DCA Quality Assurance & Improvement 4

Question 1

Which Docker Swarm feature automatically replaces a failed service task on a healthy node?

Accepted Answer

Task rescheduling via the reconciliation loop

Answer

Swarm's manager continuously reconciles desired vs actual state and schedules new tasks to replace failed ones on healthy nodes automatically.

Question 2

A team wants to prevent 'latest' tags from being deployed to production Swarm services. Which approach enforces this policy?

Accepted Answer

Use image pinning in stack files with explicit digest references

Answer

Referencing images by digest in stack compose files ensures exactly the tested image is deployed, preventing accidental 'latest' mutations.

Question 3

What does the 'docker system prune -a' command remove, and what QA risk does it carry?

Accepted Answer

All unused images including those not linked to a container, risking removal of cached base images needed for CI builds

Answer

'-a' extends the prune to all unused images (not just dangling ones), which can delete base images cached for faster CI builds if no container references them.

Question 4

Which Docker logging driver is most appropriate for a production environment that requires centralized log aggregation with structured JSON output?

Accepted Answer

fluentd

Answer

The fluentd driver forwards logs to a Fluentd aggregator in real time, enabling structured, centralized log collection suitable for production observability.

Question 5

In a CI pipeline, 'docker build' exits with code 1. Which step should be taken first to diagnose the failure?

Accepted Answer

Check the build log output for the specific RUN instruction that failed

Answer

The build log identifies the exact failing RUN step and its stderr, providing the most direct path to diagnosing the failure cause.

DCA - Docker Certified Associate Exam Practice Test

DCA - Docker Certified Associate Exam Practice Test

DCA Quality Assurance & Improvement 4