For the uninitiated deploying a clojure app to heroku can be a time consuming endeavor. Here are some of the things I learned while deploying HTTPeek.

  • Heroku can be picky about the configuration of your app. Make sure to read Heroku’s clojure support documentation carefully. I ended up needing to change a couple of things to make it work.

  • HTTPeek uses a postgres database, and Heroku makes it easy to create one for the newly deployed app: heroku addons:create heroku-postgresql:hobby-dev

  • Once a database is provisioned the only thing left is to create the tables and conduct any necessary migrations. For HTTPeek I created a leiningen alias for my migrations. So migrating my tables is as simple as heroku run lein migrate. Well it would be once the app is configured correctly. Heroku uses a “DATABASE_URL” environment variable to create a connection with the database. “DATABASE_URL” is a string with the following structure <db-type>//<username>:password@<host>:<port>/<db-name> Before Heroku this is how HTTPeek configured it’s databases:

{:dev {:env {:db-classname "com.postgresql.jdbc.Driver"
            :db-subprotocol "postgresql"
            :db-subname "//localhost:5432/httpeek"
            :db-password ""
            :db-user "admin"}}
:test {:env {:db-classname "com.postgresql.jdbc.Driver"
             :db-subprotocol "postgresql"
             :db-subname "//localhost:5432/httpeek_spec"
             :db-password ""
             :db-user "admin"}}}

And after Heroku

{:dev {:env {:database-url "postgres://httpeek:password@localhost:5432/httpeek"}}
 :test {:env {:database-url "postgres://httpeek:password@localhost:5432/httpeek_spec"}}
 :heroku {:env {:database-url #=(eval (System/getenv "DATABASE_URL"))}}}

clojure.jdbc will take a map as well as a plain string to create a database connection.

With the database configured correctly, we can migrate and once the migrations finish HTTPeek runs perfectly, But there is a significant improvement that can be made to this process, namely that a large portion of it can be automated using a tool like Travis CI. Since HTTPeek is already using Travis this equates to a couple of small changes to the .travis.yml file. You can avail yourself of the documentation to get things set-up or you can use the Travis commandline tool to take care of the set-up for you. It’s as easy as travis setup heroku. You can even configure the build to run the migrations for you th the run: key. Now every time you push changes to your app and your build passes it will also deploy to Heroku!