[Dovecot] troubles with 1.1.8 and squirrelmail over HTTPS

[Frank Bonnet]

Hello Jack

Setting up imapproxy on a third machine greatly improve
performances on my mailhub which doesn't refuse connexions
anymore.

Thanks a lot for your help !

Frank



Jack Stewart wrote:
> 
> 
> Frank Bonnet wrote:
>> Timo Sirainen wrote:
>>> On Thu, 2009-01-15 at 16:25 +0100, Frank Bonnet wrote:
>>>> I had to increase the  max_mail_processes to 8192
>>>> to have a functionnal IMAP server with normal clients AND
>>>> squirrelmail clients
>>>>
>>>> 8192 sounds enormous to me , any infos welcome !
>>>
>>> How many imap processes have you running typically?
>>>
>>
> 
> Hi,
> 
> I don't know if this will help or not - I'm taking my comments offline 
> because it isn't clear if they are related to your core problem. Also, 
> they seem to be specific to high usage servers/people.
> 
> We're not 1.1.8 yet but I've spent a reasonable amount of time tweaking 
> the Linux side.
> 
> We run at about ~1300 processes per server.
> 
> Squirrelmail does a login/logout on every single page that is clicked. 
> So I've found that running an imap proxy (such as the one at 
> imapproxy.org really helps). It creates some additional connections but 
> they get re-used pretty frequently.
> 
> If 1.1.8 isn't logging out quickly, or not cleanly shutting down the 
> connection, or something similar, that could explain additional 
> connections. What does netstat -an show? On some O/S's the process will 
> disappear from ps but not be fully released until the socket/connection 
> disappears (in this case tcp). If you have a bunch of WAIT/FIN_WAIT's 
> something like this seems pretty likely.
> 
> I've found that going through localhost allows you to bypass TLS while 
> still enforcing TLS for non-localhost connections. It's pretty nice for 
> overhead/connect speed. Also, an imap proxy may need a non-encrypted 
> connection.
> 
> Besides the dovecot max_ ... settings, in our system you need to tweak 
> limits.conf and bump up the limits via the ulimit command in the dovecot 
> init script. Open file descriptors and process limits seem to be the 
> main settings.
> 
> After this, you get into kernel tuning such as inotify settings.
> 
> Let me know if you have any questions. If some of this helps, we might 
> want to feed it back into the list.
> 
> ---Jack
> 
>