Put your app online with Heroku

Created by Terence Lee, @hone02

Get Heroku

Follow steps “Introduction” and “Set up” of the Getting Started on Heroku with Ruby to sign up, install the Heroku CLI, and login.

Help from the coach

Talk about the benefits of deploying to Heroku vs traditional servers.

Updating our database

First, we need to get our database to work on Heroku, which uses a different database. Please change the following in the Gemfile:

gem "sqlite3"


group :development do
  gem "sqlite3"
group :production do
  gem "pg"

Run bundle install --without production to setup your dependencies.

Next, update the config/database.yml file. Change the following lines in the file:

  <<: *default
  database: storage/production.sqlite3

to these lines:

  adapter: postgresql
  encoding: unicode
  database: railsgirls_production
  pool: 5

Then save the changes in Git by creating a new commit. We’ll need to update our app in Git to deploy the new version to Heroku.

git add .
git commit -m "Use postgres as production database"
Help from the coach

You can talk about RDBMS and the different ones out there, plus include some details on Heroku’s dependency on PostgreSQL.

Deploying your app

App creation

We need to create our Heroku app by typing heroku create in the terminal and see something like this:

Creating app... done, ⬢ young-reaches-87845
https://young-reaches-87845.herokuapp.com/ | https://git.heroku.com/young-reaches-87845.git

In this case “young-reaches-87845” is your app name.

Pushing the code

Next we need to push our code to heroku by typing git push heroku master. You’ll see push output like the following:

Counting objects: 115, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (97/97), done.
Writing objects: 100% (115/115), 25.62 KiB | 0 bytes/s, done.
Total 115 (delta 10), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote: -----> Ruby app detected
remote: -----> Compiling Ruby/Rails
remote: -----> Using Ruby version: ruby-2.2.4
remote: -----> Installing dependencies using bundler 1.11.2
remote:        Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin -j4 --deployment
remote:        Fetching gem metadata from https://rubygems.org/..........
remote:        Fetching version metadata from https://rubygems.org/...
remote:        Fetching dependency metadata from https://rubygems.org/..
remote:        Installing concurrent-ruby 1.0.2
remote: -----> Launching...
remote:        Released v5
remote:        https://young-reaches-87845.herokuapp.com/ deployed to Heroku
remote: Verifying deploy... done.
To https://git.heroku.com/young-reaches-87845.git
 * [new branch]      master -> master

You’ll know the app is done being pushed, when you see the “Launching…” text like above.

Migrate database

Next we need to migrate our database like we did locally during the workshop:

heroku run rails db:migrate

When that command is finished being run, you can hit the app based on the url. For this example app, you can go to https://young-reaches-87845.herokuapp.com/. You can also type heroku open in the terminal to visit the page.

Closing notes

Heroku’s platform is not without its quirks. Applications run on Heroku live within an ephermeral environment — this means that (except for information stored in your database) any files created by your application will disappear if it restarts (for example, when you push a new version).

Ephemeral filesystem

Each dyno gets its own ephemeral filesystem, with a fresh copy of the most recently deployed code. During the dyno’s lifetime its running processes can use the filesystem as a temporary scratchpad, but no files that are written are visible to processes in any other dyno and any files written will be discarded the moment the dyno is stopped or restarted. For example, this occurs any time a dyno is replaced due to application deployment and approximately once a day as part of normal dyno management.

In the App tutorial the ability to attach a file to the Idea record is added, which results in new files being written to your applications public/uploads folder. The ephemeral storage in Heroku can be seen with the following steps:

  1. Launch the app with heroku open
  2. Add a new Idea with an image
  3. Restart the application by running heroku restart
  4. Go back to your Idea and reload the page - the image should no longer be visible

Working around Ephemeral Storage

Obviously this doesn’t seem to be useful if you were running a real life application, but there are ways to work around this which is commonly used by a lot of popular websites.

The most common method is to use an external asset host such as Amazon S3 (Simple Storage Service) or Rackspace CloudFiles. These services provide (for a low cost

While this functionality is a bit out of scope for this tutorial there are some resources available which you can use to find your way:

As always if you require any more information or assistance your coaches will be able to assist.

If you’re ever stuck during a guide, please ask your coach for help and also consult this handy cheatsheet for Ruby, Rails, the console, the Text Editor etc.


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