[ArgoCD] ApplicationSetコントローラー深層分析

ApplicationSet Controller
    |
    +-- Generator: Applicationリスト生成のためのデータソース
    |
    +-- Template: Applicationリソースのテンプレート
    |
    +-- Sync Policy: Application作成/削除/更新ポリシー

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: my-appset
  namespace: argocd
spec:
  generators:
    - list:
        elements:
          - cluster: staging
            url: https://staging.example.com
          - cluster: production
            url: https://production.example.com
  template:
    metadata:
      name: 'myapp-{{cluster}}'
    spec:
      project: default
      source:
        repoURL: https://github.com/org/myapp.git
        targetRevision: HEAD
        path: 'overlays/{{cluster}}'
      destination:
        server: '{{url}}'
        namespace: myapp

spec:
  generators:
    - list:
        elements:
          - cluster: staging
            url: https://staging.example.com
            revision: develop
          - cluster: production
            url: https://production.example.com
            revision: main

spec:
  generators:
    - clusters:
        selector:
          matchLabels:
            env: production
            region: ap-northeast-2

spec:
  generators:
    - git:
        repoURL: https://github.com/org/gitops-config.git
        revision: HEAD
        directories:
          - path: apps/*
          - path: apps/excluded-app
            exclude: true

spec:
  generators:
    - git:
        repoURL: https://github.com/org/gitops-config.git
        revision: HEAD
        files:
          - path: 'clusters/*/config.json'

{
  "cluster": {
    "name": "production-east",
    "server": "https://prod-east.example.com",
    "environment": "production",
    "region": "us-east-1"
  }
}

spec:
  generators:
    - matrix:
        generators:
          - clusters:
              selector:
                matchLabels:
                  env: production
          - git:
              repoURL: https://github.com/org/apps.git
              revision: HEAD
              directories:
                - path: apps/*

spec:
  generators:
    - merge:
        mergeKeys:
          - server
        generators:
          - clusters:
              values:
                replicas: '3'
                env: default
          - list:
              elements:
                - server: https://production.example.com
                  values.replicas: '5'
                  values.env: production

spec:
  generators:
    - pullRequest:
        github:
          owner: myorg
          repo: myapp
          labels:
            - preview
        requeueAfterSeconds: 60
  template:
    metadata:
      name: 'preview-{{branch}}-{{number}}'
    spec:
      source:
        repoURL: https://github.com/myorg/myapp.git
        targetRevision: '{{head_sha}}'
        path: deploy/preview
      destination:
        server: https://kubernetes.default.svc
        namespace: 'preview-{{number}}'

spec:
  generators:
    - scmProvider:
        github:
          organization: myorg
          allBranches: false
        filters:
          - repositoryMatch: '^gitops-.*'
            pathsExist:
              - deploy/kustomization.yaml

template:
  metadata:
    name: 'app-{{cluster}}-{{path.basename}}'
  spec:
    source:
      repoURL: '{{url}}'
      path: '{{path}}'
    destination:
      server: '{{server}}'

spec:
  goTemplate: true
  goTemplateOptions: ['missingkey=error']
  template:
    metadata:
      name: 'app-{{ .cluster | lower }}'
    spec:
      source:
        path: '{{ if eq .env "production" }}overlays/prod{{ else }}overlays/dev{{ end }}'

spec:
  strategy:
    type: RollingSync
    rollingSync:
      steps:
        - matchExpressions:
            - key: env
              operator: In
              values:
                - staging
          maxUpdate: 100%
        - matchExpressions:
            - key: env
              operator: In
              values:
                - production
          maxUpdate: 25%

Step 1: stagingラベルのすべてのApplicationを同期
  -> すべてがHealthyになるまで待機

Step 2: productionラベルのApplicationの25%のみ同期
  -> Healthy確認後、次の25%に進む
  -> すべてのproduction Applicationが完了するまで繰り返し

ループ：
  1. すべてのApplicationSetリソースを監視（Informer）
  2. 各ApplicationSetに対して：
     a. Generatorを実行してパラメータセットを生成
     b. テンプレートをレンダリングして望ましいApplicationリストを生成
     c. 現在存在するApplicationリストを照会
     d. 比較して：
        - 新規追加するApplicationを作成
        - 変更されたApplicationを更新
        - 削除対象のApplicationを削除（ポリシーに従って）
  3. requeueAfterSeconds後に再実行

spec:
  syncPolicy:
    preserveResourcesOnDeletion: true # ApplicationSet削除時もApplicationを維持

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: platform-services
  namespace: argocd
spec:
  generators:
    - matrix:
        generators:
          - clusters:
              selector:
                matchLabels:
                  tier: production
          - git:
              repoURL: https://github.com/org/platform.git
              revision: HEAD
              directories:
                - path: services/*
  template:
    metadata:
      name: '{{name}}-{{path.basename}}'
    spec:
      project: platform
      source:
        repoURL: https://github.com/org/platform.git
        targetRevision: HEAD
        path: '{{path}}'
      destination:
        server: '{{server}}'
        namespace: '{{path.basename}}'
      syncPolicy:
        automated:
          prune: true
          selfHeal: true
        syncOptions:
          - CreateNamespace=true

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: preview-envs
  namespace: argocd
spec:
  generators:
    - pullRequest:
        github:
          owner: myorg
          repo: myapp
          labels:
            - deploy-preview
        requeueAfterSeconds: 30
  template:
    metadata:
      name: 'preview-{{number}}'
    spec:
      project: previews
      source:
        repoURL: https://github.com/myorg/myapp.git
        targetRevision: '{{head_sha}}'
        path: deploy/preview
        helm:
          parameters:
            - name: ingress.host
              value: 'pr-{{number}}.preview.example.com'
            - name: image.tag
              value: '{{head_short_sha}}'
      destination:
        server: https://kubernetes.default.svc
        namespace: 'preview-{{number}}'
      syncPolicy:
        automated:
          prune: true
          selfHeal: true
        syncOptions:
          - CreateNamespace=true

# ApplicationSetの状態確認
kubectl get applicationset -n argocd

# ApplicationSetの詳細情報確認
kubectl describe applicationset my-appset -n argocd

# ApplicationSet Controllerのログ確認
kubectl logs -n argocd deployment/argocd-applicationset-controller

# 生成されたApplicationの確認
argocd app list