How to Host Multiple Docker Containers on a Single Droplet with Nginx Reverse Proxy?

Prerequisites

Before you start, make sure to have Docker and Nginx installed, here’s how to do that:

• To install Docker follow the steps here:

https://www.digitalocean.com/community/questions/how-to-install-and-run-docker-on-digitalocean-dorplet

• To install Nginx follow the steps here:

https://www.digitalocean.com/community/tutorials/how-to-install-nginx-on-ubuntu-18-04

Once you have both installed, you can continue with the steps:

Step 1 - run your Docker containers

For the same of simplicity, I will run a simple and I’ll run 2 small httpd containers.

• Run your first container and map port 8080 on your host:

docker run -dit --name container-1 -p 8080:80 httpd:2.4

Now if you visit http://your-dropets-ip:8080, you should be able to see a message saying It Works!.

Just so that we could differentiate the two containers, let’s update the It works! message with Container 1 for example:

• First get your container ID

docker ps

Then run the following sed command to update the message:

docker exec CONTAINER_ID sed -i 's/It works!/Container 1/' /usr/local/apache2/htdocs/index.html
```

This would basically run a search and replace for the `It works!` string and update it with `Container 1` in the default `index.html` file in the container itself.

If you visit your Droplet's IP again in your browser the message should change from `It works!` to `Container 1`.

Let's do the same thing for container 2, but map it to port `8081` instead:

```
docker run -dit --name container-2 -p 8081:80 httpd:2.4
```

Then agian get your container ID

```
docker ps
```

Then run the `sed` command again to update the `It works!` message to `Container 2`:

docker exec CONTAINER_ID sed -i ‘s/It works!/Container 2/’ /usr/local/apache2/htdocs/index.html

Now if you visit http://your-dropets-ip:8081, you should be able to see a message saying `Container 2`. 

## Step 2 - Configure Nginx

Now that we have our containers up and running we can go ahead and configure our Nginx server blocks, I will go ahead and use the following two subdomain names for this example:

* container1.bobbyiliev.com
* container2.bobbyiliev.com

To keep things as simple as possible, I will create 2 server blocks with the following content:

* Server block #1:

Create a new file called `container1.bobbyiliev.com.conf` in the `/etc/nginx/sites-available/` directory and add the following content:

server { listen 80; server_name container1.bobbyiliev.com;

location / { proxy_pass http://localhost:8080; } }

* Server block #2:

Create a new file called `container2.bobbyiliev.com.conf` in the `/etc/nginx/sites-available/` directory and add the following content:

server { listen 80; server_name container2.bobbyiliev.com;

location / { proxy_pass http://localhost:8081; } }

Then once you have the two config files ready `cd` to the `/etc/nginx/sites-enabled` directory, and run the following commands:

ln -s …/sites-available/container1.bobbyiliev.com.conf .

ln -s …/sites-available/container2.bobbyiliev.com.conf .

Run a config test to make sure that there are no errors:

nginx -t

And if you get `Syntax OK` message, restart Nginx:

systemctl restart nginx

Note, for more information about Nginx server blocks, I would recommend taking a look at this tutorial here:

https://www.digitalocean.com/community/tutorials/how-to-set-up-nginx-server-blocks-virtual-hosts-on-ubuntu-16-04

## Step 3 - Test the setup

That is pretty much it, now if I visit container1.bobbyiliev.com I should be able to see the `Container 1` message and the same for container2.bobbyiliev.com. 

To test that I could run a simple `curl` request:

```command
curl container1.bobbyiliev.com

You should see the following output

<h1>Container 1</h1>

Then run the same request for container2.bobbyiliev.com:

curl container2.bobbyiliev.com

And agian you should see the following output

<h1>Container 2</h1>

Video Demo

Here’s a quick video demo on how to do the above:

Conclusion

Now you have 2 different containers on the same Droplet being served from different domain names! Of course, this is just a very basic example, you could go a lot further by expanding your Nginx config a lot more, for example adding more headers to your Nginx proxy pass and even installing a Let’s Encrypt SSL.

Hope that this helps! Let me know if you have any questions! Regards, Bobby