*: revert keyspace observability labels

[zeminzhou]

What problem does this PR solve?

Issue Number: ref #68405

Problem Summary:

This PR reverts #68404 (*: add keyspace observability labels). The keyspace observability feature added config, startup, log, and metrics behavior across NextGen deployments; this PR removes that feature surface and restores the previous behavior on release-nextgen-202603.

What changed and how does it work?

• Remove keyspace-observability config structures, validation, example config, and resolved values.
• Remove starter startup handling that resolves activation metadata into metric, slow-log, and statement-log fields.
• Remove metadata from standby activation requests and the related getter/tests.
• Stop appending keyspace observability fields to slow query logs and statement summary logs.
• Restore metrics registration and PD client option handling to the previous keyspace ID/name labeling behavior, and clean up related tests and Bazel metadata.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.
  • This PR only reverts *: add keyspace observability labels #68404 and removes the feature/tests introduced by that PR.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

Revert the keyspace observability configuration and labels added by #68404.

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[coderabbitai]

📝 Walkthrough

Walkthrough

This PR removes the keyspace observability feature from TiDB. It deletes the KeyspaceObservability config types, removes activation metadata from standby controller requests, eliminates observability field injections from slow-log and statement-log output, refactors metrics label initialization to occur during PD client creation, and removes associated test cases and build targets across multiple packages.

Changes

Keyspace Observability Feature Removal

Layer / File(s)	Summary
Config structure and validation removal pkg/config/keyspace_observability.go, pkg/config/config.go, pkg/config/BUILD.bazel, pkg/config/config.toml.nextgen.example	KeyspaceObservability and KeyspaceObservabilityValues fields are removed from the Config struct; the entire keyspace_observability.go file is deleted along with its types and validation logic; Config.Valid() no longer validates observability settings; the prometheus_common dependency is removed from the config library.
Startup flow integration removal cmd/tidb-server/main.go, cmd/tidb-server/main_test.go	The maps import is removed; activationMetadata extraction from the standby controller is removed; the starter-mode conditional invoking prepareKeyspaceObservabilityForStarter is deleted; the helper function that resolved and applied observability values is removed; two tests validating this behavior for TiKV and non-TiKV configurations are removed.
Standby metadata propagation removal pkg/standby/standby.go, pkg/standby/BUILD.bazel, pkg/standby/standby_test.go	The Metadata field is removed from ActivateRequest so activation requests no longer carry arbitrary key/value data; the LoadKeyspaceController.ActivationMetadata() getter method is removed; the activation-received log statement is simplified to log the entire request object; the go_test target is removed and standby_test.go is deleted, removing tests for metadata parsing and the copy-like behavior of the getter.
Logging field integration removal pkg/sessionctx/variable/slow_log.go, pkg/sessionctx/variable/tests/session_test.go, pkg/util/stmtsummary/v2/logger.go, pkg/util/stmtsummary/v2/record_test.go, pkg/util/stmtsummary/v2/BUILD.bazel	The slow-log format no longer appends observability fields from global config; the statement-log marshaling is simplified to directly use json.Marshal instead of wrapping with additional fields; config imports are removed; test assertions verifying these extra fields are deleted; config dependency is removed from the test BUILD target.
Metrics registration refactoring pkg/util/metricsutil/common.go, pkg/util/metricsutil/BUILD.bazel, pkg/util/metricsutil/common_test.go, pkg/store/driver/tikv_driver.go, pkg/store/driver/BUILD.bazel, pkg/store/driver/config_test.go	Constant label initialization is moved into PD client creation using pd.NewClient with opt.WithMetricsLabels; label-manipulation helpers (cloneConstLabels, setKeyspaceIDConstLabel, setConstLabels) are removed; the maps import is dropped; PD client options are inlined directly in OpenWithOptions instead of delegating to a pdClientOptions() helper; metrics/common and pd opt dependencies are removed; test assertions verifying metrics label manipulation are removed; the common_test.go file is deleted; test sharding is adjusted in multiple BUILD files.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• pingcap/tidb#68404: Introduced the keyspace observability feature that this PR removes, including the config types, startup initialization, logging integrations, and metrics label handling.

Suggested labels

size/XL, release-note-none, ok-to-test

Suggested reviewers

• ChangRui-Ryan
• yibin87
• D3Hunter
• yudongusa

Poem

🐰 A keyspace once observed with care,
Now fades like morning's misty air.
Config fields and metadata gone,
Metrics labels simplified at dawn.
TiDB runs cleaner, sleek and light,
Feature removed—the PR shines bright!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
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 clearly and concisely describes the main change: reverting the keyspace observability labels feature. It is directly related to the changeset.
Description check	✅ Passed	The description is comprehensive and follows the template structure. It includes issue reference, problem summary, detailed explanation of changes, appropriate checklist selections, and a release note.

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[codecov]

Codecov Report

❌ Patch coverage is 10.52632% with 51 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (release-nextgen-202603@f78c7f9). Learn more about missing BASE report.

Additional details and impacted files

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##             release-nextgen-202603     #68751   +/-   ##
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Flag	Coverage Δ
unit	76.1821% <1.7857%> (?)

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Components	Coverage Δ
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parser	∅ <0.0000%> (?)
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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: D3Hunter
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Details

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-05-29 07:28:25.783477095 +0000 UTC m=+4246.158286771: ☑️ agreed by D3Hunter.