Depends_on for service ordering in Docker - Mini Project: Build & Apply

Depends_on for service ordering

📖 Scenario: You are setting up a simple multi-service application using Docker Compose. One service depends on another to start first. For example, a web app needs the database to be ready before it starts.

🎯 Goal: You will create a docker-compose.yml file that defines two services: db and web. You will use depends_on to ensure the web service starts only after the db service.

📋 What You'll Learn

Create a docker-compose.yml file with two services: db and web.

Set the db service to use the official postgres image.

Set the web service to use the official nginx image.

Use depends_on in the web service to depend on db.

Print the content of the docker-compose.yml file to verify the setup.

💡 Why This Matters

🌍 Real World

Many applications use multiple services like databases and web servers. Docker Compose helps start them in the right order.

💼 Career

Understanding service dependencies is important for DevOps roles to ensure reliable application deployment and startup.

1

Create the basic docker-compose.yml structure

Create a file named docker-compose.yml and add the version '3.8' and an empty services section.

Docker

version: '3.8'
services:
  # Your code here

Need a hint?

Start with the version line and then add the services key with no services yet.

2

Add the db service using the postgres image

Under services, add a service named db that uses the image postgres.

Docker

version: '3.8'
services:
  # Add db service here
  # Your code here

Need a hint?

Indent the db service under services and specify the image as postgres.

3

Add the web service using nginx and set depends_on

Under services, add a service named web that uses the image nginx and add depends_on with db as its dependency.

Docker

version: '3.8'
services:
  db:
    image: postgres
  # Add web service with depends_on here
  # Your code here

Need a hint?

Indent the web service under services. Use a list under depends_on with db as the item.

4

Print the docker-compose.yml content

Print the entire content of the docker-compose.yml file exactly as created.

Docker

# Print the docker-compose.yml content
# Your code here

Need a hint?

Use a single print statement with the exact content including indentation and new lines.