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#!/usr/local/bin/ruby
require 'AWS'
require 'yaml'

class SnapshotManagement

  # initalize class, optional override path to yml file
  # * options [String] :path ('')
  #
  def initialize(params = {})
    path = params[:path] ||  File.join(RAILS_ROOT,'config','s3.yml' )
    s3 = YAML.load_file(path)
    @access_key_id = s3['access_key_id']
    @secret_access_key = s3['secret_access_key']
    @ec2 = AWS::EC2::Base.new(:access_key_id => @access_key_id, :secret_access_key => @secret_access_key)
  end

  #
  # The CreateSnapshot operation creates a snapshot of an Amazon EBS volume and stores it in Amazon S3. You can use snapshots for backups, to launch instances from identical snapshots, and to save data before shutting down an instance.
  #
  # * options [String] :volume_id ('')
  # * options [optional,String] :description ('') Description of the Amazon EBS snapshot.
  #
  def create_snapshot(params)
    @ec2.create_snapshot(:volume_id =>params[:volume_id], :description => params[:description] )
  end

  # Clean up snapshots of volume, keep specific number of snapshots
  # 
  # * options [String] :volume_id ('')
  # * options [Integer] :keep_num (10) Number of snapshots to retain, defaults to 10.
  # * options [Integer] :owner Id of owner of snapshots
  #
  def cleanup_snapshots(params)
    keep_num = params["keep_num"] || 10
    snapshots = @ec2.describe_snapshots(:owner => params[:owner])['snapshotSet']['item']
    entries = snapshots.select {|s| s['volumeId'] == params[:volume_id]}
    remove = entries.size-keep_num-1

    entries[0..remove].each do |entry|
      #puts entry
      response = @ec2.delete_snapshot( :snapshot_id => entry['snapshotId'])
      successful = response['return']
      puts "Deleting snapshot '#{entry['description']}' of volume #{entry['volumeId']}, Successful? #{successful}"
    end unless remove < 0
  end

end

volume_id = VOLUME_ID
owner = OWNER
config_path = PATH
desc = DESCRIPTION
time_str = Time.now.strftime('%Y-%m-%d_%H:%M')

s = SnapshotManagement.new(:path => config_path)
s.create_snapshot(:volume_id => volume_id, :description => "#{desc} - #{time_str}")
s.cleanup_snapshots(:volume_id => volume_id, :owner => owner)