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!