Service scaling in Docker - Mini Project: Build & Apply

Service scaling with Docker Compose

📖 Scenario: You are managing a simple web application using Docker Compose. To handle more users, you want to run multiple copies of the web service.

🎯 Goal: Learn how to scale a Docker Compose service by increasing the number of running containers.

📋 What You'll Learn

Create a Docker Compose file with a web service

Add a scale variable to control the number of containers

Use the Docker Compose command to scale the service

Display the number of running containers after scaling

💡 Why This Matters

🌍 Real World

Scaling services with Docker Compose helps handle more users by running multiple copies of the same service.

💼 Career

Understanding service scaling is essential for DevOps roles to manage application availability and load.

1

Create a Docker Compose file with a web service

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

Docker

# Your code here

Need a hint?

Use YAML syntax to define the service under services with the name web and specify the image nginx:latest.

2

Add a scale variable to control the number of containers

Create a variable called scale_count and set it to 3 to represent how many containers you want to run.

Docker

version: '3'
services:
  web:
    image: nginx:latest

# Your code here

Need a hint?

Define a variable named scale_count and assign it the value 3.

3

Use the Docker Compose command to scale the service

Write a shell command string called scale_command that uses docker-compose up -d --scale web=3 to start 3 containers of the web service using the scale_count variable.

Docker

version: '3'
services:
  web:
    image: nginx:latest

scale_count = 3

# Your code here

Need a hint?

Use an f-string to insert scale_count into the command string.

4

Display the number of running containers after scaling

Write a print statement that outputs exactly: Running 3 containers of web service using the scale_count variable.

Docker

version: '3'
services:
  web:
    image: nginx:latest

scale_count = 3

scale_command = f"docker-compose up -d --scale web={scale_count}"

# Your code here

Need a hint?

Use a print statement with an f-string to show the number of containers running.