FastAPI Kubernetes Deployment

# FastAPI Docker & Kubernetes Deployment

This skill provides production-ready patterns for containerizing FastAPI applications and deploying to Kubernetes.

## Dockerfile (Multi-Stage)

### Production Dockerfile

```dockerfile
# Build stage
FROM python:3.11-slim as builder

WORKDIR /app

# Install build dependencies
RUN apt-get update && apt-get install -y --no-install-recommends \
    build-essential \
    && rm -rf /var/lib/apt/lists/*

# Install Python dependencies
COPY requirements.txt .
RUN pip wheel --no-cache-dir --no-deps --wheel-dir /app/wheels -r requirements.txt

# Production stage
FROM python:3.11-slim

WORKDIR /app

# Create non-root user
RUN groupadd -r appuser && useradd -r -g appuser appuser

# Copy wheels and install
COPY --from=builder /app/wheels /wheels
RUN pip install --no-cache /wheels/*

# Copy application
COPY ./app /app/app

# Change ownership
RUN chown -R appuser:appuser /app
USER appuser

# Health check
HEALTHCHECK --interval=30s --timeout=10s --start-period=5s --retries=3 \
    CMD python -c "import httpx; httpx.get('http://localhost:8000/health')" || exit 1

EXPOSE 8000

CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]
```

### Development Dockerfile

```dockerfile
FROM python:3.11-slim

WORKDIR /app

COPY requirements.txt requirements-dev.txt ./
RUN pip install -r requirements.txt -r requirements-dev.txt

COPY . .

CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000", "--reload"]
```

## Docker Compose (Development)

```yaml
version: '3.8'

services:
  api:
    build:
      context: .
      dockerfile: Dockerfile.dev
    ports:
      - "8000:8000"
    volumes:
      - ./app:/app/app
    environment:
      - MONGODB_URL=mongodb://mongo:27017
      - REDIS_URL=redis://redis:6379
      - KEYCLOAK_URL=http://keycloak:8080
    depends_on:
      - mongo
      - redis

  mongo:
    image: mongo:7
    ports:
      - "27017:27017"
    volumes:
      - mongo_data:/data/db

  redis:
    image: redis:7-alpine
    ports:
      - "6379:6379"

  keycloak:
    image: quay.io/keycloak/keycloak:23.0
    environment:
      - KEYCLOAK_ADMIN=admin
      - KEYCLOAK_ADMIN_PASSWORD=admin
    command: start-dev
    ports:
      - "8080:8080"

volumes:
  mongo_data:
```

## Health Check Endpoints

```python
from fastapi import APIRouter, Response
from typing import Dict
import asyncio

router = APIRouter(tags=["Health"])

@router.get("/health")
async def health_check() -> Dict[str, str]:
    """Basic liveness probe."""
    return {"status": "healthy"}

@router.get("/health/ready")
async def readiness_check(
    db: Database = Depends(get_db),
    cache: Redis = Depends(get_cache)
) -> Dict[str, any]:
    """Readiness probe - checks all dependencies."""
    checks = {}

    # Check MongoDB
    try:
        await db.command("ping")
        checks["mongodb"] = "ok"
    except Exception as e:
        checks["mongodb"] = f"error: {str(e)}"

    # Check Redis
    try:
        await cache.ping()
        checks["redis"] = "ok"
    except Exception as e:
        checks["redis"] = f"error: {str(e)}"

    # Overall status
    all_ok = all(v == "ok" for v in checks.values())

    if not all_ok:
        return Response(
            content=json.dumps({"status": "unhealthy", "checks": checks}),
            status_code=503,
            media_type="application/json"
        )

    return {"status": "healthy", "checks": checks}

@router.get("/health/live")
async def liveness_check() -> Dict[str, str]:
    """Kubernetes liveness probe."""
    return {"status": "alive"}
```

## Kubernetes Deployment

### Deployment Manifest

```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: fastapi-app
  labels:
    app: fastapi-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: fastapi-app
  template:
    metadata:
      labels:
        app: fastapi-app
    spec:
      containers:
        - name: api
          image: registry.example.com/fastapi-app:latest
          ports:
            - containerPort: 8000
          env:
            - name: MONGODB_URL
              valueFrom:
                secretKeyRef:
                  name: app-secrets
                  key: mongodb-url
            - name: REDIS_URL
              valueFrom:
                secretKeyRef:
                  name: app-secrets
                  key: redis-url
          resources:
            requests:
              memory: "256Mi"
              cpu: "250m"
            limits:
              memory: "512Mi"
              cpu: "500m"
          livenessProbe:
            httpGet:
              path: /health/live
              port: 8000
            initialDelaySeconds: 10
            periodSeconds: 10
          readinessProbe:
            httpGet:
              path: /health/ready
              port: 8000
            initialDelaySeconds: 5
            periodSeconds: 5
          securityContext:
            runAsNonRoot: true
            runAsUser: 1000
            readOnlyRootFilesystem: true
```

### Service & Ingress

```yaml
apiVersion: v1
kind: Service
metadata:
  name: fastapi-app
spec:
  selector:
    app: fastapi-app
  ports:
    - port: 80
      targetPort: 8000
  type: ClusterIP
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: fastapi-app
  annotations:
    nginx.ingress.kubernetes.io/ssl-redirect: "true"
    cert-manager.io/cluster-issuer: "letsencrypt-prod"
spec:
  ingressClassName: nginx
  tls:
    - hosts:
        - api.example.com
      secretName: api-tls
  rules:
    - host: api.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: fastapi-app
                port:
                  number: 80
```

## Helm Chart Structure

```
fastapi-chart/
├── Chart.yaml
├── values.yaml
├── templates/
│   ├── deployment.yaml
│   ├── service.yaml
│   ├── ingress.yaml
│   ├── configmap.yaml
│   ├── secret.yaml
│   ├── hpa.yaml
│   └── _helpers.tpl
```

### values.yaml

```yaml
replicaCount: 3

image:
  repository: registry.example.com/fastapi-app
  tag: latest
  pullPolicy: IfNotPresent

service:
  type: ClusterIP
  port: 80

ingress:
  enabled: true
  className: nginx
  annotations:
    cert-manager.io/cluster-issuer: letsencrypt-prod
  hosts:
    - host: api.example.com
      paths:
        - path: /
          pathType: Prefix
  tls:
    - secretName: api-tls
      hosts:
        - api.example.com

resources:
  requests:
    memory: "256Mi"
    cpu: "250m"
  limits:
    memory: "512Mi"
    cpu: "500m"

autoscaling:
  enabled: true
  minReplicas: 3
  maxReplicas: 10
  targetCPUUtilizationPercentage: 70

mongodb:
  url: ""  # Set via secret

redis:
  url: ""  # Set via secret
```

## Horizontal Pod Autoscaler

```yaml
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: fastapi-app-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: fastapi-app
  minReplicas: 3
  maxReplicas: 10
  metrics:
    - type: Resource
      resource:
        name: cpu
        target:
          type: Utilization
          averageUtilization: 70
    - type: Resource
      resource:
        name: memory
        target:
          type: Utilization
          averageUtilization: 80
```

## Additional Resources

### Reference Files

For detailed deployment patterns:
- **`references/helm-chart.md`** - Complete Helm chart templates
- **`references/ci-cd.md`** - GitHub Actions deployment pipeline
- **`references/monitoring.md`** - Prometheus/Grafana setup

### Example Files

Working examples in `examples/`:
- **`examples/Dockerfile`** - Production Dockerfile
- **`examples/docker-compose.yml`** - Development compose
- **`examples/k8s/`** - Complete K8s manifests