Dynamic Resource Patching

Summary

We often get issues and feature requests around supporting arbitrary modification of the resources before being applied to Grafana. At the time of writing, we support limited replacement using valuesFrom in some resources but this is not very useable and inconsistent. With the upcoming addition of generic manifests, we need a stable way to perform manipulation of the resource before submitting to the Grafana instance.

Proposal

All resources that get applied to the Grafana instance should support a new section .spec.patch that contains:

• A jq script
• A list of env variables to dynamically fetch data.

This could look something like this:

apiVersion: grafana.integreatly.org/v1beta1
kind: GrafanaLibraryPanel
metadata:
  name: grpc-server-success-rate
spec:
  instanceSelector:
    matchLabels:
      env: dev
      region: us-central1
  url: http://assets.example.com/library-panels/grpc-server-success-rate.json
  patch:
    scripts:
    - '.title=env(PANEL_TITLE)'
    env:
      - name: PANEL_TITLE
        valueFrom:
          secretKeyRef:
            name: some-secret
            key: some-key

We can also extend the supported options in valueFrom to support information from the Grafana instance like a pseudo downward api:

patch:
  scripts:
  - '.title=env(PANEL_TITLE)'
  env:
    - name: PANEL_TITLE
      valueFrom:
        grafanaInstance:
          fieldPath: '.spec.version'

If the patch uses a value from the Grafana instance, that patchset will be reevaluated for each instance so the values match the target instance.

Additional notes

Initial implementation will focus on the new GrafanaManifest resource first as we don’t have to worry about the old variable substitution methods there.

For the implementation, gojq is the library of choice as it allows us to securely override the env functions and fill them with the respective valuesFrom entries.