シングルスレッドサーバー、マルチスレッドサーバー、 EventMachine (Reactor パターン) + EM.defer による非同期処理サーバー

e.rb

require 'eventmachine'

class DB
  class << self
    def connect
      sleep 1
    end

    def query
      sleep 3
    end

    def disconnect
      sleep 1
    end
  end
end

class Server < EM::Connection
  def receive_data(data)
    p '==>'
    EM.defer do
      DB.connect
      p data
      DB.query
      DB.disconnect
    end
    p '=='
  end
end

Signal.trap(:INT) do
  EM.stop_event_loop
  raise
end

EM.run do
  p 'Server boot localhost:9999'
  EM.start_server("localhost", 9999, Server)
end

nc.rb

#!/usr/bin/env ruby

n = (ARGV.shift || 1).to_i

ts = []
n.times do |i|
  ts << Thread.new(i) do |i|
    cmd = "echo #{i} | nc localhost 9999"
    puts cmd
    system cmd
  end
end

ts.each(&:join)

s.rb

require 'socket'

class DB
  class << self
    def connect
      sleep 1
    end

    def query
      sleep 3
    end

    def disconnect
      sleep 1
    end
  end
end

p 'Server boot localhost:9999'
Socket.tcp_server_loop(9999) { |sock, _|
  p '==>'
  begin
    DB.connect
    p sock.gets
    DB.query
    DB.disconnect
  ensure
    sock.close
  end
  p '=='
}

t.rb

require 'socket'

class DB
  class << self
    def connect
      sleep 1
    end

    def query
      sleep 3
    end

    def disconnect
      sleep 1
    end
  end
end

p 'Server boot localhost:9999'
Socket.tcp_server_loop(9999) { |sock, _|
  p '==>'
  Thread.new(sock) do |sock|
    begin
      DB.connect
      p sock.gets
      DB.query
      DB.disconnect
    ensure
      sock.close
    end
  end
  p '=='
}