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Scale applications based on Azure Event Hubs.

Availability: v1.0+ Maintainer: Community

Trigger Specification

This specification describes the azure-eventhub trigger for Azure Event Hubs.

triggers:
- type: azure-eventhub
  metadata:
    connectionFromEnv: EVENTHUB_CONNECTIONSTRING_ENV_NAME
    storageConnectionFromEnv: STORAGE_CONNECTIONSTRING_ENV_NAME
    consumerGroup: $Default
    unprocessedEventThreshold: '64'
    blobContainer: 'name_of_container'

Parameter list:

  • connectionFromEnv - Name of the environment variable your deployment uses to get the connection string appended with EntityPath=<event_hub_name>.
  • storageConnectionFromEnv - Name of the environment variable that provides connection string for Azure Storage Account to store checkpoint. As of now the Event Hub scaler only reads from Azure Blob Storage.
  • consumerGroup - Consumer group of Azure Event Hub consumer. (default: $default)
  • unprocessedEventThreshold - Average target value to trigger scaling actions. (Default: 64, Optional)
  • blobContainer - Container name to store checkpoint. This is needed for every checkpointStrategy except of AzureFunction. With Azure Functions the blobContainer is autogenerated and cannot be overridden.
  • checkpointStrategy - configure the checkpoint behaviour of different Event Hub SDKs. (default: "")
    • azureFunction - Suitable for Azure Functions & Azure WebJobs SDK. This is the default setting, when blobcontainer is not specified.
    • blobMetadata - For all implementations that store checkpoint information on blob metadata such as current C#, Python, Java and JavaScript Event Hub SDKs.
    • goSdk - For all implementations using the Golang SDK‘s checkpointing, for example Dapr.
    • When no checkpoint strategy is specified, the Event Hub scaler will use backwards compatibility and able to scale older implementations of C#, Python or Java Event Hub SDKs. (see “Legacy checkpointing”). If this behaviour should be used, blobContainer is also required.

💡 Legacy Checkpointing: C# applications, which use the Microsoft.Azure.EventHubs package, Java applications which use the azure-eventhubs-eph package or Python applications which use the azure-eventhub below v5 are supported if no checkpointStrategy is specified. These legacy implementations are based on the EventProcessorHost client, which stores checkpoint information as blob container content

C# Applications that use the current Azure.Messaging.EventHubs package, Java applications which use the current azure-messaging-eventhubs package or Python applications since azure-eventhub v5, have to set the checkpointStrategyto blobMetadata. All these implementations based on the EventProcessorClient which stores checkpoint information as blob metadata.

💡 The Azure Storage connection string is not compatible with connection string created from a Shared Access Signature.

Authentication Parameters

The common way of authenticating to Azure Event Hub is by using the connection string. However, you can use Pod Identity if you host your cluster in Azure AKS, and if have configured it to support Pod Identity.

To use Pod Identity, you have to add a TriggerAuthentication and configure it to use Pod Identity like so:

apiVersion: keda.sh/v1alpha1
kind: TriggerAuthentication
metadata:
  name: nameOfTriggerAuth
  namespace: default
spec:
  podIdentity:
    provider: Azure

When you do so, the Event Hub scaler will depend on the existence of two configurations you have to provide: eventHubNamespace and eventHubName.

Example

apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: azure-eventhub-scaledobject
  namespace: default
spec:
  scaleTargetRef:
    name: azureeventhub-function
  triggers:
  - type: azure-eventhub
    metadata:
      # Required
      storageConnectionFromEnv: AzureWebJobsStorage
      # Required if not using Pod Identity
      connectionFromEnv: EventHub
      # Required if using Pod Identity
      eventHubNamespace: AzureEventHubNameSpace
      eventHubName: NameOfTheEventHub
# Optional
      consumerGroup: $Default # default: $Default
      unprocessedEventThreshold: '64' # default 64 events.
      blobContainer: ehcontainer


Currently available scalers for KEDA