Combining Heroku and Dropwizard: My Own Personal Staging Environment

Think what you may about Heroku, they do offer a free tier and it’s trivially simple to use it as your own personal staging environment. In this post, I’m going to outline what it takes to take a simple Dropwizard service and get it running in Heroku. For anyone looking for a bit of depth, this example will also include database access (Heroku also gives you a free PostgreSQL database) and touch on using Dropwizard’s Liquibase integration for database migrations.

For the record, I am not particularly for nor against Heroku as a platform. I believe it’s a great service that makes it almost too easy to get off the ground and into the continuous deployment frame of mind. I simply lack the experience using it at scale, opting instead for AWS, to comment on it’s applicability across all stages of an application. 

Maybe I’m cheap (Heroku’s a few more dollars than the equivalent in AWS) or maybe I just really really enjoy (the pain of?) managing Chef and setting up my own VPCs.


Getting Started

First off, let’s get a simple Dropwizard project up and running. 

    $ git clone git://github.com/ajordens/dropwizard-example-groovy.git

Make sure it compiles and runs locally.

    $ mvn clean install
    $ java -jar my-example-service/target/my-example-service-0.1-SNAPSHOT.jar server my-example-service/config.yml

Lastly, create a simple PostgreSQL database and test database migrations.

    $ createdb myexampleDB
    $ java -jar my-example-service/target/my-example-service-0.1-SNAPSHOT.jar db migrate my-example-service/config.yml

Assuming everything worked successfully, you’ll now have a service capable of serving html views and json data as well as a simple database.


Setting up Heroku

If you have not already signed up for a free Heroku account, do so now. 

You will also need to install the appropriate Heroku Toolbelt release for your operating system.

    $ heroku login
    Enter your Heroku credentials.
    Email: example-app@xyz
    Password (typing will be hidden): 
    Authentication successful.

    $ heroku create example-app
    Creating example-app… done, stack is cedar
    http://example-app.herokuapp.com/ | git@heroku.com:example-app.git
    Git remote heroku added

Almost done, all that’s left now is to get the Heroku database connection properties. 

Update config-heroku.yml with the values listed in the PostgreSQL add-on section of your application (login to heroku.com)


Pushing Code to Heroku

    $ git push heroku master
    $ heroku ps:scale web=1

After pushing code to Heroku, it’s completely normal to see your maven build occur immediately. 

When the build finishes, the app will be accessible via http://app-name.herokuapp.com

    $ heroku open

This works in part due to the magical Procfile that I snuck into the dropwizard-example-groovy project.  

The Procfile simply tells Heroku how to start the web application and because Dropwizard is a completely self-contained jar, it runs in Heroku using the same java -jar syntax that you would use to run locally.

Almost magical.


Migrating Databases on Heroku

Managing your Heroku databases is almost as simple as if they were running locally.

    $ java -jar my-example-service/target/my-example-service-0.1-SNAPSHOT.jar db migrate my-example-service/config-heroku.yml

Want to drop everything.

    $ java -jar my-example-service/target/my-example-service-0.1-SNAPSHOT.jar db drop-all –confirm-delete-everything my-example-service/config-heroku.yml 


Using Git Flow?

If you’re accustomed to using git-flow, you will frequently want to push feature branches to Heroku.

It’s simple.

    $ git push heroku feature/BRANCH_NAME:master

This will allow you to test and deploy a non-master branch in your staging environment.  


Have further questions?  I’ve been running Dropwizard apps in Heroku for awhile now, ping me via Twitter.

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