dotnet-container-deployment

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	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

# 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

Tag Pattern	Example	Use Case
latest	myapi:latest	Development only -- never use in production
Semver	myapi:1.2.3	Release versions -- immutable
Major.Minor	myapi:1.2	Floating tag for patch updates
SHA	myapi:sha-abc1234	Unique per commit -- traceability
Branch	myapi:main	CI builds -- latest from branch

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