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.

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

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

helm create my-custom-chart

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
        }
    }
}

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.

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

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

Validation

The uploaded archive will be validated against:

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

  • 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:

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.

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.

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