Multi-environments

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Table of Contents

1. Management strategies
2. Promotion between environments
3. Kustomize for multi-env
4. Helm for multi-env
5. ApplicationSet (ArgoCD)
6. Hands-on exercises

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1 - Management strategies

Typical environments

Strategy 1: Branch per environment

main         → Production
staging      → Staging  
develop      → Development

# ArgoCD - Application par branche
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp-prod
spec:
  source:
    targetRevision: main  # Branche
---
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp-staging
spec:
  source:
    targetRevision: staging

Strategy 2: Directory per environment

gitops-repo/
├── apps/myapp/
│   ├── base/
│   └── overlays/
│       ├── dev/
│       ├── staging/
│       └── prod/

# Applications ciblant différents dossiers
spec:
  source:
    path: apps/myapp/overlays/prod

Strategy 3: Repo per environment

org/gitops-dev
org/gitops-staging
org/gitops-prod

Comparison

Strategy	Pros	Cons
Branch	Simple, PR for promotion	Merge conflicts
Directory	Atomic commits, unified view	Duplication
Repo	Total isolation, permissions	Fragmentation

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2 - Promotion between environments

Promotion workflow

Manual promotion (PR)

# 1. Tester en staging
git checkout staging
git merge develop
git push

# 2. Vérifier le déploiement staging

# 3. Promouvoir en production
git checkout main
git merge staging
git push

Automatic promotion (Image Automation)

# Flux Image Automation
apiVersion: image.toolkit.fluxcd.io/v1beta1
kind: ImagePolicy
metadata:
  name: myapp
spec:
  imageRepositoryRef:
    name: myapp
  policy:
    semver:
      range: 1.x.x

---
apiVersion: image.toolkit.fluxcd.io/v1beta1
kind: ImageUpdateAutomation
metadata:
  name: myapp
spec:
  git:
    checkout:
      ref:
        branch: main
    commit:
      author:
        email: [email protected]
        name: Flux
      messageTemplate: 'Update {{.AutomationObject.Name}}'
  update:
    path: ./apps/myapp

Gates and Approvals

# ArgoCD Sync Waves
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  annotations:
    argocd.argoproj.io/sync-wave: "1"  # Ordre de sync

# Flux - Dépendance entre Kustomizations
apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
  name: apps
spec:
  dependsOn:
    - name: infrastructure  # Déployer infra d'abord

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---

3 - Kustomize for multi-env

Structure

apps/myapp/
├── base/
│   ├── kustomization.yaml
│   ├── deployment.yaml
│   ├── service.yaml
│   └── configmap.yaml
└── overlays/
    ├── dev/
    │   ├── kustomization.yaml
    │   ├── namespace.yaml
    │   └── replicas-patch.yaml
    ├── staging/
    │   ├── kustomization.yaml
    │   ├── namespace.yaml
    │   └── replicas-patch.yaml
    └── prod/
        ├── kustomization.yaml
        ├── namespace.yaml
        ├── replicas-patch.yaml
        ├── resources-patch.yaml
        └── hpa.yaml

Common base

# base/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
  - deployment.yaml
  - service.yaml
  - configmap.yaml

commonLabels:
  app: myapp

# base/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
spec:
  replicas: 1
  template:
    spec:
      containers:
        - name: myapp
          image: myapp:latest
          env:
            - name: LOG_LEVEL
              value: info
          resources:
            requests:
              memory: "64Mi"
              cpu: "50m"

Dev Overlay

# overlays/dev/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

namespace: dev

resources:
  - ../../base
  - namespace.yaml

patches:
  - path: replicas-patch.yaml

images:
  - name: myapp
    newTag: dev-latest

configMapGenerator:
  - name: myapp-config
    behavior: merge
    literals:
      - LOG_LEVEL=debug

Prod Overlay

# overlays/prod/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

namespace: production

resources:
  - ../../base
  - namespace.yaml
  - hpa.yaml

patches:
  - path: replicas-patch.yaml
  - path: resources-patch.yaml

images:
  - name: myapp
    newTag: v1.2.3

configMapGenerator:
  - name: myapp-config
    behavior: merge
    literals:
      - LOG_LEVEL=warn

# overlays/prod/replicas-patch.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
spec:
  replicas: 5

# overlays/prod/resources-patch.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
spec:
  template:
    spec:
      containers:
        - name: myapp
          resources:
            requests:
              memory: "512Mi"
              cpu: "500m"
            limits:
              memory: "1Gi"
              cpu: "1"

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---

4 - Helm for multi-env

Values files structure

apps/myapp/
├── Chart.yaml
├── values.yaml           # Base
├── values-dev.yaml
├── values-staging.yaml
└── values-prod.yaml

values.yaml (base)

replicaCount: 1

image:
  repository: myapp
  tag: latest

resources:
  requests:
    memory: 64Mi
    cpu: 50m

config:
  logLevel: info

values-prod.yaml

replicaCount: 5

image:
  tag: v1.2.3

resources:
  requests:
    memory: 512Mi
    cpu: 500m
  limits:
    memory: 1Gi
    cpu: 1

config:
  logLevel: warn

autoscaling:
  enabled: true
  minReplicas: 3
  maxReplicas: 10

ArgoCD with Helm

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp-prod
spec:
  source:
    repoURL: https://github.com/org/gitops-repo
    path: apps/myapp
    helm:
      valueFiles:
        - values.yaml
        - values-prod.yaml  # Override

Flux with Helm

apiVersion: helm.toolkit.fluxcd.io/v2beta1
kind: HelmRelease
metadata:
  name: myapp
  namespace: production
spec:
  chart:
    spec:
      chart: ./apps/myapp
      sourceRef:
        kind: GitRepository
        name: gitops-repo
  values:
    replicaCount: 5
    image:
      tag: v1.2.3

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---

5 - ApplicationSet (ArgoCD)

Concept

ApplicationSet automatically generates ArgoCD Applications.

List Generator

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: myapp
spec:
  generators:
    - list:
        elements:
          - env: dev
            namespace: dev
            replicas: "1"
          - env: staging
            namespace: staging
            replicas: "2"
          - env: prod
            namespace: production
            replicas: "5"
  template:
    metadata:
      name: 'myapp-{{env}}'
    spec:
      project: default
      source:
        repoURL: https://github.com/org/gitops-repo
        path: 'apps/myapp/overlays/{{env}}'
      destination:
        server: https://kubernetes.default.svc
        namespace: '{{namespace}}'
      syncPolicy:
        automated:
          prune: true

Git Generator

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: myapp-envs
spec:
  generators:
    - git:
        repoURL: https://github.com/org/gitops-repo
        revision: HEAD
        directories:
          - path: apps/myapp/overlays/*
  template:
    metadata:
      name: 'myapp-{{path.basename}}'
    spec:
      source:
        path: '{{path}}'
      destination:
        namespace: '{{path.basename}}'

Cluster Generator (Multi-cluster)

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: myapp-clusters
spec:
  generators:
    - clusters:
        selector:
          matchLabels:
            env: production
  template:
    metadata:
      name: 'myapp-{{name}}'
    spec:
      destination:
        server: '{{server}}'
        namespace: production

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6 - Hands-on exercises

Quiz

Q1. Which strategy avoids merge conflicts?

Answer

Directory per environment because all environments are on the same branch (main). Changes are isolated in different folders.

Q2. How to deploy the same app to 3 clusters with ArgoCD?

Answer

Use an ApplicationSet with a Cluster Generator:

generators:
  - clusters:
      selector:
        matchLabels:
          env: production

Exercise: Multi-env configuration

Create the Kustomize overlays for dev and prod with these differences:

Aspect	Dev	Prod
Replicas	1	5
Memory	128Mi	1Gi
Log level	debug	warn

Solution

# overlays/dev/kustomization.yaml
namespace: dev
resources:
  - ../../base
configMapGenerator:
  - name: config
    literals:
      - LOG_LEVEL=debug

# overlays/prod/kustomization.yaml
namespace: prod
resources:
  - ../../base
patches:
  - path: deployment-patch.yaml
configMapGenerator:
  - name: config
    literals:
      - LOG_LEVEL=warn

# overlays/prod/deployment-patch.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
spec:
  replicas: 5
  template:
    spec:
      containers:
        - name: myapp
          resources:
            requests:
              memory: 1Gi

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Key takeaways

• 3 strategies: Branch, Directory, Repo per env
• Directory avoids merge conflicts
• Promotion via PR or automatic (Image Automation)
• Kustomize: base + overlays
• Helm: values files per environment
• ApplicationSet: automatic multi-env generation

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