> On Apr 21, 2017, at 4:43 AM, d...@evilcigi.eu wrote:
>
> Hi everyone,
>
> I'm running dovecot with quite a lot of users and lots of active imap
> connections (like 20'000). I'm using different user IDs for users, so I need
> to have imap {service_count=1} - i.e. I have a lots of imap processes running.
>
> Everything works fine, until I reload dovecot configuration. When that
> happen, every client is forced to relogin in the same time and that causes a
> huge system load spike (2-3000 5 min load).
>
> I was thinking that it would be great, if dovecot wouldn't kick all the users
> in the same time during reload, but somehow gradually, during specified
> interval. I'm aware of the shutdown_clients directive that could help, but I
> don't like it - I do want the clients get disconnected on dovecot shutdown
> and also I want them to relogin in reasonably short time after reload.
You could run a Dovecot IMAP proxy in a Docker container on your server and run
a separate Dovecot IMAP server in another container. Once both containers are
up and running, enable the Dovecot IMAP proxy to start sending IMAP sessions to
the IMAP server. When the time comes to change the Dovecot configuration,
deploy another instance of Dovecot IMAP server with the new configuration. Once
the new container is up and running, configure Dovecot IMAP proxy to direct a
few specific test users to the new Dovecot IMAP server. When satisfied that the
new server can handle new user sessions, configure Dovecot IMAP proxy to direct
all new sessions to the new instance. After everything seems to be working fine
for a period of time, start kicking users on the old Dovecot IMAP server off
(at a comfortable pace) so they will reconnect to the new Dovecot IMAP server.
When the old Dovecot IMAP server is no longer managing any sessions, it can be
removed from the server (that is, the Docker container stopped and eventually
removed completely).
Since all containers are running on the same host server, the old and new
Dovecot containers will be configured to access the same Dovecot mail storage
by mounting the host storage to both containers.
I think Docker containers are the easiest way to manage Dovecot in production.
Kevin
