metrics: migrate TiFlash Summary dashboard generation to grafanalib (#11027)

[ti-chi-bot]

This is an automated cherry-pick of #11027

What problem does this PR solve?

Issue Number: close #11025, close #11028

Problem Summary:

TiFlash Summary Grafana dashboard was maintained as a large hand-edited JSON
blob, which made panel authoring, PromQL consistency, and review hard. This PR
migrates generation to grafanalib (same pattern as TiKV: common.py +
*.dashboard.py), so the dashboard source is Python and tiflash_summary.json
is a generated artifact. We deliberately prefer Python/uv over introducing a
Go/jsonnet toolchain into TiFlash’s developer workflow and CI.

Design: docs/design/2026-08-08-grafanalib-dashboard-generation.md

What is changed and how it works?

metrics: migrate TiFlash Summary dashboard generation to grafanalib

Replace hand-maintained TiFlash Summary JSON with a grafanalib pipeline
(`common.py` + `tiflash_summary.dashboard.py`), shared PromQL/panel helpers,
and `generate_dashboard.sh` to produce `tiflash_summary.json`.

• Add metrics/grafana/common.py: PromQL builders (expr_*), graph_panel /
  yaxes / Layout, and L3 helpers (ops_panel, duration_panel,
  cpu_with_limit_panel, heatmap / hit-ratio helpers).
• Add tiflash_summary.dashboard.py as the editable source of truth for
  TiFlash Summary.
• Regenerate tiflash_summary.json (+ .sha256) via generate_dashboard.sh
  (uv + grafanalib 0.7.1).
• Document authoring / generation in metrics/grafana/README.md.
• Add design doc docs/design/2026-08-08-grafanalib-dashboard-generation.md.
• Notable dashboard behavior alignments during migration:
  • Prefer [$__rate_interval] over fixed ranges like [1m] / [30s].
  • Hide unused right Y-axes; omit redundant right_format on single-axis panels.
  • Enforce IEC byte units in yaxis() (Threads IO: Bps → binBps).
  • Threads CPU: use cpu_with_limit_panel and include $proxy_instance.
  • Split Columnar Meta Cache Gauge into Entries + Weighted Size (3-panel row).

Check List

Tests

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

Manual test:

1. cd metrics/grafana && ./generate_dashboard.sh
2. Confirm tiflash_summary.json / .sha256 are updated and review the diff.
3. Import the generated JSON into a test Grafana and spot-check key rows:
   Server, Threads CPU, Threads, Coprocessor, Columnar Storage, Raft.
4. During migration review we used scripts/compare_dashboards.py for semantic
   JSON compare against a legacy baseline. After verification that helper was
   removed from tree; it can be restored from git history if needed, e.g.
   git show <commit>:metrics/grafana/scripts/compare_dashboards.py.

Side effects

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

Notes: Generated dashboard JSON may differ cosmetically from the previous export
(schema metadata, hidden right-axis defaults, rate interval variable). PromQL /
panel coverage is intended to stay equivalent aside from the intentional
alignments listed above. tiflash_proxy_summary.json /
tiflash_proxy_details.json remain hand-maintained.

Documentation

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

Release note

None

Summary by CodeRabbit

• Documentation

  • Updated the DMFile V3 design with file-merging behavior, compatibility requirements, and downgrade guidance.
  • Added a proposal for generating TiFlash Summary Grafana dashboards from Python.
  • Documented dashboard generation, authoring conventions, PromQL guidance, and validation steps.

• New Features

  • Added tooling to generate and format dashboard definitions consistently.
  • Added reusable dashboard and query-building capabilities for TiFlash metrics.
  • Added checksum validation for generated dashboard artifacts.

[ti-chi-bot]

@JaySon-Huang This PR has conflicts, I have hold it.
Please resolve them or ask others to resolve them, then comment /unhold to remove the hold label.

[ti-chi-bot]

@ti-chi-bot: ## If you want to know how to resolve it, please read the guide in TiDB Dev Guide.

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[ti-chi-bot]

Cherry-pick conflicts appear resolved; removing the do-not-merge/hold label.

[JaySon-Huang]

/retest

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JaySon-Huang, yongman

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-08-10 14:05:35.718135595 +0000 UTC m=+3055321.754230661: ☑️ agreed by JaySon-Huang.
• 2026-08-11 02:44:42.039151093 +0000 UTC m=+3100868.075246139: ☑️ agreed by yongman.