Helm — Dependencies

In helm, one chart can be dependent on another chart. For instance, a WordPress application requires a database to start functioning. In helm, we can deploy WordPress as part of the parent chart and MySQL or any other required application as a dependency of the parent chart.

Helm charts store their dependencies in ‘charts/’. There are two different ways to add dependency charts to parent charts:

Listing all the dependencies inside the Chart.yaml file and helm will download the dependencies and store them in the ‘charts/’ Directory.

Manually populate the dependency chart inside the ‘charts/’ directory.

List dependencies inside the Chart.yaml file

Before listing dependencies in the Chart.yaml file, By default Chart.yaml file looks like this :

# Chart.yaml
apiVersion: v2
name: webserver
description: A Helm chart for Kubernetes
type: application
version: 0.1.0
appVersion: "1.16.0"

Now, let's see how we can populate the dependencies into the Chart.yaml file:

dependencies:

- name: mysql
  version: "9.3.4"
  repository: "https://charts.bitnami.com/bitnami"

After adding dependencies to the Chart.yaml file :

# Chart.yaml

apiVersion: v2
name: webserver
description: A Helm chart for Kubernetes
type: application
version: 0.1.0
appVersion: "1.16.0"
dependencies:
- name: mysql
  version: "9.3.4"
  repository: "https://charts.bitnami.com/bitnami"

Using a simple helm command we can pull the chart from the repository defined in the dependencies field:

   helm dependency update [CHART] 
>> helm dependency update ~/webserver

The above-defined command will generate .webserver/Chart.lock file as well as download all dependencies into the .webserver/charts directory

The Chart.lock file lists the exact versions of immediate dependencies and their dependencies and so on.

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