example with Madeleine https://github.com/ghostganz/madeleine **Don't know how to restore from the snapshots yet**

madeleine_example.rb

require 'rubygems'
require 'madeleine'

class Employee
  attr_accessor :name, :number, :address

  def initialize(name, number, address)
    @name = name
    @number = number
    @address = address
  end

  def to_s
    "Employee: name: #{name} num: #{number} addr: #{address}"
  end
end

class EmployeeManager
  def initialize
    @employees = {}
  end

  def add_employee(e)
    @employees[e.number] = e
  end

  def change_address(number, address)
    employee = @employees[number]
    raise "No such employee" if not employee
    employee.address = address
  end

  def delete_employee(number)
    @employees.remove(number)
  end

  def find_employee(number)
    @employees[number]
  end
end

class AddEmployee
  def initialize(employee)
    @employee = employee
  end

  def execute(system)
    system.add_employee(@employee)
  end
end

class FindEmployee
  def initialize(number)
    @number = number
  end

  def execute(system)
    system.find_employee(@number)
  end
end

store = SnapshotMadeleine.new('employees') {EmployeeManager.new}

Thread.new do
  while true
    sleep(20)
    store.take_snapshot
  end
end

tom = Employee.new('tom','1001','1 Division Street')
harry = Employee.new('harry','1002','3435 Sunnyside Ave')

store.execute_command(AddEmployee.new(tom))
store.execute_command(AddEmployee.new(harry))

puts(store.execute_command(FindEmployee.new('1001')))
puts(store.execute_command(FindEmployee.new('1002')))
# Employee: name: tom num: 1001 addr: 1 Division Street
# Employee: name: harry num: 1002 addr: 3435 Sunnyside Ave