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List:       cyrus-info
Subject:    Multi-master replication (was: Re: Cyrus IMAP 3.4.0 released)
From:       Nels Lindquist <nlindq () maei ! ca>
Date:       2023-05-19 21:12:41
Message-ID: 8435891f-12d4-98dd-b83c-e85891614495 () maei ! ca
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On 2021-04-20 6:24 PM, ellie timoney wrote:
> Hi Anatoli,
> 
> > Ellie, could you please let us, the users, know if the changes needed
> > to implement master-master replication are included in this release?
> 
> If it were clear to me that master-master replication was now safe, I would have \
> listed it as a feature in the release notes. ;) 
> I'm not directly certain what is or isn't remaining to make this work, but, it's \
> worth observing that even if the right code is now in place, afaik nobody has used \
> it in this way, so I'm not going to tell people they should start relying on it. 
> If you're willing to experiment on the side, it might work with bugs (which can be \
> fixed once found), or it might not be complete (and such limitations can be \
> addressed once identified).  Either way, feedback from actual usage would be very \
> useful! 
> But for production purposes, I would assume that 3.4 does not support master-master \
> replication, and stick with the traditional replication schemes.

On 2020-12-14 2:05 AM, Bron Gondwana wrote:
 > It's almost all good, the main problem is split brain recovery when you
 > delete or rename folders - it could wind up reverting the change if a
 > 'sync user' gets triggered by the other end.
 >
 > The last piece of the puzzle (yeah, 10 years later!) is going to be
 > having proper tombstone records in the mailboxes.db including name
 > history for each mailbox, so that we know whether a mailbox has been
 > added or deleted.  The mailboxes-by-uuid work, which should be landing
 > on master early next year, is going to add that.

Now that (as of 3.6.0) even mail storage is organized by UUID, it seems 
more likely than not that multi-master replication is at least extremely 
close.

I don't recall seeing any follow-ups from those who were intending to 
test 3.4.x.

Having never worked with Cassandane, would it be possible to build a 
test suite to validate multi-master replication functionality? If so, 
what would that look like?


-- 
Nels Lindquist
nlindq@maei.ca


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