```ruby
require "language_pack"
require "language_pack/ruby"

# Rack Language Pack. This is for any non-Rails Rack apps like Sinatra.
class LanguagePack::Rack < LanguagePack::Ruby

  # detects if this is a valid Rack app by seeing if "config.ru" exists
  # @return [Boolean] true if it's a Rack app
  def self.use?
    instrument "rack.use" do
      gemfile_lock? && LanguagePack::Ruby.gem_version('rack')
    end
  end

  def name
    "Ruby/Rack"
  end

  def default_config_vars
    instrument "rack.default_config_vars" do
      super.merge({
        "RACK_ENV" => "production"
      })
    end
  end

  def default_process_types
    instrument "rack.default_process_types" do
      # let's special case thin here if we detect it
      web_process = gem_is_bundled?("thin") ?
        "bundle exec thin start -R config.ru -e $RACK_ENV -p $PORT" :
        "bundle exec rackup config.ru -p $PORT"

      super.merge({
        "web" => web_process
      })
    end
  end

private

  # sets up the profile.d script for this buildpack
  def setup_profiled
    super
    set_env_default "RACK_ENV", "production"
  end

end

```

Use Phusion Passenger instead of WEBRick
user
```ruby
require "language_pack"
require "language_pack/ruby"

# Rack Language Pack. This is for any non-Rails Rack apps like Sinatra.
class LanguagePack::Rack < LanguagePack::Ruby

  # detects if this is a valid Rack app by seeing if "config.ru" exists
  # @return [Boolean] true if it's a Rack app
  def self.use?
    instrument "rack.use" do
      gemfile_lock? && LanguagePack::Ruby.gem_version('rack')
    end
  end

  def name
    "Ruby/Rack"
  end

  def default_config_vars
    instrument "rack.default_config_vars" do
      super.merge({
        "RACK_ENV" => "production"
      })
    end
  end

  def default_process_types
    instrument "rack.default_process_types" do
      web_process = "passenger start -e $RACK_ENV -p $PORT --max-pool-size 1"
      web_process = "bundle exec #{web_process}" if gem_is_bundled?("passenger")

      super.merge({
        "web" => web_process
      })
    end
  end

private

  # sets up the profile.d script for this buildpack
  def setup_profiled
    super
    set_env_default "RACK_ENV", "production"
  end

end

```
assistant