[Issue #1458] Reduce unnecessary creation of retry topics and DLQ topics

[zjxxzjwang]

Motivation

Reduce unnecessary creation of retry topic and DLQ topic.

The following scenarios:

1. When retryLetterTopic is not set but deadLetterTopic is set
2. When retryLetterTopic is set but deadLetterTopic is not set

These scenarios will trigger the getPartitionedTopicMetadata operation for both the retry topic and DLQ topic, resulting in the loading of the default retry topic and default DLQ topic. This leads to resource wastage.

Modifications

Perform verification separately. If retryLetterTopic or deadLetterTopic is set, do not proceed to getPartitionedTopicMetadata.

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

[Copilot]

Pull request overview

This PR optimizes the consumer initialization process by reducing unnecessary metadata lookups for retry and dead letter queue (DLQ) topics. Previously, the code always queried both old-format retry and DLQ topics regardless of whether they were already configured. The optimization now only checks for old topic formats when the corresponding fields are not set, avoiding redundant network calls.

Changes:

• Refactored metadata lookup logic into a helper function CheckTopicIsExists
• Added conditional checks to only query old topic formats when DLQ policy fields are empty
• Improved logic to handle scenarios where only retry or only DLQ topics are configured

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[RobertIndie]

Is it possible to add a test for it?

[zjxxzjwang]

Is it possible to add a test for it?

I have added a test case, please review it. @RobertIndie