LMTPD sockets

Scott Adkins adkinss at ohio.edu
Thu Aug 17 17:06:44 EDT 2006

In a cluster (multi-machine) environment, such as Tru64 or Polyserve (on
Linux), that problem is solved by the use of CDSL (a context-dependent
symbolic link).  You basically turn the file or directory into a CDSL and
suddenly each machine in the cluster gets its own personal copy of it that
is not shared.

We use TCP for LMTP, which I personally feel is a better way of delivering
messages to LMTP.  If you have to use the "deliver" program though, then
yeah, you still need the socket file.  That file needs to be a CDSL.  The
same goes with SASL and its socket file.


--On Thursday, August 17, 2006 4:50 PM -0400 David Korpiewski <davidk at cs.umass.edu> wrote:

> This is building on my original discussion about simultaneous access:
> We are having a problem where two servers accessing the same SAN now give us a LMTPD error because they are stomping on each
> other's sockets (they share the same database on the SAN with the same socket directory).  Is there any way to prevent this from
> happening or easily configuring them not to not to use the same sockets?
> I've gone into cyrus.conf and changed the socket directory listed for lmtpd but for some reason the deliver still fails on
> accessing the original socket directory.   So somewhere else in the system it is trying to access configdirectory/socket/lmtpd.
> Thanks for any help
> David
> Michael Menge wrote:
>> This subject has also been on this list a few weeks ago. Look for the
>> subject
>> "High availability email server"
>> Quoting Wesley Craig <wes at umich.edu>:
>>> On 16 Aug 2006, at 14:52, David Korpiewski wrote:
>>>> My director had us go back to using our Macs to try to build a
>>>> failover cluster.   We were able to set up two mail servers sharing
>>>>  the same backend XSAN.   We put our database for cyrus on the XSAN
>>>>  and had both mail servers use _the same_ database and the same mail
>>>> store locations.
>>>> So far in limited testing it works flawlessly.  This is very  strange
>>>> to us.  Is cyrus set up to allow multiple simultaneous  accesses to
>>>> its database without corruption or are we just lucky to  not have
>>>> corrupted the database yet?
>>>> This is cyrus 2.2.12 running on two OSX 10.4.7 servers.
>>> The main process which updates mailboxes.db etc on a backend server is
>>> imapd.  Since multiple imapd's are allowed, as long as your XSAN
>>> provides appropriate locking, you are not "just lucky".  See the
>>> compile documentation for a discussion of how to select the locking
>>> method:
>>>         --with-lock=METHOD
>>>             Specifies the locking method to use. Currently implemented
>>>             locking methods are:
>>>             flock   flock() locking
>>>             fcntl   fcntl() locking
>>>             By default, configure uses "fcntl" if the "fcntl()" function
>>>             exists, "flock" otherwise.
>>> AFAIK, fcntl( ..., F_SETLK*, ...) always locks the whole file, a la
>>> flock().  Also, I think I see a bug in master/service.c, where instead
>>> of using the locking method specified during compile-time, fcntl() is
>>> always used.
>>> :wes
>>> ----
>>> Cyrus Home Page: http://asg.web.cmu.edu/cyrus
>>> Cyrus Wiki/FAQ: http://cyruswiki.andrew.cmu.edu
>>> List Archives/Info: http://asg.web.cmu.edu/cyrus/mailing-list.html
>> --------------------------------------------------------------------------------
>> M.Menge                                 Tel.: (49) 7071/29-70316
>> Universitaet Tuebingen                  Fax.: (49) 7071/29-5912
>> Zentrum fuer Datenverarbeitung          mail: menge at zdv.uni-tuebingen.de
>> Waechterstrasse 76
>> 72074 Tuebingen
>> ----
>> Cyrus Home Page: http://asg.web.cmu.edu/cyrus
>> Cyrus Wiki/FAQ: http://cyruswiki.andrew.cmu.edu
>> List Archives/Info: http://asg.web.cmu.edu/cyrus/mailing-list.html

      Scott W. Adkins                http://www.cns.ohiou.edu/~sadkins/
   UNIX Systems Engineer                  mailto:adkinss at ohio.edu
        ICQ 7626282                 Work (740)593-9478 Fax (740)593-1944
     PGP Public Key available at http://www.cns.ohiou.edu/~sadkins/pgp/
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