How Helm, The Package Manager For Kubernetes, Works

Copyright © SUSE 2021
How Helm, The Package
Manager For Kubernetes,
Works
0 9 N O V E M BE R 2 0 2 1

Hi, I’m Matt Farina
• Helm Maintainer
• Work at SUSE on Rancher/Kubernetes
• Emeritus K8s SIG Apps / Architecture Chair
• @mattfarina

Q1 Q2 Q3 Q4
2015
Helm Started
Helm is started by Deis
October 2015
01
2016
Helm v2 Begins
Helm + Deployment
Manager Merged
January 2016
02
2017
Helm Growth
7 minor releases
and usage growth
2017
05
Helm v3
Discussion begins
Q4 2017
06
2018
08
CNCF + Helm
Helm became top level project
June 2018
07
Helm v3
V3.0.0 Released
November 2019
Q1 Q2 Q3 Q4
Q1 Q2 Q3 Q4
Q1 Q2 Q3 Q4
Q1 Q2 Q3 Q4
Helm v2
2.0.0 Released
November 2016
04
03
CNCF + K8s
Kubernetes joins the CNCF
March 2016
2019

Copyright © SUSE 2021 5
Operating System
Binaries Configuration
Package Manager
Configuration Manager

GNU Linux
ELF Binaries Config in /etc
zypper, apt, yum, etc
Chef, Puppet, Ansible, etc

Kubernetes
Images K8s Manifests
Helm
Helmfile, Flux Helm Operator, etc

Kubernetes Basics
Kubernetes API
Node Node Node Node Node Node

Kubernetes Is Declarative
Kubernetes API
Give me 3 instances
of my container (Deployment)
Instance Instance Instance

Kubernetes Remediation
Kubernetes API
Give me 3 instances
of my container (Deployment)
Instance Instance Instance

Namespace and Multi-tenancy
Kubernetes
Namespace Namespace Namespace

A Book On The API

WordPress
Deployment
Statefulset
Services
Secrets
Ingress
HPA

WordPress: More Than 500 Lines of YAML

Kubernetes
Chart
(package)
App Business Logic
Kubernetes Knowledge

Roles….
1. Application Operator – The Helm user who is installing, upgrading, and running
something (e.g., PostgreSQL) in Kubernetes
2. Application Distributor – Someone or an organization distributing an application (e.g.,
Percona distributing PostgreSQL)
3. Application Developer – Someone developing an application (e.g., a web app in
node.js)
4. Supporting Tool Developer – Those developing Helm plugins or tools that use Helm
(e.g., configuration managers)
5. Helm Developer – The developers of Helm itself
Not in scope for Helm…
• Cluster Administrators

What’s In A Chart?
Files and directories:
.helmignore
Chart.yaml
Chart.lock
charts/
crds/
templates/
values.schema.json
values.yaml
Like .gitignore but for packaged charts (optional)
Metadata and configuration
Where dependent charts are stored
Templates to generate Kubernetes manifests
JSON Schema for chart config (optional)
Chart default configuration
Custom Resource Definitions (optional)
Dependencies lock file

Chart.yaml
# Default properties in generated Chart.yaml file
apiVersion: v2
name: demo
description: A Helm chart for Kubernetes
type: application
version: 0.1.0
appVersion: "1.16.0”
# Some additional optional options
dependencies: []
maintainers: []
icon: https://example.com/img.svg
annotations: []

Chart.yaml – Dependencies
...
dependencies:
- name: mariadb
repository: https://charts.example.com
version: 2.x.x
- name: memcached
repository: https://charts.example.com
version: 1.x.x
...

Chart.yaml – More Metadata
...
keywords:
- application
- nodejs
maintainers:
- email: people@example.com
name: The team or person
annotations:
artifacthub.io/images: |
- name: img1
image: repo/img1:1.0.0
- name: img2
image: repo/img2:2.0.0
whitelisted: true
...

Templates
apiVersion: apps/v1
kind: Deployment
metadata:
name: {{ include "demo.fullname" . }}
labels:
{{- include "demo.labels" . | nindent 4 }}
spec:
{{- if not .Values.autoscaling.enabled }}
replicas: {{ .Values.replicaCount }}
{{- end }}
selector:
matchLabels:
{{- include "demo.selectorLabels" . | nindent 6 }}
template:
metadata:
{{- with .Values.podAnnotations }}
...
Start of template
of Deployment

Templates - _helpers.tpl
{{/*
Expand the name of the chart.
*/}}
{{- define "demo.name" -}}
{{- default .Chart.Name .Values.nameOverride | trunc 63 |
trimSuffix "-" }}
{{- end }}
{{/*
Create a default fully qualified app name.
We truncate at 63 chars because some Kubernetes name fields are
limited to this (by the DNS naming spec).
If release name contains chart name it will be used as a full
name.
*/}}
{{- define "demo.fullname" -}}
...
Templates starting
with _ are not
rendered and are
used for helper
functions

Templates - Notes
1. Get the application URL by running these commands:
{{- if .Values.ingress.enabled }}
{{- range $host := .Values.ingress.hosts }}
{{- range .paths }}
http{{ if $.Values.ingress.tls }}s{{ end }}://{{ $host.host
}}{{ .path }}
{{- end }}
{{- end }}
{{- else if contains "NodePort" .Values.service.type }}
export NODE_PORT=$(kubectl get --namespace {{
.Release.Namespace }} -o jsonpath="{.spec.ports[0].nodePort}"
services {{ include "demo.fullname" . }})
export NODE_IP=$(kubectl get nodes --namespace {{
.Release.Namespace }} -o
jsonpath="{.items[0].status.addresses[0].address}")
echo http://$NODE_IP:$NODE_PORT
...
NOTES.txt generates
post install/upgrade
notes to output

values.yaml
replicaCount: 1
image:
repository: nginx
pullPolicy: IfNotPresent
# Overrides the image tag whose default is the chart appVersion.
tag: ""
imagePullSecrets: []
nameOverride: ""
fullnameOverride: ""
serviceAccount:
# Specifies whether a service account should be created
create: true
# Annotations to add to the service account
annotations: {}
...

Three Places Helm Works With Charts In
1. Filesystem
2.Helm Repository
3.OCI Registry (experiment)

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

2. Helm Registry
.
├── demo-0.1.0.tgz
├── demo-0.2.0.tgz
├── demo-1.0.0.tgz
├── demo-a-0.1.0.tgz
├── demo-a-1.0.0.tgz
├── demo-b-0.1.0.tgz
├── demo-c-0.1.0.tgz
├── demo-c-1.0.0.tgz
├── demo-opt-0.1.0.tgz
├── example-service-a-0.1.0.tgz
├── example-service-b-1.0.0.tgz
├── fleet-0.3.500.tgz
├── fleet-crd-0.3.500.tgz
├── index.yaml
...
Charts as tgz files. Helm can generate these
for you.
Index listing all of the charts and their versions

index.yaml
apiVersion: v1
entries:
demo:
- apiVersion: v2
appVersion: 1.16.0
created: "2021-08-02T15:15:46.745833-04:00"
description: A Helm chart for Kubernetes
digest: 6a1e902ade5de0f4fdfa2746876b1de59c325377053bfad98b1a2d6004698010
name: demo
type: application
urls:
- demo-1.0.0.tgz
version: 1.0.0
...

3. OCI Registries (experimental)

Helm CLI – Add A Repository
$ helm repo add bitnami https://charts.bitnami.com/bitnami
"bitnami" has been added to your repositories
Short
Name
URL To The Repository
Commands

35
Helm CLI – Add
A Repository
$ helm install wordpress-rel bitnami/wordpress
NAME: wordpress-rel
LAST DEPLOYED: Thu Nov 4 14:09:14 2021
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None
CHART NAME: wordpress
CHART VERSION: 12.1.25
APP VERSION: 5.8.1
NOTES:
** Please be patient while the chart is being deployed **
Your WordPress site can be accessed through the following DNS
...
Release
Name
Chart To Install
Install It
Details on this install
Generated notes
from NOTES.txt
template

Kubernetes
Chart
(package)
Namespace
App Manifests Release
Secret

Helm CLI – Listing In Namespace
$ helm ls
NAME NAMESPACE REVISION UPDATED STATUS CHART APP VERSION
word default 1 2021-11-04 14:09:14.405292 -0400 EDT deployed wordpress-12.1.25 5.8.1

Custom Config Method 1
$ helm upgrade wordpress-rel bitnami/wordpress --set wordpressBlogName="Foo's Blog"
Release "wordpress-rel" has been upgraded. Happy Helming!
NAME: wordpress-rel
LAST DEPLOYED: Thu Nov 4 16:26:16 2021
NAMESPACE: default
STATUS: deployed
REVISION: 2
TEST SUITE: None
NOTES:
CHART NAME: wordpress
CHART VERSION: 12.1.25
...
Existing
Release
Chart To Use
Upgrading Set A Value
(--set can be repeated)

Custom Config Method 2
myvalues.yaml:
wordpressBlogName: "Bar's Blog"
$ helm upgrade wordpress-rel bitnami/wordpress –-values myvalues.yaml
Release "wordpress-rel" has been upgraded. Happy Helming!
...
Use A Config File
(-f/--values can be repeated)

❯ helm help
...
Available Commands:
completion generate autocompletion scripts for the specified shell
create create a new chart with the given name
dependency manage a chart's dependencies
env helm client environment information
get download extended information of a named release
help Help about any command
history fetch release history
install install a chart
lint examine a chart for possible issues
list list releases
package package a chart directory into a chart archive
plugin install, list, or uninstall Helm plugins
pull download a chart from a repository and (optionally) unpack it in local directory
repo add, list, remove, update, and index chart repositories
rollback roll back a release to a previous revision
search search for a keyword in charts
show show information of a chart
status display the status of the named release
template locally render templates
test run tests for a release
uninstall uninstall a release
upgrade upgrade a release
verify verify that a chart at the given path has been signed and is valid
version print the client version information

Helm CLI
Helm Client
Helm SDK
Actions
Repos
…
Kubernetes API
K8s Pkgs

Things Not Covered
• Hooks
• Custom Resource Definitions
• Signing and Provenance
• Helm Plugins
• Library Charts
• JSON Schema
• Release Records Stored Elsewhere
• Linting
• Testing

You can learn more at helm.sh
You can find me at mattfarina.com
Thanks For
Coming
45

Hooks – You Can Hook Into The Processes

Example Hook…
apiVersion: batch/v1
kind: Job
metadata:
name: "{{ .Release.Name }}"
labels:
app.kubernetes.io/managed-by: {{ .Release.Service | quote }}
app.kubernetes.io/instance: {{ .Release.Name | quote }}
app.kubernetes.io/version: {{ .Chart.AppVersion }}
helm.sh/chart: "{{ .Chart.Name }}-{{ .Chart.Version }}"
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
"helm.sh/hook-weight": "-5"
"helm.sh/hook-delete-policy": hook-succeeded
...

• View Releases
• Read Templates
• See Security Details
• Find maintainers
• Much more…
• Get Notifications of Updates
• Get Notifications of Sec Issues
• Add Your Own Repos
• Much more…

How Helm, The Package Manager For Kubernetes, Works

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