MINOR: Add metrics corresponding to consumer rebalance listener metrics

[RaidenE1]

• Background

  Add new metrics for TasksLost, TasksAssigned and TasksRevoked in StreamsRebalanceListener.

• Features Implemented

  Added three rebalance latency metrics to DefaultStreamsRebalanceListener:

  • tasks-revoked-latency-avg/max - Average/max latency when revoking tasks
  • tasks-assigned-latency-avg/max - Average/max latency when assigning tasks
  • tasks-lost-latency-avg/max - Average/max latency when losing tasks

  Main Changes

  1. Created RebalanceMetrics.java
  • Follows existing Streams ThreadMetrics pattern with static factory methods
  • Provides three methods to create sensors: tasksRevokedSensor(), tasksAssignedSensor(), tasksLostSensor()
  2. Modified DefaultStreamsRebalanceListener.java
  • Added three Sensor member variables
  • Updated constructor to accept StreamsMetricsImpl and threadId parameters
  • Records execution time in onTasksRevoked(), onTasksAssigned(), and onAllTasksLost() methods
  3. Modified StreamThread.java
  • Pass streamsMetrics and getName() when creating DefaultStreamsRebalanceListener
  4. Added Comprehensive Tests
  • DefaultStreamsRebalanceListenerTest - Added 6 tests to verify metrics recording (both normal and exception cases)
  • RebalanceMetricsTest - Verifies sensor creation logic

[Copilot]

Pull Request Overview

This PR adds latency metrics for rebalance listener callbacks in Kafka Streams to provide better observability of task rebalancing operations. The implementation follows the existing Streams ThreadMetrics pattern and introduces three new metrics for measuring the time taken during task revocation, assignment, and loss operations.

Key changes:

• Created RebalanceMetrics class with factory methods for creating sensors
• Modified DefaultStreamsRebalanceListener to record latency metrics during rebalance operations
• Updated StreamThread to pass required metrics dependencies to the rebalance listener

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
RebalanceMetrics.java	New metrics class providing static factory methods for creating rebalance latency sensors
DefaultStreamsRebalanceListener.java	Enhanced to record latency metrics for tasks revoked, assigned, and lost operations
StreamThread.java	Updated constructor calls to pass streamsMetrics and threadId to DefaultStreamsRebalanceListener
DefaultStreamsRebalanceListenerTest.java	Added comprehensive tests for metrics recording in both success and exception scenarios
RebalanceMetricsTest.java	Added unit tests to verify sensor creation logic and metric configuration

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[Copilot]

The start time is captured outside the try block, but if an exception occurs during the method execution, the sensor will still record the latency in the finally block. This could lead to recording metrics for failed operations that didn't complete normally, potentially skewing the latency measurements.

[Copilot]

Similar to onTasksAssigned, this method records latency metrics even when exceptions occur. The finally block will execute regardless of whether the operation completed successfully or failed, which may not provide accurate latency measurements for successful operations.