sudo gem install key_value

# Gemfile
gem 'key_value', :require => false # so migrations do not fail because of missing table

class CreateKeyValue < ActiveRecord::Migration
  def self.up
    create_table :key_values do |t|
      t.string :key, :null => false
      t.text :value, :null => false
    end
    add_index :key_values, :key, :unique => true
  end

  def self.down
    drop_table :key_values
  end
end

# set & get
KeyValue['xxx'] = {:baz=>'foo'})
KeyValue['xxx'] -> {:baz=>'foo'}

# delete
KeyValue['xxx'] = nil
or KeyValue.del('xxx')

# increment
KeyValue.inc('xxx') # !! Not atomic
or KeyValue.inc('xxx', 5) # increment by 5

# cache
result = KeyValue.cache('xxx'){ ..something expensive.. }

# defaults (in case the value is not stored yet)
KeyValue.defaults['xxx'] = 1
KeyValue['xxx'] -> 1
KeyValue['xxx'] = 2
KeyValue['xxx'] -> 2
KeyValue['xxx'] = nil
KeyValue['xxx'] -> 1

KeyValue.handler_socket = true
# or Hash with any of these keys :host :port :database :timeout :listen_backlog :sndbuf :rcvbuf

# all read requests use HandlerSocket
KeyValue['xxx'] # -> same as before but faster :)