Scaled service on Docker via SSL

This repository is an example of using a Go service behind an NGINX webserver that is accessible via HTTPS/SSL on https://localhost:443. It also illustrates how to scale a service in local development with Docker Compose.

Getting started

First, you need to create an SSL certificate as described on Let's Encrypt for localhost:443.

openssl req -x509 -out etc/nginx/localhost.crt -keyout etc/nginx/localhost.key \
  -newkey rsa:2048 -nodes -sha256 \
  -subj '/CN=localhost' -extensions EXT -config <( \
   printf "[dn]\nCN=localhost\n[req]\ndistinguished_name = dn\n[EXT]\nsubjectAltName=DNS:localhost\nkeyUsage=digitalSignature\nextendedKeyUsage=serverAuth")

Next, follow these steps:

1. make build will create the Go binary ./service.
2. docker-compose up --build -d will download, build, and start the application.
3. Open https://localhost:443 and accept the warning the browser will give you. You should read the current time every time the browser refreshes the page.

By default, only one instance of the service is running. So if you curl https://localhost:443 multiple times, it will also print the same hostname.

But you can scale multiple instances of the service by invoking e.g.:

docker-compose up --scale service=3

That will create 3 identical instances of the service which NGINX will proxy to all of them.

When you now curl https://localhost:443 multiple times, and it should print different hostnames. Notice that it may take up to 30 seconds (as defined in the NGINX configuration file) for the DNS resolver to purge its cache.

This works by using the default DNS resolver that Docker creates by default on 127.0.0.11.

License

MIT.