Creating New helm chart

Helm Chart development

helm create NAME flags

helm create guestbook                         
Creating guestbook

tree guestbook 
guestbook
├── Chart.yaml
├── charts
├── templates
│   ├── NOTES.txt
│   ├── _helpers.tpl
│   ├── deployment.yaml
│   ├── hpa.yaml
│   ├── ingress.yaml
│   ├── service.yaml
│   ├── serviceaccount.yaml
│   └── tests
│       └── test-connection.yaml
└── values.yaml

File/Directory

Definition

Required?

charts/

A directory that contains dependencies or Helm charts that the parent chart depends on.

Chart.yaml

A file that contains metadata about the Helm chart.

Yes

.helmignore

A file that contains a list of files and directories that should be omitted from the Helm chart’s packaging.

templates/

A directory that contains Golang templates, which are primarily used for generating Kubernetes resources.

Yes, unless the chart contains dependencies

templates/*.yaml

A template file used to generate a Kubernetes resource.

Yes, unless the chart contains dependencies

templates/_*.tpl

A file that contains boilerplate helper templates.

templates/NOTES.txt

A template file that is used to generate usage instructions after chart installation.

templates/tests/

A folder used for grouping different templates. This is strictly for aesthetics and has no effect on how the Helm chart operates – for example, templates/tests is used to group templates that are used for testing.

values.yaml

A file that contains the chart’s default values.

No, but every chart should contain this file as a best practice

Additional files not listed in the table may be included in a Helm chart, which were not generated by the helm create command.

File/Directory

Definition

Required?

Chart.lock

A file used to save, or lock in, the previously applied dependency versions.

crds/

A directory that contains Custom Resource Definition (CRD) YAML resources. These CRD resources will be installed before those under templates/.

README.md

A file that contains installation and usage information about the Helm chart.

No, but every Helm chart should contain this file as a best practice

LICENSE

A file that contains the chart’s license, which provides information about usage and redistribution rights.

values.schema.json

A file that contains the chart’s values schema in the JSON format. Used to provide input validation.

Installing helm chart using local path

helm install guestbook ./guestbook -n guestbook

We can check the manifest that got applied

helm get manifest guestbook -n guestbook

kubectl port-forward svc/guestbook 8000:80 -n guestbook

curl localhost:8000

Let's cleanup

helm uninstall guestbook -n guestbook

kubectl delete ns guestbook

chart.yaml(Chart Definition)

Holds metadata about the helm chart.

cat guestbook/Chart.yaml 
apiVersion: v2
name: guestbook
description: A Helm chart for Kubernetes
type: application
version: 0.1.0
appVersion: "1.16.0"

Chart.yaml fields:

Field

Description

Required?

apiVersion

The chart API version

Yes

name

The name of the Helm chart

Yes

description

A brief description of the Helm chart

type

The type of Helm chart (either Application or Library)

version

The version of the Helm chart, in SemVer format

Yes

appVersion

The version of the application that the Helm chart deploys. This does not need to be in the SemVer format.

apiVersion: v2 # compatible with helm3

Additional Chart.yaml supported fields:

Field

Description

Required?

kubeVersion

A range of compatible Kubernetes versions in the SemVer format.

keywords

A list of keywords used to describe the Helm chart. Keywords are also used to provide search terms for the helm search command.

home

The URL to the Helm chart’s home page.

sources

A list of URLs that link to source code used by the Helm chart.

dependencies

A list of charts that your Helm chart is reliant on.

maintainers

A list of Helm chart maintainers.

icon

An icon in SVG or PNG format used to represent the Helm chart. Displayed on the chart’s Artifact Hub page.

deprecated

Indicates whether the Helm chart has been deprecated.

annotations

A list of annotations used to provide custom metadata.

Bitnami Wordpress Chart.yaml

Updating Chart.yaml

cat guestbook/Chart.yaml
apiVersion: v2
name: guestbook
description: An application used for keeping a running record of guests
type: application
version: 0.1.0
appVersion: "1.16.0"

Chart Dependencies

Check dependencies

Supported fields under chart.yaml for dependencies:

Field

Description

Required?

Name

The name of the dependency chart

Yes

Repository

The location where the dependency chart resides

Yes

Version

The chart dependency version

Yes

Condition

A Boolean value that determines whether to include the dependency or not

Tags

A list of Boolean values that determine whether to include the chart or not

import-values

A mapping of source values to parent values

Alias

An alternative name to give the dependency

helm dependency command

Command

Description

helm dependency list

Lists the dependencies for the given chart.

helm dependency update

Downloads the dependencies listed in Chart.yaml and generates a Chart.lock file.

helm dependency build

Downloads the dependencies listed in Chart.lock. If the Chart.lock file is not found, then this command will mirror the behavior of the helm dependency update command.

Clone this repo if you want to do hands-on:

$ git clone https://github.com/desiredcloud/helm.git
$ cd helm/examples

helm dependency list deps-chart 
NAME    VERSION REPOSITORY                                                                      STATUS 
mariadb 9.5.0   https://raw.githubusercontent.com/bitnami/charts/archive-full-index/bitnami     missing

Status missing means, the dependency chart is not downloaded yet.
We can perform dependecy update to download it

helm dependency update deps-chart/

helm dependency list deps-chart/  
NAME    VERSION REPOSITORY                                                                      STATUS
mariadb 9.5.0   https://raw.githubusercontent.com/bitnami/charts/archive-full-index/bitnami     ok

Dependencies gets downloaded under charts folder and version is updated in Chart.lock file.

ls  deps-chart/charts 
mariadb-9.5.0.tgz

cat deps-chart/Chart.lock 
dependencies:
- name: mariadb
  repository: https://raw.githubusercontent.com/bitnami/charts/archive-full-index/bitnami
  version: 9.5.0
digest: sha256:6621adebbb98601072b13d904b11f42e31919298a590713229f6061795606fcd
generated: "2024-02-22T10:09:10.905206+05:30"

You can use wildcard version for dependencies.

For example:
```
name: mariadb
version: 9.x.x
```
This will download the latest version starting with major version 9.

helm dep update deps-chart 
cat deps-chart/Chart.lock 
dependencies:
- name: mariadb
  repository: https://raw.githubusercontent.com/bitnami/charts/archive-full-index/bitnami
  version: 9.8.1

helm dep update will to the latest version, to keep consistent with the version specified in Chart.lock run cmd helm deps build

tree deps-chart/
locales-launch: Data of en_IN locale not found, generating, please wait...
deps-chart/
|-- Chart.lock
|-- Chart.yaml
|-- charts
|   `-- mariadb-9.8.1.tgz
|-- templates
|   |-- NOTES.txt
|   |-- _helpers.tpl
|   |-- deployment.yaml
|   |-- hpa.yaml
|   |-- ingress.yaml
|   |-- service.yaml
|   |-- serviceaccount.yaml
|   `-- tests
|       `-- test-connection.yaml
`-- values.yaml

rm -rf deps-chart/charts/

helm dependency build deps-chart/

Conditional Dependencies

Chart.yaml

dependencies:
  - name: mariadb
    condition: mariadb.enabled

values.yaml

mariadb:
  enabled: true

helm dependency update examples/condition-example/

kubectl create ns conditional

helm install conditional-chart examples/condition-example/ -n conditional

helm get manifest conditional-chart -n conditional | grep mariadb
  name: conditional-chart-mariadb
  ...

Disabling mariadb.enabled flag

helm upgrade conditional-chart examples/condition-example/ -n conditonal --set mariadb.enabled=false
helm get manifest conditional-chart -n conditonal | grep mariadb
...

Tags based dependencies

Chart.yaml

dependencies:
  - name: mariadb
    repository: https://raw.githubusercontent.com/bitnami/charts/archive-full-index/bitnami
    version: 9.5.0
    tags:
      - backend
      - database
  - name: memcached
    repository: https://raw.githubusercontent.com/bitnami/charts/archive-full-index/bitnami
    version: 5.15.6
    tags:
      - backend
      - cache

tags:
  backend: true

helm dependency build examples/tags-example/

helm upgrade conditional-chart examples/tags-example/ -n conditonal

helm get manifest conditional-chart -n conditonal | grep 'mariadb\|memcached'
  name: conditional-chart-mariadb
  ...
  name: conditional-chart-memcached
  ...

To only include database, set --set tags.backend=false --set tags.database=true

helm upgrade conditional-chart examples/tags-example/ -n conditonal --set tags.backend=false --set tags.database=true

When both conditional and tags are used, then conditional override tags.

Overriding Dependencies names and values

Dependency mentioned in Chart.yaml:

dependencies:
  - name: mariadb
    repository: https://raw.githubusercontent.com/bitnami/charts/archive-full-index/bitnami 
    version: 9.5.0

Overriding mariadb in values.yaml:

mariadb:
  image:
    registry: <diff-registry>
    repository: <diff-repository>
    tag: <another-tag>

Dependencies Alias

Here, with the help of alais we can deploy multiple instances of mariadb with same parameters.
This way, we can also install multiple mariadb instance of different version.

dependencies:
  - name: mariadb
    repository: https://raw.githubusercontent.com/bitnami/charts/archive-full-index/bitnami
    version: 9.5.0
    alias: db1
  - name: mariadb
    repository: https://raw.githubusercontent.com/bitnami/charts/archive-full-index/bitnami
    version: 9.5.0
    alias: db2

import-values

Application chart

exports:
  image:
    registry: my-registry
    repository: my-repository
    tag: my-tag

Dependency chart

dependencies:
  - name: dependency
    repository: http://localhost:8080
    version: 1.0.0
    import-values:
      - image

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