Kubernetes/Helm

Note: This content refers to helm3 as authored in April, 2020.

Install

LATEST=$(curl --silent "https://api.github.com/repos/helm/helm/releases/latest" | jq -r .tag_name)
curl -LO https://get.helm.sh/helm-${LATEST}-linux-amd64.tar.gz
tar xzvf helm-${LATEST}-linux-amd64.tar.gz
sudo install linux-amd64/helm /usr/local/bin/helm

Operations

Helm command

helm version --short # --> v3.1.3+g0a9a9a8
helm [command] -h    # get help create|env|get|history|install|lint|list|plugin|rollback|show|status|template|uninstall|upgrade
  # Flags:
  # --kube-context string -name of the kubeconfig context to use
  # --kubeconfig string -path to the kubeconfig file
  # -n, --namespace string

Operations

# Add repo
helm repo add stable https://kubernetes-charts.storage.googleapis.com/
helm repo update                           # Make sure we get the latest list of charts

helm search repo stable/jenkins

# Set kubectl context
# Helm3 bug:does may not respect '--namespace' flag, so set default namespace
kubectl create ns jenkins
kubectl config set-context $(kubectl config current-context) --namespace=jenkins

# Install release
helm install [NAME]     [CHART]        [flags]
helm install jenkins-ci stable/jenkins                                    # release name: jenkins-ci
helm install jenkins-ci ./jenkins-2.192.1.tgz --set service.type=NodePort # install from a tarball package
helm install stable/mysql   --generate-name # release name will be generated

# Get information about releases
helm ls -A                                  # show a list of all deployed releases -A --all-namespaces
NAME       NAMESPACE REVISION UPDATED          STATUS   CHART          APP VERSION
jenkins-ci jenkins   1        2020-04-25 15:.. deployed jenkins-1.17.2 lts 

helm get all -n jenkins jenkins-ci # all|hooks|manifest|notes|values(user defined values)

# Uninstall release
helm uninstall jenkins-ci --namespace jenkins

Rollback

$> helm rollback <RELEASE> [REVISION] [flags]
$> helm rollback diy       2          --dry-run # <RELEASE> = diy
$> time helm rollback diy 2 --wait
    # --wait until all Pods, PVCs... are in a ready state before marking the release as successful. 
    # It will wait for as long as --timeout

# Note: Each rollback increments REVISION with +1
$> helm history diy
REVISION  UPDATED                   STATUS      CHART     APP VERSION DESCRIPTION
1         Mon Apr 27 10:39:38 2020  superseded  diy-0.1.0 6.4.2       Install complete
2         Mon Apr 27 12:24:54 2020  superseded  diy-0.1.0 6.4.2       Upgrade complete
3         Mon Apr 27 16:22:34 2020  superseded  diy-0.1.0 6.4.2       Upgrade complete
4         Mon Apr 27 16:35:31 2020  deployed    diy-0.1.0 6.4.2       Rollback to 2

Jenkins chart post install instructions or get notes commands

helm get notes -n jenkins jenkins-ci

NAME: jenkins-ci
LAST DEPLOYED: Sat Apr 25 15:33:36 2020
NAMESPACE: jenkins
STATUS: deployed
REVISION: 1
NOTES:
1. Get your 'admin' user password by running:
  printf $(kubectl get secret --namespace jenkins jenkins-ci -o jsonpath="{.data.jenkins-admin-password}" | base64 --decode);echo
2. Get the Jenkins URL to visit by running these commands in the same shell:
  export POD_NAME=$(kubectl get pods --namespace jenkins -l "app.kubernetes.io/component=jenkins-master" -l "app.kubernetes.io/instance=jenkins-ci" -o jsonpath="{.items[0].metadata.name}")
  echo http://127.0.0.1:8080
  kubectl --namespace jenkins port-forward $POD_NAME 8080:8080

3. Login with the password from step 1 and the username: admin


For more information on running Jenkins on Kubernetes, visit:
https://cloud.google.com/solutions/jenkins-on-container-engine

Create a chart

Note: Check The chart file structure as the helm create NAME does not include all optional files you may use

helm version --short # -> v3.1.3+g0a9a9a8

helm create diy # diy = [NAME] # this creates standard file tree not all optional files are included
$> tree diy
diy
├── charts    # any charts upon which this chart depends
├── Chart.yaml
├── templates # no rigid naming pattern, recommended .yaml for YAML files and .tpl for helper
|   |         # all files here will be sent through the template engine
│   ├── deployment.yaml
│   ├── _helpers.tpl       # template helpers that you can re-use throughout the chart
│   ├── ingress.yaml
│   ├── NOTES.txt          # Optional. “help text” for your chart, displayed after installation
│   ├── serviceaccount.yaml
│   ├── service.yaml
│   └── tests
│       └── test-connection.yaml
└── values.yaml  # default configuration values for this chart

helm template diy | bat -l yaml --style=plain # display rendered yaml manifests

kubectl create ns diy
helm install ./diy --generate-name -n diy   # Generated name
  #                                       ____NAME______
  # podName       :                   pod/diy-1587926286-866d97bb75-vskns
  # serviceName   :               service/diy-1587926286
  # deploymentName: deployment.extensions/diy-1587926286
  # NAME                                          TYPE
  # secret/sh.helm.release.v1.diy-1587926286.v1   helm.sh/release.v1

helm install foo ./diy -n diy               # Custom name
  #                                       _NAME__
  # podName       :                   pod/foo-diy-6fd79d9bbd-nh5hl
  # serviceName   :               service/foo-diy
  # deploymentName: deployment.extensions/foo-diy
  # NAME                                          TYPE
  # secret/sh.helm.release.v1.foo.v1              helm.sh/release.v1

helm list -n diy
NAME           NAMESPACE REVISION UPDATED             STATUS   CHART     APP VERSION
diy-1587926286 diy       1        2020-04-26 19:38... deployed diy-0.1.0 1.16.0     
foo            diy       1        2020-04-26 20:02... deployed diy-0.1.0 1.16.0

Template

Everything in templates/ goes through templating engine before being rendered. Basic template might look like below:

#            TEMPLATE                    --->            RENDER              --->            DEPLOYED
#                                                                             # helm install mychart ./mychart -n mychart
# cat templates/configmap.yaml             # helm template mychart/           # kubectl -n mychart get cm mychart-configmap -oyaml
| apiVersion: v1                           | apiVersion: v1                   | apiVersion: v1
| kind: ConfigMap                          | kind: ConfigMap                  | kind: ConfigMap
| metadata:                             -> | metadata:                    --> | metadata:
|   name: {{ .Release.Name }}-configmap    |   name: RELEASE-NAME-configmap   |   name: mychart-configmap
| data:                                    | data:                            | data:
|   myvalue: "Hello World Piotrek"         |   myvalue: "Hello World Piotrek" |   myvalue: Hello World Piotrek

Note: In kubectl get cm above creationTimestamp: and selfLink: data yaml keys have been not included for clarity of side-by-side comparison.

References

• Buildin objects helm.sh
• Best Practicies helm.sh
• Math Functions gohugo.io
• Go Template package golang.org

Text and spaces

Note: Details about whitespace control you can find in Flow Control in Controlling Whitespace section.

If an action's left delimiter (by default "{{") is followed immediately by a minus sign and ASCII space character ("{{- "), all trailing white space is trimmed from the immediately preceding text. Similarly, if the right delimiter ("}}") is preceded by a space and minus sign (" -}}"), all leading white space is trimmed from the immediately following text. In these trim markers, the ASCII space must be present; "{{-3}}" parses as an action containing the number -3.

For instance, when executing the template whose source is

"{{23 -}} < {{- 45}}"
// the generated output would be

"23<45"

For this trimming, the definition of white space characters is the same as in Go: space, horizontal tab, carriage return, and newline.

Package and push charts to OCI registry

• push-helm-charts-to-amazon-ecr
• Giving your Charts a Home in Docker Registry
• [ECR: Allow for alternate mediaTypes] AWS ECR

Known workarounds

Invalid spec selector after upgrading helm template

• Invalid spec selector after upgrading helm template StackOverflow

Steps to before upgrade without need of uninstalling charts:

$ kubectl delete statefulsets.apps --cascade=false my-release

# Edit the deployment:
kubectl patch deployments my-release --type=json -p='[{"op": "remove", "path": "/spec/selector/matchLabels/chart"}]'

Resources

• Using Helm Guide