Why should apt update be run twice a day if the updates are only applied to the 
system once a day?  This would be:
- a no-op for any metadata that hasn't changed in the preceding 12h
- a wasteful, redundant download for metadata that *has* changed in the 
preceding 12h
- (in rare cases) very wasteful if two SRUs are published back-to-back in the 
same day, since the first will be downloaded but not applied.

If the purpose is to ensure the updates being applied are never more
than 12 hours out of date, that can be achieved with a single apt update
scheduled in the 12h before 6am machine time.

If the purpose is to ensure downloads are spread more evenly around the
clock, that is better achieved by doing one apt update per day, with a
24h smear, instead of two per day.  (And btw, we probably want locking
between the two jobs, so that we don't try to run an 'apt update'
/while/ unattended-upgrades are being applied, but instead wait for
unattended-upgrades to finish)

If your goal is to try to achieve some sort of balance between these
goals, that at least makes sense why the design would be this way; but I
think overall it's better to just do a single 24h smear and not try to
compromise in a way that increases overall load on the mirrors with no
major benefit to the users.

Can you please also document this design on wiki.ubuntu.com, so that we
have better history tracking of any further changes (vs. edits to a bug
description) and can more easily refer to it rather than pointing to an
(at some point) ancient bug?

-- 
You received this bug notification because you are a member of Ubuntu
Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/1686470

Title:
  Apt updates that are uniformally spread across all timezones, with
  predictable application windows

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/apt/+bug/1686470/+subscriptions

-- 
ubuntu-bugs mailing list
[email protected]
https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs

Reply via email to