provider_azure_eventhubs.md

Azure Event Hub Provider for SlimMessageBus

Introduction

Please read the Introduction before reading this provider documentation.

Configuration

Azure Event Hub provider requires a connection string to the event hub:

var connectionString = ""; // Azure Event Hubs connection string
var storageConnectionString = ""; // Azure Storage Account connection string (for the consumer)
var storageContainerName = ""; // Azure Blob Storage container name (for the consumer to store last commit offset of each subscriber)

MessageBusBuilder mbb = MessageBusBuilder.Create()
    // the bus configuration here
    .WithProviderEventHub(new EventHubMessageBusSettings(connectionString, storageConnectionString, storageContainerName)); // Use Azure Event Hub as provider
    .WithSerializer(new JsonMessageSerializer());

IMessageBus bus = mbb.Build();

If your bus does only produce messages to Event Hub and does not consume any messages, then you do not need to provide a storage account as part of the config. In this case pass null for the storage account details:

var connectionString = ""; // Azure Event Hubs connection string

MessageBusBuilder mbb = MessageBusBuilder.Create()
    // the bus configuration here
    .WithProviderEventHub(new EventHubMessageBusSettings(connectionString, null, null)); // The bus will only be used to publish messages to Azure Event Hub
    .WithSerializer(new JsonMessageSerializer());

Producing Messages

To produce a given TMessage to an Azure Event Hub named my-event-hub use:

// send TMessage to Azure SB queues
mbb.Produce<TMessage>(x => x.DefaultTopic("my-event-hub")); 

Selecting message partition for producer

Azure EventHub topics are broken into partitions:

• when message key is not provided then partition is assigned using round-robin,
• when message key is provided then same partition is assigned to same key

SMB Azure EventHub allows to set a provider (selector) that will assign the partition key for a given message. Here is an example:

mbb.Produce<CustomerUpdated>(x => 
    {
        x.DefaultTopic("topic1");
        // Message key could be set for the message
        x.KeyProvider((message) => CustomerId.ToString());
    });

The partition key value is a string for AEH.

There is also an alias EhKeyProvider that might be useful in case the hybrid bus is used with multiple providers that might have an overlapping extension method name.