[Chandler-dev] Server-side backups theoretically desirable?
vajda at osafoundation.org
Thu Aug 24 10:04:28 PDT 2006
On Thu, 24 Aug 2006, Grant Baillie wrote:
>> I sure would hope so. It would be a shame if chandler lost local, more
>> accurate, data due to the re-syncing of old, out of date, data.
> Hope is not enough :). If you think it through, people end up losing changes
> in the current scheme, viz:
> 1) Let's say a user has synced an item in Chandler, and that corresponds to
> an HTTP resource with ETag E1.
> 2) The user changes the item and syncs, which results in a PUT on the
> resource, with the ETag now becoming E2.
> 3) The server crashes, and the restore rolls back its to state to where it
> was in 1).
> 4) The user syncs. We know the ETag when we last synced was E2, so we notice
> it's now E1, which is not a value Chandler knows about. So we pull the old
> version from the server, and wipe out the user's changes.
That's why I was talking about server version numbers. Using ETags + a version
number might help in determining that the ETag is older than the one I'm
comparing it against. The server version number would be the same as an svn
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