[Blueprint servercloud-q-apt-improvements] Apt Improvements

[Clint Byrum]

Blueprint changed by Clint Byrum:

Whiteboard changed:
+ Problem: Archive during development is often inconsistent due to "Hash
+ sum mismatch". This is because Packages.gz is updated in a non-atomic
+ manner with the 'Release' file.
+ 
+ Current mitigation(s):
+ * Expires header set to exact same time so caches will not cache the archive in a broken state. This reduces the window for problems to just the time between writing Packages.gz and Release.
+ 
+ Options to discuss:
+ * pdiff for smaller windows of inconsitency (still updates in a non-atomic way unfortunately)
+ * Versioned Packages.gz (Packages.1.gz, Packages.2.gz, or maybe Packages.201205021431.gz)
+ * A/B style atomic whole-directory archive refreshes.  (A is live, write new refresh to B, make B live with re-writing a symlink, then repeat with A/B swapped). [clint- I don't think this is feasible w/o CoW filesystem snapshots on the archive servers]
+ 
  Etherpad: http://pad.ubuntu.com/uds-q-servercloud-q-apt-improvements
  Blueprint: https://blueprints.launchpad.net/ubuntu/+spec/servercloud-q-apt-improvements

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Apt Improvements
https://blueprints.launchpad.net/ubuntu/+spec/servercloud-q-apt-improvements