[PATCH] increase fd_limit to max_client_limit automatically
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_limitIt could try increasing the limit first, and only report the warning if that fails. I'm attaching a patch that does just this.
Without the patch, the soft fd limit is kept at whatever it was on dovecot startup:
% pfexec plimit $(pgrep dovecot)
18737: /opt/niksula/sbin/dovecot
resource current maximum
time(seconds) unlimited unlimited
file(blocks) unlimited unlimited
data(kbytes) unlimited unlimited
stack(kbytes) 10240 unlimited
coredump(blocks) unlimited unlimited
nofiles(descriptors) 256 65536
vmemory(kbytes) unlimited unlimitedand with patch applied, it's increased to max_client_limit:
% pfexec plimit $(pgrep dovecot)
18775: /opt/niksula/sbin/dovecot
resource current maximum
time(seconds) unlimited unlimited
file(blocks) unlimited unlimited
data(kbytes) unlimited unlimited
stack(kbytes) 10240 unlimited
coredump(blocks) unlimited unlimited
nofiles(descriptors) 1000 65536
vmemory(kbytes) unlimited unlimitedIt should probably be increased to higher than that to account for fds other than client sockets, but I don't have insights into that.
-- Lauri Tirkkonen Niksula systems specialist
On 22 Jan 2015, at 14:01, Lauri Tirkkonen <ltirkkon@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. Maybe it's the Dovecot settings that are wrong and not the ulimits.
On Fri, Mar 20 2015 21:06:12 +0200, Timo Sirainen wrote:
On 22 Jan 2015, at 14:01, Lauri Tirkkonen <ltirkkon@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
participants (2)
-
Lauri Tirkkonen
-
Timo Sirainen