*: revert gRPC stream operation duration metrics

[JmPotato]

What problem does this PR solve?

Issue Number: close #11040

grpcutil.NewMetricsStream registers histogram children labeled by peer IP with no lifecycle cleanup. Long-running PD/MCS processes accumulate unbounded label series (observed ~840k series from ~18k historical IPs), inflating memory and /metrics scrape cost until scrapes fail.

What is changed and how does it work?

Revert the gRPC stream operation duration metrics introduced in #10254 and the dependent Grafana stream-send panels from #10339. This removes `grpcutil.MetricsStream` and the peer-IP-labeled `grpc_stream_operation_duration_seconds` histograms from PD and MCS services, eliminating the unbounded cardinality leak until a safer replacement lands.

Check List

Tests

• No code

Related changes

• Need to cherry-pick to the release branch

Release note

Revert gRPC stream operation duration metrics to fix unbounded peer-IP label cardinality.

Summary by CodeRabbit

• Bug Fixes
  • Removed gRPC stream send-duration metrics from server endpoints and Grafana dashboards.
  • Simplified streaming operations by eliminating the associated instrumentation layer.
  • Removed the unsupported gRPC receive error and related utility behavior.
  • Existing request handling and service functionality remain unchanged.

[coderabbitai]

📝 Walkthrough

Walkthrough

The PR removes gRPC stream send-duration instrumentation and wrappers across PD and MCS services, deletes the shared grpcutil support and related error, unregisters the metric, and removes its Grafana panels.

Changes

gRPC stream metrics removal

Layer / File(s)	Summary
Remove shared stream instrumentation pkg/utils/grpcutil/stream.go, pkg/mcs/*/server/metrics.go, server/metrics.go, pkg/errs/errno.go, metrics/grafana/pd.json	The shared stream metrics implementation, registrations, obsolete receive error, and gRPC stream-send dashboard panels are removed.
Remove endpoint stream wrappers pkg/mcs/*/server/grpc_service.go, server/grpc_service.go	Streaming RPC handlers now operate on the original gRPC streams without metrics wrappers.

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

Possibly related PRs

• tikv/pd#11042: Refactors the same gRPC stream metrics code toward lifecycle-aware cleanup.
• tikv/pd#11045: Adds lifecycle cleanup to the stream-send Prometheus instrumentation removed here.
• tikv/pd#10254: Introduced the shared gRPC stream metrics wrappers removed by this PR.

Suggested reviewers: rleungx, okjiang

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The PR removes the peer-IP-labeled stream metrics and wrappers across the affected PD and MCS RPCs, which addresses #11040.
Out of Scope Changes check	✅ Passed	The Grafana panel removal, test deletions, and metrics cleanup all support the stated revert and leak fix, with no clear unrelated changes.
Title check	✅ Passed	The title is concise and accurately summarizes the main change: reverting gRPC stream operation duration metrics.
Description check	✅ Passed	The description covers the problem, change, checklist, and release note, matching the template well enough.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bufferflies, rleungx

The full list of commands accepted by this bot can be found here.

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Details

Needs approval from an approver in each of these files:

• OWNERS [bufferflies,rleungx]

Approvers can indicate their approval by writing /approve in a comment
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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-07-24 09:10:49.876399722 +0000 UTC m=+1568835.912494778: ☑️ agreed by rleungx.
• 2026-07-24 09:11:12.985950496 +0000 UTC m=+1568859.022045553: ☑️ agreed by bufferflies.

[JmPotato]

/cherry-pick release-nextgen-202603

[ti-chi-bot]

@JmPotato: once the present PR merges, I will cherry-pick it on top of release-nextgen-202603 in the new PR and assign it to you.

Details

In response to this:

/cherry-pick release-nextgen-202603

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[JmPotato]

/retest

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.29%. Comparing base (39b6220) to head (62f4676).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #11048      +/-   ##
==========================================
+ Coverage   79.25%   79.29%   +0.03%     
==========================================
  Files         541      540       -1     
  Lines       76037    76010      -27     
==========================================
+ Hits        60262    60269       +7     
+ Misses      11534    11502      -32     
+ Partials     4241     4239       -2     

Flag	Coverage Δ
unittests	79.29% <100.00%> (+0.03%)	⬆️

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[ti-chi-bot]

@JmPotato: new pull request created to branch release-nextgen-202603: #11049.

Details

In response to this:

/cherry-pick release-nextgen-202603

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.