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Compose design

Design the structure of a docker-compose.yml file.

Project: a multi-service app with Compose

Real applications don't consist of a single container: a web app, a database, maybe a cache. Starting each with long docker run commands is tedious and error-prone. Docker Compose defines all the services in a single compose.yaml file and manages them with one command:

docker compose up -d      # create and start all services
docker compose ps         # show their status
docker compose down       # stop and remove

In this project you'll build a Python API + PostgreSQL + Redis stack step by step.

The skeleton of compose.yaml

The file's top-level keys are services (containers), volumes (named volumes) and networks (custom networks). In YAML, indentation carries meaning; spaces are used, not tabs:

services:
  web:
    image: nginx:alpine
    ports:
      - "8080:80"

Instead of the old docker-compose (hyphenated, v1), the docker compose (v2) built into Docker is used now; the version: line at the top isn't needed either.

Practice The first compose file

Write a compose.yaml: the web service uses the nginx:alpine image and maps host port 8080 to container port 80.

Starter code

terminal
# compose.yaml
# buraya yaz

Sample solution

terminal
# compose.yaml
services:
  web:
    image: nginx:alpine
    ports:
      - "8080:80"

Expected output

[+] Running 2/2
 ✔ Network proje_default  Created
 ✔ Container proje-web-1  Started

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What is Compose's main advantage over docker run commands?

  • Not needing images
  • Working only in production
  • All service settings live in one file under version control Correct answer
  • Faster containers

Explanation: Anyone who gets the file sets up the same stack with docker compose up.

2 Write the top-level key defining the services.

Question 
____:
  web:
    image: nginx:alpine
Answer 
services:
  web:
    image: nginx:alpine

Explanation: Each service corresponds to one or more containers.

3 Match.

Term Meaning
services Container definitions
volumes Named volumes
docker compose up -d Start the stack
docker compose down Remove the stack

All lessons in Beginner

1 What is Docker?

  1. What is Docker?
  2. Containers and virtual machines
  3. Images and containers
  4. Docker architecture
  5. Use cases
  6. Summary - What is Docker

2 Installation and first commands

  1. Installing Docker
  2. docker version
  3. docker info
  4. The hello-world container
  5. Docker Desktop
  6. Summary - Installation

3 First container

  1. docker run basics
  2. Running in the background
  3. docker ps
  4. docker stop and rm
  5. docker logs
  6. Summary - First container

4 Dockerfile basics

  1. What is a Dockerfile?
  2. The FROM instruction
  3. The RUN instruction
  4. COPY and ADD
  5. CMD and ENTRYPOINT
  6. Summary - Dockerfile

5 Build and images

  1. docker build
  2. Tagging images
  3. Build context
  4. Layers and cache
  5. .dockerignore
  6. Summary - Build

6 docker run options

  1. Interactive mode
  2. Naming containers
  3. Restart policy
  4. Working directory
  5. Switching users
  6. Summary - docker run

7 Image management

  1. docker images
  2. docker rmi
  3. docker pull
  4. docker push
  5. docker tag
  6. Summary - Image management

8 Port mapping

  1. The port concept
  2. The -p flag
  3. Multiple ports
  4. Random ports
  5. IP binding
  6. Summary - Port mapping

9 Volumes and data

  1. Data persistence
  2. Named volumes
  3. The -v flag
  4. Bind mounts
  5. Volume management
  6. Summary - Volumes

10 Environment variables

  1. The -e flag
  2. The ENV instruction
  3. The ARG instruction
  4. env-file
  5. The WORKDIR instruction
  6. Summary - Environment

11 Project: docker-compose

  1. Compose design
  2. Service definition
  3. Database service
  4. Volume and network
  5. Putting it together - compose

12 Docker Hub and registry

  1. What is Docker Hub?
  2. docker login
  3. Searching images
  4. Official images
  5. Private registry
  6. Summary - Registry

13 Network basics

  1. Network drivers
  2. docker network ls
  3. Bridge network
  4. Container connectivity
  5. Publishing ports
  6. Summary - Network

14 Beginner final

  1. Challenge - Dockerfile
  2. Challenge - Build and run
  3. Challenge - Volume
  4. Challenge - Compose
  5. Challenge - Beginner project