resource-manager: price remote read bytes separately

[YuhaoZhang00]

What problem does this PR solve?

Issue Number: close #11019

Remote coprocessor reads currently use the same RU-v1 byte price as local reads, so the resource manager cannot price the two factual byte subsets independently.

What is changed and how does it work?

• Add the optional read-cost-per-byte-remote request-unit configuration. When omitted, the controller uses 0.5× the normal read-byte price; an explicit zero remains valid.
• Let response adapters optionally expose factual remote read bytes. Legacy adapters continue charging all bytes at the normal price, and malformed remote subsets are clamped to total bytes.
• Settle RU-v1 reads as base + local_bytes * normal_rate + remote_bytes * remote_rate + CPU; paging precharge and token-bucket behavior are unchanged.

Add a separately configurable RU-v1 price for factual remote coprocessor read bytes. Default the remote rate to half of the normal read-byte rate while preserving legacy response behavior and the existing paging settlement and token-bucket flow.

Check List

Tests

• Unit test
• Integration test

Code changes

• Has the configuration change

Release note

Support charging remote coprocessor read bytes with a separate request-unit price.

Summary by CodeRabbit

• New Features

  • Added separate request-unit pricing for bytes processed by remote coprocessors.
  • Remote read pricing defaults to half the local read-byte rate when no override is configured.
  • Added an optional read-cost-per-byte-remote configuration setting, including support for explicit zero values.
  • Remote and local read bytes are now accounted for separately while total read usage remains unchanged.

• Tests

  • Added coverage for configuration, cost splitting, paging settlement, and configuration updates.

[ti-chi-bot]

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Details

Needs approval from an approver in each of these files:

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• client/resource_group/controller/OWNERS
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[ti-chi-bot]

Hi @YuhaoZhang00. Thanks for your PR.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Changes

Remote Read RU Accounting

Layer / File(s)	Summary
RU cost configuration and generation client/resource_group/controller/config.go, pkg/mcs/resourcemanager/server/config.go, pkg/mcs/resourcemanager/server/config_test.go, tests/integrations/mcs/resourcemanager/resource_manager_test.go	Adds an optional remote per-byte cost, derives a default from the local cost when unset, and exposes it through RUConfig.RemoteReadBytesCost.
Local and remote read accounting client/resource_group/controller/model.go, client/resource_group/controller/testutil.go, client/resource_group/controller/model_test.go	Splits total read bytes into local and remote portions, applies separate RU rates, caps remote bytes to total bytes, and validates settlement behavior.
Controller configuration snapshots pkg/mcs/resourcemanager/server/manager.go, pkg/mcs/resourcemanager/server/manager_test.go	Deep-copies the optional remote cost pointer and validates snapshot updates for present and absent remote-cost settings.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Suggested labels: type/development

Suggested reviewers: nolouch, jmpotato

Sequence Diagram(s)

sequenceDiagram
  participant ResponseInfo
  participant KVCalculator
  participant RUConfig
  ResponseInfo->>KVCalculator: report total and remote read bytes
  KVCalculator->>RUConfig: apply local and remote read cost rates
  KVCalculator-->>ResponseInfo: record total read bytes and CPU usage

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🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title is concise and accurately summarizes the main change: separate pricing for remote read bytes.
Description check	✅ Passed	The description includes the required problem statement, issue number, change summary, tests, config change, and release note.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.26%. Comparing base (c2a47d8) to head (625c020).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #11018      +/-   ##
==========================================
+ Coverage   79.22%   79.26%   +0.03%     
==========================================
  Files         541      541              
  Lines       75965    76000      +35     
==========================================
+ Hits        60187    60243      +56     
+ Misses      11531    11519      -12     
+ Partials     4247     4238       -9     

Flag	Coverage Δ
unittests	79.26% <100.00%> (+0.03%)	⬆️

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[YuhaoZhang00]

/check-issue-triage-complete