Challenge - Beginner project

Set up a project that combines all beginner concepts.

Challenge: the beginner project

All the pieces of the beginner section: an API built with your own Dockerfile, a Redis cache, a shared network, environment variables and a health check. The Compose file defines both the build and the run:

services:
  api:
    build: .
    image: api:1.0.0
    ports:
      - "3000:3000"
    env_file: api.env
    environment:
      REDIS_URL: redis://cache:6379
    depends_on:
      cache:
        condition: service_healthy
    restart: unless-stopped
  cache:
    image: redis:7
    healthcheck:
      test: ["CMD", "redis-cli", "ping"]
      interval: 5s

Exercise The project's compose file

Write a compose.yaml: the api service with build: ., image: api:1.0.0, "3000:3000", env_file: api.env, and condition: service_healthy for cache under depends_on; the cache service with redis:7 and test: ["CMD", "redis-cli", "ping"] under healthcheck.

Show example solution

# compose.yaml
services:
  api:
    build: .
    image: api:1.0.0
    ports:
      - "3000:3000"
    env_file: api.env
    depends_on:
      cache:
        condition: service_healthy
  cache:
    image: redis:7
    healthcheck:
      test: ["CMD", "redis-cli", "ping"]

Exercise Update the code

You changed the code. Write two commands: rebuild only the api service and update it in the background; then show the variables by running the env command in the api container.

Show example solution

docker compose up -d --build api
docker compose exec api env

Test yourself

When does the cache service's healthcheck succeed?
- Always after 5 seconds
- When api starts
- When redis-cli ping returns with a zero exit code (PONG)
- As soon as the container starts
Show answer

When redis-cli ping returns with a zero exit code (PONG) — The health check looks at the test command's exit code.

Load the environment variables from a file.

  api:
    build: .
    ____: api.env

Show answer

  api:
    build: .
    env_file: api.env

Match.

build: .

Your own Dockerfile
image: api:1.0.0

Build tag
env_file

Settings from file
service_healthy

Start when ready

Next lesson: Beginner section exam

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