/k8s-manifest-generator

k8s-manifest-generator — detailed patterns and worked examples

Step-by-Step Workflow

1. Gather Requirements

Understand the workload:

• Application type (stateless/stateful)
• Container image and version
• Environment variables and configuration needs
• Storage requirements
• Network exposure requirements (internal/external)
• Resource requirements (CPU, memory)
• Scaling requirements
• Health check endpoints

Questions to ask:

• What is the application name and purpose?
• What container image and tag will be used?
• Does the application need persistent storage?
• What ports does the application expose?
• Are there any secrets or configuration files needed?
• What are the CPU and memory requirements?
• Does the application need to be exposed externally?

2. Create Deployment Manifest

Follow this structure:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: <app-name>
  namespace: <namespace>
  labels:
    app: <app-name>
    version: <version>
spec:
  replicas: 3
  selector:
    matchLabels:
      app: <app-name>
  template:
    metadata:
      labels:
        app: <app-name>
        version: <version>
    spec:
      containers:
        - name: <container-name>
          image: <image>:<tag>
          ports:
            - containerPort: <port>
              name: http
          resources:
            requests:
              memory: "256Mi"
              cpu: "250m"
            limits:
              memory: "512Mi"
              cpu: "500m"
          livenessProbe:
            httpGet:
              path: /health
              port: http
            initialDelaySeconds: 30
            periodSeconds: 10
          readinessProbe:
            httpGet:
              path: /ready
              port: http
            initialDelaySeconds: 5
            periodSeconds: 5
          env:
            - name: ENV_VAR
              value: "value"
          envFrom:
            - configMapRef:
                name: <app-name>-config
            - secretRef:
                name: <app-name>-secret

Best practices to apply:

• Always set resource requests and limits
• Implement both liveness and readiness probes
• Use specific image tags (never :latest)
• Apply security context for non-root users
• Use labels for organization and selection
• Set appropriate replica count based on availability needs

Reference: See references/deployment-spec.md for detailed deployment options

3. Create Service Manifest

Choose the appropriate Service type:

ClusterIP (internal only):

apiVersion: v1
kind: Service
metadata:
  name: <app-name>
  namespace: <namespace>
  labels:
    app: <app-name>
spec:
  type: ClusterIP
  selector:
    app: <app-name>
  ports:
    - name: http
      port: 80
      targetPort: 8080
      protocol: TCP

LoadBalancer (external access):

apiVersion: v1
kind: Service
metadata:
  name: <app-name>
  namespace: <namespace>
  labels:
    app: <app-name>
  annotations:
    service.beta.kubernetes.io/aws-load-balancer-type: nlb
spec:
  type: LoadBalancer
  selector:
    app: <app-name>
  ports:
    - name: http
      port: 80
      targetPort: 8080
      protocol: TCP

Reference: See references/service-spec.md for service types and networking

4. Create ConfigMap

For application configuration:

apiVersion: v1
kind: ConfigMap
metadata:
  name: <app-name>-config
  namespace: <namespace>
data:
  APP_MODE: production
  LOG_LEVEL: info
  DATABASE_HOST: db.example.com
  # For config files
  app.properties: |
    server.port=8080
    server.host=0.0.0.0
    logging.level=INFO

Best practices:

• Use ConfigMaps for non-sensitive data only
• Organize related configuration together
• Use meaningful names for keys
• Consider using one ConfigMap per component
• Version ConfigMaps when making changes

Reference: See assets/configmap-template.yaml for examples

5. Create Secret

For sensitive data:

apiVersion: v1
kind: Secret
metadata:
  name: <app-name>-secret
  namespace: <namespace>
type: Opaque
stringData:
  DATABASE_PASSWORD: "changeme"
  API_KEY: "secret-api-key"
  # For certificate files
  tls.crt: |
    -----BEGIN CERTIFICATE-----
    ...
    -----END CERTIFICATE-----
  tls.key: |
    -----BEGIN PRIVATE KEY-----
    ...
    -----END PRIVATE KEY-----

Security considerations:

• Never commit secrets to Git in plain text
• Use Sealed Secrets, External Secrets Operator, or Vault
• Rotate secrets regularly
• Use RBAC to limit secret access
• Consider using Secret type: kubernetes.io/tls for TLS secrets

6. Create PersistentVolumeClaim (if needed)

For stateful applications:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: <app-name>-data
  namespace: <namespace>
spec:
  accessModes:
    - ReadWriteOnce
  storageClassName: gp3
  resources:
    requests:
      storage: 10Gi

Mount in Deployment:

spec:
  template:
    spec:
      containers:
        - name: app
          volumeMounts:
            - name: data
              mountPath: /var/lib/app
      volumes:
        - name: data
          persistentVolumeClaim:
            claimName: <app-name>-data

Storage considerations:

• Choose appropriate StorageClass for performance needs
• Use ReadWriteOnce for single-pod access
• Use ReadWriteMany for multi-pod shared storage
• Consider backup strategies
• Set appropriate retention policies

7. Apply Security Best Practices

Add security context to Deployment:

spec:
  template:
    spec:
      securityContext:
        runAsNonRoot: true
        runAsUser: 1000
        fsGroup: 1000
        seccompProfile:
          type: RuntimeDefault
      containers:
        - name: app
          securityContext:
            allowPrivilegeEscalation: false
            readOnlyRootFilesystem: true
            capabilities:
              drop:
                - ALL

Security checklist:

• Run as non-root user
• Drop all capabilities
• Use read-only root filesystem
• Disable privilege escalation
• Set seccomp profile
• Use Pod Security Standards

8. Add Labels and Annotations

Standard labels (recommended):

metadata:
  labels:
    app.kubernetes.io/name: <app-name>
    app.kubernetes.io/instance: <instance-name>
    app.kubernetes.io/version: "1.0.0"
    app.kubernetes.io/component: backend
    app.kubernetes.io/part-of: <system-name>
    app.kubernetes.io/managed-by: kubectl

Useful annotations:

metadata:
  annotations:
    description: "Application description"
    contact: "team@example.com"
    prometheus.io/scrape: "true"
    prometheus.io/port: "9090"
    prometheus.io/path: "/metrics"

9. Organize Multi-Resource Manifests

File organization options:

Option 1: Single file with --- separator

# app-name.yaml
---
apiVersion: v1
kind: ConfigMap
...
---
apiVersion: v1
kind: Secret
...
---
apiVersion: apps/v1
kind: Deployment
...
---
apiVersion: v1
kind: Service
...

Option 2: Separate files

manifests/
├── configmap.yaml
├── secret.yaml
├── deployment.yaml
├── service.yaml
└── pvc.yaml

Option 3: Kustomize structure

base/
├── kustomization.yaml
├── deployment.yaml
├── service.yaml
└── configmap.yaml
overlays/
├── dev/
│   └── kustomization.yaml
└── prod/
    └── kustomization.yaml

10. Validate and Test

Validation steps:

# Dry-run validation
kubectl apply -f manifest.yaml --dry-run=client

# Server-side validation
kubectl apply -f manifest.yaml --dry-run=server

# Validate with kubeval
kubeval manifest.yaml

# Validate with kube-score
kube-score score manifest.yaml

# Check with kube-linter
kube-linter lint manifest.yaml

Testing checklist:

• Manifest passes dry-run validation
• All required fields are present
• Resource limits are reasonable
• Health checks are configured
• Security context is set
• Labels follow conventions
• Namespace exists or is created

Common Patterns

Pattern 1: Simple Stateless Web Application

Use case: Standard web API or microservice

Components needed:

• Deployment (3 replicas for HA)
• ClusterIP Service
• ConfigMap for configuration
• Secret for API keys
• HorizontalPodAutoscaler (optional)

Reference: See assets/deployment-template.yaml

Pattern 2: Stateful Database Application

Use case: Database or persistent storage application

Components needed:

• StatefulSet (not Deployment)
• Headless Service
• PersistentVolumeClaim template
• ConfigMap for DB configuration
• Secret for credentials

Pattern 3: Background Job or Cron

Use case: Scheduled tasks or batch processing

Components needed:

• CronJob or Job
• ConfigMap for job parameters
• Secret for credentials
• ServiceAccount with RBAC

Pattern 4: Multi-Container Pod

Use case: Application with sidecar containers

Components needed:

• Deployment with multiple containers
• Shared volumes between containers
• Init containers for setup
• Service (if needed)

Templates

The following templates are available in the assets/ directory:

• deployment-template.yaml - Standard deployment with best practices
• service-template.yaml - Service configurations (ClusterIP, LoadBalancer, NodePort)
• configmap-template.yaml - ConfigMap examples with different data types
• secret-template.yaml - Secret examples (to be generated, not committed)
• pvc-template.yaml - PersistentVolumeClaim templates

Reference Documentation

• references/deployment-spec.md - Detailed Deployment specification
• references/service-spec.md - Service types and networking details