Re: LMTPD sockets

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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.

Scott

--On Thursday, August 17, 2006 4:50 PM -0400 David Korpiewski <davidk@xxxxxxxxxxxx> 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@xxxxxxxxx>:

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
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M.Menge                                 Tel.: (49) 7071/29-70316
Universitaet Tuebingen                  Fax.: (49) 7071/29-5912
Zentrum fuer Datenverarbeitung          mail: menge@xxxxxxxxxxxxxxxxxxxx
Waechterstrasse 76
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