Daily Collections with Mongoid 2.4

daily_collection.rb

# Daily Collections With Mongoid 2.4
#
# Author: Tilo Sloboda, 2012-06-16
# Twitter: https://twitter.com/#!/tilosloboda
# GitHub: https://gist.github.com/tilo
# Gist: https://gist.github.com/2942627
#
# This can be useful if you need to re-import certain data every day
# and need to make sure that the latest daily collection is used in production
#
# USAGE:
#    class Thing
#      include DailyCollection
#      include Mongoid::Document
#      store_in todays_collection_name
#      ...
#    end
#
# My Use Case:
#
# One App instance is using the Thing collection for an API.
# At midnight a new instance of the App starts and loads a new nightly data dump for Things.
# Once the nightly data dump is loaded, we can tell the App which runs the API to switch 
# to the new collection and we can delete any older collections in the nightly cron job.
#
# To switch collection names during runtime:
#
#    Thing.update_collection_name()
#
# To drop old collections , including "things" collection:
#
#    Thing.drop_old_collections    # pass in "true" to really drop collections
#

module DailyCollection
  def self.included(base)
    # THIS ONLY WORKS FOR Mongoid 2.4
    raise "INCORRECT Mongoid Version #{Mongoid::VERSION} instead of 2.4.x" if Mongoid::VERSION >= '2.5'
    base.extend(ClassMethods)
  end

  module ClassMethods
    def update_collection_name()
      self.collection_name = self.todays_collection_name
      self._collection = Mongoid::Collection.new(self, self.collection_name, {})
    end

    # name collections like this "things_20110712" instead of just 'things' 
    def todays_collection_name
      self.to_s.pluralize.downcase + '_' + Date.today.strftime('%Y%m%d') # collection names should not contain '-'
    end

    def latest_collection_name
      latest_collection.try(:name).to_s
    end
    def latest_collection
      matching_collections.try(:sort).try(:last)
    end

    def matching_collections
      collection_name = self.name.downcase.pluralize
      collections = Mongoid.master.collections.select{|c| c.name =~ %r{^#{collection_name}}}
    end

    # Danger Will Robinson! Handle with care!  pass in "true" to actually delete the old collections
    def drop_old_collections(force = false)
      collections = matching_collections 
      dropped_collections = []
      collections.each do |c|
        if c.name == collection_name || c.name < latest_collection_name # don't drop latest, even if it's old
            puts "dropping Collection #{c.name}"
            dropped_collections << c.name
            c.try(:drop) if force # poof!
        end
      end
      dropped_collections
    end
  end

end