rudironsoni 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.
Scope
- Kubernetes Deployment, Service, and probe YAML for .NET apps
- Docker Compose for local development workflows
- CI/CD integration for building and pushing container images
Out of scope
- Dockerfile authoring, multi-stage builds, and base image selection -- see [skill:dotnet-containers]
- Advanced CI/CD pipeline patterns (matrix builds, deploy pipelines) -- 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] and [skill:dotnet-playwright]
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
```text
### 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
```text
### 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'
```text
Reference in the Deployment:
```yaml
envFrom:
- configMapRef:
name: order-api-config
```yaml
### 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=<DB_PASSWORD_PLACEHOLDER>'
```text
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
```text
### Graceful Shutdown
.NET responds to `SIGTERM` and begins graceful shutdown. Configure `terminationGracePeriodSeconds` to allow in-flight
requests to complete:
```yaml
spec:
terminationGracePeriodSeconds: 30
```yaml
In your application, use `IHostApplicationLifetime` to handle shutdown:
```csharp
app.Lifetime.ApplicationStopping.Register(() =>
{
// Perform cleanup: flush telemetry, close connections
Log.CloseAndFlush();
});
```text
Ensure the `Host.ShutdownTimeout` allows in-flight requests to complete:
```csharp
builder.Host.ConfigureHostOptions(options =>
{
options.ShutdownTimeout = TimeSpan.FromSeconds(25);
});
```text
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=<DB_PASSWORD_PLACEHOLDER>
- 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:
```text
### Development Override
Use a separate override file for development-specific settings:
```yaml
# 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']
```bash
### Observability Stack
Add an OpenTelemetry collector and Grafana for local observability:
```yaml
# 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:
```text
Run with the observability stack:
```bash
docker compose -f docker-compose.yml -f docker-compose.observability.yml up
```bash
---
## 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
```yaml
# .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: ${{ steps.meta.outputs.labels }}
cache-from: type=gha
cache-to: type=gha,mode=max
```text
### Image Tagging Strategy
| Tag Pattern | Example | Use Case |
| ----------- | ------------------- | ------------------------------------------- |
| `latest` | `myapi:latest` | Development only -- never use in production |
| Semver | `myapi:1.2.3` | Release versions -- immutable |
| Major.Minor | `myapi:1.2` | Floating tag for patch updates |
| SHA | `myapi:sha-abc1234` | Unique per commit -- traceability |
| Branch | `myapi:main` | CI builds -- latest from branch |
### dotnet publish Container in CI
For projects using `dotnet publish /t:PublishContainer` instead of Dockerfiles:
```yaml
steps:
- uses: actions/checkout@v4
- uses: actions/setup-dotnet@v4
with:
dotnet-version: '10.0.x'
- name: Publish container image
run: |
dotnet publish src/OrderApi/OrderApi.csproj \
--os linux --arch x64 \
/t:PublishContainer \
-p:ContainerRegistry=${{ env.REGISTRY }} \
-p:ContainerRepository=${{ env.IMAGE_NAME }} \
-p:ContainerImageTag=${{ github.sha }}
```text
---
## 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.
---
## Code Navigation (Serena MCP)
**Primary approach:** Use Serena symbol operations for efficient code navigation:
1. **Find definitions**: `serena_find_symbol` instead of text search
2. **Understand structure**: `serena_get_symbols_overview` for file organization
3. **Track references**: `serena_find_referencing_symbols` for impact analysis
4. **Precise edits**: `serena_replace_symbol_body` for clean modifications
**When to use Serena vs traditional tools:**
- ✅ **Use Serena**: Navigation, refactoring, dependency analysis, precise edits
- ✅ **Use Read/Grep**: Reading full files, pattern matching, simple text operations
- ✅ **Fallback**: If Serena unavailable, traditional tools work fine
**Example workflow:**
```text
# Instead of:
Read: src/Services/OrderService.cs
Grep: "public void ProcessOrder"
# Use:
serena_find_symbol: "OrderService/ProcessOrder"
serena_get_symbols_overview: "src/Services/OrderService.cs"
```
## References
- [Deploy ASP.NET Core to Kubernetes](https://learn.microsoft.com/en-us/aspnet/core/host-and-deploy/linux-nginx)
- [Kubernetes Deployments](https://kubernetes.io/docs/concepts/workloads/controllers/deployment/)
- [Kubernetes probes](https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/)
- [Docker Compose overview](https://docs.docker.com/compose/)
- [ASP.NET Core health checks](https://learn.microsoft.com/en-us/aspnet/core/host-and-deploy/health-checks)
- [Graceful shutdown in .NET](https://learn.microsoft.com/en-us/dotnet/core/extensions/generic-host#host-shutdown)
- [GitHub Actions: Publishing Docker images](https://docs.github.com/en/actions/use-cases-and-examples/publishing-packages/publishing-docker-images)