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Reloader Stakater

Panduan lengkap instalasi dan penggunaan Stakater Reloader untuk automatic rolling restart pods ketika ConfigMap atau Secret berubah.

Pengenalan​

Stakater Reloader adalah Kubernetes controller yang memantau perubahan pada ConfigMap dan Secret, kemudian secara otomatis melakukan rolling restart pada Deployment, StatefulSet, DaemonSet, atau DeploymentConfig yang menggunakan resource tersebut.

Mengapa Reloader Diperlukan?​

Secara default, Kubernetes tidak otomatis restart pods ketika ConfigMap atau Secret yang mereka gunakan berubah. Ini dapat menyebabkan:

  • Aplikasi menggunakan konfigurasi lama
  • Inconsistency antara pods yang baru dan lama
  • Perlu manual restart untuk apply perubahan

Fitur Utama​

  • ✅ Auto-reload: Otomatis restart pods saat config berubah
  • ✅ Annotation-based: Kontrol granular per resource
  • ✅ Multi-resource: Support Deployment, StatefulSet, DaemonSet, dll
  • ✅ Flexible: Bisa monitor specific ConfigMap/Secret atau semua
  • ✅ Lightweight: Resource usage minimal
  • ✅ Production-ready: Digunakan oleh banyak perusahaan

Instalasi​

# Tambahkan Stakater Helm repository
helm repo add stakater https://stakater.github.io/stakater-charts
helm repo update

# Install Reloader
helm install reloader stakater/reloader \
  --namespace reloader \
  --create-namespace \
  --set reloader.watchGlobally=true

Metode 2: Kubectl dengan Manifest​

# Download dan apply manifest
kubectl apply -f https://raw.githubusercontent.com/stakater/Reloader/master/deployments/kubernetes/reloader.yaml

Metode 3: Kustomize​

Buat file kustomization.yaml:

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

namespace: reloader

resources:
  - https://github.com/stakater/Reloader/deployments/kubernetes

# Optional: customize
patchesStrategicMerge:
  - |-
    apiVersion: apps/v1
    kind: Deployment
    metadata:
      name: reloader-reloader
    spec:
      replicas: 2

Apply:

kubectl apply -k .

Verifikasi Instalasi​

# Check pods
kubectl get pods -n reloader

# Check logs
kubectl logs -n reloader -l app=reloader-reloader

# Expected output:
# time="..." level=info msg="Starting Reloader"
# time="..." level=info msg="Starting Controller"

Konfigurasi​

Helm Values Customization​

Buat file values.yaml:

reloader:
  # Monitor all namespaces
  watchGlobally: true
  
  # Ignore specific namespaces
  ignoreNamespaces: "kube-system,kube-public"
  
  # Ignore specific ConfigMaps/Secrets
  ignoreConfigMaps: "kube-root-ca.crt"
  ignoreSecrets: ""
  
  # Sync interval
  syncPeriod: "60s"
  
  # Log level: info, debug, warn, error
  logLevel: "info"
  
  # Resource limits
  resources:
    limits:
      cpu: 100m
      memory: 128Mi
    requests:
      cpu: 10m
      memory: 64Mi

# High availability
replicaCount: 2

# Pod disruption budget
podDisruptionBudget:
  enabled: true
  minAvailable: 1

Install dengan custom values:

helm install reloader stakater/reloader \
  --namespace reloader \
  --create-namespace \
  -f values.yaml

Cara Penggunaan​

1. Auto Reload Semua ConfigMaps/Secrets​

Tambahkan annotation reloader.stakater.com/auto: "true" pada Deployment:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
  annotations:
    reloader.stakater.com/auto: "true"
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: myapp
        image: myapp:1.0.0
        envFrom:
        - configMapRef:
            name: myapp-config
        - secretRef:
            name: myapp-secrets

Ketika myapp-config atau myapp-secrets berubah, Reloader akan otomatis rolling restart deployment.

2. Monitor Specific ConfigMap​

Tambahkan annotation dengan nama ConfigMap spesifik:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
  annotations:
    reloader.stakater.com/match: "true"
    configmap.reloader.stakater.com/reload: "myapp-config,shared-config"
spec:
  # ... rest of spec

3. Monitor Specific Secret​

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
  annotations:
    reloader.stakater.com/match: "true"
    secret.reloader.stakater.com/reload: "myapp-secrets,db-credentials"
spec:
  # ... rest of spec

4. Monitor Both ConfigMap dan Secret​

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
  annotations:
    reloader.stakater.com/match: "true"
    configmap.reloader.stakater.com/reload: "myapp-config"
    secret.reloader.stakater.com/reload: "myapp-secrets"
spec:
  # ... rest of spec

Contoh Lengkap​

Example 1: Web Application dengan ConfigMap​

ConfigMap:

apiVersion: v1
kind: ConfigMap
metadata:
  name: webapp-config
  namespace: production
data:
  app.conf: |
    server {
      listen 8080;
      server_name example.com;
    }
  LOG_LEVEL: "info"
  MAX_CONNECTIONS: "100"

Deployment:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: webapp
  namespace: production
  annotations:
    reloader.stakater.com/auto: "true"
spec:
  replicas: 3
  selector:
    matchLabels:
      app: webapp
  template:
    metadata:
      labels:
        app: webapp
    spec:
      containers:
      - name: webapp
        image: nginx:1.25-alpine
        ports:
        - containerPort: 8080
        env:
        - name: LOG_LEVEL
          valueFrom:
            configMapKeyRef:
              name: webapp-config
              key: LOG_LEVEL
        volumeMounts:
        - name: config
          mountPath: /etc/nginx/conf.d
      volumes:
      - name: config
        configMap:
          name: webapp-config

Update ConfigMap:

# Edit ConfigMap
kubectl edit configmap webapp-config -n production

# Atau update via file
kubectl apply -f webapp-config.yaml

# Reloader akan detect perubahan dan restart pods
kubectl get pods -n production -w

Example 2: Database Application dengan Secret​

Secret:

apiVersion: v1
kind: Secret
metadata:
  name: db-credentials
  namespace: production
type: Opaque
stringData:
  DB_HOST: "postgres.production.svc.cluster.local"
  DB_PORT: "5432"
  DB_USER: "appuser"
  DB_PASSWORD: "secure-password-here"
  DB_NAME: "myapp"

StatefulSet:

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: app-backend
  namespace: production
  annotations:
    secret.reloader.stakater.com/reload: "db-credentials"
spec:
  serviceName: app-backend
  replicas: 3
  selector:
    matchLabels:
      app: backend
  template:
    metadata:
      labels:
        app: backend
    spec:
      containers:
      - name: backend
        image: myapp/backend:2.0.0
        envFrom:
        - secretRef:
            name: db-credentials
        ports:
        - containerPort: 8080

Example 3: Multi-ConfigMap Setup​

apiVersion: apps/v1
kind: Deployment
metadata:
  name: microservice
  namespace: staging
  annotations:
    configmap.reloader.stakater.com/reload: "app-config,feature-flags,env-vars"
    secret.reloader.stakater.com/reload: "api-keys,db-creds"
spec:
  replicas: 2
  selector:
    matchLabels:
      app: microservice
  template:
    metadata:
      labels:
        app: microservice
    spec:
      containers:
      - name: api
        image: myapp/api:1.5.0
        envFrom:
        - configMapRef:
            name: app-config
        - configMapRef:
            name: feature-flags
        - configMapRef:
            name: env-vars
        - secretRef:
            name: api-keys
        - secretRef:
            name: db-creds

Advanced Usage​

Ignore Specific Resources​

Jika Anda ingin Reloader tidak memonitor resource tertentu:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: no-reload-app
  annotations:
    reloader.stakater.com/reload: "false"
spec:
  # ... spec

Custom Reload Strategy​

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
  annotations:
    reloader.stakater.com/auto: "true"
    # Tambahkan delay sebelum reload (dalam detik)
    reloader.stakater.com/reload-delay: "30"
spec:
  # ... spec

Search by Regex (Advanced)​

Monitor ConfigMaps/Secrets dengan pattern:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
  annotations:
    configmap.reloader.stakater.com/reload: "app-.*"  # Semua ConfigMap yang dimulai dengan "app-"
spec:
  # ... spec

Monitoring dan Troubleshooting​

Check Reloader Status​

# Lihat logs
kubectl logs -n reloader -l app=reloader-reloader --tail=100 -f

# Check events
kubectl get events -n reloader --sort-by='.lastTimestamp'

Debug Mode​

Enable debug logging:

helm upgrade reloader stakater/reloader \
  --namespace reloader \
  --set reloader.logLevel=debug \
  --reuse-values

Common Issues​

Issue 1: Pods tidak restart setelah ConfigMap berubah​

Penyebab:

  • Annotation salah atau tidak ada
  • Reloader tidak running
  • RBAC permissions kurang

Solusi:

# 1. Check annotation
kubectl get deployment myapp -o yaml | grep reloader

# 2. Check Reloader pods
kubectl get pods -n reloader

# 3. Check RBAC
kubectl auth can-i list configmaps --as=system:serviceaccount:reloader:reloader-reloader

Issue 2: Restart terlalu sering​

Penyebab: ConfigMap/Secret berubah terlalu sering

Solusi: Implementasikan reload delay atau gunakan specific matching:

annotations:
  configmap.reloader.stakater.com/reload: "production-config"  # Specific, bukan auto

Issue 3: Performance Impact​

Solusi: Limit namespaces yang dimonitor:

# values.yaml
reloader:
  watchGlobally: false
  namespaceSelector: "monitoring=enabled"

Label namespace yang ingin dimonitor:

kubectl label namespace production monitoring=enabled
kubectl label namespace staging monitoring=enabled

Metrics dan Monitoring​

Reloader expose Prometheus metrics:

apiVersion: v1
kind: Service
metadata:
  name: reloader-metrics
  namespace: reloader
  labels:
    app: reloader
spec:
  ports:
  - name: metrics
    port: 8080
    targetPort: 8080
  selector:
    app: reloader-reloader

ServiceMonitor (jika menggunakan Prometheus Operator):

apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  name: reloader
  namespace: reloader
spec:
  selector:
    matchLabels:
      app: reloader
  endpoints:
  - port: metrics
    interval: 30s

Key Metrics:

  • reloader_reload_executed_total: Total reload yang dieksekusi
  • reloader_reload_errors_total: Total reload errors
  • reloader_items_monitored: Jumlah resource yang dimonitor

Best Practices​

1. Use Specific Matching​

❌ Jangan (terlalu broad):

annotations:
  reloader.stakater.com/auto: "true"

✅ Gunakan (specific):

annotations:
  configmap.reloader.stakater.com/reload: "app-config"
  secret.reloader.stakater.com/reload: "db-credentials"

2. Label Your ConfigMaps/Secrets​

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
  labels:
    app: myapp
    managed-by: terraform
    reloader: enabled
data:
  # ... config

3. Version Your ConfigMaps​

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config-v2  # Versioning
  labels:
    app: myapp
    version: "v2"
data:
  # ... config

Update deployment untuk switch version:

envFrom:
- configMapRef:
    name: app-config-v2  # Update version

4. Use ConfigMap/Secret Checksums​

Alternative approach tanpa Reloader (manual):

spec:
  template:
    metadata:
      annotations:
        checksum/config: {{ include (print $.Template.BasePath "/configmap.yaml") . | sha256sum }}

5. Implement Health Checks​

Pastikan aplikasi Anda memiliki readiness/liveness probes:

spec:
  containers:
  - name: app
    livenessProbe:
      httpGet:
        path: /health
        port: 8080
      initialDelaySeconds: 30
      periodSeconds: 10
    readinessProbe:
      httpGet:
        path: /ready
        port: 8080
      initialDelaySeconds: 5
      periodSeconds: 5

6. Set Resource Limits​

# Deployment yang menggunakan Reloader
spec:
  template:
    spec:
      containers:
      - name: app
        resources:
          limits:
            cpu: 500m
            memory: 512Mi
          requests:
            cpu: 100m
            memory: 128Mi

7. PodDisruptionBudget​

Untuk mencegah downtime saat reload:

apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: myapp-pdb
  namespace: production
spec:
  minAvailable: 2
  selector:
    matchLabels:
      app: myapp

Integration dengan CI/CD​

GitOps Workflow​

# .gitea/workflows/deploy.yml
name: Deploy Application
on:
  push:
    branches: [main]

jobs:
  deploy:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      
      - name: Update ConfigMap
        run: |
          kubectl apply -f k8s/configmap.yaml
          # Reloader akan otomatis restart pods
      
      - name: Wait for rollout
        run: |
          kubectl rollout status deployment/myapp -n production

Helm Chart Integration​

# templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "myapp.fullname" . }}
  annotations:
    {{- if .Values.reloader.enabled }}
    reloader.stakater.com/auto: "true"
    {{- end }}
spec:
  # ... rest of template
# values.yaml
reloader:
  enabled: true
  watchConfigMaps: true
  watchSecrets: true

Uninstall​

# Helm
helm uninstall reloader -n reloader

# Kubectl
kubectl delete -f https://raw.githubusercontent.com/stakater/Reloader/master/deployments/kubernetes/reloader.yaml

# Delete namespace
kubectl delete namespace reloader

Kesimpulan​

Stakater Reloader adalah tool essential untuk automasi deployment di Kubernetes. Dengan Reloader, Anda tidak perlu lagi manual restart pods setiap kali ConfigMap atau Secret berubah.

Kapan Menggunakan Reloader?​

✅ Gunakan jika:

  • Sering update configuration
  • Butuh automatic restart
  • Ingin simplify operational workflow

❌ Pertimbangkan alternatif jika:

  • Hanya update config jarang
  • Prefer immutable deployments
  • Concern tentang unexpected restarts

Alternatif​

  • Immutable ConfigMaps: Buat ConfigMap baru dengan version, update Deployment
  • ConfigMap Reload in-app: Aplikasi watch dan reload config sendiri
  • Helm hooks: Restart via Helm upgrade hooks

Resources​