Deploying Genie apps to server with Nginx

This tutorial shows how to host a Julia/Genie app on with Nginx.

Prerequisites

To expose the app over the internet, one needs access to a server. This can be a local machine or a cloud instance such as AWS EC2 or a Google Cloud Compute Engine for example.

If using a local server, a static IP is needed to ensure continuous access to the app. Internet service provider generally charge a fee for such extra service.

The application

We assume that a Genie app has been developed and is ready for deployment and that it is hosted as a project on a git repository.

For example, the app MyGenieApp generated through Genie.Generator.newapp("MyGenieApp") being hosted at github.com/user/MyGenieApp.

The scripts presented in this tutorial are for Ubuntu 20.04.

Install and run the Genie app on the server

Access the server:

ssh -i "ssh-key-for-instance.pem" user@123.123.123.123

Install Julia if not present. Then make the clone:

git clone github.com/user/MyGenieApp
cd MyGenieAp

Install the app as any other Julia project:

julia
] activate .
pkg> instantiate
exit()

In order to launch the app and exit the console without shutting down the app, we will launch it from a new screen:

screen -S genie

Then set the GENIE_ENV environment variable to prod:

export GENIE_ENV=prod

Now the application is almost ready to start just need to configure the secret token. Go into the project directory and execute the following command. It will generate secrets.jl inside config/secrets.jl file and if it exists then it will update with a new token string.

julia --project=. --banner=no --eval="using Pkg; using Genie; Genie.Generator.write_secrets_file()"

Launch the app:

./bin/server

Now the Genie app should be running on the server and be accessible at the following address: 123.123.123.123:8000 (if port 8000 has been open - see instance security settings). Note that you should configure the Genie app so that it doesn't serve the static content (see the Settings option server_handle_static_file in config/env/prod.jl). Static content should be handled by nginx. We can now detach from the genie screen used to launch the app (Ctl+A d).

Install and configure nginx server

Nginx server will be used as a reverse proxy. It will listen requests made on port 80 (HTTP) and redirect traffic to the Genie app running on port 8000 (default Genie setting that can be changed).

Nginx will also be used to serve the app static files, that is, the content under the ./public folder.

Finally, it can as well handle HTTPS requests, which will also be redirected to the Genie app listening on port 8000.

Installation:

sudo apt-get update
sudo apt-get install nginx
sudo systemctl start nginx
sudo systemctl enable nginx

A configuration file then needs to to be created to indicate on which port to listen (80 for HTTP) and to which port to redirect the traffic (8000 for default Genie config).

Config is created in folder /etc/nginx/sites-available: sudo nano my-genie-app. Put the following content in my-genie-app:

server {
  listen 80;
  listen [::]:80;

  server_name   test.com;
  root          /home/ubuntu/MyGenieApp/public;
  index         welcome.html;

  location / {
      proxy_pass http://localhost:8000/;
  }

  location /css/genie {
      proxy_pass http://localhost:8000/;
  }
  location /img/genie {
      proxy_pass http://localhost:8000/;
  }
  location /js/genie {
      proxy_pass http://localhost:8000/;
  }
}

• server_name: refers to the web domain to be used. It can be put to an arbitrary name if the app is only to be served

directly from the server public IP.

• root: points to the public subfolder where the genie app was cloned.
• index: refers to the site index (the landing page).
• The various location following the initial proxy to the genie app are used to indicate static content folders to be

served by nginx. These are needed when the server_handle_static_file is set to false in the Genie app settings.

To make that config effective, it needs to be present in sites-enabled. The default config can be removed.

sudo ln -s /etc/nginx/sites-available/my-genie-app /etc/nginx/sites-enabled/my-genie-app

Then restart the server to make changes effective:

sudo systemctl restart nginx

Enable HTTPS

To enable HTTPS, a site-certificate will be needed for the domain on which the site will be served. A practical approach is to use the utilities provided by certbot.

Following provided instructions for nginx on Ubuntu 20.04:

sudo snap install core; sudo snap refresh core
sudo snap install --classic certbot
sudo ln -s /snap/bin/certbot /usr/bin/certbot

Then, using certbot utility, a certificate will be generated and appropriate modification to nginx config will be brought to handle support for HTTPS:

sudo certbot --nginx

Note that this step will check for ownernship of the test.com domain mentionned in the nginx config file. For that validation to succeed, it requires to have the A record for the domain set to 123.123.123.123.