How to start a minimal ruby app using Puma or Unicorn?

Question

I have a very basic ruby example running on Thin, but I would like to know how to translate this example to use Unicorn or Puma as the HTTP server instead. Here is the code I have now:

require 'rack'

class HelloWorld
  def talk()
    return "Hello World!"
  end
end

class SomeServer
  def start(server_object, port)
    app = proc do |env|
      [ 200, {"Content-Type" => "text/html"}, [server_object.talk()] ]
    end

    Rack::Handler::Thin::run(app, :Port => port)
  end
end

SomeServer.new.start(HelloWorld.new, 3000)

This runs fine and well, but I cannot figure out how to make it run using Puma or Unicorn instead. Most online documentation I find for the two is for Rails apps. How can I utilize the multi-threading capabilities of these servers with this simple program?

Answer 1

use sinatra.

So to take it step by step first install sinatra and puma gems

gem install sinatra

gem install puma

then create a file myapp.rb

require 'sinatra'
configure { set :server, :puma }

get '/' do
  "Hello World!"
end

then run the file

ruby myapp.rb

by default sinatra listens on 4567 so go to localhost:4567 you can configure puma to listen on a specific port or do a lot of other things using a config file read the documentation

Answer 2

A minimal example that doesn't require additional gems looks like this.

Using a single file

Create a puma config file config.rb with the following content:

app do |env|
  body = 'Hello, World!'
  [200, { 'Content-Type' => 'text/plain', 'Content-Length' => body.length.to_s }, [body]]
end

bind 'tcp://127.0.0.1:3000'

and run puma with

puma -C /path/to/config.rb

That's it.

Using a configuration and a rackup file

In the example above, the config file contains the application itself. It makes sense to move the application to a rackup file: Create a rackup file app.ru with the following content:

class HelloWorld
  def call(env)
    body = 'Hello, World!'
   [200, { 'Content-Type' => 'text/plain', 'Content-Length' => body.length.to_s }, [body]]
  end
end

run HelloWorld.new

Then update your config.rb, removing the app and linking the rackup file instead:

rackup '/path/to/app.ru'

bind 'tcp://127.0.0.1:3000'

and run puma as before with

puma -C /path/to/config.rb

The example configuration file for puma is helpful. (Update: This example configuration file is no longer maintained. The authors refer to dsl.rb instead.)

Answer 3

Instead of starting your app with Rack::Handler::Thin, you should be able to use the Puma Rack handler instead, like this:

Rack::Handler::Puma.run(app, :Port =>port)

You'd need to also require 'rack/handler/puma' after installing the Puma gem.