Subscriptions in Pulsar

Subscriptions in Pulsar describe which consumers are consuming data from a topic and how they want to consume that data.

Subscriptions are managed in the broker as a collection of metadata about a topic and its subscribed consumers. This metadata includes:

Topic name - which topic the consumer wants data from
Subscription name - a string representing a qualified name for the subscription
Subscription type - which type of subscription is being used
Subscription cursor - a representation of the consumer’s current place in the subscribed topic log

For example, the Pulsar consumer below has a shared subscription starting at the earliest cursor position in my-subscription to my-topic:

pulsarConsumer = pulsarClient.newConsumer(Schema.BYTES)
    .topic("my-topic")
    .subscriptionName("my-subscription")
    .subscriptionType(SubscriptionType.Shared)
    .subscriptionInitialPosition(SubscriptionInitialPosition.Earliest)
    .subscribe();

Read on to use Pulsar’s four types of subscriptions to manage your topic consumption.