Ksql 13066 - Propogate original exception

[pragatiguptaaa]

Description

Context:
Following Kafka's KIP-1043, describing a non-existent consumer group now consistently throws GroupIdNotFoundException.

In this approach, we are catching GroupIdNotFoundException and immediately re-throw it, propagating the specific " group id not found" signal to the caller. This preserves information and gives callers flexibility but requires them to implement their own handling logic for this exception.
Another approach: #10711

Testing done

Describe the testing strategy. Unit and integration tests are expected for any behavior changes.

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")
• Do these changes have compatibility implications for rollback? If so, ensure that the ksql command version is bumped.

[confluent-cla-assistant]

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[Copilot]

Pull Request Overview

This PR propagates the original GroupIdNotFoundException to clearly signal when a consumer group does not exist, in-line with Kafka's KIP-1043.

• Restores and uncomments the shouldDescribeConsumerGroup test in the integration tests.
• Introduces a try-catch block in the test to handle GroupIdNotFoundException as a signal for a group with 0 consumers.
• Updates the service implementation to explicitly catch and re-throw GroupIdNotFoundException.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
ksqldb-engine/src/test/java/io/confluent/ksql/integration/KafkaConsumerGroupClientTest.java	Uncomments a test and adds exception handling for a missing consumer group in the test scenario.
ksqldb-engine/src/main/java/io/confluent/ksql/services/KafkaConsumerGroupClientImpl.java	Adds a catch block to re-throw GroupIdNotFoundException for clear exception propagation.

Comments suppressed due to low confidence (1)

ksqldb-engine/src/test/java/io/confluent/ksql/integration/KafkaConsumerGroupClientTest.java:143

• Consider adding a dedicated test case that explicitly verifies the behavior when a consumer group does not exist, ensuring that the logged message and the returned zero counts are as expected.

}catch(final GroupIdNotFoundException exception){