This is the second post in a series. The first post is here.
In addition to the tools for part one, you’re also going to need:
- A fully-qualified domain name (FQDN). Any domain will do. I’m going to use
- A Ruby on Rails development environment
- docker to run a local PostgresQL container for our web application’s database.
Get your dokku server’s IP address like this:
$ terraform ouptut droplet_ip = "18.104.22.168"
(Your server’s IP number will be different)
We need to tell SSH to use the key we created, whenever we connect to our dokku
server, and also that we want to ssh as the
dokku user. To do this, add the
following to your
Host dokku.me Hostname dokku.me User dokku IdentityFile ~/.ssh/terraform_dokku
You should now be able to ssh to your dokku server like this:
Create an application
We’re going to create a very simple Ruby on Rails database-backed web application, "myblog", to deploy on our dokku server.
I’m going to go through the process of creating this application from scratch, and running it locally, but this is optional. In particular, if you don’t have postgres installed on your computer, you might get an error when you try to create the rails application.
You don’t actually need to get the application working locally, so if you prefer, or if you have trouble, just skip to the next section "Deploying to dokku".
Run a local database container
We need a database, so I’m going to launch a PostgresQL container with a local directory mounted into it for persistent storage:
mkdir db_files docker run -d --rm \ --name mypostgres \ -e POSTGRES_PASSWORD=mysecretpassword \ -e PGDATA=/var/lib/postgresql/data/pgdata \ -v $(pwd)/db_files:/var/lib/postgresql/data \ -p 5432:5432 \ postgres
DATABASE_URL environment variable to allow rails to connect to the
Create the rails application
You should now be able to run the application like this:
If you visit
http://127.0.0.1:3000/posts you should be able to create and
edit posts, using the default Rails scaffold web interface.
Deploying to dokku
If you didn’t create your rails application from scratch, you can get the code like this:
git clone https://github.com/digitalronin/dokku-app-myblog myblog
Before we can deploy our application, we need to do a little bit of setup on the dokku server:
$ ssh dokku.me dokku apps:create myblog dokku postgres:create myblog-db dokku postgres:link myblog-db myblog
This creates a dokku app
myblog with a postgres database. It also sets a
DATABASE_URL environment variable in the environment where our rails
application will run.
Back on our local machine, we can now deploy our rails application.
One small change we need to make is to set up a
Procfile to tell dokku to run
our database migrations whenever we deploy our application. Add this file to
web: rails server release: rails db:migrate
git add and
git commit the file, then:
git remote add dokku email@example.com:myblog git push dokku main:master
This pushes our
main branch to the dokku server. It will take a while to
install all the dependencies.
When it’s finished, the last few lines of output should be something like this:
=====> Application deployed: http://myblog.dokku.me To dokku.me:myblog * [new branch] main -> master
Since we’re using a fake domain right now, we need to add an entry to
/etc/hosts in order to view our application.
echo "22.214.171.124 myblog.dokku.me" | sudo tee -a /etc/hosts
(Use the IP number for your dokku server VM)
At this point, you should be able to visit
your browser, and use the web interface to manage posts.
Setting a domain name
We want to use a real domain name for our application, and we also need to install an SSL certificate from LetsEncrypt, so that visitors’ traffic is encrypted, and so visitors don’t get a security warning in their browsers whenever they visit the app.
Create a DNS A record
I’m going to use the hostname
dokku-myblog and the domain name
digitalronin.com, so in my case, I need a DNS A record that sets
126.96.36.199 as the IP number of the
Set up the corresponding A record with your DNS provider, using your domain name and the IP number of your dokku server.
Set the domain on dokku
Once the A record is set up, configuring the domain on the dokku server is as simple as:
$ ssh dokku.me dokku domains:set myblog dokku-myblog.digitalronin.com
You should now be able to access the application at:
(or rather, whatever FQDN you chose for your application)
Add an SSL certificate
Finally, let’s add a LetsEncrypt SSL certficate:
$ ssh dokku.me dokku config:set --no-restart myblog DOKKU_LETSENCRYPT_EMAIL=[your email address] dokku letsencrypt myblog
Now you should be able to access the application at:
https://dokku-myblog.digitalronin.com, with no security warnings.
This barely scratches the surface of what dokku can do, so I’d definitely recommend having a look at the documentation.
Don’t forget to use
terraform destroy to shut down and delete your dokku
server VM, so that you don’t incur charges on DigitalOcean.
If you’re still running your docker postgres container, you can shut it down like this:
docker stop mypostgres