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Helm cheatsheet

Get started

Struture

.
├── Chart.yaml --> metadata info
├── README.md
├── requirements.yaml --> define dependencies
├── templates
│   ├── spark-master-deployment.yaml --> configuration with template supported
│   ├── spark-worker-deployment.yaml
│   └── spark-zeppelin-deployment.yaml
│   └── NOTES.txt --> display when run "helm chart"
│   └── _helpers.tpl --> template handler
└── values.yaml --> variable list, will be interpolated on templates file during deployment
│
└── charts
    ├── apache/
        ├── Chart.yaml
  • Chart.yaml
  name: The name of the chart (required)
  version: A SemVer 2 version (required)
  description: A single-sentence description of this project (optional)
  keywords:
    - A list of keywords about this project (optional)
  home: The URL of this project's home page (optional)
  sources:
    - A list of URLs to source code for this project (optional)
  maintainers: # (optional)
    - name: The maintainer's name (required for each maintainer)
      email: The maintainer's email (optional for each maintainer)
  engine: gotpl # The name of the template engine (optional, defaults to gotpl)
  icon: A URL to an SVG or PNG image to be used as an icon (optional).
  appVersion: The version of the app that this contains (optional). This needn't be SemVer.
  deprecated: Whether or not this chart is deprecated (optional, boolean)
  tillerVersion: The version of Tiller that this chart requires. This should be expressed as a SemVer range: ">2.0.0" (optional)
  • requirements.yaml

Adding an alias for a dependency chart would put a chart in dependencies using alias as name of new dependency. Condition - The condition field holds one or more YAML paths (delimited by commas). If this path exists in the top parent's values and resolves to a boolean value, the chart will be enabled or disabled based on that boolean value. Only the first valid path found in the list is evaluated and if no paths exist then the condition has no effect. Tags - The tags field is a YAML list of labels to associate with this chart. In the top parent's values, all charts with tags can be enabled or disabled by specifying the tag and a boolean value. Conditions (when set in values) always override tags

  dependencies:
  - name: apache
    version: 1.2.3
    repository: http://example.com/charts
    alias: new-subchart-1
    condition: subchart1.enabled, global.subchart1.enabled
        tags:
          - front-end
          - subchart1

  - name: mysql
    version: 3.2.1
    repository: http://another.example.com/charts
    alias: new-subchart-2
    condition: subchart2.enabled,global.subchart2.enabled
        tags:
          - back-end
          - subchart1

General Usage

  helm list --all
  helm repo (list|add|update)
  helm search
  helm inspect <chart-name>
  hem install --set a=b -f config.yaml <chart-name> -n <release-name> # --set take precedented, merge into -f
  helm status <deployment-name>
  helm delete <deployment-name>
  helm inspect values <chart-name>
  helm upgrade -f config.yaml <deployment-name> <chart-name>
  helm rollback <deployment-name> <version>

  helm create <chart-name>
  helm package <chart-name>
  helm lint <chart-name>

  helm dep up <chart-name> # update dependency
  helm get manifest <deployment-name> # prints out all of the Kubernetes resources that were uploaded to the server
  helm install --debug --dry-run <deployment-name> # it will return the rendered template to you so you can see the output
  • --set outer.inner=value is translated into this:
  outer:
  inner: value
  • --set servers[0].port=80,servers[0].host=example:
  servers:
  - port: 80
    host: example
  • --set name={a, b, c} translates to:
  name:
  - a
  - b
  - c
  • --set name=value1,value2:
  name: "value1,value2"
  • --set nodeSelector."kubernetes.io/role"=master
  nodeSelector:
  kubernetes.io/role: master
  • --set livenessProbe.exec.command=[cat,docroot/CHANGELOG.txt] --set livenessProbe.httpGet=null
livenessProbe:
-  httpGet:
-    path: /user/login
-    port: http
  initialDelaySeconds: 120
+  exec:
+    command:
+    - cat
+    - docroot/CHANGELOG.txt
  • --timeout
  • --wait
  • --no-hooks
  • --recreate-pods

Template

Values that are supplied via a values.yaml file (or via the --set flag) are accessible from the .Values object in a template

Release.Name:
Release.Time:
Release.Namespace: The namespace the chart was released to.
Release.Service: The service that conducted the release. Usually this is Tiller.
Release.IsUpgrade: This is set to true if the current operation is an upgrade or rollback.
Release.IsInstall: This is set to true if the current operation is an install.
Release.Revision: The revision number. It begins at 1, and increments with each helm upgrade.
Chart: The contents of the Chart.yaml. Thus, the chart version is obtainable as "Chart.Version" and the maintainers are in "Chart.Maintainers".
Files: Files can be accessed using {{index .Files "file.name"}} or using the "{{.Files.Get name}}" or "{{.Files.GetString name}}" functions. You can also access the contents of the file as []byte using "{{.Files.GetBytes}}"
Capabilities: "({{.Capabilities.KubeVersion}}", Tiller "({{.Capabilities.TillerVersion}}", and the supported Kubernetes API versions "({{.Capabilities.APIVersions.Has "batch/v1")"

{{.Files.Get config.ini}}
{{.Files.GetBytes}} useful for things like images

{{.Template.Name}}
{{.Template.BasePath}}
  • default value
{{default "minio" .Values.storage}}

//same
{{ .Values.storage | default "minio" }}
  • put a quote outside
heritage: {{.Release.Service | quote }}

# same result
heritage: {{ quote .Release.Service }}
  • global variable
global:
  app: MyWordPress

// could be access as "{{.Values.global.app}}"
  • Includes a template called mytpl.tpl, then lowercases the result, then wraps that in double quotes
value: {{include "mytpl.tpl" . | lower | quote}}
  • required function declares an entry for .Values.who is required, and will print an error message when that entry is missing
value: {{required "A valid .Values.who entry required!" .Values.who }}
  • The sha256sum function can be used together with the include function to ensure a deployments template section is updated if another spec changes
kind: Deployment
spec:
  template:
    metadata:
      annotations:
        checksum/config: {{ include (print $.Template.BasePath "/secret.yaml") . | sha256sum }}
[...]

  • The annotation "helm.sh/resource-policy": keep instructs Tiller to skip this resource during a helm delete operation

  • In the templates/ directory, any file that begins with an underscore(_) is not expected to output a Kubernetes manifest file. So by convention, helper templates and partials are placed in a _helpers.tpl file.

Hooks

Read more

  • include these annotation inside hook yaml file, for e.g templates/post-install-job.yaml
apiVersion: batch/v1
kind: Job
metadata:
  annotations:
    # This is what defines this resource as a hook. Without this line, the
    # job is considered part of the release.
    "helm.sh/hook": post-install, post-upgrade
    "helm.sh/hook-weight": "-5"

Chart repository

Read more

Signing

Read more

Test

Read more

Flow Control

If/Else

{{ if PIPELINE }}
  # Do something
{{ else if OTHER PIPELINE }}
  # Do something else
{{ else }}
  # Default case
{{ end }}

data:
  myvalue: "Hello World"
  drink: {{ .Values.favorite.drink | default "tea" | quote }}
  food: {{ .Values.favorite.food | upper | quote }}
  {{- if eq .Values.favorite.drink "lemonade" }}
  mug: true
  {{- end }} # notice the "-" in the left, if will help eliminate newline before variable

With

with can allow you to set the current scope (.) to a particular object

data:
  myvalue: "Hello World"
  {{- with .Values.favorite }}
  drink: {{ .drink | default "tea" | quote }}
  food: {{ .food | upper | quote }}
  {{- end }} # instead of writing ".Values.favorite.drink"

Inside of the restricted scope, you will not be able to access the other objects from the parent scope

Range

# predefined variable
pizzaToppings:
  - mushrooms
  - cheese
  - peppers
  - onions

toppings: |-
    {{- range $i, $val := .Values.pizzaTopping }}
    - {{ . | title | quote }}  # upper first character, then quote
    {{- end }}

sizes: |-
    {{- range tuple "small" "medium" "large" }}
    - {{ . }}
    {{- end }} # make a quick list

Variables

It follows the form $name. Variables are assigned with a special assignment operator: :=

data:
  myvalue: "Hello World"
  {{- $relname := .Release.Name -}}
  {{- with .Values.favorite }}
  drink: {{ .drink | default "tea" | quote }}
  food: {{ .food | upper | quote }}
  release: {{ $relname }}
  {{- end }}

# use variable in range
 toppings: |-
    {{- range $index, $topping := .Values.pizzaToppings }}
      {{ $index }}: {{ $topping }}
    {{- end }}

#toppings: |-
#      0: mushrooms
#      1: cheese
#      2: peppers
#      3: onions

{{- range $key,$value := .Values.favorite }}
  {{ $key }}: {{ $value }}
  {{- end }} # instead of specify the key, we can actually loop through the values.yaml file and print values

There is one variable that is always global - $ - this variable will always point to the root context

...
labels:
    # Many helm templates would use `.` below, but that will not work,
    # however `$` will work here
    app: {{ template "fullname" $ }}
    # I cannot reference .Chart.Name, but I can do $.Chart.Name
    chart: "{{ $.Chart.Name }}-{{ $.Chart.Version }}"
    release: "{{ $.Release.Name }}"
    heritage: "{{ $.Release.Service }}"
...

Named Templates

template names are global

# _helpers.tpl
{{/* Generate basic labels */}}
{{- define "my_labels" }}
  labels:
    generator: helm
    date: {{ now | htmlDate }}
    version: {{ .Chart.Version }}
    name: {{ .Chart.Name }}
{{- end }}

When a named template (created with define) is rendered, it will receive the scope passed in by the template call.

# configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: {{ .Release.Name }}-configmap
  {{- template "my_labels" . }} # Notice the final dot, it will pass the global scope inside template file. Without it version & name will not be �generated.
  {{- include "my_labels" . | indent 2 }} # similar to "template" directive, have the ability to control indentation

referable to use include over template. Because template is an action, and not a function, there is no way to pass the output of a template call to other functions; the data is simply inserted inline.

Files inside Templates

# file located at parent folder
# config1.toml: |-
#   message = config 1 here
# config2.toml: |-
#   message = config 2 here
# config3.toml: |-
#   message = config 3 here

data:
  {{- $file := .Files }} # set variable
  {{- range tuple "config1.toml" "config2.toml" "config3.toml" }} # create list
  {{ . }}: |- # config file name
    {{ $file.Get . }} # get file's content
  {{- end }}

Glob-patterns & encoding

apiVersion: v1
kind: ConfigMap
metadata:
  name: conf
data:
+{{ (.Files.Glob "foo/*").AsConfig | indent 2 }}
---
apiVersion: v1
kind: Secret
metadata:
  name: very-secret
type: Opaque
data:
+{{ (.Files.Glob "bar/*").AsSecrets | indent 2 }}

+token: |-
+  {{ .Files.Get "config1.toml" | b64enc }}

YAML reference

# Force type
age: !!str 21
port: !!int "80"

# Fake first line to preserve integrity
coffee: | # �no strip
  # Commented first line
         Latte
  Cappuccino
  Espresso

coffee: |- # strip off trailing newline
  Latte
  Cappuccino
  Espresso

coffee: |+ # preserve trailing newline
  Latte
  Cappuccino
  Espresso


another: value

myfile: | # insert static file
{{ .Files.Get "myfile.txt" | indent 2 }}

coffee: > �# treat as one long line
  Latte
  Cappuccino
  Espresso