1, 2, 3: SpringBoot, Docker, Nginx, DigitalOcean

This is another step-by-step walkthrough which explains how to dockerize and deploy a SpringBoot microservice behind Nginx.

This article aims at helping Java developers who want to start using popular tools (Docker, Nginx, DockerHub, Certbot) to create a production-ready application. It will also show how to obtain a (free!) domain, setup a (free!) SSL certificate and deploy on DigitalOcean. Some Devops for developers.

Why 1–2–3? Focus on simple essential aspects, clear code samples and relevant references.

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DigitalOcean

DigitalOcean is one of the most popular cloud platforms for deploying and managing applications and web sites.

The cheapest plan starts from 5$ per month (there is a Free Trial to start with) which is absolutely worth paying: it gives you access to a Droplet (1GB memory, 25GB SSD) with several flavors available and plenty of documentation to read.

Architecture

Our architecture will be something like this:

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Few interesting remarks: the core components run on Docker while certbot is provided by the Ubuntu VM as well the storage of the SSL certificates (and any other file and static resource).

Steps

We will go through the following steps to make it happen:

• create and configure the Droplet
• run Nginx on Docker
• build and deploy the SpringBoot application
• obtain a domain
• obtain a SSL certificate (our application will run on HTTPS)

Create a Droplet

Signup for DigitalOcean (via your Github account is also possible and very convenient) and go straight into the dashboard to create a basic VM from a “Docker on Ubuntu” image.

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The setup is pretty much straight-forward, but you can also have a look at the How to Create a Droplet to understand all settings and options.

Once created you will see the IP Address and can log in into the Droplet.

Run Nginx

Nginx will run on Docker using the latest image: I don’t bother to fix a version as I have never seen regressions. Maybe it is something to consider when start serving production requests.

When deploying the Nginx base image we only need to provide our own configuration file.

# nginx.conf
http {
 server {
   listen              443 ssl;
   server_name         myapp.com;
   charset utf-8;
   access_log off;
location / {
     proxy_pass http://myapp:8080;
   }
 }
}
events { worker_connections 1024; }

The file defines the ssl access and a domain (see further), and the proxy_pass, the mechanism to delegate the incoming requests to a downstream application.

SpringBoot Application

Create a SpringBoot app using initializr: in this demo we only need a simple endpoint (ie /test) to make sure the service is reachable.

@RestController
@RequestMapping
public class AppController {
  @GetMapping(value = "/test")
  ResponseEntity<?> test(HttpServletRequest request) throws URISyntaxException {
        log.info("/web/test");
        return ResponseEntity.ok().body("Ok");
    }

You obviously need a little more than this (the SpringApplication file, unit testing, etc..), check out the source code on Github to get all you need.

Once the application is unit tested and run locally we can proceed with the most important step: dockerize it.

# base image
FROM adoptopenjdk/openjdk11:alpine-jre
# home folder in the Docker image
RUN mkdir -p /software
# copy config files (application.properties)
ADD config /software/config
# copy jar file
ADD target/myapp.jar /software/myapp.jar
# run the app
WORKDIR /software
CMD java -Dserver.port=$PORT $JAVA_OPTS -jar myapp.jar

The application is ready to be built:

docker build -t mydomain/myapp:latest .

Run the application on the local Docker to verify it is working:

docker run -it — rm — name myapp -p 8080:8080 mydomain/myapp:latest

Hit it now at http://localhost:8080/test

DockerHub

Once built the image is available on the local environment, to confirm run:

docker images

REPOSITORY       TAG      IMAGE ID       CREATED          SIZE
mydomain/myapp   latest   20de1e1496d5   5 minutes ago    95MB

Nice, but we need to make the same image available on DigitalOcean. We then need to introduce another tool: DockerHub.

DockerHub is a container registry where we can store (for free) public images. Go ahead, signup and login with the Docker cli

docker login

Push the image

docker push mydomain/myapp:latest

Congrats! You have developed, tested and pushed your Dockerized application to the DockerHub container registry.

Docker Compose

The last step in this section is to create a docker-compose file. We are going to run multiple containers so one of the options is to define a docker-compose file to keep all the configuration together.

As you application ecosystem grows (for example adding a logging container i.e. logspout) you can just add it in the compose file.

version: "3"
services:
  myapp:
    image: mydomain/myapp:v0.0.1-a
    container_name: myapp
    ports:
      - "8080:8080"
    networks:
      - my_network
nginx:
    image: nginx:latest
    container_name: nginx
    restart: always
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf
    ports:
      - 80:80
      - 443:443
    networks:
      - my_network
networks:
  my_network:

Be aware the above is a working in progress version of the final docker-compose: we are going to add the ‘letsencrypt’ configuration.

Free Domain

The application will need its own domain: head to Freenom where you can get one for free, typically with a .tk or .ml domain.

You can then create a domain in your DigitalOcean dashboard and link it with with the Droplet (configuring the relevant nameservers).

Free SSL Certificate

Let’s Encrypt is non-profit certificate authority which provides free 90 days SSL certificates, which they can be always renewed within (and after) the validity window.

We will another tool: certbot.

Certbot allows to create and renew SSL certificates from Let’s Encrypt

# install certbot
$ sudo apt install certbot
# create (or renew) cert
$ certbot certonly --force-renewal -d myapp.com

There are 2 options to proceed

How would you like to authenticate with the ACME CA?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
1: Spin up a temporary webserver (standalone)
2: Place files in webroot directory (webroot)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Select the appropriate number [1-2] then [enter] (press 'c' to cancel):

Choose #1 to let Certbot handle the challenge using its own built-in web server: it is a lot easier and it does not need any extra plugin (ie Apache for Nginx). The certificate can be found at ‘/etc/letsencrypt/live/myapp.com’

It is very important however that no process is already running on port 80. This is not the case at this stage but it will be during a future renewal: make sure to stop (docker-compose down) the Nginx container before renewing the certificate.

# renew letsencrypt ssl certificate
$ docker-compose down
$ certbot certonly --force-renewal -d myapp.com
$ docker-compose up -d

Start it up

All components are in place and there is a domain with its own SSL certificate. A final change is required in ‘nginx.conf’ to add the SSL certificate path before starting it all up.

nginx.conf
http {
 server {
   listen              443 ssl;
   server_name         myapp.com;
   ssl_certificate     /etc/letsencrypt/live/myapp.com/fullchain.pem;
   ssl_certificate_key /etc/letsencrypt/live/myapp.com/privkey.pem;   charset utf-8;
   access_log off;
location / {
     proxy_pass http://myapp:8080;
   }
 }
}
events { worker_connections 1024; }

Copy the docker.compose.yml and nginx.conf onto the Droplet using Filezilla or a scp command.

scp docker-compose.yml root@{droplet_ip}:/myapp/docker-compose.yml
scp nginx.conf root@{droplet_ip}:/myapp/nginx.conf

Log on into the Droplet and run the containers

$ cd /myapp
$ docker-compose up -d
# check containers are up
$ docker ps
# view app logs
$ docker logs myapp
# view nginx logs
$ docker logs nginx

The service should now respond at https://mydomain/test

Conclusion

Check out the source code on GitHub

Another useful reference: how to add a SSH key to your Droplet

Reach me on Twitter for questions/suggestions and more 1–2–3 tutorials