Pulsar spout fails to unsubscribe and close consumers on a shared subscription

[rdhabalia]

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Motivation

Apache Pulsar provides a messaging queue using a Shared subscription to process unordered messages in parallel using multiple connected consumers. Shared subscription is also commonly used in data processing pipelines where they need to forcefully unsubscribe from the subscription after processing messages on the topic. One example is Pulsar-Storm adapter where Pulsar spout creates Pulsar consumers on a shared subscription for distributed processing and then unsubscribe on the topic. However, PulsarSpout always fails to unsubscribe shared subscriptions and it also doesn't close the pulsar consumers if there is more than one consumer connected to the subscription which causes a leaked subscription and consumer for that application. It also causes a backlog on a topic due to failed unsubscribe and application team has to build external service to just address such failures.
In this usecases, client application can not successfully unsubscribe on a shared subscription when multiple consumers are connected because Pulsar client library first tries to unsubscribe which will not be successful as multiple consumers are still connected on the subscription and eventually Pulsar client lib fails to unsubscribe and close the consumer on the subscription. Because of that none of the consumers can disconnect or unsubscribe from the subscription. This will make it impossible for applications to unsubscribe on a shared subscription and they need an API to forcefully unsubscribe on a shared subscription using consumer API.
We already have the admin-api to unsubscribe forcefully but adding such support in consumer API will allow applications like Pulsar-storm to unsubscribe successfully and also allow consumers to close gracefully.

Solution

We already have the admin-api to unsubscribe forcefully but adding such support in consumer API will allow applications like Pulsar-storm to unsubscribe successfully and also allow consumers to close gracefully.

Alternatives

No response

Anything else?

No response

Are you willing to submit a PR?

• I'm willing to submit a PR!