Resource monitoring per container in Docker - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Check CPU usage of a running container

You want to see the current CPU usage of a container named webapp. Which command will show this information?

A docker stats webapp --no-stream

B docker inspect webapp --format '{{.State.CpuUsage}}'

C docker top webapp

D docker logs webapp --cpu

💡 Hint

Use a command that shows live resource usage statistics for containers.

The command 'docker stats webapp --no-stream' shows a snapshot of resource usage including CPU, memory, and network for the container named 'webapp'. Other options either show process info, logs, or incorrect fields.

💻 Command Output

intermediate

Memory usage output format

You run docker stats --no-stream and see the memory usage column showing 50MiB / 500MiB. What does this mean?

A The container is using 500 MiB and has 50 MiB available

B The container has 50 MiB free and 500 MiB used

C The container is using 50 MiB of memory out of a 500 MiB limit

D The container has 50 MiB total memory and 500 MiB swap

💡 Hint

The format is usually 'used / limit'.

The memory usage column shows how much memory the container is currently using and the maximum allowed memory. '50MiB / 500MiB' means 50 MiB used out of 500 MiB limit.

❓ Configuration

advanced

Limit CPU usage of a container

You want to limit a container named db to use at most 0.5 CPU cores. Which command correctly starts the container with this limit?

A docker run --cpu-shares=0.5 --name db mydbimage

B docker run --cpus=0.5 --name db mydbimage

C docker run --cpu-quota=50000 --name db mydbimage

D docker run --cpulimit=0.5 --name db mydbimage

💡 Hint

Use the flag that sets the number of CPUs directly.

The '--cpus=0.5' flag limits the container to use half a CPU core. '--cpu-shares' is a relative weight, not a hard limit. '--cpu-quota' requires specific values and units. '--cpulimit' is not a valid Docker flag.

❓ Troubleshoot

advanced

Diagnose why container memory usage is high

A container api is using more memory than expected. You want to check its memory limit and usage. Which sequence of commands helps you find this info?

A docker stats api --no-stream; docker inspect api --format '{{.HostConfig.Memory}}'

B docker exec api free -m; docker inspect api --format '{{.State.MemoryUsage}}'

C docker logs api; docker top api

D docker stats api; docker inspect api --format '{{.Config.Memory}}'

💡 Hint

One command shows current usage, the other shows configured limits.

The 'docker stats' command shows current memory usage. 'docker inspect' with '{{.HostConfig.Memory}}' shows the memory limit set on the container. Other options either show logs, processes, or invalid fields.

✅ Best Practice

expert

Efficient resource monitoring setup for multiple containers

You manage many containers and want to monitor CPU and memory usage continuously with minimal overhead. Which approach is best?

A Use 'docker stats' with --no-stream repeatedly in a script every second

B Check container logs for resource usage messages periodically

C Run 'docker top' on each container every minute and parse output

D Install a monitoring agent like cAdvisor or Prometheus node exporter on the host

💡 Hint

Look for a scalable and low-overhead monitoring solution.

Using dedicated monitoring tools like cAdvisor or Prometheus exporters is efficient and scalable for many containers. 'docker stats' in a loop causes overhead. 'docker top' shows processes, not resource usage. Logs usually don't contain resource metrics.