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module Byteback
# 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
attr_reader :dir
def initialize(dir)
@dir = Dir.new(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 snapshot_times
@dir.entries.map do |entry|
begin
Time.parse(entry)
rescue ArgumentError => error
nil
end
end.
compact.
sort
end
# 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 = [0, 1, 2, 3, 7, 14, 21, 28, 56, 112]
def snapshot_times_by_importance
now = Time.now
snapshot_times_unsorted = snapshot_times
snapshot_times_sorted = []
while !snapshot_times_unsorted.empty?
BACKUP_IMPORTANCE.each do |days|
target_time = now + (days*86400)
closest = snapshot_times_unsorted.inject(nil) do |best, time|
if best.nil? || (time-target_time).abs < (best-target_time).abs
time
else
best
end
end
break unless closest
snapshot_times_sorted << snapshot_times_unsorted.delete(closest)
end
end
snapshot_times_sorted
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 snapshot_size(time=snapshot_times.last)
`du -s -b #{snapshot_path(time)}`.to_i
end
def average_snapshot_size(number=10)
snapshot_times.sort[0..number].inject(0) { |total, time| snapshot_size(time) } / number
end
# Create a new snapshot of 'current'
#
def new_snapshot!
system_no_error("btrfs subvolume snapshot -r #{current.path} #{snapshot_path}")
end
def delete_snapshot!(time)
system_no_error("btrfs subvolume delete #{snapshot_path(time)}")
end
def current
Dir.new("#{dir.path}/current")
end
def snapshot_path(time=Time.now)
"#{dir.path}/#{time.strftime("%Y-%m-%dT%H:%M%z")}"
end
protected
def system_no_error(*args)
args[-1] += " > /dev/null" unless @verbose
raise RuntimeError.new("Command failed: "+args.join(" ")) unless
system(*args)
end
end
end
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