Upgrading dovecot 2.2 to 2.3 without downtime when using proxy/director?

[Timo Sirainen]

> On 6 May 2018, at 8.46, Niels Kobschätzki <niels at kobschaetzki.net> wrote:
> 
> Hi,
> 
> I have a setup with several dovecot-servers (2.2.35) and I use dovecot
> proxy. I upgraded one server to 2.3.1 and got the configs fixed so far
> that it started again. But when I tried to add it into the proxying
> again with "doveadm director add" I see the following in the logfiles:
> 
> May  6 07:19:30 host dovecot: director: Warning: Director
> xxx.xxx.xxx.176:9090/out disconnected us with reason: Invalid input: OPTIONS
> May  6 07:19:30 $host dovecot: director: Connecting to
> xxx.xxx.xxx.171:9090 (as xxx.xxx.xxx.176): Reconnecting after error
> 
> xxx.xxx.xxx.176 is the upgraded host, xxx.xxx.xxx.171 is one of the
> other hosts (the applicable hosts are in the range xxx.xxx.xxx.171-176).
> 
> Do I have to remove all the hosts from the proxy, upgrade them and then
> add them again? Or is there a way to handle the upgrade without a
> downtime? After all one of the reasons I use several hosts is that I do
> not want to have a downtime.

If you look at .176's error log, do you see an error about "director_consistent_hashing settings differ between directors"? Have you set director_consistent_hashing=yes in the old directors? That is needed now, because the old non-consistent-hashing method is obsoleted. Unfortunately there's no easy way to upgrade directors to use the consistent hashing method without stopping the entire ring. The hard way would be to build a secondary director ring and start moving users to that ring in proxies.