Description

This PR updates the SegmentLoadStatusFetcher to use the new SQL package's BrokerClient implementation, replacing the deprecated discovery-based BrokerClient. This change improves code maintainability and aligns with Druid's ongoing modernization efforts.

Migrated BrokerClient Implementation

• Replaced deprecated org.apache.druid.discovery.BrokerClient with org.apache.druid.sql.client.BrokerClient
• Updated SQL task handling to use proper task state management through SqlTaskStatus
• Fixed locale-dependent string formatting by using StringUtils.format

Updated Test Framework

• Refactored SegmentLoadStatusFetcherTest to properly mock SQL task lifecycle
• Added proper task state transitions (RUNNING → SUCCESS) in test cases
• Maintained existing test coverage while adapting to new API

Release note

Migrated Multi-Stage Query's segment load status checking to use the new SQL package's BrokerClient, removing dependency on the deprecated discovery-based implementation. This change improves code maintainability and provides better SQL task state handling.

Key changed/added classes in this PR

• org.apache.druid.msq.exec.SegmentLoadStatusFetcher
• org.apache.druid.msq.exec.SegmentLoadStatusFetcherTest

This PR has:

• been self-reviewed.
• added documentation for modified behaviors.
• a release note entry in the PR description.
• added comments explaining the "why" and intent of code changes.
• modified existing tests to cover new code paths.
• been tested through unit tests.

Design Decisions:

1. Task State Management:

   • Switched to using TaskState for explicit state tracking
   • Simplified error handling by properly propagating task status
   • Improved readability by separating state management from query execution

2. Test Structure:

   • Mock responses now simulate realistic task state transitions
   • Maintained existing test scenarios while adapting to new API
   • Added proper verification of task state changes

3. Error Handling:

   • Improved error propagation through SqlTaskStatus
   • Added explicit handling of failed tasks
   • Enhanced logging for better debugging