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Contributing

Guidelines on Contributing

  • Lint your changes:
    • docker run --rm -it -v ${PWD}:/charts -w /charts quay.io/helmpack/chart-testing:v2.4.0 ct lint --chart-yaml-schema scripts/schema.yaml --chart-dirs incubator --chart-dirs stable
  • End-to-end test your changes:
    • Install kind 0.7.0+
    • Install chart-testing (ct)
    • scripts/e2e-test.sh setup to set up Kubernetes in Docker
    • scripts/e2e-test.sh test to test your local changes until they pass
    • scripts/e2e-test.sh teardown when you are done testing to delete your cluster
  • Submit a PR
  • Follow the [Chart Guidelines](#Chart Guidelines)
  • Make sure your chart passes a helm lint

Pre-commit

There is a .pre-commit-config.yaml in this repo. If you use pre-commit, then you can just run pre-commit install to automatically run the linter on modified charts.

Chart Guidelines

Immutability

Chart releases must be immutable. Any change to a chart warrants a chart version bump even if it is only changes to the documentation.

Chart Metadata

The Chart.yaml should be as complete as possible. The following fields are mandatory:

  • name (same as chart's directory)
  • home
  • version
  • appVersion
  • description
  • maintainers (name should be Github username)

Dependencies

Stable charts should not depend on charts in incubator.

Names and Labels

Metadata

Resources and labels should follow some conventions. The standard resource metadata (metadata.labels and spec.template.metadata.labels) should be this:

name: {{ include "myapp.fullname" . }}
labels:
  app.kubernetes.io/name: {{ include "myapp.name" . }}
  app.kubernetes.io/instance: {{ .Release.Name }}
  app.kubernetes.io/managed-by: {{ .Release.Service }}
  helm.sh/chart: {{ include "myapp.chart" . }}

If a chart has multiple components, a app.kubernetes.io/component label should be added (e. g. app.kubernetes.io/component: server). The resource name should get the component as suffix (e. g. name: {{ include "myapp.fullname" . }}-server).

Note that templates have to be namespaced. With Helm 2.7+, helm create does this out-of-the-box. The app.kubernetes.io/name label should use the name template, not fullname as is still the case with older charts.

Deployments, StatefulSets, DaemonSets Selectors

spec.selector.matchLabels must be specified should follow some conventions. The standard selector should be this:

selector:
  matchLabels:
    app.kubernetes.io/name: {{ include "myapp.name" . }}
    app.kubernetes.io/instance: {{ .Release.Name }}

If a chart has multiple components, a component label should be added to the selector (see above).

spec.selector.matchLabels defined in Deployments/StatefulSets/DaemonSets >=v1/beta2 must not contain helm.sh/chart label or any label containing a version of the chart, because the selector is immutable. The chart label string contains the version, so if it is specified, whenever the the Chart.yaml version changes, Helm's attempt to change this immutable field would cause the upgrade to fail.

Fixing Selectors
For Deployments, StatefulSets, DaemonSets apps/v1beta1 or extensions/v1beta1
  • If it does not specify spec.selector.matchLabels, set it
  • Remove helm.sh/chart label in spec.selector.matchLabels if it exists
  • Bump patch version of the Chart
For Deployments, StatefulSets, DaemonSets >=apps/v1beta2
  • Remove helm.sh/chart label in spec.selector.matchLabels if it exists
  • Bump major version of the Chart as it is a breaking change

Service Selectors

Label selectors for services must have both app.kubernetes.io/name and app.kubernetes.io/instance labels.

selector:
  app.kubernetes.io/name: {{ include "myapp.name" . }}
  app.kubernetes.io/instance: {{ .Release.Name }}

If a chart has multiple components, a app.kubernetes.io/component label should be added to the selector (see above).

Persistence Labels

StatefulSet

In case of a Statefulset, spec.volumeClaimTemplates.metadata.labels must have both app.kubernetes.io/name and app.kubernetes.io/instance labels, and must not contain helm.sh/chart label or any label containing a version of the chart, because spec.volumeClaimTemplates is immutable.

labels:
  app.kubernetes.io/name: {{ include "myapp.name" . }}
  app.kubernetes.io/instance: {{ .Release.Name }}

If a chart has multiple components, a app.kubernetes.io/component label should be added to the selector (see above).

PersistentVolumeClaim

In case of a PersistentVolumeClaim, unless special needs, matchLabels should not be specified because it would prevent automatic PersistentVolume provisioning.

Formatting

  • Yaml file should be indented with two spaces.
  • List indentation style should be consistent.
  • There should be a single space after {{ and before }}.

Configuration

  • Docker images should be configurable. Image tags should use stable versions.
image:
  repository: myapp
  tag: 1.2.3
  pullPolicy: IfNotPresent
  • The use of the default function should be avoided if possible in favor of defaults in values.yaml.
  • It is usually best to not specify defaults for resources and to just provide sensible values that are commented out as a recommendation, especially when resources are rather high. This makes it easier to test charts on small clusters or Minikube. Setting resources should generally be a conscious choice of the user.

Persistence

  • Persistence should be enabled by default
  • PVCs should support specifying an existing claim
  • Storage class should be empty by default so that the default storage class is used
  • All options should be shown in README.md
  • Example persistence section in values.yaml:
persistence:
  enabled: true
  ## If defined, storageClassName: <storageClass>
  ## If set to "-", storageClassName: "", which disables dynamic provisioning
  ## If undefined (the default) or set to null, no storageClassName spec is
  ##   set, choosing the default provisioner.  (gp2 on AWS, standard on
  ##   GKE, AWS & OpenStack)
  ##
  storageClass: ""
  accessMode: ReadWriteOnce
  size: 10Gi
  # existingClaim: ""
  • Example pod spec within a deployment:
volumes:
  - name: data
  {{- if .Values.persistence.enabled }}
    persistentVolumeClaim:
      claimName: {{ .Values.persistence.existingClaim | default (include "myapp.fullname" .) }}
  {{- else }}
    emptyDir: {}
  {{- end -}}
  • Example pvc.yaml:
{{- if and .Values.persistence.enabled (not .Values.persistence.existingClaim) }}
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: {{ include "myapp.fullname" . }}
  labels:
    app.kubernetes.io/name: {{ include "myapp.name" . }}
    app.kubernetes.io/instance: {{ .Release.Name }}
    app.kubernetes.io/managed-by: {{ .Release.Service }}
    helm.sh/chart: {{ include "myapp.chart" . }}
spec:
  accessModes:
    - {{ .Values.persistence.accessMode | quote }}
  resources:
    requests:
      storage: {{ .Values.persistence.size | quote }}
{{- if .Values.persistence.storageClass }}
{{- if (eq "-" .Values.persistence.storageClass) }}
  storageClassName: ""
{{- else }}
  storageClassName: "{{ .Values.persistence.storageClass }}"
{{- end }}
{{- end }}
{{- end }}

AutoScaling / HorizontalPodAutoscaler

  • Autoscaling should be disabled by default

  • All options should be shown in README.md

  • Example autoscaling section in values.yaml:

autoscaling:
  enabled: false
  minReplicas: 1
  maxReplicas: 5
  targetCPUUtilizationPercentage: 50
  targetMemoryUtilizationPercentage: 50
  • Example hpa.yaml:
{{- if .Values.autoscaling.enabled }}
apiVersion: autoscaling/v2beta1
kind: HorizontalPodAutoscaler
metadata:
  name: {{ include "myapp.fullname" . }}
  labels:
    app.kubernetes.io/name: {{ include "myapp.name" . }}
    app.kubernetes.io/instance: {{ .Release.Name }}
    app.kubernetes.io/managed-by: {{ .Release.Service }}
    helm.sh/chart: {{ include "myapp.chart" . }}
    app.kubernetes.io/component: "{{ .Values.name }}"
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: {{ include "myapp.fullname" . }}
  minReplicas: {{ .Values.autoscaling.minReplicas }}
  maxReplicas: {{ .Values.autoscaling.maxReplicas }}
  metrics:
    - type: Resource
      resource:
        name: cpu
        targetAverageUtilization: {{ .Values.autoscaling.targetCPUUtilizationPercentage }}
    - type: Resource
      resource:
        name: memory
        targetAverageUtilization: {{ .Values.autoscaling.targetMemoryUtilizationPercentage }}
{{- end }}

Ingress

ingress:
  enabled: false
  annotations: {}
    # kubernetes.io/ingress.class: nginx
    # kubernetes.io/tls-acme: "true"
  path: /
  hosts:
    - chart-example.test
  tls: []
  #  - secretName: chart-example-tls
  #    hosts:
  #      - chart-example.test
  • Example ingress.yaml:
{{- if .Values.ingress.enabled -}}
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: {{ include "myapp.fullname" }}
  labels:
    app.kubernetes.io/name: {{ include "myapp.name" . }}
    app.kubernetes.io/instance: {{ .Release.Name }}
    app.kubernetes.io/managed-by: {{ .Release.Service }}
    helm.sh/chart: {{ include "myapp.chart" . }}
{{- with .Values.ingress.annotations }}
  annotations:
{{ toYaml . | indent 4 }}
{{- end }}
spec:
{{- if .Values.ingress.tls }}
  tls:
  {{- range .Values.ingress.tls }}
    - hosts:
      {{- range .hosts }}
        - {{ . | quote }}
      {{- end }}
      secretName: {{ .secretName }}
  {{- end }}
{{- end }}
  rules:
  {{- range .Values.ingress.hosts }}
    - host: {{ . | quote }}
      http:
        paths:
          - path: {{ .Values.ingress.path }}
            backend:
              serviceName: {{ include "myapp.fullname" }}
              servicePort: http
  {{- end }}
{{- end }}
  • Example prepend logic for getting an application URL in NOTES.txt:
{{- if .Values.ingress.enabled }}
{{- range .Values.ingress.hosts }}
  http{{ if $.Values.ingress.tls }}s{{ end }}://{{ . }}{{ $.Values.ingress.path }}
{{- end }}

Documentation

README.md and NOTES.txt are mandatory. README.md should contain a table listing all configuration options. NOTES.txt should provide accurate and useful information how the chart can be used/accessed.

If you would like to use helm-docs, it is included in the pre-commit file. Just make sure your chart is not in the .helmdocsignore file.

CODEOWNERS

Please create a github-style CODEOWNERS file in your chart folder and add your name to it. This will ensure that you are asked to review PRs that involve your chart.