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Helm Interoperability

Helm is the most popular package manager for Kubernetes, and many Kubernetes applications are distributed as Helm charts. Since rewriting all your Helm charts in Anemos may not be practical in short term, Anemos provides a way to use Helm charts in your Anemos applications. This allows you to use existing Helm charts in your Anemos applications while migrating to Anemos at your own pace.

For the migration process, you can define your options as JavaScript objects, then convert these objects to Helm values and pass them to Helm for rendering. You can support your Helm chart as long as you want and update the chart file in Anemos project to keep them in sync. Then when you are ready, you can generate your manifests using Anemos, removing the manifests generated from Helm charts. You can even migrate your templates one by one, replacing the manifests generated from Helm charts with manifests generated by Anemos.

Generating Anemos documents from Helm charts is pretty straightforward. Following example is a complete Anemos script that generates manifests from a Helm chart, modifies them to remove the helm.sh/chart label, and add an example label.

index.ts
import * as anemos from "@ohayocorp/anemos";

const builder = new anemos.Builder("1.31", anemos.KubernetesDistribution.Minikube, anemos.EnvironmentType.Development);

builder.onStep(anemos.steps.generateResources, (context: anemos.BuildContext) => {
    // Download hello world Helm chart to the directory where the index.js file, that is created
    // by the tsc compiler, is located before running this script:
    // https://github.com/crowdsecurity/helm-charts/releases/download/helloworld-0.2.1/helloworld-0.2.1.tgz
    const chart = new anemos.HelmChart(`${anemos.file.currentScriptDirectory()}/helloworld-0.2.1.tgz`);
    const values = anemos.dedent(`
        replicaCount: 2
        image:
          repository: hashicorp/http-echo
          tag: 1.0.0
        `);

    const documentGroup = chart.generate(context, {
        releaseName: "hello-world",
        namespace: "default",
        values: values
    });

    for (const document of documentGroup.documents) {
        document.getLabels()!.remove("helm.sh/chart");
        document.setLabel("example", "value");
    }

    context.addDocumentGroup(documentGroup);
});

builder.build();

Building this script will generate the following Kubernetes manifests from the specified Helm chart and save them to the Anemos output directory.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-world-helloworld
  labels:
    app.kubernetes.io/name: helloworld
    app.kubernetes.io/instance: hello-world
    app.kubernetes.io/version: "1.16.0"
    app.kubernetes.io/managed-by: Helm
    example: value
spec:
  replicas: 2
  selector:
    matchLabels:
      app.kubernetes.io/name: helloworld
      app.kubernetes.io/instance: hello-world
  template:
    metadata:
      labels:
        app.kubernetes.io/name: helloworld
        app.kubernetes.io/instance: hello-world
    spec:
      serviceAccountName: helloworld
      securityContext: {}
      containers:
        - name: helloworld
          securityContext: {}
          image: "hashicorp/http-echo:1.0.0"
          imagePullPolicy: IfNotPresent
          args:
            - "-text=helloworld !"
          ports:
            - name: http
              containerPort: 5678
              protocol: TCP
          livenessProbe:
            httpGet:
              path: /
              port: 5678
          readinessProbe:
            httpGet:
              path: /
              port: 5678
          resources:
            limits:
              cpu: 100m
              memory: 128Mi
            requests:
              cpu: 100m
              memory: 128Mi