[Chandler-dev] Server-side backups theoretically desirable?

[Andi Vajda]

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 accurate, data due to the re-syncing of old, out of date, data.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 
revision number.

Andi..