Puma on Heroku

database_connections.rb

#config/initializers/database_connection.rb
Rails.application.config.after_initialize do
  ActiveRecord::Base.connection_pool.disconnect!

  ActiveSupport.on_load(:active_record) do
    if Rails.application.config.database_configuration
      config = Rails.application.config.database_configuration[Rails.env]
      config['reaping_frequency'] = ENV['DB_REAP_FREQ'] || 10 # seconds
      config['pool']              = ENV['DB_POOL']      || 5
      ActiveRecord::Base.establish_connection(config)
    end
  end
end

Gemfile

gem 'foreman'
gem 'puma'

Procfile

web: bundle exec puma -t ${PUMA_MIN_THREADS:-8}:${PUMA_MAX_THREADS:-12} -w ${PUMA_WORKERS:-2} -p $PORT -e ${RACK_ENV:-development}

How do you normally start your development server when you're using this Procfile? I've gotten in the habit of just doing foreman start web and that throws errors locally with the above Procfile because my local environment doesn't seem to support that syntax. I've tried in zsh and bash 3.2.

@joshhepworth

RACK_ENV=development foreman start

For rails 6, am getting the following error
DEPRECATION WARNING: [] is deprecated and will be removed from Rails 6.2 (Use configs_for)
can't modify frozen Hash #Ln 8