Sinatra is using Thin instead of Puma

Question

I'm building a Sinatra application that needs to be threadable, as I'm using sucker-punch for jobs, and I want to use the Puma server to do it though I've never used it before.

For some reason, when I start my application it runs Thin.

I uninstalled Thin and it uses Puma, which is good, but how do I stop it from starting with Thin in the future in the case this happens again?

I start my application with rackup and I have in my main app.rb file:

class App < ::Sinatra::Base
  configure  do
    set :show_exceptions, true
    set :root, Info[:root]
    set :threaded, true

    set :server, :puma
    Tilt.register Tilt::ERBTemplate, 'html.erb'

    enable :logging
    use Rack::CommonLogger, Log.file

    if ENV['APP_ENVIRONMENT'] == 'PROD'
      set :environment, :production
      set :bind, '0.0.0.0', HOST
      set :show_exceptions, false
    end
  end
end

Answer 1

You need to set your server in the config.ru rackup file. In this file you can set

Rack::Handler.get('puma').run App.new

Documentation is available in "Module: Rack::Handler".

However an even better way is to just run Puma explicitly:

bundle exec puma config.ru

OR as suggested by @matt:

rackup -s puma