uni/slides/dhbw/08_docker.md

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true	gaia	true		Web Engineering – DHBW Stuttgart	Michael Czechowski – SoSe 2026	Docker und Service Orchestration

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Web Engineering

DHBW Stuttgart · Informatik / Wirtschaftsinformatik

Sommersemester 2026 · Sitzung 9 — Docker, Proxies and DBs

---

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

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

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

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

  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

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

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

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

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

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

→ http://localhost:10007

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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