Comment 7 for bug 1686470
Revision history for this message
| Steve Langasek (vorlon) wrote Re: Apt updates that are uniformally spread across all timezones, with predictable application windows | #7 |
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a60fb26
(Get the code!)
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If the purpose is to ensure the updates being applied are never more than 12 hours out of date, that can be achieved with a single apt update scheduled in the 12h before 6am machine time.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?