Blue-green deployment with containers in Docker - Mini Project: Build & Apply

Blue-green deployment with containers

📖 Scenario: You are managing a web application that needs to be updated without downtime. You will use blue-green deployment with Docker containers to switch between two versions smoothly.

🎯 Goal: Build a simple blue-green deployment setup using Docker containers. You will create two containers named blue and green, configure a variable to track the active container, switch the active container, and finally display which container is currently active.

📋 What You'll Learn

Create two Docker containers named blue and green running a simple web server

Create a variable called active_container to track which container is live

Write a command to switch the active_container from blue to green or vice versa

Print the name of the currently active container

💡 Why This Matters

🌍 Real World

Blue-green deployment helps update applications without downtime by switching traffic between two container versions.

💼 Career

Understanding container management and deployment strategies is essential for DevOps roles to ensure smooth application updates.

1

Create two Docker containers named blue and green

Write two docker run commands to start containers named blue and green using the nginx image in detached mode.

Docker

# Run the blue container
# Run the green container

Need a hint?

Use docker run -d --name container_name nginx to start each container.

2

Create a variable active_container to track the live container

Create a shell variable called active_container and set it to blue to indicate the blue container is currently active.

Docker

docker run -d --name blue nginx

docker run -d --name green nginx

# Set active_container to blue
# Your code here

Need a hint?

Use active_container=blue to set the variable.

3

Switch the active_container from blue to green

Write a shell command to change the value of active_container from blue to green if it is currently blue. Use an if statement to check the current value.

Docker

docker run -d --name blue nginx

docker run -d --name green nginx

active_container=blue

# Switch active_container to green if it is blue
# Your code here

Need a hint?

Use if [ "$active_container" = "blue" ]; then active_container=green; fi to switch.

4

Print the name of the currently active container

Write a echo command to display the text Active container is: followed by the value of active_container.

Docker

docker run -d --name blue nginx

docker run -d --name green nginx

active_container=blue

if [ "$active_container" = "blue" ]; then
    active_container=green
fi

# Print the active container
# Your code here

Need a hint?

Use echo "Active container is: $active_container" to print the active container.