[systemd-devel] Fwd: dovecot and systemd

[Zbigniew Jędrzejewski-Szmek]

On 03/16/2012 03:55 PM, Michal Hlavinka wrote:
> I'm forwarding this to more appropriate mailing list. Can you please
> share your thoughts about this topic? Do you know about other projects
> that were in the same situation and how did they solved it?
>
>>> Hi all,
>>>
>>> dovecot supports systemd socket activation. Together with standard unit
>>> activation (like old sysv init script), there are two ways how to
>>> configure dovecot(only interface:port, not whole configuration). This
>>> can result in situation where those configurations does not say the
>>> same. Question is what should happen then?
>>>
>>> For example, lets have dovecot configured to listen for imap(s) and lets
>>> have systemd dovecot socket configured to listen for all protocols -
>>> pop3(s) and imap(s). When dovecot is configured to start on boot,
>>> systemd will start it and dovecot will listen on imap(s) ports. But when
>>> dovecot.socket is enabled, it'll listen on pop3(s) too and when new pop3
>>> connection comes, it'll pass it to dovecot and dovecot will serve it.
>>> The question is: Should this happen? What exactly should happen when
>>> dovecot.conf does not match dovecot.socket configuration?
Hi,

daemon(7) says "If sockets are passed (i.e. when sd_listen_fds() returns 
a positive value), skip the socket creation step and use the passed 
sockets.". And sd_listen_fds(3) says "[It] is recommended to verify the 
correct socket types before using them. [...]  In order to maximize 
flexibility it is recommended to make these checks as loose as possible 
without allowing incorrect setups. i.e. often the actual port number a 
socket is bound to matters little for the service to work, hence it 
should not be verified."

I think that this is a sound recommendation -- let systemd.socket 
configuration override the configuration in dovecot.conf file. If the 
administrator disables dovecot.socket and enables dovecot.service, then 
the .service configuration overrides other sources.

If dovecot.conf says that dovecot should listen on say imap port, and 
this port is not present in one of the passed descriptors, they it might 
make sense to issue a warning, to help catch misconfigurations.

Zbyszek