Skip to main content
This is a pre-production deployment of Warehouse. Changes made here affect the production instance of PyPI (pypi.python.org).
Help us improve Python packaging - Donate today!

Grandfather-father-son backup rotation calculator

Project Description

GrandFatherSon is a backup rotation calculator that implements the grandfather-father-son rotation scheme.

This is usually done by keeping a certain number of daily, weekly, and monthly backups. Older backups should be removed to reduce the amount of space used.

Usage

This module expects either datetime.date or datetime.datetime objects as inputs. As an example, let’s assume you have daily backups for the all of year 1999 that need rotating:

>>> import datetime
>>> start_date = datetime.date(1999, 1, 1)
>>> end_date = datetime.date(1999, 12, 31)
>>> backups = [start_date + datetime.timedelta(days=i)
...            for i in range((end_date - start_date).days + 1)]
>>> backups
[datetime.date(1999, 1, 1),
 datetime.date(1999, 1, 2),
 datetime.date(1999, 1, 3),
 ...
 datetime.date(1999, 12, 30),
 datetime.date(1999, 12, 31)]

Let’s say that full backups are taken every Saturday, with incremental backups done daily. A week, or 7 days, of incremental backups should be kept. A months, or 4 weeks, of full backups are kept. In addition, for three months, the first full backup is kept for each month, with the others discarded.

It’s the last day of the year and you want to figure out which backups need to be pruned:

>>> now = datetime.date(1999, 12, 31)

To see which files will be preserved, use the dates_to_keep function:

>>> from grandfatherson import dates_to_keep, SATURDAY
>>> sorted(dates_to_keep(backups, days=7, weeks=4, months=3,
...                      firstweekday=SATURDAY, now=now))
[datetime.date(1999, 10, 1),
 datetime.date(1999, 11, 1),
 datetime.date(1999, 12, 1),
 datetime.date(1999, 12, 4),
 datetime.date(1999, 12, 11),
 datetime.date(1999, 12, 18),
 datetime.date(1999, 12, 25),
 datetime.date(1999, 12, 26),
 datetime.date(1999, 12, 27),
 datetime.date(1999, 12, 28),
 datetime.date(1999, 12, 29),
 datetime.date(1999, 12, 30),
 datetime.date(1999, 12, 31)]

If you leave off the now argument, it will default to using datetime.datetime.now().

To see which files should be deleted, use the dates_to_delete function:

>>> from grandfatherson import dates_to_delete, SATURDAY
>>> sorted(dates_to_delete(backups, days=7, weeks=4, months=3,
...                        firstweekday=SATURDAY, now=now))
[datetime.date(1999, 1, 1),
 ...
 datetime.date(1999, 9, 30),
 datetime.date(1999, 10, 2),
 ...
 datetime.date(1999, 10, 31),
 datetime.date(1999, 11, 2),
 ...
 datetime.date(1999, 11, 30),
 datetime.date(1999, 12, 2),
 datetime.date(1999, 12, 3),
 datetime.date(1999, 12, 5),
 ...
 datetime.date(1999, 12, 10),
 datetime.date(1999, 12, 12),
 ...
 datetime.date(1999, 12, 17),
 datetime.date(1999, 12, 19),
 ...
 datetime.date(1999, 12, 24)]

Finally, if you need to rotate backups that have timestamps in datetime format, you can use the corresponding to_keep and to_delete functions:

>>> now = datetime.datetime(1999, 12, 31, 23, 59, 59)
>>> start_datetime = datetime.datetime(1999, 12, 31, 0, 0, 0)
>>> end_datetime = datetime.datetime(1999, 12, 31, 23, 59, 59)
>>> backups = [start_datetime + datetime.timedelta(seconds=i)
...            for i
...            in range((end_datetime - start_datetime).seconds + 1)]
>>> backups
[datetime.datetime(1999, 12, 31, 0, 0),
 datetime.datetime(1999, 12, 31, 0, 0, 1),
 datetime.datetime(1999, 12, 31, 0, 0, 2),
 ...
 datetime.datetime(1999, 12, 31, 23, 59, 58),
 datetime.datetime(1999, 12, 31, 23, 59, 59)]

>>> from grandfatherson import to_keep
>>> sorted(to_keep(backups, hours=2, minutes=10, seconds=10, now=now))
[datetime.datetime(1999, 12, 31, 22, 0),
 datetime.datetime(1999, 12, 31, 23, 0),
 datetime.datetime(1999, 12, 31, 23, 50),
 ...
 datetime.datetime(1999, 12, 31, 23, 59),
 datetime.datetime(1999, 12, 31, 23, 59, 50),
 ...
 datetime.datetime(1999, 12, 31, 23, 59, 59)]

>>> from grandfatherson import to_delete
>>> sorted(to_delete(backups, hours=2, minutes=10, seconds=10, now=now))
[datetime.datetime(1999, 12, 31, 0, 0),
 ...
 datetime.datetime(1999, 12, 31, 21, 59, 59),
 datetime.datetime(1999, 12, 31, 22, 0, 1),
 ...
 datetime.datetime(1999, 12, 31, 22, 59, 59),
 datetime.datetime(1999, 12, 31, 23, 0, 1),
 ...
 datetime.datetime(1999, 12, 31, 23, 49, 59),
 datetime.datetime(1999, 12, 31, 23, 50, 1),
 ...
 datetime.datetime(1999, 12, 31, 23, 58, 59),
 datetime.datetime(1999, 12, 31, 23, 59, 1),
 ...
 datetime.datetime(1999, 12, 31, 23, 59, 49)]
Release History

Release History

This version
History Node

1.3

History Node

1.2

History Node

1.1

History Node

1.0

Download Files

Download Files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

File Name & Checksum SHA256 Checksum Help Version File Type Upload Date
GrandFatherSon-1.3.tar.gz (8.4 kB) Copy SHA256 Checksum SHA256 Source Sep 16, 2016

Supported By

WebFaction WebFaction Technical Writing Elastic Elastic Search Pingdom Pingdom Monitoring Dyn Dyn DNS Sentry Sentry Error Logging CloudAMQP CloudAMQP RabbitMQ Heroku Heroku PaaS Kabu Creative Kabu Creative UX & Design Fastly Fastly CDN DigiCert DigiCert EV Certificate Rackspace Rackspace Cloud Servers DreamHost DreamHost Log Hosting