CyberCode Academy

Course 31 - Dive Into Docker | Episode 9: Orchestrating Multi-Container Web Applications with Docker Compose

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In this lesson, you’ll learn about: Docker Compose, multi-container apps, and service orchestration1. What is Docker Compose?
  • Docker Compose is a tool used to:
    • Define
    • Run
    • Manage
    multi-container applications using a single command
👉 Instead of long docker run commands, you describe everything in one file2. The docker-compose.yml File
  • Core configuration file written in YAML
  • Uses version 3 syntax
Example structure:version: "3" services: web: build: . redis: image: redis
  • Defines:
    • Services (containers)
    • Networks
    • Volumes
3. Defining Services
  • Each service represents a container
Example:
  • Web app (custom build)
  • Redis (prebuilt image)
🔹 Build vs Image
  • build: → build from local Dockerfile
  • image: → pull from registry (e.g., Docker Hub)
web: build: . redis: image: redis 4. Port Mappingports: - "5000:5000"
  • Format:host_port : container_port
👉 Allows access from your browser (localhost)5. Volumes (Data Management)🔹 Host-Mounted Volumevolumes: - .:/app
  • Syncs local files with container
  • Ideal for development
🔹 Named Volumevolumes: - redis-data:/data volumes: redis-data:
  • Persistent storage
  • Managed by Docker
6. Managing Service Dependenciesdepends_on: - redis
  • Ensures:
    • Redis starts before the web app
👉 Important for backend-dependent services7. Environment Variables with .env
  • Store sensitive or dynamic values:
COMPOSE_PROJECT_NAME=myapp Benefits:
  • Cleaner config
  • Avoid hardcoding
  • Easy to manage across environments
🔹 COMPOSE_PROJECT_NAME
  • Defines a custom project name
  • Prevents conflicts between projects
👉 Useful when running multiple apps on the same machine8. Running Everything with One Commanddocker-compose up
  • Builds images
  • Creates containers
  • Starts all services
9. Why Docker Compose Matters
  • Simplifies complex setups
  • Reduces human error
  • Makes projects:
    • Reproducible
    • Shareable
    • Scalable
Key Takeaways
  • Docker Compose = multi-container management made easy
  • docker-compose.yml = your infrastructure blueprint
  • Supports:
    • Services
    • Volumes
    • Networks
    • Environment variables
  • One command replaces dozens of manual steps


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CyberCode AcademyBy CyberCode Academy