example-helm-repo

There is an inconsistency in how helm dependency update and helm dependency build work. To show this I have created a simple umbrella chart which only contains a single dependency.

Requirements

1. Helm version (3.2.0) is installed
2. Bitnamis repository should not be in the list of helm repositories. (helm repo list should not contain a repo with the url https://charts.bitnami.com/bitnami)
   • if it does, remove it with helm repo remove

Problem

Helm allows you to define chart dependencies on other helm charts and keeps track of them, we call these dependencies subcharts. Helm keeps track of which version of the subcharts should be installed using a Chart.lock file.

The command helm dependency update does two things; pulls the charts for the dependencies and stores it under the /charts folder and updates the Chart.lock file with the version that it updated to.

The command helm dependency build looks at the Chart.lock file and pulls the exact chart version specified there. This allows you to always use the same versions of a subchart installed. If there is no Chart.lock file this will run helm dependency update instead.

The problem here is that the two commands behave differently if the repository has not been added. While Helm dependency update does not require that the repository has been added Helm dependency build does.

This means that if there is a Chart.lock file present but the helm repository has not been added Helm dependency build will fail while Helm dependency update will succeed.

This is even more confusing since if the Chart.lock file isn't present Helm dependency build will succeed.

How to replicate

Go to the umbrella/ directory and run Helm dependency build, this will result in:

$ helm dependency build
Error: no repository definition for https://charts.bitnami.com/bitnami. Please add the missing repos via 'helm repo add'

Remove the Chart.lock file and run Helm dependency build, this will result in:

$ helm dependency build
Hang tight while we grab the latest from your chart repositories...
...Successfully got an update from the "stable" chart repository
Update Complete. ⎈Happy Helming!⎈
Saving 1 charts
Downloading wordpress from repo https://charts.bitnami.com/bitnami
Deleting outdated charts

This successfully downloaded the subcharts and updated the Chart.lock file. Running the command again will fail as it did before.

Solution

We should make Helm dependency build not require the user to have added the repository beforehand.