On Thu, 2005-07-14 at 23:46 -0400, Mordechai T. Abzug wrote:
> On Fri, Jul 15, 2005 at 02:16:02AM -0000, Aaron Stone wrote:
>
> > I can't find the thread at the moment, but the best plan we have so
> > far is a token passing system. There was a proposed API posted to
> > the list, which is a good starting point for anybody who'd like to
> > begin implementing it.
>
> Would a token passing system work if the network were segmented?
> Ie. if both servers in a multimaster were up and working but incapable
> of communicating with each other, because a WAN link was down. Local
> users at each site would continue generating email.
No. This is a fundamental weakness in the IMAP specification.
If the link goes down new messages cannot be introduced into the store
without updating UIDVALIDITY. However, if UIDVALIDITY is updated all
disconnected clients have to re/download all of their messages.
{{ as stated before, the clients /don't/ have to, but I don't know of
any ubiquitous IMAP client that actually attempts to work around
this. }}
If you're trying to introduce load-sharing, then this can be done.
Nobody's done it yet. I suspect it's because it's hard and because load-
sharing is generally adequate with master/slave scenarios. Multimaster
load-sharing simply isn't buying a whole lot.
However: If you're looking for a 100%-uptime imap server, it doesn't
exist, nor will it ever exist (unless, of course, it's no longer imap).
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