Устанавливаем mysql соединение через ssh-туннель, авторизуясь по ключам

#!/usr/bin/env ruby
require 'rubygems'
require 'mysql2'
require 'net/ssh/gateway'

gateway = Net::SSH::Gateway.new('productionserver.ru', 'user',
  { port: 22,
    keys: ["id_rsa.pub"],
    keys_only: true })

port = gateway.open('localhost', 3306, 3307)

client = Mysql2::Client.new(
  host: "127.0.0.1",
  username: 'root',
  password: 'qwerty',
  database: 'wp_blog',
  port: port
)
results = client.query("show tables")
results.each do |row|
  p row
end

client.close
gateway.shutdown!