dotnet-container-deployment

Imported from wshaddix/dotnet-skills (skills/dotnet-container-deployment/SKILL.md). Install upstream with npx skills add wshaddix/dotnet-skills --skill dotnet-container-deployment. Copyright stays with the author.

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:

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:

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

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:

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

Secrets for Sensitive Configuration

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 Configuration Guidelines

# 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:

spec:
  terminationGracePeriodSeconds: 30

In your application, use IHostApplicationLifetime to handle shutdown:

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

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

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

# 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:

Development Override

Use a separate override file for development-specific settings:

# docker-compose.override.yml (auto-loaded by docker compose up)
services:
  order-api:
    build:
      target: build  # Stop at build stage for faster rebuilds
    volumes:
      - .:/src       # Mount source for hot reload
    environment:
      - ASPNETCORE_ENVIRONMENT=Development
      - DOTNET_USE_POLLING_FILE_WATCHER=true
    command: ["dotnet", "watch", "run", "--project", "src/OrderApi/OrderApi.csproj"]

Observability Stack

Add an OpenTelemetry collector and Grafana for local observability:

# docker-compose.observability.yml
services:
  otel-collector:
    image: otel/opentelemetry-collector-contrib:latest
    command: ["--config=/etc/otelcol-config.yaml"]
    volumes:
      - ./infra/otelcol-config.yaml:/etc/otelcol-config.yaml
    ports:
      - "4317:4317"   # OTLP gRPC
      - "4318:4318"   # OTLP HTTP

  grafana:
    image: grafana/grafana:latest
    ports:
      - "3000:3000"
    volumes:
      - grafana-data:/var/lib/grafana

volumes:
  grafana-data:

Run with the observability stack:

docker compose -f docker-compose.yml -f docker-compose.observability.yml up

CI/CD Integration

Basic CI/CD patterns for building and pushing .NET container images. Advanced CI patterns (matrix builds, environment promotion, deploy pipelines) -- see [skill:dotnet-gha-publish], [skill:dotnet-gha-deploy], and [skill:dotnet-ado-publish].

GitHub Actions: Build and Push

# .github/workflows/docker-publish.yml
name: Build and Push Container

on:
  push:
    branches: [main]
    tags: ["v*"]

env:
  REGISTRY: ghcr.io
  IMAGE_NAME: ${{ github.repository }}

jobs:
  build-and-push:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      packages: write

    steps:
      - uses: actions/checkout@v4

      - name: Log in to container registry
        uses: docker/login-action@v3
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Extract metadata
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
          tags: |
            type=ref,event=branch
            type=semver,pattern={{version}}
            type=semver,pattern={{major}}.{{minor}}
            type=sha

      - name: Build and push
        uses: docker/build-push-action@v6
        with:
          context: .
          push: true
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}
          cache-from: type=gha
          cache-to: type=gha,mode=max

Image Tagging Strategy

dotnet publish Container in CI

For projects using dotnet publish /t:PublishContainer instead of Dockerfiles:

steps:
  - uses: actions/checkout@v4

  - uses: actions/setup-dotnet@v4
    with:
      dotnet-version: "10.0.x"

  - name: Publish container image
    run: |
      dotnet publish src/OrderApi/OrderApi.csproj \
        --os linux --arch x64 \
        /t:PublishContainer \
        -p:ContainerRegistry=${{ env.REGISTRY }} \
        -p:ContainerRepository=${{ env.IMAGE_NAME }} \
        -p:ContainerImageTag=${{ github.sha }}

Key Principles

• Use startup probes to decouple initialization time from liveness detection -- without a startup probe, slow-starting apps get killed before they are ready
• Separate liveness from readiness -- liveness checks should not include dependency health (see [skill:dotnet-observability] for endpoint patterns)
• Set resource requests and limits -- without them, pods can starve other workloads or get OOM-killed unpredictably
• Run as non-root -- set runAsNonRoot: true in the pod security context and use chiseled images (see [skill:dotnet-containers])
• Use depends_on with health checks in Docker Compose -- prevents app startup before dependencies are ready
• Keep secrets out of manifests -- use Kubernetes Secrets with external secrets operators, not plain values in source control
• Match ShutdownTimeout to terminationGracePeriodSeconds -- ensure the app finishes cleanup before Kubernetes sends SIGKILL

Agent Gotchas

1. Do not omit the startup probe -- without it, the liveness probe runs during initialization and may restart slow-starting apps. Calculate startup budget as failureThreshold * periodSeconds.
2. Do not include dependency checks in liveness probes -- a database outage should not restart your app. Liveness endpoints must only check the process itself. See [skill:dotnet-observability] for the liveness vs readiness pattern.
3. Do not use latest tag in Kubernetes manifests -- latest is mutable and imagePullPolicy: IfNotPresent may serve stale images. Use immutable tags (semver or SHA).
4. Do not hardcode connection strings in Kubernetes manifests -- use Secrets or ConfigMaps referenced via secretKeyRef/configMapRef.
5. Do not set terminationGracePeriodSeconds lower than Host.ShutdownTimeout -- the app needs time to drain in-flight requests before Kubernetes sends SIGKILL.
6. Do not forget condition: service_healthy in Docker Compose depends_on -- without the condition, Compose starts dependent services immediately without waiting for health checks.

References

• Deploy ASP.NET Core to Kubernetes
• Kubernetes Deployments
• Kubernetes probes
• Docker Compose overview
• ASP.NET Core health checks
• Graceful shutdown in .NET
• GitHub Actions: Publishing Docker images