Helm

The Helm step renders every Helm chart an application has downloaded with helm template, using values files assembled along the inheritance tree. Use it to deploy any upstream chart: set per-environment values without copying the chart, and patch what the chart cannot configure with ytt overlays afterwards.

helm is called as an external binary and must be on your PATH. The container image includes it.

Getting a chart

myks renders every directory under the application’s vendor/charts/ that contains a Chart.yaml; other entries are skipped with a warning. Charts get there through a vendir source whose path starts with charts/, see sources.md:

#! prototypes/webapp/vendir/base.ytt.yaml
apiVersion: vendir.k14s.io/v1alpha1
kind: Config
directories:
  - path: charts/podinfo
    contents:
      - path: .
        lazy: true
        helmChart:
          name: podinfo
          version: 6.17.0
          repository:
            url: https://stefanprodan.github.io/podinfo

Important

myks identifies a chart by its directory name under vendor/charts/, not by the name in its Chart.yaml. Values files and per-chart settings use that directory name. This lets one application render the same chart twice, for example as charts/redis-cache and charts/redis-queue.

Charts are rendered in alphabetical order of their directory names and their output is concatenated.

Values files

Values files live in helm/ directories and are named after the chart directory: podinfo.yaml, or any podinfo.<anything>yaml such as podinfo.ytt.yaml or podinfo.resources.yaml. Files named _global.*yaml apply to every chart of the application.

For the frontend application, based on the webapp prototype, in the envs/prod/eu environment, myks collects values files from these directories, in this order:

1. prototypes/webapp/helm/
2. envs/_proto/webapp/helm/
3. envs/prod/_proto/webapp/helm/
4. envs/prod/eu/_proto/webapp/helm/
5. envs/_apps/frontend/helm/
6. envs/prod/_apps/frontend/helm/
7. envs/prod/eu/_apps/frontend/helm/

.
├── prototypes/webapp/helm/podinfo.yaml       # 1: defaults for every application of the prototype
└── envs/
    ├── _proto/webapp/helm/podinfo.yaml       # 2: every webapp application, everywhere
    ├── _apps/frontend/helm/podinfo.yaml      # 5: frontend, everywhere
    └── prod/
        ├── _apps/frontend/helm/podinfo.yaml  # 6: frontend in every prod environment
        └── eu/
            └── _apps/frontend/helm/podinfo.yaml  # 7: frontend in prod-eu only

All _global.*yaml files go first, in the order above, then all podinfo.*yaml files, in the order above. Within one directory, files apply in alphabetical order. Later files win: maps merge key by key, lists and scalars are replaced, the way helm template -f a.yaml -f b.yaml merges them.

_env/helm/ directories are not read: Helm values are always specific to a chart, so they belong to a prototype or an application. Use _proto/<prototype>/helm/ to change all applications of a prototype at one level of the tree.

Tip

myks inspect apps prod/eu frontend lists the values files of each chart in merge order, and --provenance shows which file sets each values key. See Inspecting and debugging.

Values files are ytt templates

Each values file is rendered by ytt together with the application’s data values before merging, so values can be computed:

#! prototypes/webapp/helm/podinfo.yaml
#@ load("@ytt:data", "data")
---
ui:
  message: #@ "Hello from " + data.values.environment.id
replicaCount: #@ 2 if data.values.environment.id.startswith("prod") else 1

The chart being rendered is available as data.values.myks.context.helm.chart, which lets one _global file adapt to each chart. A values file can hold several YAML documents; they merge in order. The merged result is written to .myks/<env-dir>/_apps/<app>/helm/<chart>.yaml and passed to helm template.

Configuration

The helm scope of the data values configures the step. Set it in any app-data*.yaml or env-data*.yaml file, at any level of the tree.

Key	Default	Effect
namespace	application name	Passed as --namespace.
includeCRDs	true	Adds --include-crds.
kubeVersion	''	Passed as --kube-version when set. Set it per environment to match each cluster.
capabilities	[]	Each entry is passed as --api-versions, for example monitoring.coreos.com/v1, so charts render optional resources.
buildDependencies	false	Run helm dependencies build during sync, see below.
charts	[]	Per-chart overrides, see below.

Every entry of helm.charts overrides the settings for one chart:

Key	Default	Effect
name	required	Chart directory name under vendor/charts/. Must be unique.
releaseName	chart directory name	Release name passed to helm template.
namespace	helm.namespace	--namespace for this chart.
includeCRDs	helm.includeCRDs	--include-crds for this chart.
buildDependencies	helm.buildDependencies	Dependency build for this chart.

#! prototypes/webapp/app-data.ytt.yaml
#@data/values
---
helm:
  kubeVersion: '1.33.0'
  charts:
    - name: podinfo
      releaseName: frontend

charts is a ytt list, so a lower level that writes charts: again appends entries instead of changing them. Match the existing entry by name to change it:

#! envs/prod/eu/_apps/frontend/app-data.ytt.yaml
#@ load("@ytt:overlay", "overlay")
#@data/values
---
helm:
  charts:
    #@overlay/match by="name"
    - name: podinfo
      namespace: frontend-eu

myks always passes --skip-tests, so chart test hooks are not rendered. It warns about helm.charts entries and values files that match no downloaded chart, which usually means a typo or a renamed source.

The exact helm template command of every chart is logged with --log-level debug.

Chart dependencies

Charts downloaded from a chart repository usually bundle their dependencies. Charts taken from a Git repository often do not. Set buildDependencies: true (globally or for one chart) and myks runs, during sync:

1. helm repo add for every http(s) repository listed in the chart’s Chart.yaml dependencies, in a repository cache private to the application (.myks/<env-dir>/_apps/<app>/helm-cache/), so your own Helm configuration stays untouched;
2. helm dependencies build --skip-refresh for the chart.

A chart shared by several applications through the cache is built once per run.