[Dovecot] too many open files and v1.2

[Timo Sirainen]

On Thu, 2011-10-06 at 12:42 +0100, Michael Moritz wrote:
> Hi
> 
> I've found an older thread http://www.dovecot.org/list/dovecot/2010-March/047886.html which mentions that this is a bug in version 1. I'm on Debian squeeze (1:1.2.15-7) and got errors like these recently
> 
> Oct  5 11:29:29 mail dovecot: dovecot: pipe() failed: Too many open files
> Oct  5 11:29:32 mail dovecot: dovecot: pipe() failed: Too many open files
> Oct  5 11:29:32 mail dovecot: dovecot: Temporary failure in creating login processes, slowing down for now

These errors come from the dovecot master process. Each child process
uses up a few fds for pipes.

> As a work around I've increased login_max_processes_count from 256 to 512 and it seems to have helped (as I suspected stale opened files).

That only makes it easier to reach, since now there can be more child
processes eating up more fds.

> My colleague thinks it's hitting the kernel open file limit ulimit -n (currently at 1024) but I don't see how that could happen if the number of process is nowhere near that.

I don't remember how many fds each process takes in v1.x, probably
between 1 and 3. So if you for a while had hundreds of imap or pop3
processes, you could run into that limit.

v2.x doesn't use as many fds.