Custom Charts

Devtron includes predefined helm charts that cover the majority of use cases. For any use case not addressed by the default helm charts, you can upload your own helm chart and use it as a custom chart in Devtron.

• Who can upload a custom chart - Super admins

• Who can use the custom chart - All users

A super admin can upload multiple versions of a custom helm chart.

Custom charts

Prerequisites

1. A valid helm chart, which contains Chart.yaml file with name and version fields.

2. Image descriptor template file .image_descriptor_template.json.

3. Custom chart packaged in the *.tgz format.

1. How to create a helm chart

You can use the following command to create the Helm chart:

helm create my-custom-chart

Note: Chart.yaml is the metadata file that gets created when you create a helm chart.

Field	Description
Name	Name of the helm chart (Required).
Version	This is the chart version. Update this value for each new version of the chart (Required).
Description	Description of the chart (Optional).

Please see the following example:

Chart.yaml file

2. Create the image descriptor template file .image_descriptor_template.json

It's a GO template file that should produce a valid JSON file upon rendering. This file is passed as the last argument in helm install -f myvalues.yaml -f override.yaml command.

Place the .image_descriptor_template.json file in the root directory of your chart.

You can use the following variables in the helm template (all the placeholders are optional):

The values from the CD deployment pipeline are injected at the placeholder specified in the .image_descriptor_template.json template file.

{
    "server": {
        "deployment": {
            "image_tag": "{{.Tag}}",
            "image": "{{.Name}}"
        }
    },
    "pipelineName": "{{.PipelineName}}",
    "releaseVersion": "{{.ReleaseVersion}}",
    "deploymentType": "{{.DeploymentType}}",
    "app": "{{.App}}",
    "env": "{{.Env}}",
    "appMetrics": {{.AppMetrics}}
}

Field	Description
image_tag	The build image tag
image	Repository name
pipelineName	The CD pipeline name created in Devtron
releaseVersion	Devtron's internal release number
deploymentType	Deployment strategy used in the pipeline
app	Application's ID within the Devtron ecosystem
env	Environment used to deploy the chart
appMetrics	For the App metrics UI feature to be effective, include the appMetrics placeholder.

For example:

To create a template file to allow Devtron to only render the repository name and the tag from the CI/CD pipeline that you created, edit the .image_descriptor_template.json file as:

{
    "image": {
          "repository": "{{.Name}}",
          "tag": "{{.Tag}}"
    }
}

3. Package the custom chart in the *.tgz format

Before you begin, ensure that your helm chart includes both Chart.yaml (with name and version fields) and .image_descriptor_template.json files.

The helm chart to be uploaded must be packaged as a versioned archive file in the format <helm-chart-name>-vx.x.x.tgz.

helm package my-custom-chart

The above command will create a my-custom-chart-0.1.0.tgz file.

Uploading a custom chart

A custom chart can only be uploaded by a super admin.

• On the Devtron dashboard, select Global Configurations > Custom charts.

• Select Import Chart.

• Select tar.gz file... and upload the packaged custom chart in the *.tgz format.

Selecting custom chart

The chart is being uploaded and validated. You may also Cancel upload if required.

Uploading custom chart

Validation

The uploaded archive will be validated against:

• Supported archive template should be in *.tgz format.

• Content of values.yaml should be there in app-values.yaml file.

• release-values.yaml file is required.

• ConfigMap/Secret template should be same as that of our reference chart.
• Chart.yaml must include the name and the version number.

• ..image_descriptor_template.json file should be present and the field format must match the format listed in the image builder template section.

The following are the validation results:

Validation status	Description	User action
Success	The files uploaded are validated.	Enter a description for the chart and select Save or Cancel upload.
Unsupported template	The archive file do not match the required template.	Upload another chart or Cancel upload.
New version detected	You are uploading a newer version of an existing chart	Enter a Description and select Save to continue uploading, or Cancel upload.
Already exists	There already exists a chart with the same version.	Edit the version and re-upload the same chart using Upload another chart. Upload a new chart with a new name using Upload another chart. Cancel upload.

Chart validated

Unsupported template

New version detected

Already exists

View the custom charts

All users can view the custom charts.

To view a list of available custom charts, go to Global Configurations > Custom charts page.

• The charts can be searched with their name, version, or description.

• New custom charts can be uploaded by selecting Upload chart.

Custom charts

Use the custom chart in an application

The custom charts can be used from the Deployment Template section.

Info:

The deployment strategy for a custom chart is fetched from the custom chart template and cannot be configured in the CD pipeline.