What is the purpose of HelmRepository.spec.interval when there is a HelmChart.spec.interval

[VTimNeumann]

I was wondering what the purpose of the required HelmRepository.spec.interval when all Helm Charts also have an interval (by setting HelmRelease.spec.chart.spec.interval or leaving it empty, which causes it to default to HelmRelease.spec.interval).

As I understand, both are used to check for updates of the charts in the repository.
Obviously the interval on each chart governs the update checking for that chart only, whereas the one on the repository does check for updates in the whole repository.
But as all charts have such an interval, it seems to me the one on the repository is redundant.

See https://fluxcd.io/flux/components/source/api/v1beta2/#source.toolkit.fluxcd.io/v1beta2.HelmRepository
See https://fluxcd.io/flux/components/helm/api/v2beta2/#helm.toolkit.fluxcd.io/v2beta2.HelmChartTemplate

[souleb]

The interval is used as a reconciliation period. Each custom resource is reconciled by a different controller.
For a HelmRepository the principal action is retrieving and persisting the helm index.
For a HelmChart it is about retrieving the right chart based on the helm index provided by the corresponding HelmRepository. Different intervals will give different results as you may have a different view of the helm repository.

[souleb]

Yes, the index file list available versions, so it must be up to date. You can go around this by using a HelmRepository of type oci, where the controller will always request available versions(tags) from the registry api.

[VTimNeumann]

Ok thanks a lot. One more question: Assuming I'm not using an OCI repo, is there any point in setting the HelmChart reconciliation to be more frequent than the HelmRepository reconciliation? (I've seen tutorials where 12h for the chart and 24h for the repo have been used)

[souleb]

I'd make the HelmRepository frequency lower to make sure to catch updates before the chart reconciliation.

[VTimNeumann]

Do you mean you'd have a lower interval for the repo?
I.e. HelmRepository.spec.interval: 6h and HelmRelease.spec.chart.spec.interval: 12h
Or did you actually mean a lower frequency => higher period == higher interval for the repo?
I.e. HelmRepository.spec.interval: 24h and HelmRelease.spec.chart.spec.interval: 12h

[souleb]

Oh sorry, yes lower interval.