Compose profiles for selective services in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a service named web in a Docker Compose file.

Docker

services:
  web:
    image: nginx
    [1]: "80:80"

Drag options to blanks, or click blank then click option'

Avolumes

Bnetworks

Cports

Ddepends_on

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'volumes' instead of 'ports' to expose ports.

The ports key maps container ports to host ports, allowing access to the service.

2fill in blank

medium

Complete the code to add a profile named 'debug' to the service 'app'.

Docker

services:
  app:
    image: myapp
    profiles:
      - [1]

Drag options to blanks, or click blank then click option'

Adebug

Btest

Cproduction

Drelease

Attempts:

3 left

💡 Hint

Common Mistakes

Using a profile name that is not defined or intended.

The profiles key allows selective activation of services. Here, 'debug' is the profile name.

3fill in blank

hard

Fix the error in the profile definition for the service 'db'.

Docker

services:
  db:
    image: postgres
    profiles: [1]

Drag options to blanks, or click blank then click option'

A[debug]

B['debug']

C- debug

Ddebug

Attempts:

3 left

💡 Hint

Common Mistakes

Writing profiles as a plain string instead of a list.

The profiles key expects a list. Using ['debug'] is the correct YAML list syntax.

4fill in blank

hard

Fill both blanks to define two services with profiles 'frontend' and 'backend'.

Docker

services:
  ui:
    image: ui-image
    profiles:
      - [1]
  api:
    image: api-image
    profiles:
      - [2]

Drag options to blanks, or click blank then click option'

Afrontend

Bbackend

Cdatabase

Dcache

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing profile names between frontend and backend services.

Assigning 'frontend' to the UI service and 'backend' to the API service allows selective startup.

5fill in blank

hard

Fill all three blanks to create a service with a profile and port mapping.

Docker

services:
  cache:
    image: redis
    profiles:
      - [1]
    ports:
      - "[2]:[3]"

Drag options to blanks, or click blank then click option'

Acache

B6379

Dredis

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong port numbers or mismatching profile names.

The service 'cache' uses the profile 'cache' and maps port 6379 on host to 6379 in container.

Practice

1. What is the main purpose of using profiles in a Docker Compose file?

easy

A. To define environment variables for all services

B. To specify the Docker image version for services

C. To selectively start specific services based on the active profile

D. To set network configurations for containers

Solution

1. Step 1: Understand the role of profiles in Docker Compose

   Profiles allow you to group services so you can start only those you want by activating a profile.

2. Step 2: Compare with other options

   Environment variables, image versions, and network settings are configured differently, not via profiles.

3. Final Answer:

   To selectively start specific services based on the active profile -> Option C

4. Quick Check:

   Profiles control which services run [OK]

Hint: Profiles control service startup groups in Compose [OK]

Common Mistakes:

• Confusing profiles with environment variables
• Thinking profiles set image versions
• Assuming profiles configure networks

2. Which of the following is the correct syntax to assign a service to a profile named debug in a Docker Compose file?

easy

A. profile: [debug]

B. profiles: [debug]

C. profiles: debug

D. profile: debug

Solution

1. Step 1: Recall the correct key and format for profiles

   The key is profiles (plural) and it expects a list of profile names.

2. Step 2: Validate the syntax

   Using YAML list syntax, profiles: [debug] is correct. Other options use singular or wrong types.

3. Final Answer:

   profiles: [debug] -> Option B

4. Quick Check:

   Profiles key is plural and uses list syntax [OK]

Hint: Use plural 'profiles' with a list for service assignment [OK]

Common Mistakes:

• Using singular 'profile' instead of 'profiles'
• Not using list syntax for profiles
• Assigning profile as a string without brackets

3. Given this Compose snippet:

services:
  web:
    image: nginx
  debug:
    image: busybox
    profiles: [debug]

What happens when you run docker compose up without any profile?

medium

A. Only the web service starts

B. Both web and debug services start

C. Only the debug service starts

D. No services start

Solution

1. Step 1: Identify which services have profiles

   The debug service is assigned to the profile 'debug', web has no profile.

2. Step 2: Understand default behavior without profile

   Without specifying a profile, only services without profiles start.

3. Final Answer:

   Only the web service starts -> Option A

4. Quick Check:

   Services without profiles start by default [OK]

Hint: Without profile flag, only services without profiles run [OK]

Common Mistakes:

• Assuming all services start by default
• Thinking profile services start without activation
• Confusing service names with profile names

4. You have this Compose file snippet:

services:
  app:
    image: myapp
    profiles: [prod]
  test:
    image: mytest
    profiles: [test]

You run docker compose --profile prod up but the app service does not start. What is the likely issue?

medium

A. The profile name is misspelled in the command

B. The app service must not have any profile to start

C. You must run docker compose up without profiles to start services

D. The Compose file syntax is invalid

Solution

1. Step 1: Check profile names in Compose and command

   The service uses profile 'prod'. If the command misspells it, the service won't start.

2. Step 2: Understand profile activation

   Only services matching the activated profile start. If the profile name is wrong, no matching service starts.

3. Final Answer:

   The profile name is misspelled in the command -> Option A

4. Quick Check:

   Profile names must match exactly [OK]

Hint: Check exact profile spelling in command and Compose file [OK]

Common Mistakes:

• Assuming services without profiles start with any profile
• Thinking Compose file syntax error causes this
• Believing profiles are optional for service start

5. You want to start only the db and cache services using profiles. Your Compose file has:

services:
  db:
    image: postgres
    profiles: [backend]
  cache:
    image: redis
    profiles: [backend]
  frontend:
    image: nginx
    profiles: [frontend]

Which command will start only the db and cache services?

hard

A. docker compose up

B. docker compose --profile frontend up

C. docker compose --profile db cache up

D. docker compose --profile backend up

Solution

1. Step 1: Identify profiles assigned to db and cache

   Both db and cache are under the 'backend' profile.

2. Step 2: Use the correct command to activate the backend profile

   Running docker compose --profile backend up starts only services in 'backend'.

3. Final Answer:

   docker compose --profile backend up -> Option D

4. Quick Check:

   Activate profile matching services to start them [OK]

Hint: Use --profile with the shared profile name to start grouped services [OK]

Common Mistakes:

• Using profile name not assigned to services
• Running without profile starts no profile services only
• Trying to list services in command instead of profile