Compose profiles for selective services in Docker - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of docker-compose with profile enabled

Given the following docker-compose.yml snippet, what will be the output of docker-compose --profile debug ps?

Docker

version: '3.9'
services:
  app:
    image: alpine
    command: sleep 1000
  debug:
    image: busybox
    command: sleep 1000
    profiles:
      - debug

A Lists both 'app' and 'debug' containers running

B Lists only 'app' container running

C Lists only 'debug' container running

D No containers are listed

💡 Hint

Profiles enable selective service activation; using --profile debug activates services tagged with 'debug' plus those without any profile.

When you run docker-compose --profile debug up, it starts all services without a profile plus those with the 'debug' profile. So both 'app' and 'debug' services run.

❓ Configuration

intermediate

Enable a service only with a specific profile

Which of the following docker-compose.yml service definitions correctly enables the service monitor only when the profile monitoring is active?

A

monitor:
  image: prom/prometheus
  profiles:
    monitoring: true

B

monitor:
  image: prom/prometheus
  profiles:
    - monitoring

C

monitor:
  image: prom/prometheus
  profiles: monitoring

D

monitor:
  image: prom/prometheus
  profile: monitoring

💡 Hint

Profiles are defined as a list under the key 'profiles'.

The correct syntax uses the key profiles with a list of profile names. Option B correctly uses a list with one item 'monitoring'.

❓ Troubleshoot

advanced

Why does a service not start with a profile?

You have a service defined with a profile 'test'. You run docker-compose up without specifying any profile. Why does the service not start?

A The service requires environment variables to start

B The service image is missing, so it cannot start

C The service is disabled by default in docker-compose version 3.9

D Services with profiles only start if the profile is explicitly enabled with --profile

💡 Hint

Profiles control which services start by default.

Services tagged with a profile only start when that profile is enabled explicitly using --profile. Running docker-compose up without profiles starts only services without any profile.

🔀 Workflow

advanced

Selective service start with multiple profiles

Given this docker-compose.yml snippet, which services will start when running docker-compose --profile frontend --profile debug up?

Docker

version: '3.9'
services:
  backend:
    image: backend:latest
  frontend:
    image: frontend:latest
    profiles:
      - frontend
  debug:
    image: debug:latest
    profiles:
      - debug

A Only frontend service

B Only frontend and debug services

C backend, frontend, and debug services

D Only backend service

💡 Hint

Services without profiles always start unless profiles restrict them.

Services without profiles (backend) always start. Services with profiles start only if their profile is enabled. Here, both 'frontend' and 'debug' profiles are enabled, so all three services start.

✅ Best Practice

expert

Best practice for using profiles in production

Which is the best practice when using Docker Compose profiles to manage selective services in a production environment?

A Use profiles to separate optional services like monitoring or debugging, enabling only needed profiles in production

B Define all services without profiles and start only needed ones manually

C Use profiles to disable core services in production to save resources

D Avoid using profiles and rely on multiple compose files for service selection

💡 Hint

Profiles help manage optional services cleanly.

Profiles are designed to enable optional services like monitoring or debugging only when needed. This keeps production environments clean and efficient.