Last updated August 29, 2022

Ruby on Rails is a popular web framework written in Ruby. This guide covers using Rails 5 on Heroku. For information on running previous versions of Rails on Heroku, see the tutorial for Rails 4.x or Rails 3.x.

For this guide you will need:

• Basic familiarity with Ruby/Rails and Git
• A locally installed version of Ruby 2.2.0+, Rubygems, Bundler, and Rails 5+
• A Heroku user account: Signup is free and instant.

Local setup

Install the Heroku CLI on your development machine.

Once installed, the heroku command is available from your terminal. Log in using your Heroku account’s email address and password:

$ heroku login
heroku: Enter your Heroku credentials
Email: schneems@example.com
Password:
Could not find an existing public key.
Would you like to generate one? [Yn]
Generating new SSH public key.
Uploading ssh public key /Users/adam/.ssh/id_rsa.pub

Press Enter at the prompt to upload your existing ssh key or create a new one, used for pushing code later on.

Create a new Rails app (or upgrade an existing one)

If you are starting with an existing app that uses a previous version of Rails, upgrade it to Rails 5 before continuing. If you’re not starting from an existing app at all, a vanilla Rails 5 app works great as a sample app.

To create a new app, first make sure that you’re using Rails 5.x by running rails -v. If necessary, you can get the new version of rails by running the following:

$ gem install rails --no-document
Successfully installed rails-5.2.2
1 gem installed

Then create a new app and move into its root directory:

$ rails new myapp --database=postgresql

Then move into your application directory.

$ cd myapp

Create a database locally:

$ bin/rails db:create
Database 'myapp_development' already exists
Database 'myapp_test' already exists

Add the pg gem

If you’re using an existing app that was created without specifying --database=postgresql, you need to add the pg gem to your Rails project. Edit your Gemfile and change this line:

gem 'sqlite3'

To this:

gem 'pg'

Now re-install your dependencies (to generate a new Gemfile.lock):

$ bundle install

For more information on why Postgres is recommended instead of Sqlite3, see why you cannot use Sqlite3 on Heroku.

In addition to using the pg gem, ensure that your config/database.yml file is using the postgresql adapter. The development section of your config/database.yml file should look something like this:

$ cat config/database.yml
# PostgreSQL. Versions 9.1 and up are supported.
#
# Install the pg driver:
#   gem install pg
# On OS X with Homebrew:
#   gem install pg -- --with-pg-config=/usr/local/bin/pg_config
# On OS X with MacPorts:
#   gem install pg -- --with-pg-config=/opt/local/lib/postgresql84/bin/pg_config
# On Windows:
#   gem install pg
#       Choose the win32 build.
#       Install PostgreSQL and put its /bin directory on your path.
#
# Configure Using Gemfile
# gem 'pg'
#
default: &default
  adapter: postgresql
  encoding: unicode
  # For details on connection pooling, see Rails configuration guide
  # http://guides.rubyonrails.org/configuring.html#database-pooling
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>

development:
  <<: *default
  database: myapp_development

  # The specified database role being used to connect to postgres.
  # To create additional roles in postgres see `$ createuser --help`.
  # When left blank, postgres will use the default role. This is
  # the same name as the operating system user that initialized the database.
  #username: myapp

  # The password associated with the postgres role (username).
  #password:

  # Connect on a TCP socket. Omitted by default since the client uses a
  # domain socket that doesn't need configuration. Windows does not have
  # domain sockets, so uncomment these lines.
  #host: localhost

  # The TCP port the server listens on. Defaults to 5432.
  # If your server runs on a different port number, change accordingly.
  #port: 5432

  # Schema search path. The server defaults to $user,public
  #schema_search_path: myapp,sharedapp,public

  # Minimum log levels, in increasing order:
  #   debug5, debug4, debug3, debug2, debug1,
  #   log, notice, warning, error, fatal, and panic
  # Defaults to warning.
  #min_messages: notice

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  <<: *default
  database: myapp_test

# As with config/secrets.yml, you never want to store sensitive information,
# like your database password, in your source code. If your source code is
# ever seen by anyone, they now have access to your database.
#
# Instead, provide the password as a unix environment variable when you boot
# the app. Read http://guides.rubyonrails.org/configuring.html#configuring-a-database
# for a full rundown on how to provide these environment variables in a
# production deployment.
#
# On Heroku and other platform providers, you may have a full connection URL
# available as an environment variable. For example:
#
#   DATABASE_URL="postgres://myuser:mypass@localhost/somedatabase"
#
# You can use this database configuration with:
#
#   production:
#     url: <%= ENV['DATABASE_URL'] %>
#
production:
  <<: *default
  database: myapp_production
  username: myapp
  password: <%= ENV['MYAPP_DATABASE_PASSWORD'] %>

Be careful here. If you omit the sql at the end of postgresql in the adapter section, your application will not work.

Create a welcome page

Rails 5 no longer has a static index page in production by default. When you’re using a new app, there will not be a root page in production, so we need to create one. We will first create a controller called welcome for our home page to live:

$ rails generate controller welcome

Next we’ll add an index page:

In file app/views/welcome/index.html.erb write:

<h2>Hello World</h2>
<p>
  The time is now: <%= Time.now %>
</p>

Now we need to make Rails route to this action. We’ll edit config/routes.rb to set the index page to our new method:

In file config/routes.rb, on line 2 add:

  root 'welcome#index'

You can verify that the page is there by running your server:

$ rails server

And visiting http://localhost:3000 in your browser. If you do not see the page, use the logs that are output to your server to debug.

Heroku gems

Previous versions of Rails required you to add a gem to your project rails_12factor to enable static asset serving and logging on Heroku. If you are deploying a new application, this gem is not needed. If you are upgrading an existing application, you can remove this gem provided you have the appropriate configuration in your config/environments/production.rb file:

# config/environments/production.rb
config.public_file_server.enabled = ENV['RAILS_SERVE_STATIC_FILES'].present?

if ENV["RAILS_LOG_TO_STDOUT"].present?
  logger           = ActiveSupport::Logger.new(STDOUT)
  logger.formatter = config.log_formatter
  config.logger = ActiveSupport::TaggedLogging.new(logger)
end

Specify your Ruby version

Rails 5 requires Ruby 2.2.0 or above. Heroku has a recent version of Ruby installed by default, however you can specify an exact version by using the ruby DSL in your Gemfile. Depending on your version of Ruby that you are currently running it might look like this:

ruby "2.6.0"

You should also be running the same version of Ruby locally. You can check this by running $ ruby -v. You can get more information on specifying your Ruby version on Heroku here.

Store your app in Git

Heroku relies on Git, a distributed source control management tool, for deploying your project. If your project is not already in Git, first verify that git is on your system:

$ git --help
usage: git [--version] [--help] [-C <path>] [-c <name>=<value>]
           [--exec-path[=<path>]] [--html-path] [--man-path] [--info-path]
           [-p | --paginate | -P | --no-pager] [--no-replace-objects] [--bare]
           [--git-dir=<path>] [--work-tree=<path>] [--namespace=<name>]
           <command> [<args>]

If you don’t see any output or get command not found you need to install Git on your system.

Once you’ve verified that Git works, first make sure you are in your Rails app directory by running $ ls:

The output should look like this:

$ ls
Gemfile
Gemfile-e
Gemfile.lock
README.md
Rakefile
app
bin
config
config.ru
db
lib
log
package.json
public
storage
test
tmp
vendor

Now run these commands in your Rails app directory to initialize and commit your code to Git:

$ git init
$ git add .
$ git commit -m "init"

You can verify everything was committed correctly by running:

$ git status
On branch master
nothing to commit, working tree clean

Now that your application is committed to Git you can deploy to Heroku.

Deploy your application to Heroku

Make sure you are in the directory that contains your Rails app, then create an app on Heroku:

$ heroku create
Creating app... done, secret-tor-42278
https://secret-tor-42278.herokuapp.com/ | https://git.heroku.com/secret-tor-42278.git

You can verify that the remote was added to your project by running:

$ git config --list | grep heroku
remote.heroku.url=https://git.heroku.com/secret-tor-42278.git
remote.heroku.fetch=+refs/heads/*:refs/remotes/heroku/*

If you see fatal: not in a git directory then you are likely not in the correct directory. Otherwise you can deploy your code. After you deploy your code, you need to migrate your database, make sure it is properly scaled, and use logs to debug any issues that come up.

Deploy your code:

$ git push heroku master
remote: Compressing source files... done.
remote: Building source:
remote:
remote:  !     Warning: Multiple default buildpacks reported the ability to handle this app. The first buildpack in the list below will be used.
remote:             Detected buildpacks: Ruby,Node.js
remote:             See https://devcenter.heroku.com/articles/buildpacks#buildpack-detect-order
remote: -----> Ruby app detected
remote: -----> Compiling Ruby/Rails
remote: -----> Using Ruby version: ruby-2.6.0
remote: -----> Installing dependencies using bundler 1.15.2
remote:        Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin -j4 --deployment
remote:        The dependency tzinfo-data (>= 0) will be unused by any of the platforms Bundler is installing for. Bundler is installing for ruby but the dependency is only for x86-mingw32, x86-mswin32, x64-mingw32, java. To add those platforms to the bundle, run `bundle lock --add-platform x86-mingw32 x86-mswin32 x64-mingw32 java`.
remote:        Fetching gem metadata from https://rubygems.org/.........
remote:        Fetching rake 12.3.2
remote:        Installing rake 12.3.2
remote:        Fetching concurrent-ruby 1.1.4
remote:        Fetching thread_safe 0.3.6
remote:        Fetching minitest 5.11.3
remote:        Installing thread_safe 0.3.6
remote:        Installing minitest 5.11.3
remote:        Installing concurrent-ruby 1.1.4
remote:        Fetching builder 3.2.3
remote:        Installing builder 3.2.3
remote:        Fetching erubi 1.8.0
remote:        Installing erubi 1.8.0
remote:        Fetching mini_portile2 2.4.0
remote:        Fetching crass 1.0.4
remote:        Installing mini_portile2 2.4.0
remote:        Fetching rack 2.0.6
remote:        Installing crass 1.0.4
remote:        Installing rack 2.0.6
remote:        Fetching nio4r 2.3.1
remote:        Installing nio4r 2.3.1 with native extensions
remote:        Fetching websocket-extensions 0.1.3
remote:        Installing websocket-extensions 0.1.3
remote:        Fetching mini_mime 1.0.1
remote:        Installing mini_mime 1.0.1
remote:        Fetching arel 9.0.0
remote:        Installing arel 9.0.0
remote:        Fetching mimemagic 0.3.3
remote:        Fetching msgpack 1.2.4
remote:        Installing msgpack 1.2.4 with native extensions
remote:        Installing mimemagic 0.3.3
remote:        Using bundler 1.17.2
remote:        Fetching coffee-script-source 1.12.2
remote:        Installing coffee-script-source 1.12.2
remote:        Fetching execjs 2.7.0
remote:        Installing execjs 2.7.0
remote:        Fetching method_source 0.9.2
remote:        Installing method_source 0.9.2
remote:        Fetching thor 0.20.3
remote:        Installing thor 0.20.3
remote:        Fetching ffi 1.9.25
remote:        Installing ffi 1.9.25 with native extensions
remote:        Fetching multi_json 1.13.1
remote:        Installing multi_json 1.13.1
remote:        Fetching pg 1.1.3
remote:        Installing pg 1.1.3 with native extensions
remote:        Fetching puma 3.12.0
remote:        Installing puma 3.12.0 with native extensions
remote:        Fetching rb-fsevent 0.10.3
remote:        Installing rb-fsevent 0.10.3
remote:        Fetching tilt 2.0.9
remote:        Installing tilt 2.0.9
remote:        Fetching turbolinks-source 5.2.0
remote:        Installing turbolinks-source 5.2.0
remote:        Fetching tzinfo 1.2.5
remote:        Installing tzinfo 1.2.5
remote:        Fetching nokogiri 1.9.1
remote:        Installing nokogiri 1.9.1 with native extensions
remote:        Fetching i18n 1.4.0
remote:        Installing i18n 1.4.0
remote:        Fetching websocket-driver 0.7.0
remote:        Installing websocket-driver 0.7.0 with native extensions
remote:        Fetching mail 2.7.1
remote:        Installing mail 2.7.1
remote:        Fetching rack-test 1.1.0
remote:        Installing rack-test 1.1.0
remote:        Fetching sprockets 3.7.2
remote:        Installing sprockets 3.7.2
remote:        Fetching marcel 0.3.3
remote:        Installing marcel 0.3.3
remote:        Fetching coffee-script 2.4.1
remote:        Installing coffee-script 2.4.1
remote:        Fetching uglifier 4.1.20
remote:        Installing uglifier 4.1.20
remote:        Fetching bootsnap 1.3.2
remote:        Installing bootsnap 1.3.2 with native extensions
remote:        Fetching rb-inotify 0.10.0
remote:        Installing rb-inotify 0.10.0
remote:        Fetching turbolinks 5.2.0
remote:        Installing turbolinks 5.2.0
remote:        Fetching activesupport 5.2.2
remote:        Installing activesupport 5.2.2
remote:        Fetching loofah 2.2.3
remote:        Fetching sass-listen 4.0.0
remote:        Installing loofah 2.2.3
remote:        Installing sass-listen 4.0.0
remote:        Fetching rails-dom-testing 2.0.3
remote:        Installing rails-dom-testing 2.0.3
remote:        Fetching globalid 0.4.1
remote:        Installing globalid 0.4.1
remote:        Fetching activemodel 5.2.2
remote:        Installing activemodel 5.2.2
remote:        Fetching jbuilder 2.8.0
remote:        Installing jbuilder 2.8.0
remote:        Fetching sass 3.7.2
remote:        Installing sass 3.7.2
remote:        Fetching rails-html-sanitizer 1.0.4
remote:        Installing rails-html-sanitizer 1.0.4
remote:        Fetching activejob 5.2.2
remote:        Installing activejob 5.2.2
remote:        Fetching activerecord 5.2.2
remote:        Fetching actionview 5.2.2
remote:        Installing activerecord 5.2.2
remote:        Installing actionview 5.2.2
remote:        Fetching actionpack 5.2.2
remote:        Installing actionpack 5.2.2
remote:        Fetching actioncable 5.2.2
remote:        Fetching activestorage 5.2.2
remote:        Fetching actionmailer 5.2.2
remote:        Installing actioncable 5.2.2
remote:        Installing actionmailer 5.2.2
remote:        Installing activestorage 5.2.2
remote:        Fetching railties 5.2.2
remote:        Installing railties 5.2.2
remote:        Fetching sprockets-rails 3.2.1
remote:        Installing sprockets-rails 3.2.1
remote:        Fetching coffee-rails 4.2.2
remote:        Fetching sass-rails 5.0.7
remote:        Fetching rails 5.2.2
remote:        Installing rails 5.2.2
remote:        Installing coffee-rails 4.2.2
remote:        Installing sass-rails 5.0.7
remote:        Bundle complete! 18 Gemfile dependencies, 61 gems now installed.
remote:        Gems in the groups development and test were not installed.
remote:        Bundled gems are installed into `./vendor/bundle`
remote:        Post-install message from i18n:
remote:
remote:        HEADS UP! i18n 1.1 changed fallbacks to exclude default locale.
remote:        But that may break your application.
remote:
remote:        Please check your Rails app for 'config.i18n.fallbacks = true'.
remote:        If you're using I18n (>= 1.1.0) and Rails (< 5.2.2), this should be
remote:        'config.i18n.fallbacks = [I18n.default_locale]'.
remote:        If not, fallbacks will be broken in your app by I18n 1.1.x.
remote:
remote:        For more info see:
remote:        https://github.com/svenfuchs/i18n/releases/tag/v1.1.0
remote:
remote:        Post-install message from sass:
remote:
remote:        Ruby Sass is deprecated and will be unmaintained as of 26 March 2019.
remote:
remote:        * If you use Sass as a command-line tool, we recommend using Dart Sass, the new
remote:          primary implementation: https://sass-lang.com/install
remote:
remote:        * If you use Sass as a plug-in for a Ruby web framework, we recommend using the
remote:          sassc gem: https://github.com/sass/sassc-ruby#readme
remote:
remote:        * For more details, please refer to the Sass blog:
remote:          http://sass.logdown.com/posts/7081811
remote:
remote:        Removing bundler (1.15.2)
remote:        Bundle completed (42.62s)
remote:        Cleaning up the bundler cache.
remote:        The dependency tzinfo-data (>= 0) will be unused by any of the platforms Bundler is installing for. Bundler is installing for ruby but the dependency is only for x86-mingw32, x86-mswin32, x64-mingw32, java. To add those platforms to the bundle, run `bundle lock --add-platform x86-mingw32 x86-mswin32 x64-mingw32 java`.
remote: -----> Installing node-v8.10.0-linux-x64
remote: -----> Detecting rake tasks
remote: -----> Preparing app for Rails asset pipeline
remote:        Running: rake assets:precompile
remote:        Yarn executable was not detected in the system.
remote:        Download Yarn at https://yarnpkg.com/en/docs/install
remote:        I, [2019-01-03T17:16:39.683335 #1309]  INFO -- : Writing /tmp/build_020cb65e00979312f798ba48446f2064/public/assets/application-9622f0fe63bfad91bdeaa3a771e86262263840678fd66849b311b6cfb3f7cc85.js
remote:        I, [2019-01-03T17:16:39.683750 #1309]  INFO -- : Writing /tmp/build_020cb65e00979312f798ba48446f2064/public/assets/application-9622f0fe63bfad91bdeaa3a771e86262263840678fd66849b311b6cfb3f7cc85.js.gz
remote:        I, [2019-01-03T17:16:39.693392 #1309]  INFO -- : Writing /tmp/build_020cb65e00979312f798ba48446f2064/public/assets/application-e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855.css
remote:        I, [2019-01-03T17:16:39.693515 #1309]  INFO -- : Writing /tmp/build_020cb65e00979312f798ba48446f2064/public/assets/application-e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855.css.gz
remote:        Asset precompilation completed (3.72s)
remote:        Cleaning assets
remote:        Running: rake assets:clean
remote: -----> Detecting rails configuration
remote:
remote: ###### WARNING:
remote:
remote:        You set your `config.active_storage.service` to :local in production.
remote:        If you are uploading files to this app, they will not persist after the app
remote:        is restarted, on one-off dynos, or if the app has multiple dynos.
remote:        Heroku applications have an ephemeral file system. To
remote:        persist uploaded files, please use a service such as S3 and update your Rails
remote:        configuration.
remote:
remote:        For more information can be found in this article:
remote:          https://devcenter.heroku.com/articles/active-storage-on-heroku
remote:
remote:
remote: ###### WARNING:
remote:
remote:        We detected that some binary dependencies required to
remote:        use all the preview features of Active Storage are not
remote:        present on this system.
remote:
remote:        For more information please see:
remote:          https://devcenter.heroku.com/articles/active-storage-on-heroku
remote:
remote:
remote: ###### WARNING:
remote:
remote:        No Procfile detected, using the default web server.
remote:        We recommend explicitly declaring how to boot your server process via a Procfile.
remote:        https://devcenter.heroku.com/articles/ruby-default-web-server
remote:
remote:
remote: -----> Discovering process types
remote:        Procfile declares types     -> (none)
remote:        Default types for buildpack -> console, rake, web
remote:
remote: -----> Compressing...
remote:        Done: 41.3M
remote: -----> Launching...
remote:        Released v6
remote:        https://secret-tor-42278.herokuapp.com/ deployed to Heroku
remote:
remote: Verifying deploy... done.
To https://git.heroku.com/secret-tor-42278.git
 * [new branch]      master -> master

It is always a good idea to check to see if there are any warnings or errors in the output. If everything went well you can migrate your database.

Migrate your database

If you are using the database in your application, you need to manually migrate the database by running:

$ heroku run rake db:migrate

Any commands after the heroku run are executed on a Heroku dyno. You can obtain an interactive shell session by running $ heroku run bash.

Visit your application

You’ve deployed your code to Heroku. You can now instruct Heroku to execute a process type. Heroku does this by running the associated command in a dyno, which is a lightweight container that is the basic unit of composition on Heroku.

Let’s ensure we have one dyno running the web process type:

$ heroku ps:scale web=1

You can check the state of the app’s dynos. The heroku ps command lists the running dynos of your application:

$ heroku ps
Free dyno hours quota remaining this month: 967h 44m (96%)
Free dyno usage for this app: 0h 0m (0%)
For more information on dyno sleeping and how to upgrade, see:
https://devcenter.heroku.com/articles/dyno-sleeping

=== web (Free): bin/rails server -p $PORT -e $RAILS_ENV (1)
web.1: starting 2019/01/03 11:16:50 -0600 (~ 6s ago)

Here, one dyno is running.

We can now visit the app in our browser with heroku open.

$ heroku open

You should now see the “Hello World” text we inserted above.

Heroku gives you a default web URL for simplicity while you are developing. When you are ready to scale up and use Heroku for production you can add your own custom domain.

View logs

If you run into any problems getting your app to perform properly, you will need to check the logs.

You can view information about your running app using one of the logging commands, heroku logs:

$ heroku logs
2019-01-03T17:15:46.454068+00:00 app[api]: Enable Logplex by user developer@example.com2019-01-03T17:15:46.277667+00:00 app[api]: Initial release by user developer@example.com2019-01-03T17:15:46.454068+00:00 app[api]: Release v2 created by user developer@example.com2019-01-03T17:15:48.000000+00:00 app[api]: Build started by user developer@example.com2019-01-03T17:16:49.295117+00:00 app[api]: Release v3 created by user developer@example.com2019-01-03T17:16:49.295117+00:00 app[api]: Set LANG, RACK_ENV, RAILS_ENV, RAILS_LOG_TO_STDOUT, RAILS_SERVE_STATIC_FILES, SECRET_KEY_BASE config vars by user developer@example.com2019-01-03T17:16:50.054946+00:00 app[api]: Running release v4 commands by user developer@example.com2019-01-03T17:16:50.490534+00:00 app[api]: Scaled to console@0:Free rake@0:Free web@1:Free by user developer@example.com2019-01-03T17:16:50.075764+00:00 app[api]: Release v5 created by user developer@example.com2019-01-03T17:16:50.075764+00:00 app[api]: @ref:postgresql-colorful-78926 completed provisioning, setting DATABASE_URL. by user developer@example.com2019-01-03T17:16:53.668660+00:00 heroku[web.1]: Starting process with command `bin/rails server -p 21857 -e production`
2019-01-03T17:16:53.000000+00:00 app[api]: Build succeeded
2019-01-03T17:16:59.442990+00:00 heroku[web.1]: State changed from starting to up

You can also get the full stream of logs by running the logs command with the --tail flag option like this:

$ heroku logs --tail

Dyno sleeping and scaling

By default, new applications are deployed to a free dyno. Free apps will “sleep” to conserve resources. You can find more information about this behavior by reading about free dyno behavior.

To avoid dyno sleeping, you can upgrade to a hobby or professional dyno type as described in the Dyno Types article. For example, if you migrate your app to a professional dyno, you can easily scale it by running a command telling Heroku to execute a specific number of dynos, each running your web process type.

Run the Rails console

Heroku allows you to run commands in a one-off dyno - scripts and applications that only need to be executed when needed - using the heroku run command. Use this to launch a Rails console process attached to your local terminal for experimenting in your app’s environment:

$ heroku run rails console
irb(main):001:0> puts 1+1
2

Another useful command for debugging is $ heroku run bash which will spin up a new dyno and give you access to a bash session.

Run Rake commands

Rake can be run as an attached process exactly like the console:

$ heroku run rake db:migrate

Configure your webserver

By default, your app’s web process runs rails server, which uses Puma in Rails 5. If you are upgrading an app you’ll need to add puma to your application Gemfile:

gem 'puma'

Then run

$ bundle install

Now you are ready to configure your app to use Puma. For this tutorial we will use the default config/puma.rb of that ships with Rails 5, but we recommend reading more about configuring your application for maximum performance by reading the Puma documentation.

Finally you will need to tell Heroku how to run your Rails app by creating a Procfile in the root of your application directory.

Create a Procfile

Change the command used to launch your web process by creating a file called Procfile and entering this:

In file Procfile write:

web: bundle exec puma -t 5:5 -p ${PORT:-3000} -e ${RACK_ENV:-development}

Note: This file must be named Procfile exactly.

We recommend generating a Puma config file based on our Puma documentation for maximum performance.

To use the Procfile locally, you can use heroku local.

In addition to running commands in your Procfile heroku local can also help you manage environment variables locally through a .env file. Set the local RACK_ENV to development in your environment and a PORT to connect to. Before pushing to Heroku you’ll want to test with the RACK_ENV set to production since this is the environment your Heroku app will run in.

$ echo "RACK_ENV=development" >>.env
$ echo "PORT=3000" >> .env

Note: Another alternative to using environment variables locally with a .env file is the dotenv gem.

You’ll also want to add .env to your .gitignore since this is for local environment setup.

$ echo ".env" >> .gitignore
$ git add .gitignore
$ git commit -m "add .env to .gitignore"

Test your Procfile locally using Foreman. You can now start your web server by running:

$ heroku local
[OKAY] Loaded ENV .env File as KEY=VALUE Format
11:17:03 AM web.1 |  Puma starting in single mode...
11:17:03 AM web.1 |  * Version 3.12.0 (ruby 2.6.0-p-1), codename: Llamas in Pajamas
11:17:03 AM web.1 |  * Min threads: 5, max threads: 5
11:17:03 AM web.1 |  * Environment: development
11:17:04 AM web.1 |  * Listening on tcp://0.0.0.0:3000
11:17:04 AM web.1 |  Use Ctrl-C to stop

Looks good, so press Ctrl+C to exit and you can deploy your changes to Heroku:

$ git add .
$ git commit -m "use puma via procfile"
$ git push heroku master

Check ps. You’ll see that the web process uses your new command specifying Puma as the web server.

$ heroku ps
Free dyno hours quota remaining this month: 967h 44m (96%)
Free dyno usage for this app: 0h 0m (0%)
For more information on dyno sleeping and how to upgrade, see:
https://devcenter.heroku.com/articles/dyno-sleeping

=== web (Free): bundle exec puma -t 5:5 -p ${PORT:-3000} -e ${RACK_ENV:-development} (1)
web.1: starting 2019/01/03 11:17:26 -0600 (~ 5s ago)

The logs also reflect that we are now using Puma.

$ heroku logs

Rails asset pipeline

There are several options for invoking the Rails asset pipeline when deploying to Heroku. For general information on the asset pipeline please see the Rails 3.1+ Asset Pipeline on Heroku Cedar article.

The config.assets.initialize_on_precompile option has been removed is and not needed for Rails 5. Also, any failure in asset compilation will now cause the push to fail. For Rails 5 asset pipeline support see the Ruby Support page.

Troubleshooting

If you push up your app and it crashes (heroku ps shows state crashed), check your logs to find out what went wrong. Here are some common problems.

Runtime dependencies on development/test gems

If you’re missing a gem when you deploy, check your Bundler groups. Heroku builds your app without the development or test groups, and if your app depends on a gem from one of these groups to run, you should move it out of the group.

One common example is using the RSpec tasks in your Rakefile. If you see this in your Heroku deploy:

$ heroku run rake -T
Running `bundle exec rake -T` attached to terminal... up, ps.3
rake aborted!
no such file to load -- rspec/core/rake_task

Then you’ve hit this problem. First, duplicate the problem locally:

$ bundle install --without development:test
…
$ bundle exec rake -T
rake aborted!
no such file to load -- rspec/core/rake_task

Note: The --without option on bundler is sticky. You can get rid of this option by running bundle config --delete without.

Now you can fix it by making these Rake tasks conditional on the gem load. For example:

begin
  require "rspec/core/rake_task"

  desc "Run all examples"

  RSpec::Core::RakeTask.new(:spec) do |t|
    t.rspec_opts = %w[--color]
    t.pattern = 'spec/**/*_spec.rb'
  end
rescue LoadError
end

Confirm it works locally, then push to Heroku.

Next steps

Congratulations! You have deployed your first Rails 5 application to Heroku. Here’s some recommended reading:

• Visit the Ruby support category to learn more about using Ruby and Rails on Heroku.
• The Deployment category provides a variety of powerful integrations and features to help streamline and simplify your deployments.