Docker Compose CI/CD Build Essentials Checklist Quiz Quiz

Assess your understanding of Docker Compose CI/CD build checklist practices in cloud-based DevOps pipelines. This quiz covers crucial concepts including best practices, file patterns, environment configuration, versioning, build optimization, and common pitfalls in Docker Compose continuous integration and delivery workflows.

1. Selecting the Correct Build File

   Which filename will Docker Compose look for by default when you run a build command without specifying the file?

   1. docker-compose.yml
   2. compose-docker.yaml
   3. docker-buildfile.yml
   4. composefile.json

   Explanation: Docker Compose automatically uses 'docker-compose.yml' as the default file when no -f argument is provided. Other options like 'compose-docker.yaml' and 'docker-buildfile.yml' do not follow standard naming conventions and will only be used if explicitly referenced. The format 'composefile.json' is incorrect since Docker Compose uses YAML, not JSON, for its structured data.

2. Using Multi-Stage Builds in CI/CD

   Why are multi-stage builds beneficial in Docker CI/CD pipelines?

   1. They reduce image size by removing unnecessary build dependencies
   2. They allow simultaneous container deployments
   3. They speed up application code execution
   4. They automatically update the base operating system

   Explanation: Multi-stage builds help minimize Docker image size by compiling code in one stage and copying only the required artifacts to the final image, leaving out development tools and dependencies. Simultaneous deployments, speeding up app code, and auto-updating the operating system are not direct benefits gained from using multi-stage builds.

3. Storing Sensitive Information

   What is the recommended method to handle sensitive environment variables, such as API keys, in a Docker Compose CI/CD workflow?

   1. Store them in a .env file excluded from version control
   2. Hardcode them in the docker-compose.yml file
   3. Include them directly in the image
   4. Write them in a plain text file within the repository

   Explanation: Storing secrets in a .env file outside of version control keeps them out of your source history and helps prevent accidental sharing. Hardcoding or adding them to images or plaintext files inside the repository increases the risk of exposure, which is unsafe for sensitive data.

4. Best Practice for Dependency Caching

   In a Docker Compose build, which technique helps speed up builds by caching dependencies?

   1. Copying dependency files first in the Dockerfile
   2. Using only ENTRYPOINT instructions
   3. Editing dependencies during each build stage
   4. Omitting dependency files from the image

   Explanation: Placing dependency COPY instructions before other changes leverages Docker's build cache, so unchanged dependencies aren't reinstalled in each build. ENTRYPOINT has no effect on caching dependencies, and editing or omitting files limits or breaks the caching process.

5. Handling Multiple Environments

   If you have different development and production settings, what is the effective way to manage multiple Docker Compose configurations?

   1. Use separate override YAML files like docker-compose.override.yml
   2. Keep all configurations in the main Docker Compose file
   3. Use only environment variables for all differences
   4. Write one YAML file for every possible setting

   Explanation: Override files allow customization for different environments by extending or overwriting the main Compose file. Storing everything in one file reduces clarity; depending solely on environment variables can become unmanageable. Creating many YAML files leads to redundancy and configuration drift.

6. Build Trigger Best Practices

   Which approach ensures reliable and repeatable builds in CI/CD pipelines for Docker Compose?

   1. Pinning image versions and dependencies explicitly
   2. Using 'latest' for all image tags
   3. Pulling images only from unverified sources
   4. Allowing dependencies to update automatically on each build

   Explanation: Pinning versions guarantees consistent results and avoids unexpected changes during future builds. Using 'latest' or unverified sources can make builds unpredictable, and letting dependencies auto-update risks introducing breaking changes without notice.

7. Docker Compose Command in CI/CD

   Which command is commonly used in CI/CD steps to build images from a Compose file?

   1. docker-compose build
   2. compose-build
   3. docker build-compose
   4. compose up --build

   Explanation: The 'docker-compose build' command builds images as defined in the Compose YAML file. 'compose-build' and 'docker build-compose' are not recognized commands, while 'compose up --build' brings up services but is less commonly used solely for build steps.

8. Optimizing Layer Caching

   Why is minimizing the number of RUN commands in a Dockerfile important for CI/CD efficiency?

   1. It reduces the number of image layers and speeds up build times
   2. It makes error logs harder to read
   3. It increases the final image size
   4. It ensures images won't run locally

   Explanation: Fewer RUN commands mean fewer layers, making images smaller and improving build speed due to efficient caching. More layers do not make logs harder to read by themselves, nor do they prevent local runs or always increase image size.

9. Ignoring Unnecessary Files

   What file should you use to prevent sending unnecessary files to the Docker build context in a Compose pipeline?

   1. .dockerignore
   2. docker-exclude.txt
   3. .composeignore
   4. build.config

   Explanation: A '.dockerignore' file specifies patterns for files and directories to exclude from the Docker build context, which streamlines builds and reduces image sizes. The other filenames listed are not recognized by Docker Compose for this purpose.

10. Ensuring Service Health

    How should you use healthchecks in Docker Compose for CI/CD validation?

    1. Define healthcheck sections to monitor service readiness
    2. Rely only on container start status
    3. Use only external monitoring tools
    4. Disable all healthchecks to speed up builds

    Explanation: Healthchecks in Docker Compose provide a way to verify services are fully operational before running dependent steps. Relying solely on container start does not guarantee readiness. External tools can supplement, but Compose healthchecks are integrated and efficient. Disabling healthchecks risks failing to catch issues early.

11. Versioning Compose Files

    What is the impact of specifying a version key in your docker-compose.yml file in CI/CD pipelines?

    1. It defines the syntax and features supported in the file
    2. It pins the base image version
    3. It controls the runtime environment version
    4. It updates images from the registry automatically

    Explanation: The version key in a Compose YAML file indicates which syntax and features can be used. It is unrelated to image versions, runtime versions, or the auto-updating of images from a registry.

12. Networking Between Services

    By default, how does Docker Compose manage networking between services defined in the same file?

    1. All services are connected to a shared virtual network
    2. Each service is fully isolated with no communication
    3. A physical network needs to be created manually
    4. Services use random external ports for communication

    Explanation: Docker Compose sets up an isolated virtual network by default, allowing services to communicate by name. Services are not isolated unless explicitly specified, don't require physical network setup, and don't communicate via random external ports by default.

13. Automating Tests in CI/CD

    What is a good practice for running tests on services defined in docker-compose.yml during CI/CD?

    1. Spin up containers in detached mode and execute tests against them
    2. Run tests directly on host without containers
    3. Test only compiled images before CI/CD
    4. Skip testing if build was successful

    Explanation: Launching containers in detached mode lets test scripts interact with real service instances as they appear in production. Running tests on the host doesn’t ensure container correctness. Testing only after building, or skipping tests, may miss integration issues.

14. Reusing Build Artifacts

    How can you reuse build artifacts between stages in a multi-stage Docker build for a CI/CD process?

    1. Copy them from earlier build stages to the final image using the 'COPY --from' statement
    2. Mount host directories into the running container
    3. Use only environment variables to pass artifacts
    4. Store artifacts on the container filesystem during runtime

    Explanation: The 'COPY --from' syntax allows artifacts from one stage to be included in a later stage, efficiently leveraging results of previous builds. Mounting host directories, using environment variables, or relying on runtime container files are not reliable or reproducible for artifact transfer during builds.

15. Limiting Build Context Size

    Why is it recommended to keep the Docker build context small in a Compose CI/CD pipeline?

    1. A smaller context uploads faster to the Docker daemon and reduces build time
    2. A large context increases container RAM usage
    3. It prevents port conflicts
    4. It disables service scaling

    Explanation: Smaller build contexts reduce data transfer overhead, speeding up builds and minimizing potential for including unwanted files. Build context size has no effect on service RAM, port conflicts, or scaling configurations.

16. Failing Early in CI/CD

    What is a benefit of running 'docker-compose config' as part of your CI/CD pipeline checklist?

    1. It validates your Compose configuration before build and deployment
    2. It starts all containers automatically
    3. It creates environment variables automatically
    4. It resets the container registry

    Explanation: The 'docker-compose config' command checks the syntax and merges configuration files, helping to catch errors early. It does not start containers, generate environment variables, or interact with any registry operations.