bus namespace, the storage connection string for the queue, the name of the consumer group and a host name. You can then create a processor factory implementation using the
IEventProcessorFactory interface to provide a factory implementation for processing the incoming messages. The host instance can then register the factory to listen for ingress using the
RegisterEventProcessorFactoryAsync method. Similarly from the client, you can create an instance of the Event Hub Client using the EventHubClient.CreateFromConnectionString method, and then start sending messages using the SendAsync method that the client exposes.