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module Byteback
# Represents a particular timestamped backup directory
class Snapshot
class << self
# What order to remove snapshots in to regain disk space?
#
# Order backups by their closeness to defined backup times, which are
# listed in a set order (i.e. today's backup is more important than yesterday's).
#
BACKUP_IMPORTANCE = [1, 2, 7, 14, 21, 28, 56, 112]
def sort_by_importance(snapshots_unsorted, now = Time.now)
return snapshots_unsorted if snapshots_unsorted.size < 1
#
# Keep the last 7 days backups
#
snapshots_sorted = []
snapshots_unsorted = snapshots_unsorted.sort_by(&:time).reverse
#
# Group snapshots by host
#
snapshots_by_host = Hash.new { |h, k| h[k] = [] }
snapshots_unsorted.each do |snapshot|
snapshots_by_host[snapshot.host] << snapshot
end
#
# We want the snapshot nearest to the middle of the day each day.
#
today_midday = Time.mktime(*([0, 0, 12] + now.utc.to_a.last(7)))
#
# We want today, and the previous seven days
#
targets = [today_midday]
targets += 6.times.map { today_midday -= 86_400 }
#
# Now the previous four Sundays (we should bump on a week if today is a Sunday!)
#
today_midday -= (today_midday.wday == 0 ? 7 : today_midday.wday) * 86_400
targets << today_midday
targets += 3.times.map { today_midday -= 7 * 86_400 }
#
# Our 28 day periods are anchored on Time.at(0). However this was a
# Thursday, so we have to add 3 days to get it to Sunday.
#
targets << (today_midday -= ((today_midday.to_i / 86_400.0).floor % 28 - 3) * 86_400)
#
# Continue removing 28 day periods until we get beyond the oldest backup time.
#
targets << (today_midday -= 28 * 86_400) while today_midday > snapshots_unsorted.last.time
#
# This has records the last nearest snapshot for each host
#
last_nearest = {}
#
# For each target, and for each host, find the nearest snapshot
#
targets.each do |target|
snapshots_by_host.each do |host, snapshots|
next if snapshots.empty?
nearest = snapshots.sort { |a, b| (a.time - target).abs <=> (b.time - target).abs }.first
#
# Don't process any more if the last snapshot for this for this
# host was more recent, i.e. we've reached the oldest, and are
# bouncing back again.
#
if last_nearest[host].nil? || last_nearest[host].time > nearest.time
last_nearest[host] = nearest
snapshots_by_host[host] -= [nearest]
snapshots_sorted << nearest
end
end
end
#
# Remove any snapshots we've already sorted and add in the remaining snapshots
#
snapshots_unsorted -= snapshots_sorted
snapshots_sorted += snapshots_unsorted
snapshots_sorted
end
end
attr_reader :backup_directory, :path
def initialize(backup_directory, snapshot_path)
@backup_directory = backup_directory
@path = snapshot_path
@time = Time.parse(File.basename(path)) # throws ArgumentError if it can't parse
nil
end
attr_reader :time
def host
File.basename(File.dirname(path))
end
def <=>(b)
time <=> b.time
end
def create!(from)
system_no_error("/sbin/btrfs subvolume snapshot #{from} #{path}")
end
def delete!
system_no_error("/sbin/btrfs subvolume delete #{path}")
end
# Returns the size of the given snapshot (runs du, may be slow)
#
# Would much prefer to take advantage of this feature:
# http://dustymabe.com/2013/09/22/btrfs-how-big-are-my-snapshots/
# but it's not currently in Debian/wheezy.
#
def du
`du -s -b #{path}`.to_i
end
protected
def system_no_error(*args)
args[-1] += ' > /dev/null' unless @verbose
fail RuntimeError.new('Command failed: ' + args.join(' ')) unless
system(*args)
end
end
# Represent a directory full of backups where "current" is a subvolume
# which is snapshotted to frozen backup directories called e.g.
# "yyyy-mm-ddThh:mm+zzzz".
#
class BackupDirectory
class << self
# Return all backup directories
#
def all
Dir.new(ENV['HOME']).entries.map do |entry|
next if entry[0] == '.'
name = File.expand_path(ENV['HOME'] + '/' + entry)
File.directory?(name + '/current') ? BackupDirectory.new(name) : nil
end
.compact
end
# Returns every snapshot in every backup directory
#
def all_snapshots
all.map(&:snapshots).flatten
end
end
attr_reader :dir
def initialize(dir)
@dir = Dir.new(dir)
fail Errno::ENOENT unless File.directory?(dir)
current
end
# Return total amount of free space in backup directory (bytes)
#
def free
df = DiskFree.new(@dir.path)
df.total - df.used
end
# Return an array of Times representing the current list of
# snapshots.
#
def snapshots
@dir.entries.map do |entry|
next if entry[0] == '.' || entry == 'current'
snapshot_path = File.expand_path(@dir.path + '/' + entry)
next unless File.directory?(snapshot_path)
begin
Snapshot.new(self, snapshot_path)
rescue ArgumentError => ae
# directory name must represent a parseable Time
nil
end
end
.compact
end
# Create a new snapshot of 'current'
#
def new_snapshot!(time = Time.now)
snapshot_path = time.strftime(dir.path + '/%Y-%m-%dT%H:%M%z')
Snapshot.new(self, snapshot_path).create!(current.path)
end
def current
Dir.new("#{dir.path}/current")
end
end
end
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