Deploying a Sinatra + DataMapper + SQLite app to Heroku
Recently I followed the excellent Nettuts’ session on Singing with Sinatra, and I learned a lot about Rack-only apps.
I pushed the app to Heroku and all I was getting was “Application Error”. I found out that Heroku only uses PostgreSQL as database, so SQLite will not work at all. This is what you should do:
a) Make sure you have a .gems file on the top folder with all the gems you need:
sinatra
data_mapper
rack-flash
sinatra-redirect-with-flash
builder
dm-postgres-adapter
Did you notice the dm-postgres-adapter at the end?. That gem is ABSOLUTE NECESSARY if you coded your app using SQLite and DataMapper and you want to push it to Heroku. I repeat. ABSOLUTE NECESSARY.
b) We also need a configure.ru file at the top folder:
require 'your_sinatra_app_file_name'
run Sinatra::Application
c) On your Sinatra file (the one that has all the code) we need to tell DataMapper which database to use:
# Setting up the database
DataMapper.setup(:default, ENV['DATABASE_URL'] || "sqlite3://#{Dir.pwd}/mydatabase.db")
The part ENV['DATABASE_URL'] is used by Heroku to assign a database to our app. If we are developing locally, we just use mydatabase.db, which is SQLite. Got it?
d) Finally, we push the DB to Heroku:
heroku db:push sqlite://mydatabase.db #assuming you are on your app directory
Our SQLite database will be translated to a PostgreSQL database automatically. No hassle!
Just push it (the app, I mean) and there you go. It will work. You are a hero.
