CPU limits and reservations in Docker - Mini Project: Build & Apply

CPU Limits and Reservations with Docker

📖 Scenario: You are managing a Docker container that runs a small web server. You want to control how much CPU the container can use to keep your system stable and responsive.

🎯 Goal: Learn how to set CPU limits and CPU reservations for a Docker container using the docker service create command.

📋 What You'll Learn

Create a Docker container running the nginx image

Set a CPU reservation to guarantee minimum CPU share

Set a CPU limit to cap maximum CPU usage

Verify the container runs with the specified CPU settings

💡 Why This Matters

🌍 Real World

Controlling CPU usage of containers helps keep your system responsive and prevents one container from using too much CPU.

💼 Career

Understanding CPU limits and reservations is important for managing containerized applications in production environments.

1

Create a Docker container running nginx

Write a docker service create command to start a service named webserver using the nginx image.

Docker

# Write the docker service create command to start nginx service named webserver
# Your code here

Need a hint?

Use docker service create --name webserver nginx to start the service.

2

Add a CPU reservation to guarantee minimum CPU share

Modify the docker service create command to add a CPU reservation of 0.5 CPUs using the --reserve-cpu option.

Docker

docker service create --name webserver nginx
# Add --reserve-cpu=0.5 to the command above
# Your code here

Need a hint?

Add --reserve-cpu 0.5 to reserve half a CPU for the container.

3

Add a CPU limit to cap maximum CPU usage

Modify the docker service create command to add a CPU limit of 1.0 CPUs using the --limit-cpu option, keeping the CPU reservation from Step 2.

Docker

docker service create --name webserver --reserve-cpu 0.5 nginx
# Add --limit-cpu=1.0 to the command above
# Your code here

Need a hint?

Add --limit-cpu 1.0 to limit the container to one CPU maximum.

4

Verify the container runs with the CPU settings

Write a docker inspect command to display the CPU reservation and CPU limit settings of the webserver service.

Docker

docker service create --name webserver --reserve-cpu 0.5 --limit-cpu 1.0 nginx
# Write docker inspect command to show CPU settings of webserver service
# Your code here

Need a hint?

Use docker inspect --format='{{.Spec.TaskTemplate.Resources.Reservations.NanoCPUs}} {{.Spec.TaskTemplate.Resources.Limits.NanoCPUs}}' webserver to see CPU reservation and limit in nanoseconds.