Blue-green deployment routing in Nginx - Mini Project: Build & Apply

Blue-green deployment routing with Nginx

📖 Scenario: You are managing a web service that needs zero downtime during updates. To do this, you use a blue-green deployment strategy. This means you have two versions of your app running: blue and green. You want to configure Nginx to route all user traffic to only one version at a time.

🎯 Goal: Build an Nginx configuration that routes all incoming requests to either the blue or green backend server based on a variable. This will let you switch traffic between versions easily.

📋 What You'll Learn

Create an upstream block for blue servers

Create an upstream block for green servers

Add a variable $active_version to select which upstream to use

Configure the server block to proxy requests to the selected upstream

Print the active version in the response header for verification

💡 Why This Matters

🌍 Real World

Blue-green deployment routing is used in production to update applications without downtime. It allows switching user traffic between two identical environments safely.

💼 Career

Understanding how to configure Nginx for blue-green deployments is valuable for DevOps engineers and site reliability engineers who manage continuous delivery pipelines and high-availability services.

1

Create upstream blocks for blue and green servers

Create two upstream blocks named blue_backend and green_backend. Each should have one server: blue.example.com:8080 for blue and green.example.com:8080 for green.

Nginx

# Your code here

Need a hint?

Use the upstream directive to define backend groups.

2

Add a variable to select the active backend

Add a variable $active_version and set it to blue_backend to start routing traffic to the blue version.

Nginx

upstream blue_backend {
    server blue.example.com:8080;
}

upstream green_backend {
    server green.example.com:8080;
}

# Your code here

Need a hint?

Use the map directive to set $active_version to blue_backend by default.

3

Configure server block to proxy to the active backend

Create a server block listening on port 80. Inside it, add a location / block that proxies requests to the backend selected by $active_version using proxy_pass http://$active_version;. Also add a header X-Active-Version with the value of $active_version.

Nginx

upstream blue_backend {
    server blue.example.com:8080;
}

upstream green_backend {
    server green.example.com:8080;
}

map $http_host $active_version {
    default blue_backend;
}

# Your code here

Need a hint?

Use proxy_pass with the variable $active_version to route traffic dynamically.

4

Print the active version header for verification

Add a line to print the value of the X-Active-Version header in the response. Then reload Nginx and test by sending a request to port 80. The output should include the header X-Active-Version: blue_backend.

Nginx

upstream blue_backend {
    server blue.example.com:8080;
}

upstream green_backend {
    server green.example.com:8080;
}

map $http_host $active_version {
    default blue_backend;
}

server {
    listen 80;

    location / {
        proxy_pass http://$active_version;
        add_header X-Active-Version $active_version;
    }
}

# Your code here to test or print output

Need a hint?

Use curl -I http://localhost to see response headers including X-Active-Version.