Chart Dependencies

Some charts may depend on others. For instance, because WordPress requires a database to store its data, it will not function properly otherwise. A WordPress chart depends on a database chart, such as MariaDB or MySQL.

Another example is kube-prometheus-stack, a comprehensive monitoring toolkit for Kubernetes clusters that integrates Prometheus, Alertmanager, and Grafana into a single Helm chart. Therefore, it has some dependencies on other charts, such as:

• kube-state-metrics
• node-exporter
• Grafana

To better understand how chart dependencies work, let's explore how the author of the kube-prometheus-stack chart has defined its dependencies. Run the following commands to download the chart and inspect its Chart.yaml file:

# Install yq if you don't have it already
apt-get install -y yq

# Add the Prometheus Community Helm repository
helm repo add prometheus-community \
  https://prometheus-community.github.io/helm-charts

# Download the chart locally
cd $HOME &&
  helm pull prometheus-community/kube-prometheus-stack \
  --version 80.0.0

# Extract the chart:
tar -xvf kube-prometheus-stack-*.tgz

# Check the `Chart.yaml` file and extract the dependencies section:
cat kube-prometheus-stack/Chart.yaml | yq '.dependencies' --yaml-output

You should see the following output representing the dependencies of our chart:

- condition: crds.enabled
  name: crds
  repository: ''
  version: 0.0.0
- condition: kubeStateMetrics.enabled
  name: kube-state-metrics
  repository: https://prometheus-community.github.io/helm-charts
  version: 6.4.2
- condition: nodeExporter.enabled
  name: prometheus-node-exporter
  repository: https://prometheus-community.github.io/helm-charts
  version: 4.49.2
- condition: grafana.enabled
  name: grafana
  repository: https://grafana.github.io/helm-charts
  version: 10.3.0
- condition: windowsMonitoring.enabled
  name: prometheus-windows-exporter
  repository: https://prometheus-community.github.io/helm-charts
  version: 0.12.*

ℹ️ Dependencies used to be defined in the requirements.yaml file in older Helm versions (v2.x). Now, they are defined directly in the Chart.yaml file.

When installed, the kube-prometheus-stack chart, based on the dependencies section above, will automatically install the following charts:

• Kube State Metrics chart version 6.4.2
• Node Exporter chart version 4.49.2
• Grafana chart version 10.3.0
• Windows Exporter chart version 0.12.*

If you were the author of the chart, after carefully selecting the dependencies and their versions, and after defining them in the Chart.yaml file, you would need to download the dependencies locally before releasing the chart. You can do this by running the following commands:

helm dependency build $HOME/kube-prometheus-stack

This command will download the required dependencies and place them in the charts/ directory of the extracted chart, and create a lock file named Chart.lock that contains the exact versions of the dependencies used. You can list the contents of the charts/ directory using:

ls $HOME/kube-prometheus-stack/charts/