[PATCH] increase fd_limit to max_client_limit automatically

[Lauri Tirkkonen]

On Fri, Mar 20 2015 21:06:12 +0200, Timo Sirainen wrote:
> On 22 Jan 2015, at 14:01, Lauri Tirkkonen <ltirkkon at niksula.hut.fi> wrote:
> > 
> > Hi, with a low soft limit on file descriptors, dovecot 2.2.15 warns on
> > startup:
> > 
> >    Warning: fd limit (ulimit -n) is lower than required under max. load
> >    (256 < 1000), because of default_client_limit
> > 
> > It could try increasing the limit first, and only report the warning if that
> > fails. I'm attaching a patch that does just this.
> 
> It could .. But somehow it doesn't seem like a good idea to me to do
> automatically. Maybe the limits are there intentionally.

I would make the argument that that's why there are both soft and hard
limits. Any program can raise their soft ulimits to the current hard
limit - I see the soft limit as more of a guard against misconfiguration
than a resource control, so I don't think there is anything wrong with
raising it when you have a legitimate reason to do so. On systems with
low default fd limits (such as some illumos distributions; see
https://www.illumos.org/issues/3772), the alternative is requiring
administrators to create startup wrappers for dovecot that raise the
limit, but since it's not a privileged operation that just seems silly.

-- 
Lauri Tirkkonen
Niksula systems specialist