CODEWITHSUNDEEP
ruby-on-railsrubyruby-on-rails-3caching
madprogrammer
madprogrammer

Reputation: 801

Implement caching in the right way

I'm new to Ruby on Rails (just started using it a few days ago). I'm making a simple web frontend to display various system information, including S.M.A.R.T information. I've made this little class:

class SmartValues
    attr_reader :data
    KEYS  = [:id, :name, :flag, :value, :worst, :thresh, :type, :updated, :failed, :raw]

    def initialize(devices)
            @data = Hash[devices.map {|dev| [dev, SmartValues.getValues(dev)]}]
    end

    def self.getValues(device)
            lines = `sudo /usr/sbin/smartctl -A #{device}`.split("\n")[7..-1].collect! { |line| line.split }
            return lines.map { |line| Hash[KEYS.zip line] }
    end
end

It works fine, except that it's included into my controller like this:

class HomeController < ApplicationController
    def index
        @smart = SmartValues.new(["/dev/sda", "/dev/sdb", "/dev/sdc", "/dev/sdd", "/dev/sde", "/dev/sdf"]).data
    end
end

So it must be that the smartctl binary is executed multiple times for each request of the page. I would like to add some kind of caching, so that the information is updated periodically, but not on every request. What's the right RoR-ish way of doing it?

Upvotes: 0

Views: 335

Answers (1)

apneadiving
apneadiving

Reputation: 115511

def self.lines(device)
  Rails.cache.fetch("#{device}_lines", :namespace => "smart_values", :expires_in => 15.minutes) do
    `sudo /usr/sbin/smartctl -A #{device}`.split("\n")[7..-1].collect! { |line| line.split }
  end
end

def self.getValues(device)
  lines(device).map { |line| Hash[KEYS.zip line] }
end

Upvotes: 3

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