Google Compute Engine Snapshot Create and Rotate in Ruby

snapshotAndRotate.rb

#!/usr/bin/ruby

require 'json'
require 'time'
require 'optparse'
require 'ostruct'

class Snapshot

  def initialize(args)

    @options = OpenStruct.new 
    # Default options
    @options.rotate_days = 7
    @options.rotate_keep_days_of_month = 1 # Keep snapshots on first of every month
    @options.primary_disk_only = false
    @options.silent = false

    opt_parser = OptionParser.new do |opts|
      opts.banner = "Usage: snapshotAndRotate.rb [options]"
    
      opts.on('--rotate_days NUMBEROFDAYSTOKEEP', OptionParser::DecimalInteger, "Keep last X days of snapshots") { |o| @options.rotate_days = o }
      opts.on('--rotate_keep_days_of_month DAYOFMONTHTOKEEP', OptionParser::DecimalInteger, "Keep snapshots created on this day of the month") { |o| @options.rotate_keep_days_of_month = o }
      opts.on('--primary_disk_only', "Only backup primary disk. Only deletes snapshots if from primary disk too.") { |o| @options.primary_disk_only = true }
      opts.on('--silent', "Supress output") { |o| @options.silent = true }
    end
    
    opt_parser.parse!(args)

    # Non-configurable settings
    @zone = get_zone
    @hostname = hostname
    @time = Time.now.to_i
    @snapshot_name_regex = "^#{@hostname}--.*" # n.b. see create_snapshot_name - must match
    @rotate_period = @options.rotate_days * 60 * 60 *24
  end

  def get_zone
    output = `curl --silent "http://metadata.google.internal/computeMetadata/v1/instance/zone" -H "Metadata-Flavor: Google"`
    output.split("/").last
  end

  def hostname
    hostname = `curl --silent "http://metadata.google.internal/computeMetadata/v1/instance/hostname" -H "Metadata-Flavor: Google"`
    hostname.split(".").first
  end

  def get_disks
    instance = `gcloud compute instances describe #{@hostname} --format json --zone #{@zone}`
    instance = JSON.parse instance
    disks = []
    if @options.primary_disk_only 
        disks.push( instance["disks"][0]["deviceName"] )
    else 
        instance["disks"].each do |d| 
            disks.push( d["deviceName"] )
        end
    end
    disks
  end

  def run_backup
    disks_backed_up = create_snapshot
    delete_old_snapshots(disks_backed_up)
  end

  def create_snapshot_name(disk_name)
    "#{@hostname}--#{disk_name}--#{@time}"
  end

  def create_snapshot
    disks = get_disks
    disks.each do |disk_name|
      snapshot_name = create_snapshot_name(disk_name)
      puts "Creating snapshot #{snapshot_name}" if !@options.silent
       `gcloud compute disks snapshot #{disk_name} --snapshot-name #{snapshot_name} --zone #{@zone}`
    end
    disks
  end

  def delete_old_snapshots(disks)
    snapshots = get_snapshots(disks)
    if snapshots.length > 0
      snapshots.each do |name|
        puts "Deleting snapshot #{name}" if !@options.silent
        `gcloud compute snapshots delete #{name} --quiet`
      end
    else
      puts "No snapshots to delete" if !@options.silent
    end
  end

  def get_snapshots(disks)
    puts "Finding snapshots older than #{Time.now - @rotate_period} for all attached disks (unless primary_disk_only), excluding those created on day #{@options.rotate_keep_days_of_month} of any month." if !@options.silent
    instances = `gcloud compute snapshots list --format json --regex #{@snapshot_name_regex}`
    instances = JSON.parse instances
    instances.select { |instance| Time.parse(instance["creationTimestamp"]) <= Time.now - (@rotate_period) && Time.parse(instance["creationTimestamp"]).day != @options.rotate_keep_days_of_month && disks.include?(instance["sourceDisk"].split("/").last) }.map { |instance| instance["name"] }
  end
end


snapshot = Snapshot.new(ARGV)
snapshot.run_backup

Usage: snapshotAndRotate.rb [options]
        --rotate_days NUMBEROFDAYSTOKEEP
                                     Keep last X days of snapshots
        --rotate_keep_days_of_month DAYOFMONTHTOKEEP
                                     Keep snapshots created on this day of the month
        --primary_disk_only          Only backup primary disk. Only deletes snapshots if from primary disk too.
        --silent                     Supress output