enhance: Add target manager to ReplicaObserver initialization

[sunby]

issue: #47072

[gemini-code-assist]

Summary of Changes

Hello @sunby, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a significant enhancement to the ReplicaObserver by integrating a TargetManagerInterface directly into its construction. This change allows the observer to leverage target management capabilities, which is crucial for maintaining accurate and consistent replica states. The update ensures that the ReplicaObserver has access to necessary target-related functionalities from its inception, improving its operational robustness and enabling more sophisticated replica management strategies.

Highlights

• ReplicaObserver Initialization: The NewReplicaObserver function now accepts an additional parameter, targetMgr meta.TargetManagerInterface, which is then stored within the ReplicaObserver instance.
• Dependency Injection: The targetMgr is now explicitly passed during the initialization of ReplicaObserver in the main server setup (server.go) and various test files, ensuring proper dependency injection.
• Test Suite Updates: The ReplicaObserverSuite and relevant test functions have been updated to include and initialize a mock TargetManager to facilitate testing with the new dependency.

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[sre-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: sunby
To complete the pull request process, please assign xiaofan-luan after the PR has been reviewed.
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Details

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• internal/querycoordv2/OWNERS

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[sre-ci-robot]

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[gemini-code-assist]

Code Review

This pull request enhances the ReplicaObserver by adding a targetMgr dependency. This change is necessary to support the ChannelLevelScoreBalancer by allowing the observer to fetch DM channels and enable channel exclusive mode on replicas. The dependency injection is correctly implemented across the component and its usages in the server and tests. My main feedback is regarding test coverage: the new logic path that utilizes the targetMgr is not currently tested. I've added a comment with a suggestion to add a test case for this.

[gemini-code-assist]

The mock targetMgr is created here, but there are no tests that set expectations on it. The new logic in ReplicaObserver.checkNodesInReplica that uses targetMgr is not covered by any test. Please add a test case to cover this new functionality. You would need to set the balancer to meta.ChannelLevelScoreBalancerName to trigger this code path, set expectations on targetMgr.GetDmChannelsByCollection, and then assert that the replica's channel exclusive mode is enabled.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.15%. Comparing base (9373518) to head (9b464e5).
⚠️ Report is 11 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #47094       +/-   ##
===========================================
+ Coverage   76.46%   82.15%    +5.68%     
===========================================
  Files        2016      598     -1418     
  Lines      325600    96523   -229077     
===========================================
- Hits       248972    79295   -169677     
+ Misses      68670    17176    -51494     
+ Partials     7958       52     -7906     

Components	Coverage Δ
Client	∅ <ø> (∅)
Core	82.95% <99.47%> (+0.05%)	⬆️
Go	∅ <ø> (∅)
see 1421 files with indirect coverage changes

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