[CamiloSierraH]

Why

dashboard.html loads Chart.js from a public CDN. When the file is opened on a machine with no internet access (air-gapped networks, locked-down workstations, browsers that block CDNs), the script never loads and the page renders nothing: no charts, no tables and no alerts, not only the charts.

What

A new -airgap flag embeds Chart.js 4.4.3, which ships inside the binary, directly in dashboard.html, so the page opens with no network access. Without the flag nothing changes: the output is the same CDN page as today, and a test checks this.

• airgap/README.md: how and when to use it, with examples (single node, cluster ... -- -airgap, and combined with other flags), how to verify it from the footer, and the size cost. The flag is documented only there. The main README's "Dashboard charts blank" entry now links to that folder.
• internal/dashboard/assets/chart.umd.js: dist/chart.umd.js from the npm chart.js@4.4.3 tarball, unmodified. The tarball matches the registry's sha512 integrity hash, and the test pins the file's sha256. The MIT licence (LICENSE.chartjs.md) is embedded too, and its full text is inlined as a comment just ahead of the library, so every standalone dashboard.html carries the permission notice.
• internal/dashboard/airgap.go: go:embed plus WithAirgap, which replaces the CDN <script> tag and the footer text.
• Makefile: airgap added to DATA_DIRS, so release archives ship the README.
• Gov mode produces no dashboard, so the flag has no effect there. schema_graph.html was already network-free.

Testing

• make test passes and gofmt -l is clean.
• New tests:
  • the checksum is pinned;
  • the CDN tag and the embedded banner name the same release;
  • the library and the licence contain no </script or */ that would end the script or the comment early;
  • the full MIT permission notice comes before the library;
  • the default output still uses the CDN;
  • the -airgap output has no remote <script>/<link>, and Chart.js comes before the dashboard script.
• When the replacement was disabled on purpose, the air-gap test failed.
• I ran the binary against a local lab cluster both ways and opened each dashboard in headless Chrome with all hosts unresolvable:

Build	Network	Charts	Table rows
default	online	22	177
default	offline	0 (Chart undefined)	0
-airgap	offline	22	177

• dashboard.html grows from about 300 KB to about 510 KB with the flag (about 70 KB once gzipped in the bundle).
• make release: every archive contains airgap/README.md.
• cluster -- -airgap passes the flag through to every host's command.

🤖 Generated with Claude Code

[Copilot]

🟡 Changes recommended

Distributed artifacts need the full MIT notice, and release archives need the linked offline usage guide.

2 open issues

• Include the complete Chart.js MIT licence notice in releases · New
• Package the airgap directory in downloaded releases · New

What changed in this PR

Adds optional offline viewing for ClickHouse diagnostic dashboards while preserving default CDN loading.

Changes:

• Adds -airgap and embeds Chart.js 4.4.3.
• Tests asset integrity, rendering, and script order.
• Documents offline usage and links troubleshooting guidance.

File	Description
README.md	Links offline dashboard instructions.
internal/​dashboard/​generator.go	Selects offline or CDN rendering.
internal/​dashboard/​assets/​LICENSE.chartjs.md	Adds Chart.js licence text.
internal/​dashboard/​assets/​chart.umd.js	Vendors Chart.js 4.4.3.
internal/​dashboard/​airgap.go	Embeds Chart.js and updates the footer.
internal/​dashboard/​airgap_test.go	Tests asset integrity and rendering modes.
cmd/​main.go	Registers and forwards -airgap.
airgap/​README.md	Documents offline usage and limitations.

_{Review effort: Balanced}

[ugosan]

The -airgap version of the same report adds about 300kb to the html with the embedded chart.js, which is reasonable.

We could consider of a "self-hosted" support diagnostics in the future, e.g. with a flag -serve that would spawn a local webserver (using golang's http.ListenAndServe() ) to serve the diagnostics. It would provide better separation between our code and libraries, and then the page could have an export function+api that would generate the airgapped dashboard if needed. Something to think about.

[ugosan]

LGTM