dotnet-container-deployment

What this skill does

# dotnet-container-deployment

Deploying .NET containers to Kubernetes and local development environments. Covers Kubernetes Deployment + Service + probe YAML, Docker Compose for local dev workflows, and CI/CD integration for building and pushing container images.

**Out of scope:** Dockerfile authoring, multi-stage builds, base image selection, and `dotnet publish` container images are covered in [skill:dotnet-containers]. Advanced CI/CD pipeline patterns (matrix builds, deploy pipelines, environment promotion) -- see [skill:dotnet-gha-deploy] and [skill:dotnet-ado-patterns]. DI and async patterns -- see [skill:dotnet-csharp-dependency-injection] and [skill:dotnet-csharp-async-patterns]. Testing container deployments -- see [skill:dotnet-integration-testing] for Testcontainers patterns and [skill:dotnet-playwright] for E2E testing against deployed containers.

Cross-references: [skill:dotnet-containers] for Dockerfile and image best practices, [skill:dotnet-observability] for health check endpoint patterns used by Kubernetes probes.

---

## Kubernetes Deployment

### Deployment Manifest

A production-ready Kubernetes Deployment for a .NET API:

```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: order-api
  labels:
    app: order-api
    app.kubernetes.io/name: order-api
    app.kubernetes.io/version: "1.0.0"
    app.kubernetes.io/component: api
spec:
  replicas: 3
  selector:
    matchLabels:
      app: order-api
  template:
    metadata:
      labels:
        app: order-api
    spec:
      containers:
        - name: order-api
          image: ghcr.io/myorg/order-api:1.0.0
          ports:
            - containerPort: 8080
              protocol: TCP
          env:
            - name: ASPNETCORE_ENVIRONMENT
              value: "Production"
            - name: OTEL_EXPORTER_OTLP_ENDPOINT
              value: "http://otel-collector.monitoring:4317"
            - name: OTEL_SERVICE_NAME
              value: "order-api"
            - name: ConnectionStrings__DefaultConnection
              valueFrom:
                secretKeyRef:
                  name: order-api-secrets
                  key: connection-string
          resources:
            requests:
              cpu: "100m"
              memory: "128Mi"
            limits:
              cpu: "500m"
              memory: "512Mi"
          livenessProbe:
            httpGet:
              path: /health/live
              port: 8080
            initialDelaySeconds: 10
            periodSeconds: 15
            timeoutSeconds: 3
            failureThreshold: 3
          readinessProbe:
            httpGet:
              path: /health/ready
              port: 8080
            initialDelaySeconds: 5
            periodSeconds: 10
            timeoutSeconds: 3
            failureThreshold: 3
          startupProbe:
            httpGet:
              path: /health/live
              port: 8080
            initialDelaySeconds: 0
            periodSeconds: 5
            failureThreshold: 30
      securityContext:
        runAsNonRoot: true
        runAsUser: 1654
        fsGroup: 1654
      terminationGracePeriodSeconds: 30
```

### Service Manifest

Expose the Deployment within the cluster:

```yaml
apiVersion: v1
kind: Service
metadata:
  name: order-api
  labels:
    app: order-api
spec:
  type: ClusterIP
  selector:
    app: order-api
  ports:
    - port: 80
      targetPort: 8080
      protocol: TCP
      name: http
```

### ConfigMap for Non-Sensitive Configuration

```yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: order-api-config
data:
  ASPNETCORE_ENVIRONMENT: "Production"
  Logging__LogLevel__Default: "Information"
  Logging__LogLevel__Microsoft.AspNetCore: "Warning"
```

Reference in the Deployment:

```yaml
envFrom:
  - configMapRef:
      name: order-api-config
```

### Secrets for Sensitive Configuration

```yaml
apiVersion: v1
kind: Secret
metadata:
  name: order-api-secrets
type: Opaque
stringData:
  connection-string: "Host=postgres;Database=orders;Username=app;Password=secret"
```

In production, use an external secrets operator (e.g., External Secrets Operator, Sealed Secrets) rather than plain Kubernetes Secrets stored in source control.

---

## Kubernetes Probes

Probes tell Kubernetes how to check application health. They map to the health check endpoints defined in your .NET application (see [skill:dotnet-observability]).

### Probe Types

| Probe | Purpose | Endpoint | Failure Action |
|-------|---------|----------|---------------|
| **Startup** | Has the app finished initializing? | `/health/live` | Keep waiting (up to `failureThreshold * periodSeconds`) |
| **Liveness** | Is the process healthy? | `/health/live` | Restart the pod |
| **Readiness** | Can the process serve traffic? | `/health/ready` | Remove from Service endpoints |

### Probe Configuration Guidelines

```yaml
# Startup probe: give the app time to initialize
# Total startup budget: failureThreshold * periodSeconds = 30 * 5 = 150s
startupProbe:
  httpGet:
    path: /health/live
    port: 8080
  initialDelaySeconds: 0
  periodSeconds: 5
  failureThreshold: 30

# Liveness probe: detect deadlocks and hangs
# Only runs after startup probe succeeds
livenessProbe:
  httpGet:
    path: /health/live
    port: 8080
  periodSeconds: 15
  timeoutSeconds: 3
  failureThreshold: 3

# Readiness probe: control traffic routing
readinessProbe:
  httpGet:
    path: /health/ready
    port: 8080
  periodSeconds: 10
  timeoutSeconds: 3
  failureThreshold: 3
```

### Graceful Shutdown

.NET responds to `SIGTERM` and begins graceful shutdown. Configure `terminationGracePeriodSeconds` to allow in-flight requests to complete:

```yaml
spec:
  terminationGracePeriodSeconds: 30
```

In your application, use `IHostApplicationLifetime` to handle shutdown:

```csharp
app.Lifetime.ApplicationStopping.Register(() =>
{
    // Perform cleanup: flush telemetry, close connections
    Log.CloseAndFlush();
});
```

Ensure the `Host.ShutdownTimeout` allows in-flight requests to complete:

```csharp
builder.Host.ConfigureHostOptions(options =>
{
    options.ShutdownTimeout = TimeSpan.FromSeconds(25);
});
```

Set `ShutdownTimeout` to a value less than `terminationGracePeriodSeconds` to ensure the app shuts down before Kubernetes sends `SIGKILL`.

---

## Docker Compose for Local Development

Docker Compose provides a local development environment that mirrors production dependencies.

### Basic Compose File

```yaml
# docker-compose.yml
services:
  order-api:
    build:
      context: .
      dockerfile: src/OrderApi/Dockerfile
    ports:
      - "8080:8080"
    environment:
      - ASPNETCORE_ENVIRONMENT=Development
      - ConnectionStrings__DefaultConnection=Host=postgres;Database=orders;Username=app;Password=devpassword
      - OTEL_EXPORTER_OTLP_ENDPOINT=http://otel-collector:4317
    depends_on:
      postgres:
        condition: service_healthy
      redis:
        condition: service_healthy
    # Note: CMD-SHELL + curl requires a base image with shell and curl installed.
    # Chiseled/distroless images lack both. For chiseled images, either use a
    # non-chiseled dev target in the Dockerfile or omit the healthcheck and rely
    # on depends_on ordering (acceptable for local dev).
    healthcheck:
      test: ["CMD-SHELL", "curl -f http://localhost:8080/health/live || exit 1"]
      interval: 10s
      timeout: 3s
      retries: 3
      start_period: 10s

  postgres:
    image: postgres:17
    environment:
      POSTGRES_DB: orders
      POSTGRES_USER: app
      POSTGRES_PASSWORD: devpassword
    ports:
      - "5432:5432"
    volumes:
      - postgres-data:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U app -d orders"]
      interval: 5s
      timeout: 3s
      retries: 5

  redis:
    image: redis:7-alpine
    ports:
      - "6379:6379"
    healthcheck:
      test: ["CMD", "redis-cli", "ping"]
      interval: 5s
      timeout: 3s
      retries: 5

volumes:
  postgres-data:
```

### Develo