2021-09-21 14:05:33 +02:00

99 lines
3.3 KiB
Python

import time
from .ThinnerRule import ThinnerRule
class Thinner:
"""progressive thinner (universal, used for cleaning up snapshots)"""
def __init__(self, schedule_str=""):
"""
Args:
schedule_str: comma seperated list of ThinnerRules. A plain number specifies how many snapshots to always keep.
"""
self.rules = []
self.always_keep = 0
if schedule_str == "":
return
rule_strs = schedule_str.split(",")
for rule_str in rule_strs:
if rule_str.lstrip('-').isdigit():
self.always_keep = int(rule_str)
if self.always_keep < 0:
raise (Exception("Number of snapshots to keep cant be negative: {}".format(self.always_keep)))
else:
self.rules.append(ThinnerRule(rule_str))
def human_rules(self):
"""get list of human readable rules"""
ret = []
if self.always_keep:
ret.append("Keep the last {} snapshot{}.".format(self.always_keep, self.always_keep != 1 and "s" or ""))
for rule in self.rules:
ret.append(rule.human_str)
return ret
def thin(self, objects, keep_objects=None, now=None):
"""thin list of objects with current schedule rules. objects: list of
objects to thin. every object should have timestamp attribute.
return( keeps, removes )
Args:
objects: list of objects to check (should have a timestamp attribute)
keep_objects: objects to always keep (if they also are in the in the normal objects list)
now: if specified, use this time as current time
"""
if not keep_objects:
keep_objects = []
# always keep a number of the last objets?
if self.always_keep:
# all of them
if len(objects) <= self.always_keep:
return objects, []
# determine which ones
always_keep_objects = objects[-self.always_keep:]
else:
always_keep_objects = []
# determine time blocks
time_blocks = {}
for rule in self.rules:
time_blocks[rule.period] = {}
if not now:
now = int(time.time())
keeps = []
removes = []
# traverse objects
for thisobject in objects:
# important they are ints!
timestamp = int(thisobject.timestamp)
age = int(now) - timestamp
# store in the correct time blocks, per period-size, if not too old yet
# e.g.: look if there is ANY timeblock that wants to keep this object
keep = False
for rule in self.rules:
if age <= rule.ttl:
block_nr = int(timestamp / rule.period)
if block_nr not in time_blocks[rule.period]:
time_blocks[rule.period][block_nr] = True
keep = True
# keep it according to schedule, or keep it because it is in the keep_objects list
if keep or thisobject in keep_objects or thisobject in always_keep_objects:
keeps.append(thisobject)
else:
removes.append(thisobject)
return keeps, removes