uni/slides/dhbw/07_docker.md

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header: "Web Engineering – DHBW Stuttgart"
footer: "Michael Czechowski – SoSe 2026"
title: Docker und Service Orchestration
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# Docker

## Service Orchestration

---

# Inhalt

1. Architektur: Reverse Proxy + API + DB
2. Container vs VM
3. `Dockerfile`
4. `compose.yml`
5. Docker CLI / Compose Befehle
6. Live Demo: `dhbw-docker`

---

# Architektur

```
            Browser (localhost:10007)
                    │
                    ▼
         ┌──────────────────┐
         │  Reverse Proxy   │  (nginx / traefik)
         └─────────┬────────┘
              ┌────┴────┐
              ▼         ▼
        ┌─────────┐  ┌────────┐
        │  Web    │  │  API   │
        │  App    │  │ (Node) │
        └────┬────┘  └────┬───┘
             └─────┬──────┘
                   ▼
              ┌────────┐
              │   DB   │ (Postgres)
              └────────┘
```

---

# Container vs VM

| | VM | Container |
|---|----|-----------|
| Kernel | eigener | Host-Kernel |
| Boot | Minuten | Sekunden |
| Größe | GB | MB |
| Isolation | stark | namespaces, cgroups |
| Image | komplett | Layer (diff) |

→ **Docker** = Container-Engine + Image-Format + Registry.

---

# Dockerfile – Express API

```dockerfile
FROM node:lts-slim AS builder

WORKDIR /app

COPY ./package*.json ./
RUN npm ci --no-audit --no-fund --no-progress --loglevel=error

COPY ./ ./

ENV NODE_ENV="production"

EXPOSE 8080

CMD ["npm", "start"]
```

**`npm ci`** statt `npm i` für reproduzierbare Builds.

---

# Multi-Stage Build

```dockerfile
FROM node:lts-slim AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

FROM node:lts-slim AS runtime
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
COPY package*.json ./
EXPOSE 8080
CMD ["node", "dist/index.js"]
```

→ kleines Final-Image, keine Build-Tools im Runtime.

---

# .dockerignore

```
node_modules
dist
.git
.env
*.log
coverage
```

Spart Build-Kontext und verhindert Geheimnis-Leaks.

---

# compose.yml – Services

```yaml
name: dhbw-docker-app

services:
  api:
    build: ./api
    container_name: dhbw-api
    environment:
      DATABASE_USERNAME: ${DATABASE_USERNAME}
      DATABASE_PASSWORD: ${DATABASE_PASSWORD}
      DATABASE_NAME: ${DATABASE_NAME}
      DATABASE_HOST: db
      DATABASE_PORT: 5432
    ports:
      - "10000:8080"
    networks: [net, data]
    depends_on:
      db:
        condition: service_healthy
```

---

# compose.yml – Datenbank + Proxy

```yaml
  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_USER: ${DATABASE_USERNAME}
      POSTGRES_PASSWORD: ${DATABASE_PASSWORD}
      POSTGRES_DB: ${DATABASE_NAME}
    volumes:
      - dbdata:/var/lib/postgresql/data
    networks: [data]
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U $$DATABASE_USERNAME"]
      interval: 5s
      retries: 5

  proxy:
    image: nginx:alpine
    ports: ["10007:80"]
    volumes: ["./nginx.conf:/etc/nginx/nginx.conf:ro"]
    networks: [net]
    depends_on: [api]

volumes:
  dbdata:

networks:
  net:
  data:
```

---

# Docker Compose – Befehle

```bash
docker compose -p "dhbw-docker-app" \
  -f compose.yml \
  --env-file .env \
  up \
  --build \
  --remove-orphans \
  --force-recreate
```

| Flag | Bedeutung |
|------|-----------|
| `-p` | Projektname |
| `-f` | mehrere Compose-Files möglich |
| `--env-file` | `.env` einlesen |
| `--build` | Images neu bauen |
| `--remove-orphans` | verwaiste Container weg |
| `--force-recreate` | Container neu starten |

---

# Compose – Alltag

```bash
docker compose up -d              # detached starten
docker compose ps                 # Status
docker compose logs -f api        # Logs streamen
docker compose exec api sh        # Shell im Container
docker compose down -v            # Stop + Volumes löschen
docker compose restart api        # Neustart einzelner Service
```

---

# Health Checks

```yaml
api:
  healthcheck:
    test: ["CMD", "curl", "-f", "http://localhost:8080/health"]
    interval: 10s
    timeout: 3s
    retries: 3
    start_period: 5s
```

`depends_on: { condition: service_healthy }` wartet, bis Health passt.

---

# Networks: Segmentierung

- **`net`** – öffentlich erreichbar (Proxy ↔ App)
- **`data`** – nur intern (App ↔ DB)
- DB ist **nicht** vom Internet erreichbar
- Service-DNS: `api`, `db`, `proxy` (Container-Name = Hostname)

→ Defense in Depth.

---

# Volumes – Daten persistent

```yaml
volumes:
  dbdata:               # benannt
  - ./code:/app         # bind mount (dev)
  - /app/node_modules   # anonymous (überschreibt bind)
```

`docker compose down` ohne `-v` lässt Volumes leben.

---

# Live Demo

Repo: https://github.com/nextlevelshit/dhbw-docker

```bash
git clone https://github.com/nextlevelshit/dhbw-docker
cd dhbw-docker
cp .env.example .env
docker compose up --build
```

→ http://localhost:10007

---

# 100 Concepts of Docker (Exkurs)

- Image · Container · Volume · Network
- Dockerfile · Layer Cache · BuildKit
- Compose · Stack · Swarm · Kubernetes
- Registry · Tag · Digest
- Dev/Prod-Parity (12-Factor)
- Secrets · Configs
- Logging Drivers
- Health Checks · Restart Policies

---

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# Fragen?

**Hausaufgabe:** Eigenes Projekt mit `Dockerfile` + `compose.yml` containerisieren.