dovecot - Jun 2008 - No log for hitting login_max_processes_count?

I think today just due to increased use, my mail servers hit 
login_max_processes_count.  It wasn't obvious what was happening, logins 
just weren't acting like they should and sometimes would get 
disconnected before given a prompt from the server.  Something made me 
think to check if I had too many of certain dovecot processes and I 
found I had 128 imap-login processes on both servers, but nothing in the 
logs seemed to point that out for me.  Should there be?  It would have 
been alot easier to debug.  Also, this seems to be from general use, 
doesn't seem like a DoS, so is this just a setting I should keep an eye 
on and increase it by reasonable amounts as needed?  Thanks.

We ran into a similiar problem after migrating to Dovecot on Solaris with 
an LVS in front. Tweaking some config options cleared it up. Specifically 
turning on auth_cache:

# Authentication Cache
auth_cache_size = 10240
auth_cache_ttl = 18000

It went from hundreds of login processes down to 20-60.


Bryan Polk
Unix Systems Administrator
Communication and Multimedia Services
FAMU-FSU College of Engineering
(850) 410-6164
bpolk at eng.fsu.edu


On Mon, 30 Jun 2008, Adam McDougall wrote:
> I think today just due to increased use, my mail servers hit 
> login_max_processes_count.  It wasn't obvious what was happening,
logins just
> weren't acting like they should and sometimes would get disconnected
before
> given a prompt from the server.  Something made me think to check if I had 
> too many of certain dovecot processes and I found I had 128 imap-login 
> processes on both servers, but nothing in the logs seemed to point that out
> for me.  Should there be?  It would have been alot easier to debug.  Also, 
> this seems to be from general use, doesn't seem like a DoS, so is this
just a
> setting I should keep an eye on and increase it by reasonable amounts as 
> needed?  Thanks.
>

On Mon, 2008-06-30 at 11:49 -0400, Adam McDougall wrote:
> I think today just due to increased use, my mail servers hit 
> login_max_processes_count.  It wasn't obvious what was happening,
logins
> just weren't acting like they should and sometimes would get 
> disconnected before given a prompt from the server.  Something made me 
> think to check if I had too many of certain dovecot processes and I 
> found I had 128 imap-login processes on both servers, but nothing in the 
> logs seemed to point that out for me.  Should there be?  It would have 
> been alot easier to debug.  Also, this seems to be from general use, 
> doesn't seem like a DoS, so is this just a setting I should keep an eye
> on and increase it by reasonable amounts as needed?  Thanks.
That should probably redesigned at some point.. The setting should
probably only control how many processes there should be with users that
haven't logged in, so (SSL) proxying processes shouldn't be counted.. Or
perhaps a different setting should limit them.

And you're right that it doesn't currently log anything if all of the
processes are in use. Hmm. This is a bit difficult to solve currently. I
think I'll just leave it for the master rewrite, which should make it
easier. :)

Anyway setting login_process_per_connection=no would make it work better
and probably also log something if limits are reached.
http://wiki.dovecot.org/LoginProcess
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