Container resource usage stats in Docker - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of the command to show live CPU and memory usage of a running container?

You run the command docker stats my_container --no-stream. What output will you see?

A A list of all containers with their IDs and names only, no resource usage details.

B An error message saying 'container not found' because --no-stream is invalid.

C A table showing CPU %, memory usage, network IO, block IO, and PIDs for 'my_container' at the moment of running the command.

D A continuous live stream of resource usage stats until you stop it manually.

💡 Hint

The --no-stream option shows a snapshot, not a live stream.

The 'docker stats' command with --no-stream shows a single snapshot of resource usage for the specified container. It includes CPU %, memory usage, network IO, block IO, and PIDs.

🧠 Conceptual

intermediate

Which Docker command option limits the CPU usage of a container?

You want to restrict a container to use only 50% of one CPU core. Which option do you use when running the container?

A --cpus 0.5

B --memory 512m

C --cpu-shares 1024

D --blkio-weight 500

💡 Hint

CPU shares are relative weights, not exact limits.

The --cpus option limits the container to a specific number of CPUs or fractions. --cpus 0.5 limits to half a CPU core.

❓ Troubleshoot

advanced

Why does 'docker stats' show 0% CPU usage for a busy container?

You notice that 'docker stats' shows 0% CPU usage for a container that is actively processing tasks. What is the most likely reason?

A The container is using CPU in a way that docker stats cannot measure, like GPU usage.

B The container is running on a different CPU core not monitored by docker stats.

C The container is paused, so no CPU is used.

D The container is running with CPU limits set to zero, preventing CPU usage.

💡 Hint

Docker stats measures CPU usage of the container's CPU time, not GPU or other hardware.

Docker stats measures CPU usage based on CPU time used by the container processes. If the container uses GPU or other hardware accelerators, CPU usage may appear as zero.

🔀 Workflow

advanced

Order the steps to monitor and limit memory usage of a Docker container

Arrange the following steps in the correct order to monitor and limit memory usage of a Docker container.

A 2,1,3,4

B 1,2,3,4

C 1,3,2,4

D 2,3,1,4

💡 Hint

You must set limits before monitoring and adjusting.

First, set the memory limit when running the container. Then monitor usage with docker stats. Analyze if the limit is exceeded, then adjust and restart if necessary.

✅ Best Practice

expert

Which practice is best for ensuring accurate container resource usage monitoring in production?

You want to monitor CPU and memory usage of containers in production with minimal performance impact and accurate data. Which practice is best?

A Manually SSH into each container and run top or free commands.

B Run 'docker stats' continuously on each host and parse output manually.

C Rely on container logs to estimate resource usage periodically.

D Use a dedicated monitoring tool like cAdvisor or Prometheus with container metrics exporters.

💡 Hint

Automated tools designed for container monitoring provide better accuracy and less overhead.

Dedicated monitoring tools like cAdvisor and Prometheus collect detailed container metrics efficiently and provide dashboards and alerts, which is best practice for production environments.