Tag: Ruby on Rails

Paperclip, Bootstrap and SimpleForm working together on Rails

May 24, 2013 /

Few days ago, I've decided to get back to the "original" Paperclip. Until now, in one of my projects I've been using forked version with additional tweaks. However, supporting it for 3 years was enough. Getting back on track was fairly simple. It took me 1 day to fix the file structure, next day to rewrite validators and that would be all except one thing. Paperclip attaches error to 3 fields (example for thumb file):

  • thumb_file_name
  • thumb_file_size
  • thumb_content_type

I don't like this idea, since those are basically the internals of Paperclip implementation and in my opinion, all the errors should be attached to the "base" attribute (which in this case is called thumb). Furthermore this is not only the architectural problem but it also affect my views. I use Bootstrap with a SimpleForm attached to it and adding Paperclip to it seams fairly simply:

= simple_form_for @user, :html => { :class => 'form-horizontal' } do |f|
  = f.input :avatar

And... this should be it. However, as I mentioned above, Paperclip attaches errors to fields different than "thumb" (not all of them but it doesn't matter), so they aren't displayed on the interface. I could use something like that:

= f.errors :thumb_content_type

and well, this indeed works, unfortunately without any Bootstrap stylings. Also it requires extra line for each attachment that I use. So it sucks! That's why I've decided to do a little hack on it: let's just copy all the error messages into original "base" attachment name. This should solve our problem (and it did):

# lib/paperclip_extensions.rb
module PaperclipExtensions

  extend ActiveSupport::Concern

  module ClassMethods
    # Changes the default Paperclip behaviour so all the errors from attachments
    # are assigned to an attachment name field instead of 4 different once
    # This allows us to use Bootstrap and SimpleForm without any other extra
    # code
    def has_attached_file(name, options = {})
      # Initialize Paperclip stuff
      super
      # Then create a hookup to rewrite all the errors after validation
      after_validation do
        self.errors[name] ||= []
        %w{file_name file_size content_type updated_at}.each do |field|
          field_errors = self.errors["#{name}_#{field}"]
          next if field_errors.blank?

          self.errors[name] += field_errors
          field_errors.clear
        end
        self.errors[name].flatten!
      end
    end
  end

end

ActiveRecord::Base.send(:include, PaperclipExtensions)

Just put this code into a file in lib/ and create an initializer where you will require it:

# config/initializers/paperclip_extensions.rb
require 'paperclip_extensions'

After that, you are ready to go :) Enjoy using Paperclip with Bootstrap and SimpleForm without any problems!

Clear memcached without restart with Ruby and Capistrano (Rake task)

April 16, 2013 /

After successful Capistrano update (cap deploy) if we use Memcached - we should clear it. How can we do it without root access to the server? There are two ways to clear memcached without restarting it:

  • Memcached command: flush_all
  • Rails.cache.clear

One flush to rule them all - flush_all

If we have a dedicated server with one application on it - we can clear whole memcached memory, to do so, we create a rake task (/lib/tasks/memcached.rake):

require 'socket'

namespace :memcached do
  desc 'Flushes whole memcached local instance'
  task :flush do
    server  = '127.0.0.1'
    port    = 11211
    command = "flush_all\r\n"

    socket = TCPSocket.new(server, port)
    socket.write(command)
    result = socket.recv(2)

    if result != 'OK'
      STDERR.puts "Error flushing memcached: #{result}"
    end

    socket.close
  end
end

Usage:

bundle exec rake memcached:flush

It is worth mentioning, that this task doesn't require the Rails environment to be loaded. If it goes about the server address and port - you can always modify it so it will accept the env settings instead of hardcoding it.

Be aware, that this command will clear out all the data that is stored in Memcached instance, even the data that was used by other applications (other than our). If you want to clear out data used by one of many apps that are using same Memcached server, see the solution presented below.

Clearing single Rails app memcached data - Rails.cache.clear

Apart from flushing all the data that is in Memcached, we can always clear only the Rails cache by creating a really simple rake task (/lib/tasks/memcached.rake):

namespace :memcached do
  desc 'Clears the Rails cache'
  task :flush => :environment do
    Rails.cache.clear
  end
end

The execution process is exactly like in the previous case:

bundle exec rake memcached:flush

In this Rake task we do load the Rails environment (because we want to use Rails.cache instance). In multi application environment, this Memcached cleaning method seems way better because we work with our application scope only.

Capistrano task for clearing Memcached

So we have our rake task, but it would mean nothing without a Capistrano hookup:

namespace :memcached do

  desc "Flushes memcached local instance"
  task :flush, :roles => [:app] do
    run("cd #{current_path} && rake memcached:flush")
  end

end

Now we can use it like this:

bundle exec cap memcached:flush

Or we can hookup it to update process:

after 'deploy:update' do
  memcached.flush
end

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