Subscriptions API

Subscriptions in Fusion allow you to create and configure subscriptions using Apache Pulsar.

UI configuration options

These configuration options are used in the Subscriptions panel in the Fusion UI.

Field Description Value


The index pipeline or index profile used with the subscription.



The name of the Pulsar topic you are subscribing to.


Number of listener threads

Defines the number of concurrent threads to read from a topic. If there is a high number of messages to read from a topic, this number scales to ensure the messages are consumed efficiently.


Subscription type

The subscription type: shared or key_shared:

  • shared - Shared with multiple consumers, with a given message delivered to a single consumer. Although message delivery ordering is guaranteed by Pulsar, messages can be delivered to different consumer threads or index pipeline service instances. Therefore, the order that messages are processed by Fusion may differ.

  • key_shared - Shared with multiple consumers, with consumers receiving messages based on a key or orderingKey value. Messages with the same orderingKey will always be processed by the same consumer, which guarantees the processing order. With key_shared subscriptions, a key or orderingKey must be specified.


Subscription initial position

Specifies the initial position, earliest or latest, to consume messages from. For example, if you want to consume messages from the beginning of time, use earliest. If you want to consume messages created after the subscription was created, use latest.


Maximum Number of Retries

Sets the number of times you want to try to consume a message before you stop trying. This can be set so that if the connection to the resource crashes, Pulsar will keep trying to deliver the message before sending the message to the Dead Letter topic.


Context properties

The default context properties passed to the index pipeline when processing a message. Incoming messages may contain their own context properties, which take precedence over the default context properties you create here. See Property Name and Property Value below for configuration options.

Property Name

The name of the context property.


Property Value

The value of the context property.