Health checks in Compose in Docker - Mini Project: Build & Apply

Health checks in Compose

📖 Scenario: You are setting up a simple web service using Docker Compose. To make sure your service is running correctly, you want to add a health check. This health check will help Docker know if your service is healthy or not.

🎯 Goal: Build a Docker Compose file that defines a web service with a health check. The health check will run a command inside the container to verify the service is working.

📋 What You'll Learn

Create a Docker Compose file with a service named web

Use the official nginx:alpine image for the web service

Add a health check to the web service that runs wget --no-verbose --tries=1 --spider http://localhost/

Set the health check interval to 10 seconds

Print the health status of the web service using docker compose ps

💡 Why This Matters

🌍 Real World

Health checks help keep your applications running smoothly by letting Docker know if a service is working correctly. This is important in real projects to restart or replace failing containers automatically.

💼 Career

Understanding health checks in Docker Compose is useful for DevOps roles, site reliability engineers, and developers who deploy applications using containers.

1

Create the basic Docker Compose file

Create a file named docker-compose.yml with a service called web that uses the image nginx:alpine.

Docker

# Create a docker-compose.yml file with a service named web using nginx:alpine
# Your code here

Need a hint?

Use the services key and define web under it with the image set to nginx:alpine.

2

Add a health check command

Add a healthcheck section under the web service with a test command that runs wget --no-verbose --tries=1 --spider http://localhost/.

Docker

version: '3.8'
services:
  web:
    image: nginx:alpine
    # Add healthcheck with test command here
    # Your code here

Need a hint?

The test command should be an array starting with CMD followed by the wget command.

3

Set the health check interval

Add the interval key under healthcheck with the value 10s to run the health check every 10 seconds.

Docker

version: '3.8'
services:
  web:
    image: nginx:alpine
    healthcheck:
      test: ["CMD", "wget", "--no-verbose", "--tries=1", "--spider", "http://localhost/"]
      # Add interval: 10s here
      # Your code here

Need a hint?

The interval key controls how often the health check runs. Use 10s for 10 seconds.

4

Display the health status of the web service

Run the command docker compose ps in your terminal to see the health status of the web service.

Docker

# Run the command below in your terminal
# Your code here

Need a hint?

Use docker compose ps to check the status. The health column should show healthy after some time.