On 05-03-14 03:12, Lee Howard wrote: > I am running dbmail 3.0.2 in a MySQL multi-master (2) replication > configuration. > > I understand that this will work fine as long as the IMAP unique_id does > not become invalid due to the same user connecting to both nodes > concurrently or because of a failure in the replication and the user > connecting to both nodes during the fault.
It's not just concurrent connections by the same user, iirc. Basically, IMAP relies on consistency at the storage level. Any change to a mailbox or message should be visible in the same way to all connected clients. However, in case of asynchronous replication that becomes just about impossible: no way to tell if the slave has caught up with the master. One proposal was to introduce a token-passing mechanism that would be used to implement two-phased commit style transactions at the application layer: ask the broker to generate a new primary key which doesn't return until it was successfully inserted on all the participating nodes. Given the complexity of such a solution it was never actually attempted. Of course, now we're 10 years later and there are some good tools to build such stuff, but also, two-phase commits are now provided by most rdbm systems. > I understand that a proposed resolution to these issues is discussed here: > > http://www.dbmail.org/dokuwiki/doku.php/unique_id_guid That page references a lot of email threads urls that are no longer available. But yes, this was discussed quite extensively. > Can someone confirm that this *is* the current status of full support > for complete multi-head database replication? Namely, "that this is the > last thing holding DBMail back from a complete failover system using > MySQL replication"? (Quoted from the URL'ed page.) No idea who wrote that. > I am willing to pay for this development to be done... if someone here > would like to do it. Any takers? Let me know how much you want for the > work. Otherwise, I am willing to do the development, myself, pointers > appreciated. I would put my money on synchronous replication. So mariadb or mysqldb with galera. http://codership.com/content/using-galera-cluster -- ________________________________________________________________ Paul J Stevens pjstevns @ gmail, twitter, github, linkedin www.nfg.nl/i...@nfg.nl/+31.85.877.99.97 _______________________________________________ Dbmail-dev mailing list Dbmail-dev@dbmail.org http://mailman.fastxs.nl/cgi-bin/mailman/listinfo/dbmail-dev
