Azure Event Hubs

Component format

To setup Azure Event Hubs pubsub create a component of type pubsub.azure.eventhubs. See this guide on how to create and apply a pubsub configuration. Apart from the configuration metadata fields shown below, Azure Event Hubs also supports Azure Authentication mechanisms.

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: eventhubs-pubsub
spec:
  type: pubsub.azure.eventhubs
  version: v1
  metadata:
  - name: connectionString    # Either connectionString or eventHubNamespace. Should not be used when 
  # Azure Authentication mechanism is used.
    value: "Endpoint=sb://{EventHubNamespace}.servicebus.windows.net/;SharedAccessKeyName={PolicyName};SharedAccessKey={Key};EntityPath={EventHub}"
  - name: eventHubNamespace   # Either connectionString or eventHubNamespace. Should be used when 
  # Azure Authentication mechanism is used.
    value: "namespace"
  - name: enableEntityManagement
    value: "false"
    ## The following four properties are needed only if enableEntityManagement is set to true
  - name: resourceGroupName
    value: "test-rg"
  - name: subscriptionID
    value: "value of Azure subscription ID"
  - name: partitionCount
    value: "1"
  - name: messageRetentionInDays
  ## Subscriber attributes
  - name: storageAccountName
    value: "myeventhubstorage"
  - name: storageAccountKey
    value: "112233445566778899"
  - name: storageContainerName
    value: "myeventhubstoragecontainer"

Spec metadata fields

Azure Active Directory (AAD) authentication

The Azure Event Hubs pubsub component supports authentication using all Azure Active Directory mechanisms. For further information and the relevant component metadata fields to provide depending on the choice of AAD authentication mechanism, see the docs for authenticating to Azure.

Example Configuration

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: eventhubs-pubsub
spec:
  type: pubsub.azure.eventhubs
  version: v1
  metadata:
  # Azure Authentication Used
  - name: azureTenantId
    value: "***"
  - name: azureClientId
    value: "***"
  - name: azureClientSecret
    value: "***"
  - name: eventHubNamespace 
    value: "namespace"
  - name: enableEntityManagement
    value: "false"
    ## The following four properties are needed only if enableEntityManagement is set to true
  - name: resourceGroupName
    value: "test-rg"
  - name: subscriptionID
    value: "value of Azure subscription ID"
  - name: partitionCount
    value: "1"
  - name: messageRetentionInDays
  ## Subscriber attributes
  - name: storageAccountName
    value: "myeventhubstorage"
  - name: storageAccountKey
    value: "112233445566778899"
  - name: storageContainerName
    value: "myeventhubstoragecontainer"

Create an Azure Event Hub

Follow the instructions here on setting up Azure Event Hubs. Since this implementation uses the Event Processor Host, you will also need an Azure Storage Account. Follow the instructions here to manage the storage account access keys.

See here on how to get the Event Hubs connection string. Note this is not the Event Hubs namespace.

Create consumer groups for each subscriber

For every Dapr app that wants to subscribe to events, create an Event Hubs consumer group with the name of the dapr id. For example, a Dapr app running on Kubernetes with dapr.io/app-id: "myapp" will need an Event Hubs consumer group named myapp.

Note: Dapr passes the name of the Consumer group to the EventHub and so this is not supplied in the metadata.

Entity Management

When entity management is enabled in configuration, as long as the application has the right role and permissions to manipulate the Event Hub namespace, creation of Event Hubs and consumer groups can be done on the fly.

The Evet Hub name is the topic field in the incoming request to publish or subscribe to, while the consumer group name is the name of the dapr app which subscribes to a given Event Hub. For example, a Dapr app running on Kubernetes with name dapr.io/app-id: "myapp" requires an Event Hubs consumer group named myapp.

Entity management is only possible when using Azure Authentication mechanisms and not via connectionString.

Note: Dapr passes the name of the Consumer group to the EventHub and this is not supplied in the metadata.

Subscribing to Azure IoT Hub Events

Azure IoT Hub provides an endpoint that is compatible with Event Hubs, so the Azure Event Hubs pubsub component can also be used to subscribe to Azure IoT Hub events.

The device-to-cloud events created by Azure IoT Hub devices will contain additional IoT Hub System Properties, and the Azure Event Hubs pubsub component for Dapr will return the following as part of the response metadata:

For example, the headers of a delivered HTTP subscription message would contain:

{
  'user-agent': 'fasthttp',
  'host': '127.0.0.1:3000',
  'content-type': 'application/json',
  'content-length': '120',
  'iothub-connection-device-id': 'my-test-device',
  'iothub-connection-auth-generation-id': '637618061680407492',
  'iothub-connection-auth-method': '{"scope":"module","type":"sas","issuer":"iothub","acceptingIpFilterRule":null}',
  'iothub-connection-module-id': 'my-test-module-a',
  'iothub-enqueuedtime': '2021-07-13T22:08:09Z',
  'message-id': 'my-custom-message-id',
  'x-opt-sequence-number': '35',
  'x-opt-enqueued-time': '2021-07-13T22:08:09Z',
  'x-opt-offset': '21560',
  'traceparent': '00-4655608164bc48b985b42d39865f3834-ed6cf3697c86e7bd-01'
}

Related links

• Basic schema for a Dapr component
• Read this guide for instructions on configuring pub/sub components
• Pub/Sub building block
• Authentication to Azure