Microsoft Azure Service Bus TopicSubscriber

The TopicSubscriber trigger is used to subscribe to a particular topic for any messages that may be posted by one or more publishers in a one-to-many message delivery pattern. Messages posted to a topic by publishers are copied to subscriptions registered on that topic and are pushed out to many subscribers behind the subscription. Therefore, a single message published by a publisher to a topic can be pushed out to more than one subscriber. You can create multiple subscriptions and have receivers listen to those subscriptions. When creating a subscription, you can check the box to specify whether to enable sessions.

You can enable Application properties for some fields by turning on the toggle if one is available. Application properties allow you to provide values for configuration fields.

Trigger Settings

The Configuration tab has the following fields:

Field Description
AzureServiceBus Connection The Azure Service Bus connection chosen for the TopicSubscriber while creating the trigger is displayed here automatically.

If you wish to choose a different AzureServiceBus connection than what was chosen in the settings page of Trigger creation, you can click the dropdown and choose a different one.

Topic Name of the Topic to subscribe to. A topic by that name must exist in the Namespace of the broker.

Application Properties has been enabled for this field.

DeadLetter Subscription

The possible values are true or false.

When you set the DeadLetter Subscription value as "true", the unsuccessfully processed messages are stored in the dead letter queue and can be retrieved as needed.
Subscription Name Name for a subscription that subscribes to messages on a Topic. A subscription by that name may or may not exist already on that topic. If it does not exist, it is created by the Trigger.

Application Properties has been enabled for this field.

SessionId Name of the session from which to receive messages. When enabled, allows the QueueReceiver to listen for messages from the specified SessionID.

If a queue is session-enabled, but a SessionID is not specified, then the QueueReceiver does not send any message.

Receive Mode

Determines the quality of service while receiving messages from a queue.

  • ReceiveAndDelete: Messages are consumed and marked acknowledge on a trigger itself.

  • ModePeekLock: This allows consumers to peek at a message from the queue or subscription and then lock it for processing.
Timeout Timeout in milliseconds for the operation of an activity.
Retry Count

The number of times the flow attempts to run the trigger.

Default: 0

Note: The Retry Count value can also be set from the connections details, but the value set here are preferred.
Retry Interval

The time (in milliseconds) to wait in between each attempt to run the trigger.

Default: 0 milliseconds

Note: The Retry Interval value can also be set from the connections details, but the value set here are preferred.

Output Settings

The Output Settings tab has the following fields:

Field Description
Custom Properties User can add the custom properties while receiving the messages.

Output

The Output tab displays the schema in a tree format. The output is read-only.

  1. output: The root of the output
    1. messageString: The string representation of the byte array of the received message.
    2. brokerProperties: A complex object that acts as a container for broker properties of the received message. The TopicSubscriber trigger displays the following broker properties of a received message if available:
      • ContentType
      • CorrelationId
      • Label
      • PartitionKey
      • ReplyTo
      • SessionId
      • TimeToLive
      • To
      • DeliveryCount
      Note: For more information about brokerproperties, see the Microsoft Azure Service Bus documentation.
    3. customProperties: These properties are populated when you add custom properties on the Output Settings tab of the TopicSubscriber trigger.