Understanding Network Seggregation in Docker-Compose

Did you ever wonder why use different networks in docker-compose?

There are a number of reasons. I think the most important one is to test how proxies etc work. And this is exactly what we try now in this lecture - create two different networks and see how seggregation really works.

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Using networks in docker-compose for better segregation

Let’s use this docker-compose.yml file:

version: "3.7"
 
services:
  web:
    image: nginx:alpine
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf
    ports:
      - 8080:80
    networks:
      - app1_net
      - app2_net
 
  app1:
    image: httpd:latest
    networks:
      - app1_net
 
  app2:
    image: httpd:latest
    networks:
      - app2_net
 
networks:
  app1_net:
  app2_net:
 

And the following nginx.conf configuration file in the same directory:

events {}
http {
    server {
    listen 80;
    listen [::]:80;

    server_name example.com;

    location / {
        proxy_pass http://app1:80/;
    }
    location /app2 {
        proxy_pass http://app2:80/;
    }
  }
}

• It will create two apache containers, “app1” and “app2”
• The apache containers won’t be reachable from the host
• “app1” cannot reach “app2” (that’s the important part 😉)
• Both “app1” and “app2” can be reached from the reverse nginx proxy

Now go to the terminal and type in:

docker-compose up

And wait for the services to come up and shows the log-output.

Go to http://localhost:8080  and observer the command line

• It will show you the nignx-container web_1 container (reverse_proxy) was requested
• And forwarded the request to “app1” container
• Reload a few times to make this more obvious

Go to http://localhost:8080/app2  and observe the command line

• It will show you again that nginx-container web_1 container (reverse_proxy) was requested
• And now forwards to “app2” container
• Reload a few times to make this more obvious

With this, you can see that network seggregation works fine.

And with this, the course is also complete. This is an introduction course to Docker and you are now equipped with all you need to get started using Docker and Docker-Compose!