Package Managers

What is a package manager?

Helm

• Helm is a configuration management tool for Kubernetes
• It uses a set of templates to allow customization of application configuration
• It is a CNCF project with a large community built around it
• Key Concepts:
• Helm chart is a bundle of information necessary to create an instance of a Kubernetes application.
• The chart contains configuration information that can be merged into a packaged chart to create a releasable object.
• A release is a running instance of a chart, combined with a specific config.

Helm Charts

• Application Packages are called Helm Charts
• A chart is a way to define an application
• File Structure:
• Chart.yaml: Author, version, description, image location
• values.yaml: default configuration values for chart
• templates: Templatized Kubernetes resources that will be paramterized at installation time.
• Helm CLI is available from GitHub or Homebrew

Helm Chart Structure

MyChart/
|── Chart.yaml                     #Required
|── LICENSE
|── values.yaml                    #Required
|── values.schema.json
|── charts/                        #Required
    └── dependent charts
|── crds/
    └── needed crds
└── templates/                     #Required
    |── deployment.yaml
    |── ingress.yaml
    |── service.yaml
    |── NOTES.txt
    └── tests/
        └── test-connection.yaml

Example Helm Chart Files

Example values.yaml

# The istio profile to use
profile: default

# The hub to use for the image (note: the image is built as
hub: registryl.dsop.io/ironbank/opensource/istio

# The tag to use for the image
tag: 1.7.3
# The hostname to use for the default gateway
hostname: bigbang.dev

imagePullSecrets: []
# - private-registry

tls:
  credentialName: wildcard-cert
  mode: SIMPLE

Example tempalte file

apiVersion: install.istio.io/vlalpha1
kind: IstioOperator
metadata:
  name: istiocontrolplane
  namespace: {{ .Release. Namespace }}
spec:
  profile: {{ .Values.profile }}
  hub: {{ .Values.hub }}
  tag: {{ .Values.tag }}

  components:
    ingressGateways:
      - name: istio-ingressgateway
      namespace: {{ .Release.Namespace }}
      enabled: true
      k85:
        hpaSpec:
          minReplicas: {{ .Values.ingressGateway.minReplicas }}
          maxReplicas: {{ .Values.ingressGateway.maxReplicas }}
          metrics:
            - type: Resource
              resource:
                name: cpu
                targetAverageUtilization: 60
          scaleTargetRef:
            apiVersion: apps/v1
            kind: Development

How Big Bang uses Helm

• Helm can manage a charts lifecycle
• Flux can manage the chart lifecycle
• All Core Big Bang components are installed as Helm Charts

Kustomize

Kustomize is template free configuration customization for Kubernetes that allows you to reuse manifests across all of your environments (dev, stage, prod) and then overlay unique specifications for each.

• Kustomize has a CLI for managing kubernetes style objects in a declarative way
• It is built into kubectl natively
• You will declaratively define customizations to any file where needed
• This is done through overlay files that customize the base yaml configurations
• kustomize build .

Kustomize File Structure

hello-world/
|── base
| ├── deployment.yaml
| └── kustomization.yaml
└── overlays
    |── production
    | ├── replica_count.yaml
    | └── kustomization.yaml
    └── staging
      ├── replica_count.yaml
      └── kustomization.yaml

Kustomize File Rendering

Assuming the structure above, let’s see how kustomize combines base files and overlays to arrive at a materialized file. Assume the files below:

hello-world/base/deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-world
spec:
  replicas: 1
  selector:
    matchLabels:
      app: hello-world
  template:
    metadata:
      labels:
        app: hello-world
    spec:
      containers:
        - name: hello-world
      image: nginx
      resources:
        limits:
          memory: "128Mi"
          cpu: "500m"
      ports:
        - containerPort: 80

hello-world/base/kustomization.yaml

resources:
  - deployment.yaml

hello-world/overlays/staging/replica_cound.yaml

apiVersion: apps/v1
kind: Deployment
metatdata:
  name: hello-world
spec:
  replicas: 3

hello-world/base/kustomization.yaml

bases:
  - dep../../base
patches:
  - replica_count.yaml

The resultant output of running the following command, notice that the replicas spec has been updated to 3.

kustomize build hello-world/overlays/staging/

Will be the below:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-world
spec:
  replicas: 3
  selector:
    matchLabels:
      app: hello-world
  template:
    metadata:
      labels:
        app: hello-world
    spec:
      containers:
        - name: hello-world
      image: nginx
      resources:
        limits:
          memory: "128Mi"
          cpu: "500m"
      ports:
        - containerPort: 80

Additional Kustomize Features

• Name prefix
• Add a prefix to all resource names
• Common Labels
• Adds labels to all resources
• Common Annotations
• Adds annotations to all resources
• ConfigMap Generator
• Take a file and turns the contents into a configmap
• SOPS Secret Generator
• (Big Bang Enabled alpha plugin) Take a file and turns the contents into a Secret