Running Luminus on Dokku

Luminus provides a great way to get up and running with a Clojure web application. However, building your app is only half the work. Once you've got your app working, the next step is to host it somewhere so that the users can access it.

Cloud platforms, such as AWS, are a popular choice for deploying large scale solutions. On the other hand, VPS services like Digital Ocean and Linode provide a more economical alternative for small scale applications. The downside of running your own VPS is that managing it can be labor intensive. This is where Dokku comes in. It's a private PaaS modelled on Heroku that you can use to provision a VPS.

Let's take a look at what's involved in provisioning a Digital Ocean droplet with Dokku and deploying a Luminus web app to it.

set up the server

Let's create a droplet with Ubuntu LTS (18.0.4 at the time of writing) and SSH into it. We'll need to add new APT repositories before we install Dokku.

sudo add-apt-repository universe
wget -nv -O - https://packagecloud.io/dokku/dokku/gpgkey | apt-key add -
echo "deb https://packagecloud.io/dokku/dokku/ubuntu/ bionic main" > /etc/apt/sources.list.d/dokku.list

Once the repositories are added, we'll need to update the dependencies and install Dokku.

sudo apt-get update && sudo apt-get upgrade
apt-get install dokku

Once Dokku is installed, we'll create an application and a Postgres database instance.

• create the app dokku apps:create myapp
• install dokku-postgres plugin sudo dokku plugin:install https://github.com/dokku/dokku-postgres.git
• create the db dokku postgres:create mydb
• link the db to the app dokku postgres:link mydb myapp

We're now ready to deploy the app.

Create a new Luminus application

Let's create a Luminus application on your local machine.

lein new luminus myapp +postgres
cd myapp

Let's update the app to run migrations on startup by updating the myapp.core/start-app function to run the migrations.

(defn start-app [args]
  (doseq [component (-> args
                        (parse-opts cli-options)
                        mount/start-with-args
                        :started)]
    (log/info component "started"))

  ;;run migrations  
  (migrations/migrate ["migrate"] (select-keys env [:database-url]))

  (.addShutdownHook (Runtime/getRuntime) (Thread. stop-app)))

Next, we need to update env/prod/resources/logback.xml to use STDOUT for the logs:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <statusListener class="ch.qos.logback.core.status.NopStatusListener" />
    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <!-- encoders are assigned the type
             ch.qos.logback.classic.encoder.PatternLayoutEncoder by default -->
        <encoder>
            <charset>UTF-8</charset>
            <pattern>%date{ISO8601} [%thread] %-5level %logger{36} - %msg %n</pattern>
        </encoder>
    </appender>
    <logger name="org.apache.http" level="warn" />
    <logger name="org.xnio.nio" level="warn" />
    <logger name="com.zaxxer.hikari" level="warn" />
    <root level="INFO">
        <appender-ref ref="STDOUT" />
    </root>
</configuration>

Deploy the application to Dokku

We're now ready to deploy the app. Let's create a Git repo and add the app contents to it:

git init
git add .gitignore Procfile project.clj README.md src/* env/* test/* resources/*
git commit -a -m "initial commit"
git remote add dokku dokku@<server name>:myapp
git push dokku master

The app will be pushed to the server where it will be compiled and run. If everything went well you should see output that looks something like the following:

...
-----> Building with Leiningen
       Running: lein uberjar
       Compiling sample.app
       2019-01-18 01:10:30.857:INFO::main: Logging initialized @6674ms to org.eclipse.jetty.util.log.StdErrLog
       Created /tmp/build/target/myapp-1.0.1.jar
       Created /tmp/build/target/myapp.jar
...
=====> web=1
...
-----> Waiting for 10 seconds ...
-----> Default container check successful!
-----> Running post-deploy
-----> Configuring myapp.<server name>...(using built-in template)
-----> Creating http nginx.conf
-----> Running nginx-pre-reload
       Reloading nginx
-----> Setting config vars
       DOKKU_APP_RESTORE:  1
=====> 8dc31ac11011111117f71e4311111ca5962cf316411d5f0125e87bbac26
=====> Application deployed:
       http://myapp.<server name>

To http://<server name>:myapp
   6dcab39..1c0c8b7  master -> master

We can check the status of the application in the logs by running dokku logs myapp command on the server. The output should looks something like the following.

JAVA_TOOL_OPTIONS defaults based on dyno size. Custom settings will override them.
Picked up JAVA_TOOL_OPTIONS: -Xmx300m -Xss512k -XX:CICompilerCount=2 -Dfile.encoding=UTF-8
2019-01-19 19:09:48,258 [main] INFO  myapp.env -
-=[myapp started successfully]=-
2019-01-19 19:09:50,490 [main] INFO  luminus.http-server - starting HTTP server on port 5000
2019-01-19 19:09:50,628 [main] INFO  org.xnio - XNIO version 3.3.6.Final
2019-01-19 19:09:51,236 [main] INFO  org.projectodd.wunderboss.web.Web - Registered web context /
2019-01-19 19:09:51,242 [main] INFO  myapp.core - #'myapp.config/env started
2019-01-19 19:09:51,243 [main] INFO  myapp.core - #'myapp.db.core/*db* started
2019-01-19 19:09:51,243 [main] INFO  myapp.core - #'myapp.handler/init-app started
2019-01-19 19:09:51,244 [main] INFO  myapp.core - #'myapp.handler/app started
2019-01-19 19:09:51,249 [main] INFO  myapp.core - #'myapp.core/http-server started
2019-01-19 19:09:51,249 [main] INFO  myapp.core - #'myapp.core/repl-server started
2019-01-19 19:09:51,250 [main] INFO  myapp.core - running migrations
2019-01-19 19:09:51,257 [main] INFO  migratus.core - Starting migrations
2019-01-19 19:09:51,418 [main] INFO  migratus.database - creating migration table 'schema_migrations'
2019-01-19 19:09:51,992 [main] INFO  migratus.core - Running up for [20190118214013]
2019-01-19 19:09:51,997 [main] INFO  migratus.core - Up 20190118214013-add-users-table
2019-01-19 19:09:52,099 [main] INFO  migratus.core - Ending migrations

You should now be able to check your application in the browser by navigating to http://<server name> .

Set up HTTPS

As the last step we'll set up HTTPS for the application using dokku-letsencrypt plugin. We'll set the app to run on the root domain on the server.

dokku domains:add myapp <server name>
dokku domains:remove myapp myapp.<server name>
sudo dokku plugin:install https://github.com/dokku/dokku-letsencrypt.git
dokku config:set --no-restart myapp DOKKU_LETSENCRYPT_EMAIL=<your email>
sudo dokku letsencrypt myapp
dokku letsencrypt:auto-renew

That's all there is to it. The application is now deployed to the droplet, it's hooked up to the database, and it's using Let's Encrypt SSL/TLS Certificates.

Any further updates to the application simply involve committing the changes to the local Git repo and pushing them to the server as we did with our initial deploy.

I recommend taking look at the official documentation on the Dokku site for more information about Dokku. I think it provides an excellent solution for running your VPS. If you're evaluating different options for deploying your Clojure apps give Dokku a look.