rails mysql database backed lock

lock.rb

class TimeoutError < StandardError
end

# used to prevent code running on the same object twice
def answer
  begin
    eq = EnrollmentQuestion.find_by_enrollment_id_and_question_id(@enrollment.id, @question.id)
    Lock.new(eq,0).synchronize do
      if @enrollment.is_valid_attempt?(@question)
        ...
      end
      respond_to do |format|
        ...
      end
    end
  rescue TimeoutError
    redirect_somewhere
  end
end

class Lock
  def initialize(name,timeout)
    @name = generate_name(name)
    @timeout = timeout || 10
  end

  def synchronize(&block)
    lock
    begin
      block.call()
    ensure
      release
    end
  end

  private
  def generate_name(name)
    if name.respond_to?(:to_model)
      "#{ActiveModel::Naming.singular(name)}_#{name.to_model.to_key.join('_')}"
    else
      name
    end
  end
  def lock
    res = ActiveRecord::Base.connection.execute("SELECT GET_LOCK('#{@name}',#{@timeout});")
    res = res.first if res
    res = res.first if res
    #Rails.logger.error "lock(#{@name},#{@timeout}) => #{res}"
    raise TimeoutError, "Getting Lock #{@name} timeout" unless res == 1
  end

  def release
    res = ActiveRecord::Base.connection.execute("SELECT RELEASE_LOCK('#{@name}');")
    res = res.first if res
    res = res.first if res
    #Rails.logger.error "release(#{@name}) => #{res}"
    res
  end
end