The Helm Grain

The HELM Grain

The HELM grain is Torque's native support for HELM v3 charts. Torque allows designers to use HELM specific features to easily orchestrate self-developer and community charts in a standard way and share them with others as building blocks. For a full blueprint yaml example, see Example 1: Helm Application with MySQL and S3 Deployed by Terraform.

Namespace

Torque will install the helm release in the namespace referred to in target-namespace. The target namespace must exist in the cluster prior to the deployment. It must not be equal to the namespaces used by Torque for agent deployments. Make sure the service account has enough permissions to create/read/delete everything in the helm chart and also create/read/delete secrets and volumes.

In your blueprint YAML, configure the following configuration for Helm grains

helloHelm:
  kind: helm
  spec:
    source:
      store: my-repo
      path: folder/my-app
    target-namespace: '{{ .inputs.namespace }}'  # This is the namespace which is passed along to the helm installation.
    agent:
      name: '{{.inputs.agent}}'
      service-account: '{{ .inputs.service_account }}'

It's also possible to use parameters for the service-account name. Note that when service account is not provided in the grain, the default service account provided on the agent will be used.

Tools and technologies

The following tools and technologies are installed out of the box on our agents in the Kubernetes pods and can be used when writing grain scripts (pre/post, etc.):

• dotnet
• curl
• tar
• unzip
• kubectl
• kustomize
• helm
• awscli

source

Please see the grain source for more details.

agent

Please see the grain agent for more details.

inputs

Similar to blueprint inputs and Terraform inputs, the HELM grain inputs allow you to reuse the same HELM chart in different ways using different values overrides. Inputs provided to the HELM grain are used when launching the HELM chart. We recommend using Torque's auto-discovery capability to quickly model your HELM chart within Torque including all defined inputs.

grains:
  nginx:
    kind: helm
    spec:
      source:
        store: my-repo 
        path: my-asset     
      agent:
      ...
      inputs:
        - replicaCount: '{{ .inputs.replicaCount }}'
        - service.image: '{{ .inputs.image }}'

info

Note that in the above example, blueprint input is used as the value of the HELM grain input, so the environment's owner is able to choose the replicaCount required for his need. The information provided by the user will be passed to HELM chart as values and affect the deployment process.

outputs

Helm does not natively expose outputs. However, this can be done using a post-helm-install script that assigns environment variables after the grain's deployment. The script must be referenced, along with the names of the environment variables in the grain's scripts. To expose the outputs to the environment, the names of the environment variables must be referenced in the blueprint's outputs section.

tip

For illustration purposes, here's a Helm chart that declares a URL environment variable and references the post-install script that publishes that environment variable as an output.

For example:

spec_version: 2
description: 
  ...

inputs:
  ...

outputs:
  output1:
    kind: regular
    value: '{{.grains.<grain name>.scripts.post-helm-install.outputs.<output name>}}'
  output2:
    kind: regular
    value: '{{.grains.<grain name>.scripts.post-helm-install.outputs.<output name>}}'

commands

The commands section allows to execute CLI code prior to the HELM chart deployment to make sure all dependencies are met to ensure a successful deployment. Common use for commands is to execute HELM dependencies update to collect all the sub-charts required for the deployment.

grains:
  nginx:
    kind: helm
    spec:
      source:
        store: my-repo 
        path: my-asset     
      agent:
        name: aws-demo
      inputs:
        - replicaCount: '{{ .inputs.replicaCount }}'
      commands:
        - dep up bitnami/nginx

scripts

Torque provides the ability to execute custom code after Torque executes the Helm chart. This is useful for generating and using outputs, as explained in helm outputs.

For example - grain with a post-install script and outputs "test1" and "test2":

grains:
  nginx:
    kind: helm
    spec:
      source:
        path: ...
      agent:
        name: ...
        service-account: ...
      inputs:
        - replicaCount: ...
      commands:
        - dep up bitnami/nginx
      scripts:
        post-helm-install:
        source:
          store: my-repo 
          path: my-asset     
        arguments: "{{.inputs.ACCOUNT_ID}},{{.inputs.ID2}},3"
        outputs:
          - test1
          - test2