Rename max_age to min_age

Also clarify a comment and remove an unneeded type check

management/backup.py

@@ -18,10 +18,11 @@ from utils import exclusive_process, load_environment, shell, wait_for_service
 backup_root = os.path.join(load_environment()["STORAGE_ROOT"], 'backup')
 
 # Default settings
-# Destroy backups when the most recent increment in the chain
-# that depends on it is this many days old.
+# min_age_in_days is the minimum amount of days a backup will be kept before
+# it is eligble to be removed. Backups might be kept much longer if there's no
+# new full backup yet.
 default_config = {
-	"max_age_in_days": 3,
+	"min_age_in_days": 3,
 	"target": "file://" + os.path.join(backup_root, 'encrypted')
 }
 
@@ -101,11 +102,11 @@ def backup_status(env):
 	# when the threshold is met.
 	deleted_in = None
 	if incremental_count > 0 and first_full_size is not None:
-		deleted_in = "approx. %d days" % round(config["max_age_in_days"] + (.5 * first_full_size - incremental_size) / (incremental_size/incremental_count) + .5)
+		deleted_in = "approx. %d days" % round(config["min_age_in_days"] + (.5 * first_full_size - incremental_size) / (incremental_size/incremental_count) + .5)
 
 	# When will a backup be deleted?
 	saw_full = False
-	days_ago = now - datetime.timedelta(days=config["max_age_in_days"])
+	days_ago = now - datetime.timedelta(days=config["min_age_in_days"])
 	for bak in backups:
 		if deleted_in:
 			# Subsequent backups are deleted when the most recent increment
@@ -248,7 +249,7 @@ def perform_backup(full_backup):
 	shell('check_call', [
 		"/usr/bin/duplicity",
 		"remove-older-than",
-		"%dD" % config["max_age_in_days"],
+		"%dD" % config["min_age_in_days"],
 		"--archive-dir", backup_cache_dir,
 		"--force",
 		config["target"]
@@ -307,17 +308,17 @@ def run_duplicity_verification():
 	], get_env())
 
 
-def backup_set_custom(target, target_user, target_pass, max_age):
+def backup_set_custom(target, target_user, target_pass, min_age):
 	config = get_backup_config()
 	
-	# max_age must be an int
-	if isinstance(max_age, str):
-		max_age = int(max_age)
+	# min_age must be an int
+	if isinstance(min_age, str):
+		min_age = int(min_age)
 
 	config["target"] = target
 	config["target_user"] = target_user
 	config["target_pass"] = target_pass
-	config["max_age_in_days"] = max_age
+	config["min_age_in_days"] = min_age
 	
 	write_backup_config(config)
 
@@ -332,11 +333,7 @@ def get_backup_config():
 
 	merged_config = default_config.copy()
 	merged_config.update(config)
-	
-	# max_age must be an int
-	if isinstance(merged_config["max_age_in_days"], str):
-		merged_config["max_age_in_days"] = int(merged_config["max_age_in_days"])
-	
+
 	return config
 
 def write_backup_config(newconfig):

management/templates/system-backup.html

@@ -26,7 +26,7 @@
   <div class="form-group">
     <label for="target" class="col-sm-2 control-label">Maximum time to keep old backups (in days)</label>
     <div class="col-sm-8">
-      <input type="number" class="form-control" rows="1" id="max-age"></input>
+      <input type="number" class="form-control" rows="1" id="min-age"></input>
     </div>
   </div>
   <div class="form-group form-advanced">
@@ -147,7 +147,7 @@ function show_custom_backup() {
         $("#target-type").val(target_type);
         $("#target-user").val(r.target_user);
         $("#target-pass").val(r.target_pass);
-        $("#max-age").val(r.max_age_in_days);
+        $("#min-age").val(r.min_age_in_days);
         toggle_form()
       })
 }
@@ -157,7 +157,7 @@ function set_custom_backup() {
   var target_type = $("#target-type").val();
   var target_user = $("#target-user").val();
   var target_pass = $("#target-pass").val();
-  var max_age = $("#max-age").val();
+  var min_age = $("#min-age").val();
   api(
     "/system/backup/custom",
     "POST",
@@ -165,7 +165,7 @@ function set_custom_backup() {
       target: target,
       target_user: target_user,
       target_pass: target_pass,
-      max_age: max_age
+      min_age: min_age
     },
     function(r) {
       // Responses are multiple lines of pre-formatted text.