Upgrade Grafana from v11.6.2 to v13.0.1 and Fix dashboard datasource referenes

[shajjar-emumba]

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Summary

Upgrades the bundled Grafana image (devlake-dashboard) from v11.6.2 to v13.0.1.

The primary motivation for this upgrade is native Git Sync support, which reached GA in Grafana v13. Organizations using DevLake often build and maintain custom dashboards on top of DevLake data and also Grafana v13 brings a range of improvements worth exploring.

Changes

grafana/Dockerfile

• Bumped FROM grafana/grafana:11.6.2 → FROM grafana/grafana:13.0.1
• Removed RUN grafana-cli plugins install grafana-piechart-panel
  • grafana-cli (hyphenated) was deprecated in v10 and fully removed in v13
  • grafana-piechart-panel was deprecated starting from Grafana v8+ and is now
    a built-in core panel; no installation needed

grafana/dashboards/*.json (all dashboard files)

• Updated all panel and target datasource references from the legacy bare string form ("datasource": "mysql") to the modern object form
  ("datasource": {"type": "mysql", "uid": "mysql"})
• In Grafana v13, the bare string form causes panels to fall back to the built-in Grafana datasource instead of MySQL, resulting in all SQL panels showing no data
• As a secondary benefit, this ensures correct datasource binding in v2 schema exports, the v2 migration silently drops the datasource field entirely from panels that use the string form

Does this close any open issues?

Closes 8881

Screenshots

Include any relevant screenshots here.

Other Information

Since all DevLake dashboards are provisioned with allowUiUpdates: false, users cannot save changes through the Grafana UI. The only way to get modified dashboard JSON back out is to copy it from the dashboard settings panel. In Grafana v13, that copy action now exports the new v2 Kubernetes-style schema by default rather than the classic flat JSON format

It would be worth also updating the bundled dashboard JSON files to the v2 schema format so that users who customise dashboards and copy the JSON to commit back to their own forks get a format that works with provisioning out of the box. This is not included in the current PR but is a natural follow-up