Trigger Specification

This specification describes the azure-servicebus trigger for Azure Service Bus Queue or Topic.

⚠️ WARNING: KEDA is not in charge of managing entities. If the queue, topic or subscription does not exist, it will not create them automatically.

triggers:
- type: azure-servicebus
  metadata:
    # Required: queueName OR topicName and subscriptionName
    queueName: functions-sbqueue
    # or
    topicName: functions-sbtopic
    subscriptionName: sbtopic-sub1
    # Optional, required when pod identity is used
    namespace: service-bus-namespace
    # Optional, can use TriggerAuthentication as well
    connectionFromEnv: SERVICEBUS_CONNECTIONSTRING_ENV_NAME
    # Optional
    messageCount: "5" # Optional. Count of messages to trigger scaling on. Default: 5 messages
    activationMessageCount: "2"
    cloud: Private # Optional. Default: AzurePublicCloud
    endpointSuffix: servicebus.airgap.example # Required when cloud=Private

Parameter list:

• messageCount - Amount of active messages in your Azure Service Bus queue or topic to scale on.
• activationMessageCount - Target value for activating the scaler. Learn more about activation here. (Default: 0, Optional)
• queueName - Name of the Azure Service Bus queue to scale on. (Optional)
• topicName - Name of the Azure Service Bus topic to scale on. (Optional)
• subscriptionName - Name of the Azure Service Bus queue to scale on. (Optional*, Required when topicName is specified)
• namespace - Name of the Azure Service Bus namespace that contains your queue or topic. (Optional*, Required when pod identity is used)
• connectionFromEnv - Name of the environment variable your deployment uses to get the connection string of the Azure Service Bus namespace. (Optional)
• useRegex - Provides indication whether or not a regex is used in the queueName or subscriptionName parameters. (Values: true, false, Default: false, Optional)
• operation - Defines how to compute the number of messages when useRegex is set to true. (Values: sum, max, or avg, Default: sum, Optional).
• cloud - Name of the cloud environment that the service bus belongs to. Must be a known Azure cloud environment, or Private for Azure Stack Hub or Air Gapped clouds. (valid values: AzurePublicCloud, AzureUSGovernmentCloud, AzureChinaCloud, AzureGermanCloud, Private; default: AzurePublicCloud)

When cloud is set to Private, the endpointSuffix parameter is required. Otherwise, it is automatically generated based on the cloud environment. endpointSuffix represents the service bus endpoint suffix of the cloud environment that the service bus belongs to, e.g. servicebus.usgovcloudapi.net for AzureUSGovernmentCloud.

💡 NOTE: Service Bus Shared Access Policy needs to be of type Manage. Manage access is required for KEDA to be able to get metrics from Service Bus.

Authentication Parameters

You can authenticate by using pod identity or connection string authentication.

Connection String Authentication:

• connection - Connection string for the Azure Service Bus Namespace.

  The following formats are supported.

  • With SharedAccessKey - Endpoint=sb://<sb>.servicebus.windows.net/;SharedAccessKeyName=<key name>;SharedAccessKey=<key value>
  • With SharedAccessSignature -
    Endpoint=sb://<sb>.servicebus.windows.net/;SharedAccessSignature=SharedAccessSignature sig=<signature-string>&se=<expiry>&skn=<keyName>&sr=<URL-encoded-resourceURI>
    Refer to this page for more information on using Shared Access Signatures.

Pod identity based authentication:

Azure AD Workload Identity provider can be used.

Example

Here is an example of how to use managed identity:

apiVersion: keda.sh/v1alpha1
kind: TriggerAuthentication
metadata:
  name: azure-servicebus-auth
spec:
  podIdentity:
    provider: azure-workload
---
apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: azure-servicebus-queue-scaledobject
  namespace: default
spec:
  scaleTargetRef:
    name: azure-servicebus-queue-function
  triggers:
  - type: azure-servicebus
    metadata:
      # Required: queueName OR topicName and subscriptionName
      queueName: functions-sbqueue
      # or
      topicName: functions-sbtopic
      subscriptionName: sbtopic-sub1
      # Required: Define what Azure Service Bus to authenticate to with Managed Identity
      namespace: service-bus-namespace
      # Optional
      messageCount: "5" # default 5
      cloud: AzureGermanCloud # Optional. Default: AzurePublicCloud
    authenticationRef:
        name: azure-servicebus-auth # authenticationRef would need either podIdentity or define a connection parameter

Troubleshooting

KEDA is unable to get queue information due to “invalid queue runtime properties: no CountDetails element”

When KEDA logs show errors similar to invalid queue runtime properties: no CountDetails element it usually is caused because of throttling by Azure Service Bus.

Consider applying one of the following mitigations:

• Scaling the Azure Service Bus namespace to a higher SKU, or use premium
• Increase the polling interval of the ScaledObject/ScaledJob
• Use caching of metrics