Trying new calculation for amount of space needed for prune, forbid snapshot at more than 6 hour intervals.

1 files changed, 28 insertions, 10 deletions

diff --git a/byteback-snapshot b/byteback-snapshot
index dfd216f..daf368b 100644
--- a/byteback-snapshot
+++ b/byteback-snapshot
@@ -115,14 +115,18 @@ class BackupDirectory
 		snapshot_times_sorted
 	end
 
-	# Returns the size of the last completed snapshot (runs du, maybe slow)
+	# 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 latest_snapshot_size
-		`du -s -b #{snapshot_path(snapshot_times.last)}`.to_i
+	def snapshot_size(time=snapshot_times.latest)
+		`du -s -b #{snapshot_path(time)}`.to_i
+	end
+
+	def average_snapshot_size(number=10)
+		snapshot_times.sort[0..number].inject(0) { |time, total| snapshot_size(time) } / number
 	end
 
 	# Create a new snapshot of 'current'
@@ -159,6 +163,7 @@ opts = Trollop::options do
     opt :snapshot, "Take a new snapshot"
 
     opt :prune, "Prune old backups"
+    	:type => :string
 
     opt :list, "List backups (by 'age' or 'importance')",
     	:type => :string
@@ -179,16 +184,28 @@ error("--root not readable") unless File.directory?(@root)
 
 @backups = BackupDirectory.new(@root)
 
+def get_snapshots_by(method)
+	if method == 'importance'
+		@backups.snapshot_times_by_importance.reverse # least important first
+	elsif method == 'age'
+		@backups.snapshot_times
+	else
+		raise ArgumentError.new("Unknown snapshot sort method #{method}")
+	end
+end
 
 if @do_snapshot
+	last_snapshot_time = @backups.snapshots.last
+	error("Last snapshot was less than six hours ago") unless 
+		!last_snapshot_time || 
+		Time.now - @backups.snapshots.last >= 6*60*60 # FIXME: make configurable
+
 	verbose "Making new snapshot"
 	@backups.new_snapshot! 
 end
 
 if @do_list
-	list = @do_list == 'age' ? 
-		@backups.snapshot_times : # oldest first
-		@backups.snapshot_times_by_importance.reverse # least important first
+	list = get_snapshots_by(@do_list)
 	print "Backups in #{@root} by #{@do_list}:\n"
 	list.each_with_index do |time, index|
 		print "#{sprintf('% 3d',index)}: #{time}\n"
@@ -196,16 +213,17 @@ if @do_list
 end
 
 if @do_prune
-	target_free_space = @backups.latest_snapshot_size
+	verbose "Counting last 10 backups"
+	target_free_space = 1.5 * @backups.average_snapshot_size(10)
 	verbose "Want to ensure we have #{target_free_space}"
 
 	if @backups.free >= target_free_space
 		verbose "(we have #{@backups.free} so no action needed)"
 	else
-		snapshot_times_by_importance = @backups.snapshot_times_by_importance
+		list = get_snapshots_by(@do_prune)
 
-		while @backups.free < target_free_space && !snapshot_times_by_importance.empty?
-			to_delete = snapshot_times_by_importance.pop
+		while @backups.free < target_free_space && !list.empty?
+			to_delete = list.pop
 			verbose "Deleting #{to_delete}"
 			@backups.delete_snapshot!(to_delete)
 			verbose "Leaves us with #{@backups.free}"